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.