Low pressure passed by to the west as it tracked into the Ohio Valley and Great Lakes on the 18th into the morning of the 19th, before transferring its energy to a coastal low along the Mid-Atlantic Coast. The coastal low moved out to sea later on the 19th.
Canadian high pressure supplied plenty of low-level cold air, but warmer air worked its way in aloft, and this caused a wintry mix of snow, sleet, and freezing rain. Snow and sleet overspread the area on the early morning of the 18th. Snow and sleet changed to a light wintry mix including freezing rain by the evening of the 18th. Precipitation ended as a period of light snow and sleet on the morning of the 19th.
The highest snowfall accumulations (around 4 to 8 inches) were across the northern Shenandoah Valley toward the northern Blue Ridge Mountains of Virginia where the heaviest precipitation occurred, and temperatures aloft were cold enough for precipitation to start off as snow. However, mostly sleet occurred across central Virginia toward the Washington Metropolitan area, so accumulations were less (around an inch or two).
Ice accumulation from freezing rain was up to a tenth of an inch for most areas, but around a tenth to a quarter inch in the Virginia Piedmont where warmer air aloft cause more freezing rain vs. snow or sleet.

Winter Weather in WESTERN HIGHLAND, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in EASTERN HIGHLAND, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Department of Highways

Winter Weather in FAIRFAX, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Department of Highways

The ramp from westbound I-66 Custis Memorial Highway to northbound I-495 Capital Beltway Inner Loop was closed due to multiple accidents from ice due to freezing rain.

Winter Weather in EASTERN LOUDOUN, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Department of Highways

VA-621 Bull Run Post Office Road was closed due to ice from freezing rain and an accident between Hollyspring Lane and Sudley Road around 9 PM on the evening of the 18th.
There were also multiple accidents from icy roads on VA-643 between VA-659 and VA-653.

Winter Storm in FREDERICK, VIRGINIA
From 18-FEB-21 04:00:00 to 18-FEB-21 13:00:00 (EST-5)
Reported by: Trained Spotter

Winter Storm in KING GEORGE, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Storm in CLARKE, VIRGINIA
From 18-FEB-21 04:00:00 to 18-FEB-21 13:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in FREDERICK, VIRGINIA
From 18-FEB-21 13:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in CLARKE, VIRGINIA
From 18-FEB-21 13:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in ROCKINGHAM, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in SHENANDOAH, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in WARREN, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in CLARKE, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in GREENE, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in MADISON, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in RAPPAHANNOCK, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in CULPEPER, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in PRINCE WILLIAM, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in ARLINGTON, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in NORTHERN FAUQUIER, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in SOUTHERN FAUQUIER, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in WESTERN LOUDOUN, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in NORTHERN VIRGINIA BLUE RIDGE, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter

Winter Weather in AUGUSTA, VIRGINIA
From 18-FEB-21 04:00:00 to 19-FEB-21 09:00:00 (EST-5)
Reported by: Trained Spotter