* Winter weather advisory from 1 p.m. Sunday to 1 a.m. Monday for immediate area | Winter storm warning from 1 p.m. Sunday to 7 a.m. Monday for northern Fauquier, western Loudoun and Frederick counties and locations to the west *
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6:15 p.m. — Forecast on track — snow probably develops mid-afternoon Sunday
Afternoon computer models support our outlook posted below. They suggest a brief period of snow starting Sunday afternoon - probably between about 1 and 4 p.m. It won’t last long before the switch to sleet and freezing rain. Here’s how much snow afternoon models project before the changeover in the District:
HRRR: 3 inches | High-resolution Canadian: 2 inches | American (GFS): 1-inch | NAM and high-resolution NAM: 1-inch
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For areas along and just east of Interstate 95, we’d lean more toward one inch than 3 inches.
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Even if there’s not much snow, the mix of icy precipitation on frozen roads will mean hazardous travel conditions.
Original article from 1 p.m.
A winter storm that will create treacherous roads in the Washington region is still on track for Sunday afternoon and evening. However, more ice and less snow is now anticipated.
Snow is expected to develop in the region from south to north between about 2 and 5 p.m. Sunday. However, high-altitude winds roaring off the ocean will quickly change the snow to ice, probably by around 6 or 7 p.m. in most of the immediate area. Snow might hang on a little longer in our western areas, but even there, it is expected to flip to sleet and freezing rain, meaning lower snowfall totals than previously projected.
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Ahead of the storm, temperatures on Saturday and Sunday will reach only the 20s, meaning all surfaces will be frozen as the precipitation develops. Any snow and ice that falls will stick immediately, quickly producing a hazardous coating on untreated roads and walkways. We would advise avoiding any unnecessary travel after 4 or 5 p.m. Sunday.
After walloping central U.S., winter storm sweeps toward East Coast
The icy mix should turn to plain rain from east to west across the region between about 8 p.m. and midnight, when conditions should gradually transition from icy to slushy. However, in our far western areas, freezing temperatures could last longer, prolonging the duration of hazardous roads.
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A winter weather advisory is in effect for the immediate area for the potential of 1 to 3 inches of snow, a light glaze of ice and wind gusts to 45 mph before precipitation changes to rain.
A more serious winter storm warning covers areas to the west, including northern Fauquier, western Loudoun and Frederick counties and locations to the west. Here, about 2 to 4 inches of snow is most probable, with a heavier coating of ice up to 0.25 inches or so. Amounts may increase to about 3 to 6 inches toward Interstate 81 but, even there, the snow should change to ice.
The potential for several hours of ice buildup on trees, especially west and northwest of Fairfax County, along with strong winds, could cause some limbs to snap, triggering scattered power outages. However, we don’t expect widespread power problems because temperatures will be rising and the storm will be fairly fast-moving.
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On the backside of the storm early Monday morning, some scattered snow showers could redevelop, with a quick coating possible. However, we expect area roads to be mostly passable on Monday — except perhaps in our far western areas.
Snow and ice accumulation
This isn’t going to be a big snowstorm for most of the region.
Along and east of Interstate 95, the limited duration of snowfall before a change to ice means probably just a dusting to an inch or two of snow.
In the District, here’s how much snow is projected by different models: High-resolution NAM: 0.5 inch | NAM: 0.5-1 inch | Canadian: 1 inch | American (GFS): 1-2 inches | High-resolution Canadian: 1-2 inches | European: 1-2 inches | HRRR: 3 inches.
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West of downtown Washington through Fairfax, Montgomery and Prince William counties, generally 1 to 3 inches is most probable.
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Areas including Leesburg and Frederick could see a few inches but also should change over to ice before more significant snowfall might occur.
Even in the mountains, the snow may change to freezing rain, so we’ve somewhat trimmed amounts there as well compared to earlier forecasts.
In terms of ice amounts, most of the area should see at least a light glaze before the switch to rain. The more significant ice potential, where 0.25 inch or so could fall, is generally in central Loudoun and Fauquier counties to northwest Montgomery County and to the west and north. This is where we’ll need to monitor the potential for power outages.
Timeline and temperatures
The earlier the snow arrives, the longer the window it will have to accumulate before flipping to ice (most likely between 6 and 7 p.m.). Models that bring the snow in soonest, closer to 2 p.m. in the immediate area, tend to show the highest amounts, whereas those that delay the onset toward 4 or 5 p.m. show little accumulation (less than an inch).
Temperatures shown in the timeline below will be lowest in our northwest areas (toward Leesburg and Frederick) and highest in our southeast areas (toward Southern Maryland) through the course of the storm.
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Overnight Sunday, we expect a very large range in temperatures across the region; it’s possible that parts of southern Maryland warm above 45 degrees and that temperatures in places like Leesburg and Frederick hover closer to freezing for the duration.
1 to 4 p.m. Sunday: Snow develops from southwest to northeast. Temperatures 25 to 31, mid- to upper 20s inside the Beltway. Winds gusting up to 20 mph.
4 to 8 p.m.: Snow, heavy at times, changing to sleet and freezing rain from southeast to northwest. Temperatures rising to 27 to 34, near freezing inside the Beltway. Winds gusting up to 30 mph.
8 p.m. to 11 p.m.: Sleet and freezing rain changing to rain from southeast to northwest. Temperatures rising to 30 to 40, mid-30s inside the Beltway. Winds gusting to 30-40 mph.
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11 p.m. to 2 a.m. Monday: Rain tapers off as dry slot comes through area. Temperatures rising to 32 to 42, probably mid-30s inside the Beltway. Winds gusting to 30-40 mph.
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2 a.m. to 5 a.m.: Mostly dry, scattered snow showers possible in far west. Temperatures falling to 32 to 37. Winds gusting to 20-30 mph.
5 a.m. to 8 a.m.: Scattered snow showers with a coating possible. Temperatures: 31 to 35. Winds gusting to 20-30 mph.
8 a.m. to 11 a.m.: Partial clearing. Temperatures rising to mid- to upper 30s. Winds gusting to 25-35 mph.
Storm impacts
Very treacherous roads and walkways are anticipated late Sunday afternoon and evening; however, the duration of hazardous conditions will be limited by rising temperatures except in our far western areas.
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Because this storm is happening on a holiday weekend and during a time with generally low traffic, its overall impact on the region should be lower than if it occurred during the week. It also won’t affect schools or the federal government on Monday because of the Martin Luther King Jr. holiday.
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That said, we could see some flight delays at the airports on Sunday evening and, in our western areas, untreated roads could remain slick into Monday morning before conditions gradually improve as the day wears on.
On our winter storm impact scale, this event rates as a Category 2 “disruptive” event within a one-county radius of the District and increases to Category 3 “significant” storm west of Fairfax County. However, as noted, school and government operations are mostly not pertinent for this event because of the holiday.