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| Just one ominous sign of the storm approaching us. Forecast calls for major flooding along the Otter Creek in Rutland County, Vermont. Widespread, damaging floods are likely today and/or tomorrow from Pennsylvania to Maine. |
This isn't just minor inconvenience stuff. Some areas are in for some serious, maybe life-threatening floods. Tornadoes threaten North Carolina. Damaging winds will roar from the Carolinas to Maine.
It started with a full blown blizzard with zero visibility and winds gusting to more than 60 MPH in the northern Plains yesterday.
Today and tomorrow bring heavy snow, dangerous floods, damaging winds and even tornadoes, depending upon on where you are.
As usual with these large storms, I'll get into the big picture first, and tell you what us Vermonters are in for.
That opening storm salvo, the blizzard in the Dakotas and Minnesota, left a trail of highway pileups ad closed roads. It was so bad that plows and police wouldn't go out onto the roads. Too dangerous.
The storm center that caused the blizzard has moved into Canada, but the storm's strong cold front extends all the way down to the Gulf Coast. A new storm is forming on that front. This is what will cause the chaos today and tomorrow in the eastern United States.
This frontal system is developing something of what is called a negative tilt. Most cold fronts are aligned northeast to southwest or directly north to south. This one is becoming aligned northwest to southeast.
That's a sign of a strong system, and one that's able to bring a boatload of subtropical moisture northward. That flow of moisture is being aided and abetted by strong winds aloft, bringing all this weather north.
With that negative tilt, the cold front will go through Florida and the Carolinas before it gets to New England.
The strong, veering winds aloft has eastern North Carolina at risk for tornadoes today. The storm already has a history of producing a few tornadoes in Mississippi. With even stronger dynamics, this system is almost guaranteed to produce at least a couple spinups.
The orientation of this cold front will help massive amounts of moisture come inland over the Mid-Atlantic States and New England. That means heavy rain.
Unfortunately, the heaviest rain will fall precisely where the heaviest snow fell last week. This goes from central Pennsylvania, central New York, southern and central New England and on up into New Hampshire and Maine.
This rain will be accompanied by very warm, humid air, especially for this time of year. Snow melts most rapidly in humid air. So it will go fast. One to three inches of "rain" will come from the snowmelt, combined with one to four inches of rain from the sky.
This sets the region I mentioned just above for a serious flood threat. This won't be just nuisance flooding. It could get quite serious in some of these areas.
High winds are also a problem, especially in southern New England, parts of New Hampshire and Maine, and the high elevations throughout the Northeast.
Incredible winds will be howling just off the surface, roughly 5,000 feet above the surface. Peak gusts on summits like Mount Washington in New Hampshire, Mount Mansfield in Vermont and Mount Marcy in New York are likely to exceed 100 mph.
There won't be anything that strong in lower elevations where people actually live, but damaging winds gusts are still a possibility.
All in all, between the tornadoes, floods and winds, it seems like some sad Christmas tragedies are inevitable. Totally on brand for the year 2020
VERMONT IMPACTS
Southern Vermont is within the larger target zone from serious flooding with this storm. The snow pack there is deep. This part of Vermont will also get the most rain from this storm, likely 1.5 to 2 inches, with locally higher amounts.
That very warm, humid air I mentioned will also envelope all of the state tonight and the first part of Christmas Day. While it rains. Hard.
I'm definitely concerned that in southern Vermont, at least, this won't be just another, "Oh, look, there's some water in Farmer Smith's field again."
If you're in a flood prone area, especially from Route 4 south, keep an eye out. Small streams and brooks will be first to go nuts later on tonight. There's definitely a risk of culverts failing, back roads washing out and water collecting rapidly in basements.
It seems that Vermont has become more flood prone in recent decades. The most recent serious flood we had was on October 31-November 1, 2019. I think the upcoming flood will be nearly as bad as that, but will hit an entirely different part of the state. The Halloween storm hit northern Vermont. This one will focus on southern Vermont.
It's very hard to see flooding when driving when it's dark out, so be very careful, or better yet, don't venture out at all tonight and tomorrow. We're supposed to say home because of Covid anyway.
I think there will also be a lot of street flooding in towns. Many roads in flood plains will go under water. Whatever you do, don't drive into flood waters. That's always a very dangerous move. It's especially true now, when the water will be frigid and nail you with hypothermia almost instantly.
The flood warnings, initially only in effect for far southern Vermont, have been extended north to about Route 2. There's less snow further north, but there's enough to melt, combined with the heavy rains, to trigger flooding.
As Christmas Day wears on the flooding small streams and brooks will feed into the larger rivers. At this point, Otter Creek in Center Rutland is expected to go into major flood stage, at 13.1 feet. Flood stage is 8 feet. The expected crest would be the highest since the record highs of Tropical Storm Irene in 2011.
The Walloomsac River in Bennington County is also expected to go into major flood stage, while numerous other rivers in Vermont will probably hit at least moderate flood stage.
Strong winds are a secondary threat with this storm in Vermont. It won't be as bad as in southern and coastal New England, but we could seem some gusts as high as 50 mph mix down to the surface from those screaming winds aloft. Scattered power outages are a threat.
Ahead of the cold front in the rain Christmas morning, it will be strangely balmy and, as I said, humid. Lots of us will be in the upper 50s, which is getting close to record highs. After the cold front passes in the afternoon, the rain will mercifully shut off as temperatures fall through the 40s and 30s.
The storm will be over by then, and we'll be left once again, fixing damaged roads, culverts, bridges and likely some homes and businesses.
Not a good forecast, for sure. It's worth repeating: Totally on brand for 2020.
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