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Mostly rain in immediate D.C. region, some snow well north and west (LIVE BLOG)

*Winter Weather Advisory for Frederick county through 8 p.m. and points N & W (see map) | Social media snow reports and photos *

Overview: Today’s snow event is a minor one and may even be more rain than snow south and east of the District. Nonetheless, the coincidence of the storm’s heaviest precipitation with the afternoon commute may cause some slow going, especially in the colder north and west suburbs. Please see our blog post “Key points for today’s snow and rain event” for a detailed overview of what to expect.

4:00 p.m. update: This live blog has concluded. See our PM Update for our latest forecast and continued updates...

3:45 p.m. update: This continues to be largely a rain event inside the beltway, although we’ve received a few reports of flakes mixing with the rain in the District. To the west and southwest, locations like Reston, Oakton, and Gainesville are seeing rain transition to snow and may get a coating before this ends. Farther to the north and west, some accumulation is occurring, particularly at elevations above 1,000 feet.

I expect we’ll see more reports of rain changing to snow farther east over the next couple hours, but in some cases, the precipitation may shut off before this can happen. In most spots, this event should end by 6 p.m. or so.

3:15 p.m. update: The Winter Weather Advisory has been discontinued for Montgomery, Howard, northern Fauquier and Loudoun counties. It remains in effect for Frederick and Carroll counties through 8 p.m.

3:10 p.m. update: Inside the beltway, most spots are getting rain, with rain mixing with and changing to snow north and west, but not accumulating (except at high elevations).

The big question now is whether the District, places inside the beltway, and to the east see any flakes at all? We still think yes, but with temperatures still from the upper 30s to low 40s in this area, it’s not a given. Another factor that will cut down any snow we might see? The precipitation looks to end on the early side of the our predicted 6-9 p.m. window, not giving temps much time to drop.

2:40 p.m. update:With temperatures still hovering around 40 with rain inside the beltway and snow only sticking in elevated locations well north and west, it’s becoming clear snow is going to be at the low end of our projections. We still expect rain to transition to snow before ending in the immediate metro area, but anything more than a coating on grassy areas is doubtful. And north and west of the beltway, accumulations on grassy areas will be light, probably less than 1”.

Keep reading for earlier updates...

2:15 update:For the time being, rain seems to be the predominant precipitation type inside the beltway, though snow is being reported to the west and north in places like Reston and Gaithersburg. Where it’s raining, temperatures range from 37-41 degrees. As precipitation increases in intensity, temperatures should fall a bit and rain should transition to snow. Still, the most likely window for steady snow and any accumulation is between 4 and 6 p.m. But any accumulation will probably be limited to mainly grassy areas except well north and west of town.

1:50 p.m. update: Reports of light snow, light rain, and a mix are starting to come in from the District and points east, but the precipitation remains a bit patchy. Steadier precipitation is showing up on radar to the southwest and should move into the immediate metro region between 2 and 3 p.m. Snow continues not sticking anywhere except the hills of Frederick and Loudoun county. That will be the case until probably 4 p.m. or so.

1:10 p.m. update: Snow - mixed with sleet and rain in a few spots - is starting to fill-in on radar to the south and west. So areas which have been dry so far inside the beltway and to the east should start seeing some snow or possibly rain to start within the next hour or so.

Except at higher elevations (above 500 feet) in Frederick and Loudoun county where some light accumulations have been reported on grassy areas, snow is mostly melting on contact.

12:50 p.m. update: Reports of light snow and/or flurries now in Potomac, Olney, and Twinbrook in Maryland as well as Reston and Sterling in Virginia. Rain is mixing in with the snow in a few spots. The steadiest snow remain in northern Maryland.


Flow at 500 mb (18,000 feet) and vorticity (spin) at 4 p.m. today from NAM model (StormVistaWxmodels.com)

When might some steadier snow move into the metro region?

That will occur when the mid-level energy at about 18,000 ripples through. The image on the right shows a simulation of it around 4 p.m. It shows the wave in the atmosphere just to our west along with the vorticity (or spin) which aids in lifting of the air for the development of precipitation.

Noon update: Radar shows mainly light snow into western Loudoun county and much of Frederick and Carroll counties. Except in elevated areas - where some accumulation on grassy areas has been reported - snow is not sticking with the temperatures in the mid-30s. This activity is generally heading off to the north and west. While it may graze western Montgomery and Howard county, should miss D.C. and its close-in suburbs, where temperatures are in the upper 30s to near 40 degrees.

Jason is the Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science, and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association.
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