A mix of rain and snow will probably change to snow during the predawn hours Sunday with light accumulation possible through midday, especially in our colder areas north and west of downtown Washington. The National Weather Service has issued a winter weather advisory for the District and counties to the north and west, including Fairfax, Prince George’s and Montgomery, from 1 a.m. to 4 p.m. Sunday. The advisory does not include Southern Maryland.
“Plan on slippery road conditions,” the advisory states. “The heaviest accumulations will be on non-paved surfaces.”
We would anticipate the most hazardous conditions between about 5 and 9 a.m., when temperatures are lowest and snow is falling most steadily, especially in our colder areas north and west of downtown Washington.
We generally project about a coating to 2 inches of snow in the region, with the greatest amounts north and west of downtown and especially toward the mountains, where it will be coldest.
Since Friday, models have their increased their precipitation projections for this event as well as how long it will last, with the potential for snowfall to continue through a good part of Sunday morning.
However, especially around downtown Washington and points south and east, the ground may be too warm for much accumulation. Most models indicate temperatures won’t drop to around freezing until sunrise or even a little later, and will remain at or above freezing through midday. This limits accumulation prospects, especially on paved surfaces. Even though several models show 2 to 4 inches of snow, they are not taking into account that the snow that falls will not stick.
Because of only marginal temperatures to support snowfall, we are predicting slightly lower totals than the National Weather Service, which is calling for 1 to 2 inches and localized amounts of 4 inches, even in the District. We think lower elevation areas around downtown Washington, southeast Washington and near Reagan National Airport will struggle to see much accumulate from this event, especially on the roads.
“It’s hard to get much accumulation with temperatures above freezing unless you have at least moderate snowfall,” said Wes Junker, Capital Weather Gang’s winter weather expert. “Most accumulations from the city east and south will likely be on grass and mulch.”
As you get west of Interstate 95, lower temperatures increase the possibility of at least a coating and up to a couple of inches or so. Any areas that see an extended burst of heavier snow could even see a bit more, especially locations with more elevation.
After 9 or 10 a.m. Sunday, with more daylight and temperatures hovering at or above freezing, the chance of much additional accumulation will diminish even if it keeps snowing through midday.
Here’s how much various computer models project for the District, not taking into account melting as a result of above-freezing temperatures:
European: 1 to 2 inches | ICON, Canadian, high-resolution Canadian, SREF and HRRR: 2 inches | NAM and High-resolution NAM: 3 inches | American: 3 to 4 inches
The National Weather Service blend of models (which averages the different projections together) projects about 2 inches in the District but, again, is not taking into account melting.
Throughout this event, the lowest temperatures will be in areas north and west of the Beltway, especially in Loudoun, western Montgomery, Frederick and northern Fauquier counties. The mildest temperatures will focus from Alexandria and downtown Washington toward Southern Maryland.
9 p.m. Saturday to 1 a.m. Sunday: Rain or a rain-snow mix develops. Temperatures: falling from mid-40s to 35 to 40.
1 to 5 a.m.: Rain-snow mix changes to snow from northwest to southeast. Some accumulation northwest. Temperatures: falling to 32 to 35.
5 to 9 a.m.: Snow — most probable period for slick roads and accumulation. Temperatures: 30 to 34.
9 a.m. to 1 p.m.: Snow tapers off from northwest to southeast. Little additional accumulation. Temperatures: rising to 32 to 35.
1 to 5 p.m.: Some lingering light snow possible far southeast; partial clearing elsewhere. Temperatures: 32 to 36.
- Temperatures ahead of the storm will be mild, meaning the ground won’t be frozen. This means snow will initially melt before accumulating.
- Even at the height of the storm, temperatures in the milder parts of our region may not be cold enough for snow to stick much to paved surfaces.
- Most of the snow is predicted to fall Sunday morning, when there is lighter traffic and most schools are closed (outside of religious/Sunday schools).
- The likelihood of heavy snow, falling at the rate of an inch an hour or more, is low.
However, snow may fall steadily enough for a time Sunday morning for some accumulation on roads and slick travel, especially in the colder parts of our region.