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PM Update: Light snow and sleet likely for morning commute, especially in southern part of region

5 p.m. update: The National Weather Service has issued a winter weather advisory from 4 a.m. to noon for the immediate D.C. and Baltimore metro areas for around 1 inch of snow, mixing with sleet at times. It predicts an onset of snow between 4 and 6 a.m. and precipitation dissipating by early afternoon.

Original post from 4:41 p.m.

Some snow, or mixture of snow and sleet, is likely Wednesday morning, coinciding with rush hour. Temperatures well below freezing will allow precipitation to accumulate. However, this storm system is unlikely to produce as much snow or the intensity of snow as the storm last Tuesday (January 6). The best chance of more than an inch or so of snow is in our southern suburbs. Northern suburbs may only receive a flurries or a dusting.

This remains a fairly low confidence forecast as the region is on the edge of a storm passing to our southeast.  Amounts somewhat lower or greater than our most likely forecast are certainly possible.  However, model trends suggest a bust (less snow) may be somewhat more likely than a boom (more snow).

We will live blog the newest model information coming in this evening beginning around 9 p.m.  Go to our main blog page to find it at that time.

Through Tonight: Increasing clouds and cold. Light snow or a snow-sleet mix may develop in our southern suburbs between 4 and 6 a.m. and in the immediate metro area around sunrise. Northern areas probably stay dry for the balance of the overnight period. Lows range from near 20 in our colder suburbs to the mid-20s downtown. Light winds from the northeast at 5-10 mph.

Tomorrow (Wednesday): A 50-50 chance of light snow and flurries in the morning in our northern and northwestern suburbs. Snow chances increase to 60 percent inside the Beltway and to the southwest, and 70 percent south, east, and southeast of the Beltway. The snow may mix with or alternate with sleet in our southern and east suburbs. Precipitation ends between late morning and mid-afternoon from west to east. Accumulations range from a dusting or less in our northern areas to a coating to a couple inches in our southern areas. High temperatures are right around freezing, with light winds from the north.

See Matt Rogers’ forecast through the holiday weekend. And if you haven’t already, join us on Facebook and follow us on Twitter . For related traffic news, check out Dr. Gridlock.

SchoolCast

This will be a very tough call for schools.  Snow will likely not begin, assuming it develops, until after a decision needs to be made.  Forecast amounts are less than the forecast for the January 6 event – although temperatures are similarly cold.  Schools should consider consulting meteorologists very early Wednesday morning for updates based on the latest radar and model data – which can help inform their decisions.

  • Prince George’s, Calvert, Charles, St. Mary’s, Stafford, and Prince William counties: schoolcast-2-apples(2 apples – good chance for delay; 50-50 chance schools close)
  • Fauquier, Arlington, Fairfax, Loudoun, Anne Arundel, Montgomery, Howard counties, and the District: schoolcast-1.5-apples(1.5 apples – 50-50 chance for a delay)
  • Frederick County, Md.: 1_apple(1 apples – schools probably open on time)

FedCast: fedcast-1.5-domes(1.5 domes – slight chance of a delay or unscheduled leave-telework option)

Model update

On balance, models are forecasting somewhat less snow than they were earlier this morning. That is why we shaved snow amounts slightly from earlier forecasts in our northern and western areas.

Here’s a look at the evolution of the precipitation output from three models:

Last three runs of NAM model

Last three runs of high resolution NAM model

Last three runs of SREF model

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