Sunday Evening Update on Nor’easter: My latest DC Metro and DC Region Accumulation Map & Headlines

Washington DC Metropolitan Area Snowfall Potential through 12AM Wednesday:

DC Regional View:

  • There remains a higher than average amount of uncertainty in the forecast along and east of interstate 95 (Prince Georges county, Anne Arundel county, Fredericksburg VA & southern Maryland) as how much snow falls will depend on how much mid-level warm air moves eastward off of the warmer Chesapeake Bay.

 

  • If the Nor’easter were to shift eastward by about 50 to 75 miles, much higher snowfall totals would be a “home run” for these areas. This is why the National Weather Service has not ‘pulled the trigger’ on the Winter Storm Watch currently in effect in Stafford, Prince Georges and Anne Arundel counties.  
  • Those of you in southern Maryland who got raked by the January 2017 storm with over a half-foot of snow (while the rest of us were screwed over royally) may see mostly rain and sleet with this system. Still it is possible that a light coating of wet snow and sleet (1 to 4″) accumulate.  If the track of the Nor’easter shifts east in future model runs you might squeeze out a bit more. Again, a very low-confidence forecast in these areas. 

DC_Region_Snow_Map_DCstorms.com_031517

Headlines:

Latest Models (so you can make up your own minds):

  • European models shows mid-level warm air working into the interstate 95 corridor which would cause the snow flakes to melt and then refreeze (frozen rain drop = sleet) cutting down on snowfall accumulations here.
  • If the track shifts further east, the threat of sleet will push further east and heavier snowfall amounts will shift further east.

Latest GFS Model (images below courtesy WxBell):

  • This model shows both sleet and snow accumulation, so you can’t just look at the map at National Airport (for example) and assume that it means you’re getting 9″ of snow.
  • The GFS also shows warmer air moving into the boundary layer at 850mb which if true, means sleet may cut down on accumulations along and east of interstate 95. The GFS and European model are currently in agreement that sleet will mix with the snow overnight Monday along and east of the 95 corridor. 

North American Model (NAM):

  • The latest NAM also agrees with the European and GFS that sleet will mix in with the snow along and just east of interstate 95.
  • The NAM is currently the furthest west in track so any shift east tomorrow would indicate that the threat of sleet mixing in may push off further to the east, bringing higher snowfall totals into the southern and eastern zones.

Finally the Canadian Model:

  • Track is furthest to the east (could be considered an outlier at this time)… but it has very hefty totals in DC, Prince Georges, Anne Arundel counties. Also for those of you in Charles county Maryland, the Canadian model (if it is onto something with track) would at least provide you with enough snow to make a snowman. 

2 Replies to “Sunday Evening Update on Nor’easter: My latest DC Metro and DC Region Accumulation Map & Headlines”

  1. Hi Tim,
    I follow your site and trust it before believing the local news channels. Could you provide a time line of when to expect this event? Thanks!!

    Like

    1. Hi Michelle, the start time of precipitation in the metro area should be between 5 and 9pm depending upon your location. http://www.weather.gov/lwx/winter will have hourly updates on start time. Or you can go to my website and click on “Snowfall Forecast”, “NWS” and then scroll down to “Other Snow/Ice Information” (the middle graphic has the start time onset). The heaviest snow will fall from midnight to 8am. Then we will have widespread back-lash snow showers through Tuesday afternoon with flurries continuing off and on through Wednesday. We may even get in on some strong snow squalls Wednesday afternoon as the upper level energy rotates across our region. (yes, additional light (1 to 2″+) accumulation possible with the snow showers, flurries and squalls (Tuesday night through Wednesday). Happy Winter

      Like

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