Capital Weather Gang's snowfall forecast for Sunday, second version. (CWG)

* Winter weather advisory for southern Fauquier and Stafford counties Sunday from 11 a.m. onward *

10:15 p.m. update

The latest information suggests the north trend in where snow will fall has stopped and models more or less agree the zone where accumulating snow will begin and end is around southern Prince William and Charles counties. Locations south of this area have a good chance for some accumulation and, to the north, very little.

Of course, the models could be wrong and very small differences from what they predict will have important consequences for the forecast. For this reason, the forecast snowfall map above is mostly low confidence and has significant boom/bust odds.

The map shown above is revised from earlier. We increased predicted amounts some in the southern two zones, although we shifted the northern edge of the zone which is now 1 to 3 inches (it was previously a coating to 2 inches) a bit south (from southern Fairfax County to central Prince William County). The southernmost zone, where we had previously called for 1 to 3 inches, we have increased to 2 to 4 inches.

Snow should begin in our southwest areas by mid-morning and reach our southeast areas by midday or early afternoon. Snow could fall moderately in our far southern areas in the late afternoon and early evening hours Sunday before tapering off overnight.

Around the Beltway, the best chance to see flakes would be between mid-afternoon and early evening.

Original post from 4:55 p.m.

With high temperatures reaching only the mid-30s to around 40, plus a breeze still refusing to quit, today certainly had a wintry feel. If that wasn’t enough to set the scene, continued shifts in the snowstorm shaping up across portions of the Mid-Atlantic are keeping us on our toes. Today’s trends have again increased our odds of seeing snowfall from the sky and perhaps even stick to the ground in spots.

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Through tonight: Clouds should tend to thicken through the night, although a couple of clearer periods are possible in the first half. Lows range from around 21 to 28. Winds calm a good deal after sunset.

View the current weather at The Washington Post.

Tomorrow (Sunday): It’s a cold and mostly cloudy start to the day. Snow is marching toward the area in the morning, possibly breaking out as close as southern Maryland and toward Fredericksburg by midday. From there, it’s still uncertain how far north the flurries will make it, but it’s possible some light accumulation works into the immediate area, especially the farther south you go.

Given that today’s temperatures were on the cool side of expectations, and that we should see thicker clouds plus some precipitation, highs may struggle to get much past the low and mid-30s. This, of course, means any places that see steadier snow face the potential for light accumulation.

Accumulation potential in our area is anywhere from a dusting to two inches, as seen in the map up top, but there is potential for more well south.

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Detailed storm update: While we continue to conclude that the majority of Sunday’s snowfall will pass to the south, models have been trending the snow shield northward since last night or so.

Winter storm watches are now as close by as Charlottesville, with warnings now hoisted to the south of that.

The recently run NAM weather model showed a bump north in a similar fashion to other model runs today. While we shouldn’t take its totals verbatim, it is a signal that we can’t rule out a snowier Sunday than has been anticipated, especially should these trends continue through storm arrival.


Changes in precipitation forecast over recent runs of the high resolution NAM model. (Capital Weather Gang and Pivotal Weather)

For now, modeled solutions would still tend to keep accumulating snow from about the District to the south. The northern extent would currently be rather light and perhaps inconsequential. Some of the newer model runs do bring heftier totals closer to our area. There is some potential for moderate to even briefly heavy snow as close a Fredericksburg to southern Maryland line. If north shifts persist, that could come north.

There is also some chance that we are seeing the northernmost solutions now and they will shrink back a bit in the end. The snow will be running into some very dry air once it reaches Northern Virginia. Living on the edge is tricky. We’ll have more as this continues to evolve.

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