Tuesday, January 27, 2009

12z model guidance is warm

Very warm. Both the GFS and NAM raise 850mb temperatures above freezing across SNH. The GFS has major shortwave amplification with concentrated vorticity and keeps the primary low strong and inland across SNY, not letting the secondary take over until late. Both models still dont take the surface above freezing, and I don't buy any model that does, mainly because of the strong antecedent cold and region wide snow pack. This translates to the potential for a significant icing event following the snowfall. Along with the northward shift in temperatures, QPF has shifted north, with 1.5" looking more and more likely here. We are still in line for a large front-end dump of snow Wednesday morning through early afternoon, which will amount to about 5 to 8 inches. Mid level warming will change snow to sleet and maybe freezing rain by the evening, with a quarter inch of icing likely before the secondary low takes over, and we end as light snow through midnight. Total accumulations of 6" to 10" of snow through Wednesday night.

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