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Posted at 03:33 PM ET, 01/16/2013

Washington D.C. snow forecast for Thursday, January 17: accumulation map, timeline

* Winter storm watch for most of Washington, D.C. metro area *

A wound-up storm passing to our south combined with some modestly cold air streaming in from the north provides the opportunity for some snow in Washington, D.C. Thursday. The most likely timing for precipitation spans from late morning through early-to-mid evening. The afternoon and evening rush hour *may* be impacted by snow.


Forecast confidence: Low-Medium

Because it’s not clear exactly how much moisture will make it into the region, snow accumulation is a huge question mark. For most of the D.C. area, we think just some conversational flakes to a couple inches is most likely, with more south and southwest of town and less to the north. However, these amounts may need to be adjusted. Most of the latest model data suggest less snow rather than more.

Little to no snow accumulation is more likely than over 1 inch of snow for most of the Washington, D.C. metro area. But we stress uncertainty in forecasting this storm is considerably higher than normal, and shovelable snow would not surprise us.

STORM TIMELINE

6 a.m.-10 a.m. Thursday: 20-30 percent chance of light rain or snow, highest odds southwest of D.C. Temps: 32-37

10 a.m.-2 p.m. Thursday: 30-50 percent chance of snow developing, possibly starting as rain. Precipitation increases in intensity to southwest. Temps: 33-38.

2 p.m.- 6 p.m. Thursday: 40-60 percent chance of snow (most likely to southwest), heaviest south and southwest of D.C. Temps: 32-37.

6 p.m.- 10 p.m. Thursday: Any snow gradually tapers off southwest to northeast. Temps: 30-35.

STORM IMPACTS

Schoolcast commentary: There is a chance of pre-emptive closures in counties south and southwest of D.C., particularly Fauquier and Stafford counties - even if it is not snowing early in the morning. Early dismissals are possible - though not particularly likely - at other school systems throughout the region (including Fairfax, Montgomery, and Prince George’s county) if snow materializes.

FREQUENTLY ASKED QUESTIONS


The “bowling ball” upper level disturbance that may bring us precipitation is impressively robust, but it may track a bit too far south for snow lovers. (StormVistaWxModels.com)
When/where will the heaviest frozen precipitation fall? The heaviest precipitation is likely during the afternoon and evening, mainly southwest of the District. Locations like Charlottesville - where winter storm warnings are in effect - could receive 3-6 inches or more of snow.

Will the frozen precipitation stick? Not initially, and precipitation may begin as rain and/or sleet. Assuming steady snow develops, it should begin to stick first on grassy areas. By around rush hour, as the sun goes down, temperatures will drop and snow may begin to stick on roads if precipitation moves far enough north.

When will travel be most difficult? Late afternoon and early evening appears to be window when steady snow and falling temperatures could create slick travel.

What about precipitation type? Assuming precipitation falls heavily enough, temperatures aloft (at higher altitudes) are cold enough for snow. But if the snow is light in intensity, it might turn into rain before hitting the ground, especially early in the storm.

When will conditions improve? Snow should taper off after the evening rush hour.

Could the storm fizzle out? YES. There will be a sharp cutoff to the precipitation, somewhere between Fredericksburg, Va. and the Mason Dixon line. If the cutoff ends up south of D.C.., the District and especially the northern suburbs may see little if any precipitation.

Could the storm bring more ice/snow expected? Yes. If more moisture surges northward and the precipitation cutoff ends up in southern Pennsylvania, 3-6” of snow could fall in the D.C. area, but this now appears to be the least likely scenario.

What are other forecast outlets calling for?

National Weather Service (2 to 4 inches)
WJLA-ABC7 (1-3 inches)
WUSA-9 (1-3 inches)
NBC4 (Dusting to 2 inches)

By  |  03:33 PM ET, 01/16/2013

Categories:  Latest, Winter Storms

 
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