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Central PA OMG SNOW thread -- Winter 2016


neff

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Doesn't the NAM often go nuts t-48 and throw out crazy numbers?

If the 0z GFS shifts north, I'll be a bigger believer. As it stands that NAM run seems way overdone to my untrained eyes.

 

The amounts are probably overdone, but as I said earlier, with the shift in the SREFs and the better placement of the precip over Kansas/Nebraska on the 00z NAM, it wouldn't surprise me if the placement was correct. And perhaps that will be reflected in the other 00z runs.

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RGEM nailed the Feb 2010 stores fwiw. It is pretty good at grabbing trends. IF true, this is good news.

 

Definitely a lot closer to the 00z NAM than to the 18z NAM. If anything, the precip shield may be a bit further north on the RGEM, except in the westernmost part near southern Illinois (where it's similar but a bit lighter overall). Nothing like the 18z NAM.

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Well, the only thing I have to say about the NAM is that the precipitation depiction is what I have been talking about for a few days now.

 

The 300mb level jet will be so anomalous and expansive over the NE that I find it extremely hard to believe that we wont see a well-developed coma head when the coastal matures due to the amount of divergence aloft (Fig 1) and location of the 500mb low. In addition, the rapidly intensifying coastal will carry a large area of mid-level forcing that will also be extremely favorable for moderate to heavy precipitation over a rather expansive area.This should be a precip shield that is comparable to some of the more prolific Miller B and Miller C events for the Mid-Atlantic and Southern New England. Within this coma head, there should be at least one, if not two strong deformation bands that slowly drift from north to south. Those are the areas that could see elevated rates of 2-4"/hr with occasional Blizzard conditions. 

 

(Figure 1. 300mb heights/divergence courtesy of Doug S):

 

9d5721ff74fab9d97e91886a7fb6c3ac.png

 

We know that the precipitation shield should reach at least southern NY at this point, but now where do these bands set up? You tell me. I could see a band posting up near DC/Balt that moves up to Southern PA late Saturday morning into the afternoon, but the zone that is really a wildcard is without a doubt the NJ/NYC/LI/CT area. Since you have an insane easterly jet screaming in at around 85 knots @ 850mb, I could see how something tries to get going near Central NJ that eventually moves up to near TEB, but these details will not be ironed out until the snow is actually falling. I have to say that the NAM has had an area of prolific 700mb frontogenesis for quite a few cycles now that would be near ideal for the aforementioned banding to take place and really lay down some impressive snow numbers. This easterly fetch would also be carrying in moisture from a very warm Atlantic, which would further support heavy snow in this area. 

 

 

d2934f9f58723db68bc395ee37735e3c.png

 

The point to take away from this, is that despite all the model-watching and QPF analysis, these depictions WILL NOT be the final outcomes. Any shift with the general SLP placement will cause all of these incredibly complex meso-scale details to shift accordingly, so try not to grasp onto any solution too tight yet. 

 

The trends tonight look very good so far, and the new PARA SREF were similar to the OP SREF with most of the members leaning NW of the mean. I'm fairly confident we'll see another shift NORTH in the foreign guidance tonight, especially with the ECMWF, since most of its ensembles were more NW when compared to its final SLP track. Also, as we get closer to this event, look for the precipitation field to expand in aerial coverage and overall intensity. 

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I'm not that surprised with the NAM & SREF north trend tonight.

The 12z Euro ensemble mean showed 10-12 inches around MDT.

There was still about a 10 member cluster ( out of its 51 members)

That were taking the storm hundreds of miles out in to the Atlantic.

The vast majority of members had the low tucked in to the coast of VA/NC.

A quick count showed at least 30 members with good hits to the LSV.

If you eliminate the l cluster of 10 drunk members that stumbled insanely

Way out to sea, the mean would be even closer to the coast , & the mean QPF & snow amounts would only increase.

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