From the ABC 7 Weather team

Winter Weather Advisory for parts of the D.C. area

January 28, 2014 - 03:06 PM
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Light snow is possible for D.C. and areas south and east tonight. Light accumulations are possible, find out where here.

We'll go ahead and start off this blog by saying there was a very slight chance for light snow southeast of D.C. yesterday. We mentioned the best chance was over Southern Maryland and the Eastern Shore, but as of today some of the latest guidance is showing snow as far north and west as the D.C. Metro.

Winter Weather Advisory south and east of D.C.

While we're not expecting heavy snow, with temperatures as cold as they are, anything that falls is expected to stick not only to the grass, but also the area roadways. A Winter Weather Advisory has been issued for areas southeast of D.C. in Maryland and Virginia for the potential of a few inches of snow from 5pm tonight through 6am Wednesday.

Timing

A trough of low pressure is expected to push the best forcing through the D.C. area tonight through early tomorrow morning. Light snow is expected to begin around 5pm tonight through much the area (best chance D.C. and points east) and continue to fall through the early morning hours. Snow should end earlier closer to the D.C. Metro (possibly 3-4am) than the Chesapeake Bay (closer to 5-6am).

Expected Snowfall Totals

Our forecast:  While light snow may accumulate up to a dusting in D.C., slightly higher amounts are expected south and east of D.C. We are confident in an inch or more snow accumulating in parts of Charles, Calvert and St. Mary's Counties. Isolated amounts to 2 or 3 inches will be possible closer to the Chesapeake Bay. The Advisory from the NWS even indicates the potential for up to 5 inches of snow in spots, though it looks like at this point in time that would be on the high end.

Oddly enough, this is about as opposite as you can get from the majority of winter storms that affect the D.C. area where areas north and west are hardest hit.

6z 4km NAM Model Forecast Snowfall (Courtesy: WeatherBell Models)

Model Guidance:  Above is a look at the 6z 4km NAM Model Snowfall Accumulations through Wednesday morning. Showing model output for snowfall isn't one of my favorite things but I wanted to show this just to give you an idea of where heavier snow is expected. Areas south and east definitely have the best chance for accumulating snow.

This model also only depicts a snow ratio of 10:1, which means for every inch of rain, 10 inches of snow would fall. The ratios should be much higher since it is so cold, so expect ratios closer to 15 or 20:1, meaning a dry, light snow, not wet, heavy snow. This snow should be sweepable.

NWS Products:  The local NWS office puts out a few winter products that are often quiet helpful to people such as emergency management officials. Below is a look at the 90th percentile snow totals, or basically a look at what would happen if this storm reached close to its maximum potential. Still only a few inches of snow are possible in D.C. but up to 5 inches would be possible in extreme Southern Maryland. Do not focus on this map as there is only a 10% chance of this occurring, hence the 90th percentile of accumulating snowfall.

Maximum snowfall potential for the D.C. area

Below is a look at the probability of greater than 1" of snow falling in the D.C. area. This product is developed by the National Weather Service Baltimore/Washington office. As of this morning, a 30% chance for greater than an inch of snow is possible in D.C. where it rises to 60% in southern Maryland.

Probability of greater than 1" of snow

Impacts

Slick spots will develop tonight on area roadways and travel will become difficult southeast of D.C. Luckily Calvert County schools are already closed tomorrow for a teacher work day but other school closings may be possible by tomorrow morning. Winds shouldn't be a big concern with this system, but they will become breezy at times tomorrow around 10 to 15 mph keeping chills in the teens.

Snow will come to an end tomorrow morning, the sunshine will return and temperatures will be *slightly* warmer in the mid to upper 20s on Wednesday. Milder air should return by the weekend, though with highs back in the 40s expected Saturday and Sunday.

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