The Washington Post

Evening update: Precipitation headed north; winter weather advisory posted along and west of I-95

Our general forecast for the region hasn’t changed from earlier this afternoon. We’re still expecting a sharp transition from mostly rain around the District (possibly changing to snow before ending) to heavy snow toward the mountains during the day Saturday. Here are a few notes...

* The winter storm watch was dropped for Montgomery and Howard counties and replaced with a winter weather advisory, which was also issued for Fairfax, Prince William, and southern Fauquier counties. The winter weather advisory calls for 1-4” of snow, with the lowest amounts toward I-95. The District, Prince George’s County and points to the south and east are not under a winter weather advisory.

* Radar and observations indicate a mix of precipitation moving into central Virginia. Snow has already begun at Wintergreen Resort and Hot Springs in west central Virginia and a mix of sleet and cold rain has been reported in Blacksburg and Roanoke, where temperatures are in the mid-30s. Even Richmond, with temperatures in the 40s, experienced a brief period of sleet as the precipitation began due to a cold pocket of air aloft before changing to all rain. Here in the D.C. area, we may see some sleet mix with the rain initially, before mostly rain overnight (snow chances enter the picture during the day Saturday).

* We probably haven’t addressed wind sufficiently in previous forecasts. Winds will pick up from the north during the day Saturday, increasing to near 20 mph by late afternoon and early evening with some higher gusts. The combination of wind and snow in outlying north and west areas may lower visibility. Not to mention winds may bring added to pressure to tree limbs weighed down by snow (toward the mountains).

* The latest GFS model is quite warm, and would imply mostly rain even into Frederick and Loudoun counties, currently under a winter storm warning. On the other hand, the latest NAM model continues to suggest the potential for heavy snow in our outlying north and western suburbs. So taking a blend of these two models, no need to change our forecast but signficant uncertainty remains.

* For those interested in climatology, here is some information on snow and temperature records for tomorrow, October 29 (courtesy CWG reader Chris Laudicina):

Reagan National Airport:
Daily Snowfall Record: T (1925)
Record Low High: 44 (1925)

Dulles Airport:
No snow on record to have fallen on this date
Record Low High: 47 (1965)

Baltimore Washington International
Daily Snowfall Record: T (1952)
Record Low High: 46 (1925)

All of these records may be challenged Saturday.

* The National Weather Service Office in Sterling posted a great discussion this afternoon, which I found myself agreeing with (it closely mirrors our forecast). Here are some key excerpts from it:

Highest elevations will see total snowfall in the 4-8 range w/ locally higher amounts. Valley regions will see a more general 2-4 or 1-3 depending on the elevation and proximity to these ridgelines. Across the Va/Md piedmont, a mix of rain and snow during the mid-late morning hours may give some light accumulations but w/ a very close rain-snow transition line not expecting significant accums other than grassy surfaces - and maybe briefly if it begins to rain again.

Metro DC areas may receive a brief mix-in of heavy snow toward the afternoon hours as the low tracks off the coast and the backend snow band slides east northeast. Gusty winds will also be an issue during the afternoon/evening hours.

* Well be back with another update later this evening. In the mean time, view our video summary with my latest forecast thoughts

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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