Los Angeles Bracing For Scary Christmas Storm

The most severe Christmas storm since at least 1971
looms in the Los Angeles area as atmospheric 
rivers continue to batter the West Coast. 

Perhaps the scariest of the barrage of atmospheric rivers tormenting the West Coast is now targeting the Los Angeles area. 

The heavily populated, sprawling area around Los Angeles, the coast north and south, and the mountains to the east all face torrents of rain and strong, damaging winds. 

In their forecast discussion this morning, the National Weather Service wrote in all caps, that I'll avoid, "This is a very dangerous holiday storm. Anyone traveling on Christmas Eve or Christmas Day will need to exercise extreme caution. Make sure to take the proper action before the storm hits."

The rain is starting today, then turn more intense tonight, and peak tomorrow morning. Rainfall rates during the peak hours of the storm in and near Los Angeles will be somewhere around an inch per hour. 

Total rainfall between now and Christmas in southern California is forecast to be in the four to seven inch range, with locally higher amounts. 

NOAA's Weather Prediction Center has put parts of the L.A area under a rare high risk zone for a "significant  threat of flash flooding, landslides, rock falls and mud slides. The greater than normal travel during the Christmas holiday will likely expose a potentially larger number of people to these life-threatening hazards."

On Tuesday, as light rain began making inroads in Los Angeles County, residents were stacking sandbags and other barriers in Pacific Palisades, Altadena, Malibu and other areas where there were big fire last year. They're hoping debris flows won't outmatch these efforts. Crews were also installing Jersey barriers in hopes of diverting landslides away from vulnerable homes. 

Some debris-prone roads, like Topanga Canyon Boulevard, were closed even before the first drops of rain fell. 

Thousands of people have been told to pack "to go" bags and be ready to evacuate at a moment's notice.  

High winds will complicate this whole mess. In the L.A basin, winds could reach up to 55 mph, and in the foothills and mountains nearby, those winds could reach as high as 80 mph. 

As the soils get soggier and soggier, it'll be easier and easier for the wind to blow trees over. 

The intensity of the storms should wane somewhat by Christmas Day, but scattered downpours will continue to vex the L.A basin.

Further north in California, atmospheric river storms that caused serious flooding in the Sierra Nevada foothills have diminished somewhat. But more rain, sometimes heavy and mixed with thunderstorms, will continue the flood risk.  There's even a low risk of brief spin-up tornadoes with the thunderstorms. 

High winds warnings remain in effect until the afternoon of Christmas Day for a wide area of central and northern California. 

Meanwhile, in the Sierra Nevada, several more feet of snow are expected in the next few days. 

Another Atmospheric River Menaces Pacific Northwest; Also, Flood Videos

Another photo of flooding in 
Washington. Renewed atmospheric
rivers this week will cause 
flooding to return. 

Another series of atmospheric rivers is smashing into the Pacific Northwest this week, raising worries about renewed flooding. 

The flooding won't be as bad as the catastrophic stuff we saw last week, but it's just another headache for all those people trying to recover from one of the worst disasters in Washington State history. 

Already, it's causing real problems. With the first wave of rain moving in today, local media is reporting mandatory evacuations today in parts of Auburn, Washington, and in other areas. Roads are closed. 

Initially, today, the storminess is much like last week. The rain is accompanied by very warm air. That means the rain will fall high up on the mountain slopes where it usually snows. That increases the flooding risk. 

The next in a series of storms will come into Washington toward the end of the day tomorrow, and this one looks windy as hell. A high wind watch is in effect for much of western Washington for wind gusts that could range between 55 to 65 mph.

Since the ground is so soggy, tree roots no longer have a firm hold into the soil. The wind will make it easy for trees to blow over. Officials are also worried about power outages.

This second storm will be the one that make rivers peak again. However, the Snoqualmie River near the town of Carnation looks like it will reach major flood stage again, but not quite as high as last week.  Other rivers will also approach major flood stage. 

Temperatures will also crash, too. The valley floors, in places like Seattle, Tacoma, Everett and Olympia will continue to rain. But in the mountain passes, it'll snow like hell. This is actually a return to normalcy in the Washington.

By midday Wednesday, the mountains above Puget Sound could have a foot or two of new snow. The changeover to snow in the high elevations will come too late to prevent runoff into the valleys below. 

After that, the next wave of the atmospheric river looks to arrive Thursday. This one will hit further south in Oregon, so the risk of flooding will rise there. 

VIDEOS

First, a great overview video of the flooding from KOMO. Click on this link to view, or if you see the image below, click on that. 

Today Show Summary showing rescues, the interior of flooded homes and other dramatic footage. Click  on this link to view, or if you see the image below, click on that. 

Another aerial view of rescuers arriving at a swamped house in Duvall, Washington to take the occupants to safety.  Again, click on this link to view, or if you see image below click on that. 

 A big logjam formed against bridge abutments over the Snohomish River along a major highway. Also note how close the water is to overtopping the levee. Again, click on this link to view, or if you see the image below, click on that.

The atmospheric river extended all the way into western Montana, causing flooding and landslides. This is a video of a bridge collapsing in the Montana floods. Click on this link or if you see the image below, click on the image below. 

 

Washington State Flood Update: Record River Crests As Unrelenting Rain Finally Starts To Diminish

A mudslide closed part of Interstate 90 in Washington 
State, hitting some vehicles in the process. Record
flooding continue in Washington today. 

The Great Flood of 2025 is peaking in western Washington today after days of torrential rain from a series of atmospheric rivers have swamped vast areas of the states. 

This is one of those disasters that have so much going on that it's hard to keep track. A network of rivers flow out of the Cascades and Olympic mountains. Within that large river network, numerous areas in these hills got more than 10 inches of rain over the past five days. I saw one report of more than 16 inches.  

The area most under the gun is roughly the size of New England, excluding Maine. Major flooding is occurring or forecast on 17 rivers in the region. Some of those will reach record crests.

The flood in Washington also reminds of the big flood we had here in Vermont back in 2023. All those torrents coming down from those hills and mountains, the river valleys with their small towns and cities filling up with water, landslides obliterating parts of roads.

The only big difference is this is a winter, not summer flood. And I'd say more people are being affected than that horrible Green Mountain State disaster in July, 2023.

Up to 100,000 people in Washington have been evacuated in the Skagit River valley alone. It's a densely populated area about an hour north of Seattle. 

In the town of Mount Vernon, the Skagit River is forecast to rise two feet above the previous record high level. "This is a flood we haven't seen before.....The potential for catastrophe flooding is real," said Mount Vernon Mayor Peter Donovan, as reported by KUOW an NPR-affiliated station in Seattle. 

A flood wall was built around Mount Vernon in 2018. Residents are nervously watching to see whether that wall will be enough. 

There is no good time for a catastrophic flood, but one coming in the weeks before Christmas, especially people whose homes and businesses are destroyed by the high water. 

The good news so far is I haven't seen any reports of deaths, but I fear at least a few people have lost or will lose their lives as more information comes in from flooded areas. There have already been some close misses. 

Two people - one clinging to the roof of a vehicle, another in a tree - were rescued via helicopter in eastern King County, as seen on dramatic video posted on X

Video from Live Storms Media shows water from the Snohomish River overtopping levees and flowing into already flooded roads, homes and businesses. 

Another video by Jonathan Petramala shows residents and business owners of Sultan, Washington rapidly sandbagging and evacuating as water rose rapidly from a nearby river. 

Road travel in western Washington today is trying at best. Even part of Interstate 90 shut down due to a mudslide. Amtrak trains between Seattle and Vancouver are suspended due to flooding. 

Atmospheric rivers hit the Pacific Northwest every winter but this one is a doozy. It originated southeast of China and stretched 1,700 miles to Washington. Atmospheric moisture content over Washington broke December records.  

The atmospheric river is so strong it was able to trigger flooding and flood alerts all the way over into northern Idaho and extreme western Montana. Severe flooding was report in Lincoln County, Montana. 

Despite crossing several mountain ranges, the moisture plume from the atmospheric river is setting off a snowstorm in central Montana.

Remaining moisture from the atmospheric river will ride the jet stream southeastward in a long, narrow path from southwestern North Dakota all the way to southwestern Virginia. 

Back in Washington, the short-term forecast is pretty good  Rainfall is much lighter today. Only scattered showers are in the cards for Friday. Saturday will actually be fairly sunny, which is an infrequent occurrence in western Washington.

But the good news is temporary. Rain will restart Sunday and continue all week. It won't be as heavy as what they just saw, but the daily grind of rain will probably prolong the flooding. 

This is also your reminder that climate change has led to more intense rainfall.  We don't know - at least not yet - how much climate change had to do with the Pacific Northwest flood. But it is consistent with the effects of a warmer world. 

 

 

  

Atmospheric River Drowning Pacific NW As Expected, Idaho Of All Places, Too. Meanwhile, California Dries Out

Snoqualmie Falls in Washington State
is at its highest level in at least a 
decade due to this week's 
atmospheric river. Major flooding
is occurring or forecast on at least
18 river sites in western Washington. 
Photo via Facebook,
Washington Weather Chasers

As we all expected, the Pacific Northwest is drowning in an atmospheric river, with widespread flooding  covering roads, homes and businesses throughout western Washington.  

Round One of the flooding hit yesterday and last night, with major flooding and some reports of record high crests on some rivers.

Seattle area meteorologist Scott Sistek, in his Emerald City Weather Blog, painted a pretty grim picture of the flooding underway in 'Washington State: 

"The Skagit River is now forecast to reach several feet beyond its record crest. The predicted peak at out Vernon was 41.54 feet Thursday night - over 4 feet above the record crests from 1990, 1995 and 2021. 

The Snohomish River at Snohomish forecast was back at peaking a few inches over record flood stage Thursday and Friday."

Sistek went on to describe several other rivers that have or are expected to reach record crests. 

The flood in Washington is coming in two waves. The atmospheric river moved south into Oregon yesterday, so the rain largely stopped in Washington and rivers started to recede.

But now that atmospheric river off the Pacific Ocean is back in Washington. This time around, the rainfall isn't quite as heavy as in the first round, but will last longer than in the initial blast. With rivers already flooding or at least very high, it won't take much for the major flooding to take hold again today. 

To make matters worse, forecasts for amount of rain in today's wave of the atmospheric river in Washington have increased. 

Eighteen river locations in Washington are expected to reach major flood stage. Washington Gov. Bob Ferguson said the state's Emergency Operations Center is at level 1, the highest response level. 

The weirdest part of this is in northern Idaho. Atmospheric rivers with heavy rain hit the Pacific Northwest most winters. The moisture sometimes carries over all the way to the mountains of Idaho, producing some rain in the valleys and nice winter storms with heavy snow in the Bitterroot Range ad other tall Idaho mountains.

This time, the atmospheric river is much stronger than usual. The moisture, and the tropical air associated with it, is raising flood concerns in the normally wintry mountainous terrain of Idaho.

Total rainfall in much of central and northern Idaho was expected to be in the higher elevations and one to four inches in the valleys. Snow levels were expected to rise to maybe 6,000 feet to as high as 9,000 feet, which is pretty wildly high for December. 

Record high temperatures are also melting existing snow. As you can imagine, this is a recipe for high water. 

The atmospheric river is strong enough so the some moisture will probably make it over the Continental Divide into Montana. There, the wet air will collide with a blast to Arctic air coming in from Canada to  produce heavy snow and strong winds across much of Montana late this week. 

An atmospheric river is a long narrow band of moisture that can travel thousands of miles before making landfall. They can happen almost anywhere near a coastline, but they are common in the winter along the Pacific coastlines of the United States and  Canada.

Many of them are beneficial, as they bring needed rain and mountain snows to the West Coast. However, stronger ones, as we're seeing now, can cause serious flooding. 

Climate change can make atmospheric rivers warmer and wetter than they otherwise might be. That increases the risk of flooding. The added warmth  also makes rain more likely and snow less likely up in the mountains. 

That less mountain snow scenario can increase flooding, since rain fall where it normally snows. High elevation rain also reduces the winter snow pack. That leaves less snow to melt in the spring to feed into reservoirs.  

Pacific Northwest Braces For Atmospheric Rivers, Flooding Over Next Few Days

Atmospheric rivers could bring up to 10 inches
of rain in the next few days parts of the Pacific
Northwest, raising flooding fears. This map is
forecast rain for the next 7 days. 

The Pacific Northwest has a wet, dark reputation this time of year. The people are nice enough, the weather is not. Sufferers of seasonal affective disorder will do well to avoid places like Seattle and Portland this time of year. 

Usually, it's a grinding, boring day after day realm of drizzle, light rain, fog and chill. Sometimes, though, things can really get out of hand. 

The next few days look what one of those out of hand periods.

A strong atmospheric river is due to hit Washington and Oregon beginning tomorrow and lasting through much of the week. This long lasting deluge is sure to cause at least some flooding and landslides as inches and inches of rain bombard the western halves of Washington and Oregon. 

Some areas of Washington and Oregon could get four to as much as 10 or more inches of rain by Wednesday night.   The Willamette Valley, which runs roughly from Portland to Eugene, Oregon, is expecting three to five inches of rain. 

The Seattle metro area could get two to five inches of rain, which means clogged drains and street flooding, landslides on steep slopes and shallow-rooted trees toppling over as soil turns to loose mud. 

But the real problem looks like it will be in the Cascade Mountains east of Seattle and Portland, and the Olympic Mountains of northwest Washington. 

Five to ten inches of rain could pour down on these mountains, which would quickly race down steep slopes into populated valleys below.  

The atmospheric river - really a series of atmospheric rivers - are tapping into tropical moisture which of course involves warm air. That means snow levels will be high.  You'll probably have to get above 6,000 above sea level to hit snow. That leaves only the higher peaks and volcanoes in the wintry weather. . 

The higher the snow level, the more water will race down the slopes, which is why everybody is so worried about flooding. Flood watches are up for all of the western third of Washington and much of western Oregon. 

Officials in both states said people in flood prone areas should have spent Saturday and as much of the day Sunday as they could getting ready for high water. 

It's always hard to predict exactly how high rivers will get in these situations. But the flood-prone Snoqualmie River is forecast to reach near major flood stage Tuesday, then have a secondary major flood stage peak on Thursday. 

Some of the flooding could extend across the border to Vancouver Island and other areas of southwest British Columbia, Canada, but the worst effects still look like they'll hit south of the border. 

The Cascade Mountains will wring out some of the moisture, so eastern Washington won't get much rain. But the storms will then hit the mountains of Idaho and western Montana, where more rain and snow will fall.

The snow levels in Idaho will be oddly high because of the warm air. Elevations below 8,200 feet or so will probably see mostly rain.  

This type of weather pattern often brings incredibly strong winds to parts of Montana and Wyoming, so those two states will be looking out for that this week.  

Late this week, the super rainy weather in the Pacific Northwest will slow down or stop for about a week, give or take. Then the atmospheric rivers might resume again. 

 

Weird Out Of Season Atmospheric River Hits Pacific Northwest, Does More Good Than Harm

Satellite view of atmospheric river hitting the 
Pacific Northwest Friday. Those are 
exceptionally rare in the summer. 

The Pacific Northwest has a cloudy, wet reputation, but in the summer, the water shuts off over there, and this area is usually pretty dry in August. 

Not at the moment, though. 

An atmospheric river has hit Washington and Oregon, dumping near record amounts of rain for this time of year.  

Seattle averages about an inch of rain each August. That much fell just in the past two days.  It was the most rain at once in August in at least a decade.  

Atmospheric rivers are fairly common along the U.S. West Coast in the winter but are super rare in the summer. 

These weather systems are narrow bands of atmospheric moisture that can travel hundreds or even thousands of miles across the Pacific Ocean and then come ashore, unleashing torrential rains.  Atmospheric 

The atmospheric river is doing far more good than harm since almost all of Washington and much of Oregon is in a drought.  

This atmospheric river won't entirely solve the problem, but at least it will help. Maybe. 

The drought made it difficult to forecast the impacts of the atmospheric river. The National Weather Service in Seattle had this to say in a hydrologic outlook ahead of the storm,

"Very dry antecedent conditions has left the area soils dry and hard. This amount of rainfall in one storm will not have much tie to soak into the very dry soil, which will result in heavy surface runoff. Impacts are uncertain due to how much moisture will be able to be absorbed by the soil."

Most rivers won't flood, since they're starting out so low. But outdoor enthusiast might be taken by surprise by unusually high water for this time of year. For instance, people who might be used to setting up camp in or near a dry river bed during the summer might fall victim to fast flowing water.

The atmospheric river also hit parts of British Columbia, Canada. It was actually beneficial there, too. Wildfires were spreading in western British Columbia so this is a big help, since it was a real soaker. Vancouver picked up 1.69 inches of rain Friday, its fifth wettest August day on record. 

 The rainy weather was starting to clear up in the Pacific Northwest today. Clouds, cool weather and light showers will continue the rest of the weekend. But the Seattle, Portland and other cities in the region will revert to their usual dry, sunny August weather during the upcoming week. 

Inland parts of eastern Oregon are still under a flood watch today as the remnants of the atmospheric rive remove inland to trigger shower and storms. Some downpours over wildfire burn scars could cause some debris flows. 

Hawaii Storm Creates Floods, High Winds, Even Snow And Tornado Risk

A KHON reporter gets splashed by water from passing
vehicles as she reports on flooding in Hawaii Thursday.
The island chain is being hit by an unusually
strong storm that will also bring heavy rains
to California this weekend. 

An unusually powerful storm is slapping Hawaii with a wide variety of rough weather. 

The entire island chain was under a high wind warning until noon Friday. Flooding was developing. There was a risk of severe thunderstorms and even the risk of a tornado or two, which is very rare for Hawaii. 

Power outages were already increasing across Hawaii during the day Thursday. Residents inMaui were told to stay off roads due to high winds and flooding. 

As of early Friday several roads were blocked by flooding as rain came down at a rate of one to as much as three inches per hour. 

The city of Kahului on Maui reported an inch of rain in an hour and wind gusts to 50 mph, which is highly unusual stormy for the location. The National Weather Service warned Maui residents of impending significant and life-threatening flash floods and landslides. 

One town in Maui received 13 inches of rain in the storm. A weather station atop a Maui mountain reported a wind gust to 120 mph. 

Honolulu was slammed by more than 3.5 inches of rain, including just under two inches of rain in two hours. That two inches in two hours is more rain than what normally falls on Honolulu during the entire month of January.  

Winter storms sometimes affect Hawaii this time of year, but this one is especially powerful. 

The storm was expected to deepen to 986 millibars, at a latitude a little south of 30 degrees N which is unusual for a storm that far south. It's about the same latitude as northern Mexico.

The storm is close enough to drag a cold front through Hawaii, which is kind of rare for that far south. Ahead of the front, forecasters were worried about rotating thunderstorms that could produce those waterspouts or potential tornadoes. 

 Early Friday our time on the East Coast, the torrential rains were just moving into the Big Island of Hawaii, and new flash flood warnings were issued for parts of that island.  

Atop the highest volcanoes on the Big Island of Hawaii, winter storm warnings were in effect.  Winter storm warnings up there are actually not all that weird for Hawaii.  The summits are expecting five to ten inches of snow, with wind gusts possibly reaching as high as 90 mph. 

ATMOSPHERIC RIVERS

What goes on in Hawaii doesn't stay in Hawaii.  The storm north of Hawaii will contribute to atmospheric rivers that will start hitting California today and intensify over the weekend. 

Flood watches are already up for central California, including San Francisco and Sacramento.  This is a "Pineapple Express" from near Hawaii, as we mentioned so it's a warm atmospheric river. That means rain instead of snow will fall pretty high up the slopes of the Sierra Nevada range. Elevations as high as 7,800 to 8,000 feet look like they are in for rain instead of snow. 

There could even be some flooding near Lake Tahoe. 

Southern California, still suffering from a drought, is expected to mostly miss out on this atmosphere river. It probably won't rain down there until Tuesday. It's just as well the rain in southern California won't be torrential, as that would lead to more mudslides and debris flows in areas that suffered through those huge January wildfires. 

Eventually the atmospheric river could consolidate into a storm that might affect us here in Vermont around next Thursday. Watch this space for updates in the coming days. 

 

First Major West Coast Atmosphere River Getting Their Wet Season Off To A Doozy Of A Start

We've entered the season in which pretty big storms come off the Pacific Ocean and hit various parts of the West Coast, sometimes intensely, sometimes not.  

Satellite view shows the strong "bomb" cyclone centered off
the Washington and British Columbia coast this afternoon.
It's the comma shaped thing on the right hand side of the 
image. Part of the atmospheric river is visible as that
long white streak heading west from the storm

The first major storm of the season looks like quite a doozy. What is known as a bomb cyclone will team up with an atmospheric river .

A bomb cyclone is a storm that's intensifying super fast. A storm is a center of lower air pressure. In general, the lower the air pressure in a storm, the stronger it is.

 Technically, if the air pressure in a storm drops by 24 millibars within 24 hours, the storm is a bomb. 

Bomb storms are often dangerous they are simply strong and getting stronger. You can plan on a lot of wind and precipitation if you're hit with a bomb cyclone, and that will be the case with this "bomb"

This storm could be the most intense in the region since at least the 1940s. 

 An atmospheric river is a long narrow corridor of deep moisture.  When one of these comes a shore, a 200 to 400 mile wide band,

So we have a strong storm and a stronger than usual atmospheric river. The result is a West Coast mess that started today. 

THE RESULT

Between this afternoon and Sunday evening, ten to as much as 15 inches of rain to northwestern California and southwestern Oregon. 

NOAA's Weather Prediction Center says that by Thursday, there's a high risk of dangerous flooding in parts of northwestern California. High risk flood alerts from NOAA happen only about four times a year and it's exceedingly rare for them to be issued three days before the event, as this one was.

High risk days account for two-fifths of all U.S flood deaths and at least 80 percent of all flood damage. So this is serious. 

Emergency managers are especially worried about mudslides and debris flows, especially on slopes that suffered wildfires in recent years.

The storm is accompanied by those high winds. Many neighborhoods are pretty heavily forested, which means trees could fall on houses. People are being warned to stay in interior rooms on the lowest floors of their homes because of this risk, 

Those winds tonight could gust to 70 mph, with possible 85 mph gusts near the beaches. 

Ten to as much as 20 inches of rain could
fall in the yellow shaded area of 
northwest California and southwest
Oregon over the next several days. 

The rough weather extends all the way to Washington and British Columbia. High winds are expected even in the big cities of Seattle, Tacoma and Vancouver, Canada. 

Blizzard warnings are up for Washington's Cascade mountains, 

Previous to this storm, some strong systems have hit British Columbia, and sideswiped Washington State with some decent rains. But points further south have had just small introductory systems to introduce the rainy season.  

This will be a real slap of reality and could be the start of a rough winter on the West Coast, especially roughly from San Francisco north.  There's a La Nina weather pattern, albeit a weak one, and that often cause extra storminess in the Pacific Northwest

WEST COAST STORM AND VERMONT

The West Coast storminess is unrelated to the super welcome precipitation that we're expecting starting Thursday. That one got energy from a previous storm that came ashore from the Pacific a few days ago. 

Despite the power of what's hitting the West this week, I so far see few signs of that storm spawning anything extreme in our neck of the woods.   

One piece of that atmosphere river should come through New England in about a week as a modest system with light precipitation. After that, the weather pattern seems like it could be active for us, but that's uncertain.  

Atmospheric Rivers, Famous On U.S. West Coast, Are A Peril To East, Including Vermont, Too

The atmospheric river that caused the big New England
flood of December 18-19 turned the tiniest stream
in front of my house into a raging river too.

 The December flooding that befell New England, especially Maine, New Hampshire and Vermont, was largely the handiwork of an atmospheric river.  

If you've heard of atmospheric rivers, you probably associate them with storms that sometimes slam into the West Coast during the winter. 

But these so-called atmospheric rivers can come off of the Atlantic Ocean or Gulf of Mexico, too. As we've seen lately, these sometimes have disastrous results. 

As the Washington Post describes it in an article published Thursday: 

"Atmospheric rivers - jets of intense precipitation that curl around powerful ocean storms - are generally considered a West Coast phenomenon. But it turns out a top tier atmospheric river - rated Category 5 on a scale of 1 to 5 - was part of the East Coast storm that killed at least five people and cut power to more than 800,000 customers this week."

Every state along the eastern seaboard from Florida to Maine - including Vermont - saw at least four inches of rain and wind gusts of over 50 mph. 

The December storm will almost certainly join the long list of weather disasters this year costing $1 billion or more. 

Atmospheric rivers are long narrow corridors of deep tropical moisture that are pulled into the mid-latitudes by storms. These atmospheric rivers usually aren't that wide in the grand scheme of things. The one that just hit us in New England was probably about 400 miles wide.

But they can be thousands of miles long. Some of the atmospheric rivers that strike the West Coast extend as far west as Hawaii, which is why those storms are often dubbed a "Pineapple Express."

The distance between Los Angeles and Honolulu by the way is about is about 2,500 miles.

The reason we hear so much more about atmospheric rivers on the West Coast than elsewhere is because of geography.

The West Coast atmospheric rivers that come generally west to east across the Pacific encounter California, Oregon and Washington with land that rises from sea level to mountains in perpendicular to the flow of this wet air.  

That atmospheric rivers collision with mountain ranges such as the Sierra Nevada forces the air to rise.   The rising air forces all that moisture in the atmospheric river to condense in rain and snow, which dumps big time on the Pacific coast. 

One reason why the December flooding was actually worse than the already bad inundation in Vermont was for the same reason California gets slammed by those atmospheric rivers,

The one last week that came off the Atlantic approached New England from the southeast. The air flow was only partly perpendicular to the north/south oriented Green Mountains, so the rising air releasing moisture was impressive, but not as efficient as it was in New Hampshire and Maine.  

Map shows strong atmospheric river hitting the Northeast
and a weaker one hitting California on December 18.
Map and data from the Center for Western Weather
and Water Extremes. 

The White Mountains of New Hampshire and the mountains of western Maine run generally southwest to northeast. That was a perfect arrangement to wring out the most rain possible.

Other historic storms in New England - including Vermont  - were products of atmospheric rivers.   The Great Flood of 1927 in Vermont also stemmed from an atmospheric river off the Atlantic Ocean. 

In some unlucky years, you can have multiple atmospheric rivers. In October 1996, an episode caused severe flooding in eastern New England, and another one in November the year triggered serious flooding in eastern New York.

Atmospheric rivers can also cause flood disasters far from a coastline. One such event in May, 2010, caused what was probably the worst flood in Tennessee history. 

These atmospheric rivers are surprisingly common along the East Coast, actually. One estimate pegs the number per year to about 40 in the Mid-Atlantic states, though they are seldom severe enough to cause significant flooding. 

Atmospheric rivers are categorized in a one to five ranking system, similar to tornadoes. Not surprisingly, the one we had on December 18 was a Category 5, the most severe you can get. 

But here's something to worry about. As the Washington Post points out, atmospheric rivers have been around ever since there was an actual atmosphere on Earth.

Climate change, though, is tending to make them worse, in general. Per WaPo:

"....data suggests they're becoming wetter. Winter is the fastest-warming season run the Northeast and Mid-Atlantic, and warmer air can hold and transport more water and thus release more of it. In fact, for every degree Fahrenheit the air temperature rises, the air can hold 4 percent more water. Most atmospheric rivers happen in the cool season."

The bottom line for us in Vermont is: Most atmospheric rivers will remain tame and not cause too many problems. But a growing percentage of them will cause trouble, expense and danger like the one a week ago did. 

 

Nasty Flood In Pacific Northwest. And Perhaps Some Flooding In Vermont Coming Up?

National Weather Service expected rainfall map for
the next seven days shows several inches additional rain
in the flooded Pacific Northwest, with more than an
inch here in Vermont. An expected warm storm
Sunday would melt mountain snow, raising the
risk of some flooding in Vermont by then. 

 An atmospheric river - a ribbon of deep Pacific moisture - slammed into the Pacific Northwest over the past couple of days, causing a lot of flooding that led to at least one death, and a lot of damage. 

The death was of a man swept away in a creek near Portland, Oregon. In Washington State, more than eight inches of rain soaked some areas.  The Stillaguamish River north of Seattle got to a record high crest, CNN reported.

The Skagit and Snoqualmie rivers were at major flood stage.

The atmospheric river was accompanied by record warmth, meaning rain fell at high elevations above 9,000 feet. 

That added melting snow to the mix. At low elevations, Portland, Oregon reached 65 degrees, tying the record high for the entire month of December.

Seattle had a record high of 59 degrees and also a record for the wettest December 5 on record with 2.01 inches.

The rain is temporarily tapering off in the Pacific Northwest today, but another atmospheric river with more heavy rain and possible flooding is due over the weekend.

VERMONT STORM/FLOOD?

The Green Mountain State Sunday night and Monday could see a smaller, more minor but still concerning version of what happened in the Pacific Northwest.

It's drier and cold in Vermont this week as daytime highs stay in the 20s today through Thursday. There's' very little snow on the ground in the valleys, but he mountains have already piled up one to three feet of snow, well ahead of where we should be this time of year.

Near the summit of Mount Mansfield, 39 inches of snow was on the ground compared to a normal of about a foot and a half this time of year.

I mention this because a warm, wet storm seems likely Sunday and Monday, which could bring flooding and some strong winds. 

Some of the energy from the Pacific Northwest storminess will dive down into the southern Plains and Gulf Coast states. That will spin up a storm that will scoop up quite a bit of moisture from the Gulf of Mexico and bring it northward.

Since this storm is still likely to go by to our west, we'll get a shot of quite warm air on Sunday. At this point highs are forecast to reach the 50s by then.  A burst of pretty heavy rain seems like it wants to come through later Sunday and Sunday night. 

The combination of rain and mountain snow melt could easily be enough to put some Vermont rivers over flood stage. So far, this doesn't look nearly as bad as the flooding we had back in July. But still, we'll want to pay attention to this as water might be high enough to close some roads and create problems in low lying areas.

As always, the forecast will be fine-tuned between now and Sunday, so just keep the idea in your head that there might be some trouble with high water by the time Sunday night and Monday roll around. 

The storm might also produce areas of strong winds, so we'll keep an eye on that, too.

  

California Can't Catch A Break: Atmospheric River, Snowmelt, Flooding, More Blizzards?

The entire roof of this supermarket in Lake Arrowhead,
California collapsed under the weight of feet of snow.
Rain falling atop the snow at the end of the week
could cause further collapses and flooding. 

 One storm after another has hit California since December, with disastrous results. 

Now, after a series of rather low elevations blizzards dumped feet of snow, a warmer storm seems poised to unleash heavy rain, snow melt and possibly serious flooding. 

The biggest threat seems to be in the Sierra Nevada foothills.  Tons of snow piled up in recent weeks at elevations of between roughly 2,000 and 6,000 feet above sea level. There's a lot more snow on the ground in these places than there usually is, thanks to recent cold storms. 

An atmospheric river - a ribbon of highly wet air, is forecast to hit California late Thursday night and Friday.  This type of storm carries with it rather warm, subtropical air. That means a lot of rain will fall at elevations as high as 8,000 feet above sea level. 

At first, the heavy rain will get absorbed into the snow. This would add tons of weight to roofs already overburdened by the heft of the snow on them. 

The rain, and the warm, humid air, will then rapidly melt snow, causing some pretty sudden flooding. 

The National Weather Service office in Hanford, California expects four to six inches of rain between Thursday night and late Saturday in the foothills.  Up to eight inches of rain could fall in spots just below 8,000 feet. Above that, another few feet of snow is in the cards. 

It seems flooding is inevitable, but since it's a few days before the actual storm, it's hard to say how severe it will turn out. At this point at least, I haven't seen anybody forecast catastrophic flooding, but given the kind of winter California has had, any high water is bad news.

As the Washington Post reports: 

"'If we see a fast melt event from warm temperatures or a warm atmospheric river, we could certainly see significant flooding,' the Central Sierra Snow Lab tweeted. 'How significant depends on the atmospheric conditions at the time, but it's something we need to be vigilant about."'

 In southern California, snow levels will increase to more than 9,000 feet in the San Bernardino Mountains. That means rapid snow melt and flooding could occur in blizzard-wracked towns there. Luckily, preliminary forecasts indicate rainfall there won't be as heavy as it will further north in the Sierra Nevada mountains.

No matter what happens on Friday, the risk is isn't over. California should see something of a break from the rain and storminess on Sunday, only to see more heavy rain and mountain snow early next week.  

In the Sierra Nevada, this is turning out to be a near record breaking snow season.  So far, as of Monday, Mammoth Mountain had received 555 inches of snow so far this winter. If you're counting, that's more than 46 feet of snow. Mammoth Mountain's all time snowiest winter was in 2010-11 with 669 inches, or nearly 56 feet.

Given the forecasted stormy pattern Mammoth Mountain has a shot at receiving another 10 feet of snow before spring, which would set a record. 

All this precipitation is at least partly erasing the long-running drought in California, which od course is a good thing. 

STORMS HAVE TO GO SOMEWHERE

Once the series of storms hit California, they have to go somewhere. Usually, they take a cross-country trek across the United States and end up along or near the East Coast eventually. 

However, the weather pattern that has set up might spare us in Vermont from the storms. But that's a big maybe 

Massive high pressure in central Canada and stalled low pressure of Canada's east coast might keep the storms too far south of Vermont to have much of an effect on us. 

The first in a series of storms of varying intensity that are expected to cross the US. should be somewhere near the Mid-Atlantic coast on Saturday. Though the forecast might change, it seems like as of Tuesday, the bulk of the storm will go by to our south. If any part of Vermont has effects from this it will be the far southern parts of the state.

However, if you enjoyed the slight taste of spring Sunday and Monday, don't hold your breath for any balmy weather any time soon. Temperatures should remain below normal, or at best near normal, through at least March 20 or so.

California Keeps Getting Whacked By Atmospheric Rivers; Next One To Be The Worst Yet

In this screen grab from a video, a storm surge slams into
Santa Cruz, California over the weekend, causing a lot of 
damage. An even stronger storm and atmospheric river
is hitting California today.

 California is getting blasted again today. This one is even worse than the previous parade of storms. 

Yet another atmospheric river is slamming into central and northern California and will slowly slip southward across the state through tomorrow. 

As far as atmospheric rivers go, the one that started early today and will probably go into tomorrow is even stronger than most of those that strike California during the winter.   It's about the strength you'd expect only once every decade or so.

An atmospheric river this strong would always cause havoc. But since California has already experienced several other of these great gushes of rain and mountain snow in recent weeks, the danger is quite high. The saturated soil can't handle any more heavy rain.

To review, an atmospheric river is a long, skinny ribbon of air with a LOT of moisture.  These things can travel thousands of miles across oceans.  When atmospheric rivers  hit land, as this series has done in California, they unleash huge amounts of rain and snow.

The precipitation comes down at such a fast rate that rivers overflow, landslides develop and mountain highways become hopelessly blocked by snow. 

Northern and central California experienced very heavy rains, damaging winds and coastal flooding Thursday from another atmospheric river  Though the Thursday storm wasn't quite as intense as some forecasts suggested, the flooding was extensive, and tree damage was widespread.

Tragically, the Thursday storm killed a two year old boy when a large tree fell on his family's mobile home in Occidental, California. 

A smaller, but still potent storm added to the flooding and wind damage over the weekend.

So far this winter , the series of storms have killed 12 Californians

Now, California is dealing with an escalation of this super stormy regime. Before this latest storm hit, patches of blue sky appeared over the Bay Area Sunday.  

The National Weather Service office in San Francisco urged people to take advantage of the brief break in the weather to clear storm drains, pack a "to go bag" to quickly evacuate today if necessary, and stock up on food, water, batteries and other necessities before the battering ram of the next atmospheric river would hit early this morning. 

A number of schools in the Bay Area and around Sacramento announced Sunday they would be closed due to the storm.  Parts of vulnerable towns like Wilton have been evacuated. Other evacuations are happening in Sonoma County as the Russian River is expected to flood today. 

Officials are especially worried about areas that experienced big wildfires in the past couple of years. Vegetation that would hold soils and rocks and such in place is mostly gone.

The soil is already saturated to the max, and now some of those burn areas could see five to 10 inches of rain today. Rain could fall at a rate of an inch an hour, which is pretty extreme. 

Meanwhile, the Sierra Nevada mountains above an elevation of 7,000 feet expect another three to six feet of snow from this storm, along with winds gusting to more than 80 mph. 

The "weaker" storm early Sunday felled plenty of trees and power lines around Sacramento, and many residents were still without power as the new, larger storm bore down. 

I'm sure I'll need to pass along updates as the storm fully strikes the West Coast today and tomorrow. 

This stormy nightmare is expected to continue for awhile yet. San Francisco does receive a fair amount of rain during the winter, but there's usually breaks in between the storms. When I looked last night, their forecast either called for definite rain, or rain likely, daily through at least Saturday.

Forecasts into the third week on January suggest the parade of very wet storms smacking California will continue at least into the third week of this month. It's too soon to say exactly how wet those storms might turn out, but the flood risk will certainly continue and spread for the next couple weeks.

VERMONT EFFECTS

As I always say, what smashes into California from the Pacific Ocean doesn't stay in California. 

The storm that hit Thursday is mercifully passed through the southern United States as a weak storm spreading showers and non-severe thunderstorms. This lame storm is moving off the southeastern coast today, and will hit parts of Newfoundland as it intensifies into a pretty good nor'easter tomorrow. This will have no effect on us here in Vermont. 

The same is not true with the big storm hitting California today.  It appears it's going to affect us one way or another here in Vermont. 

I'm pretty sure it won't be nearly as extreme as what California is dealing with. It seems like the lead storm that hit California early Sunday might spread some snow, mixed precipitation or rain our way Thursday. 

The main event for us in Vermont should be Thursday night and Friday.  We also don't know if the storm will be rain, snow, ice, wind or all of the above. Current forecasts are leaning toward a mostly rain scenario for us again, but nobody's absolutely sure.

As always, check for further updates on this one. 

Vermonters Thrilled That Merriam-Webster Has Added This Term To Its Dictionary

A, um, pleasant walk through mud season  last March.
Merriam-Webster has just added the term mud season
to its dictionary. 

 The English language is always changing. New words and terms are always being added to the lexicon.

Dictionaries always try to keep up.  On Wednesday, Merriam-Webster added 370 new words to its dictionary. Among the terms added is "mud season".  

Us Vermonters are so, so familiar with that word combo, but perhaps much of the rest of the world is not. People would have to look it up.  Now, they can. 

For the record, Merriam-Webster defines "mud season" as "A time of year (such as early spring) that is characterized by excessively muddy ground." 

That defines it pretty well. Of course Merriam-Webster is a "just the facts, ma'am" kind of organization, so they omit the often colorful descriptions we use when mud season leaves our cars mired in muck and our house tracked with so much dirt we could grow an indoor garden. 

I'm happy to report that Merriam-Webster has added a few other words that are at least tangentially related to weather and climate. 

In one case, I've never heard of the term before, but I love it. 

Do this: Close your eyes and picture yourself stepping outside at dawn on a gorgeous May morning. The trees are just starting to explode with green, and the aroma of lilac, tulip, hyacinth and bleeding heart fills the air

The air also holds the sounds of a beautiful concert. All the birds are singing happily, and if you're not a curmudgeon who doesn't like being awakened early by all that chirping, the bird song fills you with joy. 

That wonderful sound has a term and it was added to Merriam-Webster this week. It's called, appropriately enough "bird chorus."  The official definition of this is, "The singing of wild birds that closely precedes and follows sunrise, especially in spring and summer."

Another weather related term added this year to Merriam-Webster has been around for decades, at least in meteorological circles. It's "atmospheric river."

Atmospheric rivers are those narrow channels of deep moisture that travel often thousands of miles over oceans and come ashore to produce heavy rain and flooding. Or at Merriam-Webster defines it: "A concentrated band of water vapor that flows through the atmosphere and that is a significant part of the global hydrologic cycle and an important source of regional precipitation."

There's one more relevant new Merriam-Webster listing. At least as it relates to this here weather/climate blog thingy. The word is "greenwash."

The definitions of this are (1): To make something such as a product, policy or practice appear to be more environmentally friendly or less environmentally damaging than it really is. (2): To mislead (someone) by means of greenwashing. greenwash noun : something (such as a claim or action) that is intended to make a product, policy, activity, etc. appear to be ore environmentally friendly or less environmentally damaging than it really is."

Since I like to make up words that make more sense than the English language, I'll have to think up some new weather related terms to propose to Merriam-Webster. 

Any ideas, anyone?

 

 

Nice Vermont, King Tides, Atmospheric RIver And Oddly Lingering Wanda

Unusually sunny weather for November this morning light up
the deep yellows of large poplar trees on my St. Albans property.
Leaves are still on awfully late in the season. My home office
window looks out on these trees, so right now the office
is glowing an angelic golden color from the reflected light. 

In a post yesterday, I talked about how gloomy November usually is in Vermont. 

But, we do have a treat for you.  For the second year in a row, we've got a stretch of unusually bright weather to talk about. 

There's been some sun for the past couple days, and it looks like we'll have partly to mostly sunny skies daily through Thursday, though Wednesday could be a bit more on the cloudy side.  

Temperatures will also be a little warmer than normal, sneaking up into the 50s most days.

This won't compare to the string of sunny days with near record temperatures in the low 70s that lasted nearly a week last November. But still, it you're like me and way behind in getting the last of your fall chores done, we're catching a break.

After all, in some Novembers, like in 2019, winter hits at the beginning of the month, and you're screwed with winter prep in those cases.

Since the weather is going to be quiet here in Vermont for awhile, we can talk about some other noteworthy things going on out there.

ATMOSPHERIC RIVER

Northern California is getting more good news in that another atmospheric river is set to hit that area early next week.

Atmospheric rivers are long, narrow channels of deep moisture in the atmosphere, like a river in the sky. It's how California gets much of its winter seasonal rainfalls.

Since California is in a drought, an atmospheric river is mostly a good thing. They had a pretty strong one last month, which was so intense it led to a lot of flash flooding and debris flows. This one is going to be weaker than the last, but will still bring beneficial rains to the northern half of the state.

Southern California, unfortunately, will mostly miss out. 

This unsettled California weather will eventually consolidate into what will probably be a pretty good sized storm in the center the nation late next week. That storm could give us a pretty good slug of rain next weekend. 

KING TIDE AND STORM

A nasty storm is meandering off the coast of Georgia and Florida which is causing a big fetch of east and northeast winds off the Atlantic Ocean into the coastline.  That's driving a lot of ocean water onto the shore, too.

The timing couldn't be worse. Tides are higher when there's a new or full moon.  At certain times of the year, the new or full moon can produce even slightly higher tides than at other times of year. That's called a King Tide and it's going on now.

Plus, with climate change, ocean levels have risen, so it's easier to get nuisance flooding during King Tides even when there's sunny, calm weather.

The combination of this year's King Tide and that storm is pushing coastal flooding in northern Florida, Georgia and South Carolina to near record highs. They're expecting that quite a few homes and businesses could get flooded this morning.

Even though this storm won't go up the coast like the last nor'easter in October, the King Tide will cause minor flooding on the Atlantic shores all the way up to Maine. 

WANDA LIVES! 

Meanwhile, the nor'easter that hit coastal New England on October 23 and 24 eventually headed east and turned into Tropical Storm Wanda. Believe it or not, Tropical Storm Wanda is still wandering out there in the central Atlantic.   Wanda is expected to turn back into a non-tropical storm over the weekend and race toward Ireland early next week.  

Hardcore Winter Finally Arrives In New England

A debris flow damaged this California home amid a 
big storm hitting that region today. The same storm or its
offspring could create some "interesting" weather in 
New England early next week.
Photo via twitter  @mcrfd

 New England winters are almost always harsh, or at least parts of them are.

After a long wait, the traditional nasty, unpleasant to say the least winter weather is arriving right now. 

As previously advertised, a broken off piece of the Polar Vortex is coming straight at us and will make things unhappy outdoors for the next couple of days. After that, a possible nasty storm.

More on the storm in a moment, but first the cold. 

A storm that overnight brought snow (and thundersnow!) to parts of North Carolina is headed out to sea and will become a powerful ocean storm. 

It will move northward, well off the coast. And turn big. Really big. 

The storm will be too far away to cause much havoc in New England. However, the difference in air pressure between that big offshore storm and Arctic high pressure up in northern Ontario will propel sharp, strong north winds through here, increasing today and continuing through Friday at least. 

Temperatures will fall here in Vermont all day as the winds ramp up.  By tonight, you'll really feel the wind chills out there. 

Those wind chills will make the air feel as cold as 25 below late tonight and tomorrow. Actual temperatures will go to near zero overnight, and only rise a few degrees during the day Friday as those cold north winds continue to make the bare trees roar. Expect gusts in the 25-30 mph range. 

Skies will remain cloudy Friday, and there will continue to be some snow showers around. In the mountains, a couple or few inches of windblown, light powder might be added to the snow pack. 

Yet Friday won't be the day for great outdoor recreation, given those awful wind chills. 

The wind will be calmer Saturday and the core of the polar vortex piece with its frigid air will be beginning to depart. 

Saturday will still be teeth-chattering, but a few degrees warmer than Friday. Plus the wind will be a little calmer. And some breaks of sun will help. 

With at least partly clear skies and calm winds Saturday night, temperatures will go way below zero in most of Vermont and the rest of northern New England. 

Temperatures will finally start to get closer to normal Sunday afternoon.

This won't be the most epic cold wave ever, but it is a pretty typical blast for this time of year in this part of the world. But that doesn't make it any more comfortable. 

Then there's a potential new problem after that.

EARLY WEEK STORM?

While it's warming up, somewhat, there's trouble on the horizon. Let's put it this way: What happens in California doesn't stay in California.

As I wrote yesterday, the Golden State is receiving less than golden weather. A storm, accompanied by an atmospheric river, is battering California with torrential rains, mudslides, debris flows, damaging winds and feet of snow in the mountains. 

Sounds wonderful, huh?

Energy from that storminess will create a new storm that will start somewhere near Colorado Friday night and then move east to somewhere in the Mid-Atlantic states Sunday.  It'll lay down yet another stripe of snow across the Midwest as it makes this move. 

Then what? Nobody is actually sure what the storm will do once it reaches the Mid-Atlantic States. But there's a lot of early signals this could turn into a big storm involving plenty of snow in the those Mid-Atlantic States and New England. 

Some of the models spin up a really strong storm.  Early indications are the bulk of the snow would fall south of Vermont, but that's is by NO means guaranteed. 

We won't have a good handle on what this storm will do for a good couple of days yet. It seems likely some snow will fall somewhere in Vermont during this, but where and how much is a great question. Same questions exists for the rest of New England. Stay tuned! 

The Slamming Of California Begins

Residents who live near areas where wildfires burned last
year evacuate ahead of a soaking storm that promises 
to produce dangerous debris flows in fire zones.

 The well-advertised storm in California has arrived, and will be getting worse through the day. 

Already, strong winds have swept through central and northern parts of the state, with many felled trees and power lines in and around Sacramento, for instance. 

The real trouble with this winter storm in California is of course the rain and mountain snow. 

Even ahead of the storm, highways were closed and emergency managers ordered evacuations near areas where wildfires raged last year.  Some of these areas anticipate up to eight inches of rain over the next couple of days. 

The fires burned away trees and roots that hold soil and rocks in place, so they'll start sliding when the rain really hits. The Santa Cruz Mountains are a particular danger spot, and at least 5,000 people have been evacuated from that region. Some holdouts remain, refusing to leave, so we just have to hope they'll stay safe.

Ominously, the National Weather Service office in San Francisco early this morning detected rainfall rates as high as a half inch in 15 minutes, which could really set off the debris flows.  

To give you an idea of how bad it could get, we might look back at a debris flow in January 2018 that hit Montecito, California.  A large wildfire burned above the community the year prior.  Rainfall, similar  to intensity to what's going on in parts of California now, swept a massive mud and debris flow through neighborhoods in the middle of the night, killing 23 people. 

You can see why a lot of people in California are taking no chances with this one. 

On Tuesday, the National  Weather Service office in San Francisco put out a pointed warning in their forecast discussion as the threat of mud slides, debris flows and flooding grew, especially near where wildfires burned in 2020:

"This is the type of event that usually causes numerous rock and mudslides along Highway 1.  Residents of Big Sur should be prepared for extended periods of isolation."

Blizzards that will drop many feet of snow in the Sierra Nevada mountains are also signaling danger. 

The National Weather Service office in Reno was also in hair on fire mode Tuesday:

"Be where you need to be by sundown today (midnight at the absolute latest) -- you might be there for a couple of days. Have a backup plan for school/work/childcare/etc. Ground travel could become impossible at times tonight through Thursday, especially in the Sierra" 

Obviously, this storm isn't all bad. California needs the rain and snow, given the drought the state has experienced. This storm might be coming too hard, too fast, but at least it will help recharge ground water. It will add nicely to the Sierra Nevada snow pack, an important source of water for California when that snow melts in the summer. 

I surmise this is at least partly a symptom climate change. The atmospheric river and the strength of the storm hitting California are only moderately powerful. Big certainly, but they've seen worse. The problem is the widespread nature of last year's wildfires have turned what would have been a somewhat risky storm into one that packs real danger.

And I'm convinced last year's fires were made worse by climate change. And yes, I know poor forest management and increasing housing development in fire risk areas also play a big part in this. 

Stay tuned for more California storm news as the next couple days wear on. I'm sure there will be more drama out there. 

"Atmospheric River" Soaking Pacific Northwest

Satellite view from yesterdayof a long narrow band of clouds
stretching from the Philippines to the Pacific Northwest. 
That's the atmospheric river dumping torrential rains and
causing flooding and landslides today in 
Washington and Oregon 

 As many of us know, it's really rainy during the winter in the Pacific Northwest. 

The first half of this week, though, is a super soaker out there due to an atmospheric river off the Pacific.

An atmospheric river is a relatively narrow plume of deep moisture that crosses large sections of oceans, and dump heavy rainfall wherever they make landfall.  They're called atmospheric rivers because they act like real, land based rivers.

The amount of moisture in these atmospheric rivers is often equivalent to the water flow near the mouth of the Mississippi River.

These atmospheric rivers usually have their origins in the tropics. The one hitting the Pacific Northwest has its origins near the Philippines. 

The more intense atmospheric rivers can cause catastrophic flooding.  There was a nasty one that caused record rainfall and dangerous, fatal landslides in southeastern Alaska earlier this winter, for instance. 

The atmospheric river now hitting the Pacific Northwest seems pretty impressive, too, so it is or will cause I  plenty of problems with flooding. And landslides. 

Remember I said that atmospheric rivers have their origins in the tropics.  Which means these are often quite warm.  In this case, snow levels in the Cascade Mountains will rise to as high as 8,000 feet above sea level. This will create melting snow, which will feed runoff into already flooding rivers.

Higher elevations are also prone to avalanches, as rain or heavy wet snow falling on top of drier snow layers can start the snow sliding down steep mountainsides. 

Even more dangerous is the risk of landslides which is often a problem in the Pacific Northwest. It's already been a rather rainy winter up there, even by their standards. Soils are saturated and heavy, and the torrential rains with this atmospheric river will make things worse. 

Most of the moisture from the atmospheric river will get wrung out in the Cascade Mountains and in the Rocky Mountains of central and northern Idaho. 

 But the strong jet stream that organized this atmospheric river will continue eastward, contributing to expected high winds today and especially tomorrow in most of Montana, much of Wyoming and the western Dakotas.

Winds could gust to 70 mph or more in some of these areas. 

The jet stream will buckle over the eastern Pacific Ocean in the next couple of days, shutting off the atmospheric river and turning the rain much lighter and more showery in the Northwest starting tomorrow.