Tuesday PM 2/26/13: We’ve talked about the strong likelihood of a cold weather pattern in the eastern states for at least the first part of March based in large part on the negative NAO and developing positive PNA and there is no reason at all to waiver from that thinking. In fact, the latest (Tuesday) 12Z GFS Ensemble run is forecasting a persistently colder-than-normal pattern in much of the central and eastern US right into mid-March and there is reason to believe that this could become the coldest March in several years. The 3 plots below from the 12Z GFS Ensemble runs show the 850 mb temperature anomaly pattern in 3 different time frames (top: days 1-5; middle: days 6-10; bottom: days 11-15) and in all 3 periods there is very impressive cold. (Plots from raleighwx.americanwx web site).
What about chances for snow in the snow-starved Mid-Atlantic? The second half of this week will feature enough instability and (marginally) cold air that snow showers are possible at just about any time in the Mid-Atlantic, but the more serious threat for snow comes during the middle of next week (Wed., March 6th or so) as a wave of low pressure likely moves out of the Midwest towards the Mid-Atlantic coast. Both today’s (ie Tues) 12Z GFS Ensemble and 12Z Euro runs feature a serious threat for snow in the Mid-Atlantic region. In addition, it is possible that there will be another threat about 3 or 4 days later (March 10th or so) and we’ll continue to both monitor possibilities.
Bottom line, for now the cold pattern is quite certain and the snow threat appears to be growing with the overall pattern looking quite active in the East from the middle of next week to mid-March.
Latest Euro continues to have a snow threat for DC to Philly to NYC for the middle of next week (and this would include parts of Virginia). Stay tuned - this time of year (really any time of the year) everything has to go just right for snow.