First heavy snow event!!

Well I haven't posted in quite awhile and there has sure been some events where I should have, but now we have snowstorms to forecast and watch and this is what I love doing, being up to my neck in data. So even though the first good snow event of the winter, or should I say fall...(with temps in the 60's and 70's here this week) isn't over northern IL, I am still geeking out of this system because it is fairly impressive and should have some moderate to heavy snow accumulations associated with it beginning tonight and through the day tomorrow from northwest IA to southern/central MN to to norhwest WI by tomorrow night.

Like always I will start with the 24 hour WV loop

http://weather.cod.edu/loops/US-WV24.loop.html

We currently have our upper level trof moving into the midwest with well defined vort max over the NE/IA border reflected by the closed 700mb low. this system has been moving northeast throughout the evening and intensifying nicely as it does so. precip has also been steadily increasing in coverage and intensity from northeast KS up to the MN/IA border. The temperatures in the area have been dropping throughout the afternoon and evening but are marginal for snow but due to some good CAA going on and the intense precip rates, rain has been able to changeover to snow in some areas and has been quite heavy at that with a few lightning strikes in the OAX area earlier due to CCB's

At the time before that, the temps were above freezing up to 800mb but due to the insane amount of insentropic ascent going on, the 925mb temps crash 3 to 4 degrees in an hour which lead the the BL temps to cool below freezing to allow for snow to reach the surface. This is what happened this morning in AMA where they had +TSSN with the column not supportive of snow but due to the amount of convection, it was able to make it all the way down.

Here is the 0z OAX sounding..



Over the past few hours the deformation band has really began to take off and areas have began to changeover to snow and the temps/dew points slowly drop to near or below freezing. There is a really nice moisture plume that is feeding northwestward into the colder air. It looks like the snow axis will follow the H85-H7 frontogenesis axis. Also, the dry slot was filling in with precip from southeast NE up into southwest NE.



The deformation band will continue to move northeast overnight into southern/central MN where there are currently winter storm warnings in place for 6-10" of snow. I wouldn't be suprised if there ended up being a total near a foot given the intense precip rates/possible thundersnow due to it being pretty unstable aloft, and the dynamics this thing has going for it. all in all, a nice, intense first snow system to forecast for.




Hopefully this is a sign of things to come this winter!


Matt