4:40 p.m. update
Radar shows snow and mixed precipitation decreasing in intensity and starting to drift off to the northeast. In most places, it should end in the next hour, except possibly lingering in the Baltimore area a little after 6 p.m.
The winter weather advisory has been dropped for the D.C. metro area but, even after the precipitation ends, untreated roads are likely to remain slick or even ice over more with the loss of daylight. Temperatures will hover in the 20s. While you should be able to get where you’re going, we urge folks to take it easy… especially on untreated roads, parking lots, bridges, ramps, overpasses and driveways.
Icy roads and sidewalks are expected tonight. Use abundant caution if you must travel, and leave plenty of time to get to your destination.
— NWS DC/Baltimore (@NWS_BaltWash) December 15, 2017
Treated roads are in fine shape, for the most part, but Friday afternoon traffic is still terrible so allow plenty of extra time.
Preliminary snow totals reported to the National Weather Service through 4 p.m. include:
Reagan National Airport: 0.2 inches
Dulles International Airport: 0.1 inches
Columbia, Md.: 0.3 inches
Baltimore, Md.: 0.5 inches
Annapolis, Md.: 0.5 inches
This is our last update in this post. For the forecast for the rest of the night and the weekend, watch for our PM Update, which should publish at the top of the following link by 5:15 p.m.: Capital Weather Gang’s latest posts
(For earlier updates, scroll to the bottom of this post…)
Original post from 10:40 a.m.
A very light amount of snow is possible in the Washington and Baltimore regions this afternoon, coming at an inconvenient time. The snow will fall leading up to the start of the afternoon commute, potentially slowing things down some and causing a few slick spots, especially from the District and to the east and north.
The latest model information coming in suggests a dusting to an inch is most likely in Washington and Baltimore and locations to the east and north, which are under a winter weather advisory. It’s not out of the question that a few spots — mainly northeast of Baltimore — exceed an inch.
In the advisory area, allow extra time for commuting and, if you’re averse to driving in the snow, consider waiting for the snow to end rather than leaving in the midst of it. It should rapidly taper off by around 4 or 5 p.m.
West and southwest of the Beltway, spotty light snow or flurries are possible, but shouldn’t amount to much more than a dusting, if that.
Patchy light snow could break out as early as this morning, especially across northern Maryland, but snow should cover the most territory during the early to midafternoon hours, before quickly moving away late this afternoon. The bulk of the snow will probably happen before the peak of the afternoon commute. However, many commuters leave earlier than normal on Fridays, so a little snow could coincide with its front end.
Because air temperatures have been cold and pavement temperatures are near freezing, snow that falls should be able to accumulate on untreated roads, which could become slippery. Treated roads should remain wet and safe for travel.
The snow intensity should generally be light, which would prevent rapid buildup. The threat of more disruptive snow would increase if a localized moderate to heavy band of snow developed. But, “right now, we’re not expecting such a feature” said Wes Junker, Capital Weather Gang’s winter weather expert. Better chances of localized heavy snowfall will focus from northern Delaware to southern New Jersey.
On our winter storm impact scale, which rates snow events on a scale from 1 to 5, this one meets the criteria for a Level One “nuisance event” in the winter weather advisory area. Snow is expected to be light, but it could cause some minor impacts due to cold temperatures and slick roads, and its timing near a commuting period.
3:35 p.m. update
Snow and mixed precipitation continue, light in most areas, but turning heavier from around Columbia and Baltimore to the northeast. The combination of precipitation is putting down a slick, icy film on untreated surfaces. Temperatures are only in the mid-to-upper 20s and we are even seeing reports of some more well-traveled roads becoming slippery.
In a matter of minutes, Route 123 is getting covered. We're salting all lanes now. Pls stay back and give us room. We're trying to melt this as quickly as possible. pic.twitter.com/ANZe9SBPsf
— VDOT Northern VA (@VaDOTNOVA) December 15, 2017
Short-range models continue to indicate precipitation will taper off between 4 and 5:30 p.m. from southwest to northeast.
In terms of total snow/ice accumulation, most areas in metro D.C. should end up in the coating range, increasing to around an inch near Baltimore, and even more northeast of Baltimore, potentially.
2:30 p.m. update
A light mix of frozen precipitation expands from around the Beltway north and east through Baltimore. Temperatures are well below freezing, in the mid-to-upper 20s, so untreated surfaces are becoming slippery.
— Ian Livingston (@islivingston) December 15, 2017
Where it is precipitating lightly, we are seeing a mix of snow flakes, graupel (snow pellets) and/or freezing drizzle. Where the precipitation is a bit heavier, from around Columbia to the north and northeast, more snow is occurring and accumulation of up to an inch or so is possible. Northeast of Baltimore, one to two inches of snow are possible.
1:15 p.m. update:
Light frozen precipitation continues to fall across the area. The small wrinkle in this event, so far, is that rather than snow flakes – we’re seeing snow pellets (white pellets; this is not exactly the same as sleet which are more clear) fall in a number of areas from around the District eastward. Capital Weather Gang winter weather expert Wes Junker explains that the pellets are falling rather than flakes due to temperatures around 7,000 feet being a little warmer than ideal for snowflake crystal growth.
In our northern and western areas, more pure snow is falling and, so far, has left behind a light coating in spots like Leesburg and Frederick.
— Erik Pitzer (@pitz2) December 15, 2017
Light snow and pellets should continue for the next couple of hours. Areas seeing snow pellets may see an increase in flakes if and when the precipitation increases in intensity.
So far, we’re not seeing indications of bad road conditions but with temperatures well below freezing (in the upper 20s to around 30), we urge caution on untreated surfaces. ” A thin slippery layer on untreated roads is the main concern this afternoon,” the National Weather Service said in a recent tweet.
12:10 p.m. update
Very light snow is breaking out across the region, with the steadiest activity in northern Maryland. A dusting has already been reported around Frederick. Snow should continue to increase in coverage over the next hour with many places getting a light dusting by then. Temperatures are below freezing, ranging from 26 to 31 degrees in most spots (except around 32 or 33 in Southern Maryland), so snow will stick to untreated surfaces.