UPDATE THE SHIFT EAST REAL OR NOT? right NOW my Model of choice is the RGEM --high resolution shore range Canadian model Quite frankly I dont know. For those of us who are convinced that the shift east is the REAL deal may I remind you of some of the recent flaws / busts of the NAM GFS Just within this particular event some of these models which are now shifting east with the Low and the heaviest snow have also on a few mode runs showed huge snow mounts close to what the European model was showing. So lets not say this as a case where the GFS has never showed huge snow amounts in NYC / NJ or Philly because that is not true. It is safe to say that the GFS has not had as much snow as the European... But to argue that the GFS model has never had as much knows the European is just well wrong. If you take a look of the temperatures in and around the VA MD you wIll see the temperatures are much too warm to support snow. at 11pm DCA is 46. Even Winchester is 37 with dew point fo 32. The HRRR (high resolution shore range model) has precipitation going over snow around 4AM in Northwest a AND 6AM in dca. It only snow in DCA fpor a few houts but it snows pretty good over the northwest 25% of VA central and Western Maryland into at least Noon. So those areas could in fact the actually get 4 inches of snow... but NOT DC and the immediate metro area. With regard to the issue of huge snow amounts in Philly NJ and NYC and interior se NY... Obviously the issue has to do with where does the main ocean low develop? The early Monday morning models are now showing a much more east track and that is entirely possible. However it is not at all certain and perhaps the European track might be correct after all. So if we take down the big snow amounts too far and it turns out that these short range models are too far to the east ...we end up with another complication in this difficult forecast ! Looking at the latest actual upper air data and soundings I am inclined to shift things more to the east and lower the snow mounts in Philly NJ and NYC. I do this not because of the weather models per se but I am noticing that the Friday night Saturday Low from two days ago ....which was supposed to move up into southeastern Canada and become a 50 / 50 Low ....has fallen apart and is much weaker than some of the data had suggested yesterday. This in turn means that the system coming off the coast of the Middle Atlantic states on Monday can swing further out into the Atlantic and this may be what some of the short range models are seeing a more east track. As I have said many times before for a Middle Atlantic snowstorm -- not new England --you need ideally a -AO... a -NAO and 50 / 50 low. The AO is only neutral and the 50/50 Low has fallen apart.
Posted on: Mon, 26 Jan 2015 05:23:20 +0000
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