* Winter weather advisory for Washington’s far north and northwest suburbs 6 a.m. to 6 p.m. Tuesday | Winter storm watch late Tuesday night through Wednesday evening entire region except far south *
10:35 p.m. update: We’re sticking with our forecast map below for snowfall Tuesday night into Wednesday. We may consider increasing amounts in the morning, but for now there’s too much conflicting model information to do so. As for tonight into tomorrow, we continue to expect the precipitation to start as rain around 2-4 a.m., before transitioning to sleet from northwest to southeast around 6-9 a.m., although areas south and east of the Beltway may stay all rain for the duration. The sleet could be moderate to heavy for a several hour period north and west of the Beltway, and may mix with a bit of snow and freezing rain, with sleet/snow accumulations up to an inch or so possible before this first wave of the storm tapers mid-afternoon. Slick spots on roads and sidewalks are likely north and west of the Beltway, and possible inside the Beltway, as temperatures drop to right around freezing during the day tomorrow.
6:20 p.m. update: Afternoon model runs (with the exception of the North American Mesoscale Model) have us leaning toward upping our snowfall totals for the second wave of this winter weather event starting during the predawn hours Wednesday (see forecast map below) and continuing through Wednesday afternoon. But we want to review one more set of model runs before doing so. We’ll be back between 10 and 10:30 p.m. with an update.
[Winter storm to bring wintry mix to D.C. area Tuesday and Wednesday with accumulation possible]
Original post from 5:05 p.m.
It was such a beautiful day that it’s hard to imagine icy messes and snowflakes are in our future. Such is the transitional season, although this is a bit extreme. Increasing clouds in the sky are the first sign of things to come. There are a few hours left to enjoy the mild weather, so get to it!
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Through tonight: Temperatures slowly fall this evening. It’s in the upper 40s and lower 50s by sunset. Still pretty pleasant. We should stay dry until a few hours after midnight or so, then precipitation becomes likely in the predawn hours through sunrise. While this may start mainly as rain, falling temperatures allow sleet and some snow to start mixing in toward sunrise, especially in our far-northwest areas. Temperatures fall into the mid-30s as the precipitation starts.
View the current weather conditions at The Washington Post.
Tomorrow (Tuesday): Rain transitions to sleet first in our northwest areas and then progresses toward the Interstate 95 corridor by midmorning. The sleet could be moderate to heavy at times, with even some thunder possible. With temperatures dipping to near freezing, some slick spots are possible on roadways and other paved arteries, mainly in our northwest areas, but we cannot rule out some spotty slippery travel closer to the Beltway. Our farthest south and east suburbs may stay entirely cold rain, while those northwest areas may see not only sleet, but some snow and freezing rain as well. Morning temperatures in the low to mid-30s are steady or might fall a degree or two during the day.
The heaviest precipitation should taper off by midafternoon, with just some spotty drizzle, freezing drizzle or sleet lingering into the evening commute. With temperatures near or below freezing after sunset, both pedestrians and motorists should look out for slick spots on untreated surfaces through the evening.
Then accumulating snow may move in during the predawn hours Wednesday.
The World War II Memorial on the Mall. (Miki Jourdan via Flickr)
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Pollen update: Tree pollen is MODERATE at 30.03 grains/cubic meter. Other pollens are low.
A rare “Particularly Dangerous Situation” (PDS) Tornado Watch has been issued for Northern and central Alabama, Northeast Mississippi, and Southern Tennessee. Tornadoes are expected including the possibility of a few intense/strong tornadoes. https://t.co/Rt0DvfgpFk pic.twitter.com/91JHGvQL4m
— NWS SPC (@NWSSPC) March 19, 2018
Severe weather: Spring is coming, whether winter storms want to give in. Large parts of the South are under the gun today. A Particularly Dangerous Situation tornado watch is up for northern Alabama and surrounding areas through the evening, where strong tornadoes are likely in the hours ahead. This is the same storm that delivers us the rainy and sleety mess into tomorrow.
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