As an Arctic front descends on the D.C. area early Sunday, some snow will likely breakout. It could fall briskly for a time, bringing a light accumulation to parts of the area, but it won’t last long, and some locations may get missed.
This is a snow that will fall while many Washingtonians are sleeping, arriving between 10 p.m. Saturday and 2 a.m. Sunday and probably winding down between 4 and 8 a.m. Precipitation could briefly begin as rain or a rain-snow mix. Areas near and northeast of Interstate 95 have the best chance of seeing accumulating snowfall while there will probably be a sharp cutoff to the west and south.
Our initial estimate is for a coating to 2 inches for the Beltway area. The zone from Annapolis to Baltimore and to the north and northeast, could see a bit more than that. But to the west and south of Fairfax County, just a coating or less is anticipated.
Because the snow will have a sharp cutoff and is still two days away, changes to this forecast are probable and just small shifts could alter projected snow amounts substantially.
As most of the snow will end before sunrise Sunday (or perhaps an hour or two later to the northeast of D.C.), it should have relatively minor impacts. Some untreated roads may be slick so you may want to allot extra time for heading out to Sunday morning activities.
Irrespective of how much snow falls, bitter cold air will follow in its wake, with temperatures falling through the 20s in the afternoon and wind chills in the single digits by Sunday evening. Any snow that falls will stick around. Some late morning and early afternoon sun should help melt some of the snow on paved surfaces before a hard freeze later in the day.
The snow forecast continues to be complicated because of these two factors, which we also discussed yesterday:
- Temperatures will probably be above freezing when the precipitation arrives. This weather system will herald the coldest weather of the season but, before it arrives, temperatures will probably be in the mid- to upper 30s. This means that the precipitation could start as rain before changing to snow and that the snow will not immediately stick. Once the snow gets going, it should cool the air and ground enough to allow for accumulation. But, because of the snow’s short duration, the window for accumulation may only be a few hours.
- The heaviest precipitation may focus northeast of D.C. The most energetic part of this weather system and the zone of heaviest precipitation may focus concentrate in the zone between Baltimore and southern New Jersey. Models differ on exactly where the heaviest precipitation will occur but the overall setup supports more snow to the northeast. There’s an outside chance it extends into the D.C. area and its eastern suburbs; in that scenario, up to a few inches of snow could occur. Exactly where and how quickly a band of heavier snow develops is critical to the forecast.
Here’s how much different models project for the Beltway area:
- UKMet: 2 to 3 inches
- NAM and German: 1 to 3 inches
- High resolution Canadian: 2 inches
- European: 1 to 2 inches
- High resolution NAM and American: Coating to 2 inches
- American AI: 1-inch
- Canadian and European AI: Coating
(These model forecasts assume all snow will stick, so are probably overdone slightly because of above freezing temperatures when precipitation begins.)
The models differ on a critical issue. Some, like the high-resolution NAM and AI models, simulate less precipitation and the air is slow to cool; as such, little snow accumulates. The models, which simulate more precipitation, cool the air faster, because the snow falling through the air helps lower temperatures nearer the ground.
Forecast confidence in amounts remains low, and we will continue to refine this forecast. Be sure to look for our updates on Saturday for the latest projections.
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