Sunday, 25 November 2012

Snow for Mid Atlantic, Another Storm Potential Nov 30-Dec 2

I am watching a storm which may effect the  midwest, great lakes and northeast later this week. In terms of  the storm potential early this week I believe a more northern track is likely then currently depicted on the GFS/NAM modelling. I believe that the 12z euro has the right idea with a 1-3" swath of snow for washington DC, Baltimore, Philly extending as far north as NYC. Now to the longer range... 
With the heat moving into the plains by the end of this week and the trough holding its ground across eastern canada a thermal gradient will set up and a wave of low pressure will move in from the west. It could be a more potent feature then the models are currently showing due to the -NAO as well as the thermal gradient setting up with more favourable atmospheric dynamics. Some less favourable factors include:
1)Temps will be marginal at the surface as well as the boundary layer with WAA in advance of the system
2) GFS ensembles are all over the place with track and timing of the storm.
12z GFS at hour 132:
 Reduced 38%
Attached Image
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3) Euro shows a less potent feature in the form of a clipper moving in from the northwest. This is caused by a stronger system developing in the plains states which is taking some of the vort energy from the first, less potent feature.

Nonetheless, I will wait until the 0z runs tonight to get a better handle on the potential storm but right now there is a large degree of uncertainty as to track and timing of frozen precipitation with two disturbances organizing across central NA. The interacting of said features will determine home much snow/rain/sleet we pick up across ontario,quebec and the maritimes.

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