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Jan 17-18th disco thread--1st big threat of the year


Midlo Snow Maker

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If you go to the PSU Ewall and click the DGEX links and then go up top to where it says 00/06/12/18 UTC and click there it takes you to a page where you can view the regional breakdowns for the NAM/GFS/ARW and the "NMM" which is the old ETA.

Gotcha, it's just a labeling thing.  The NMM (non-hydrostatic mesoscale model) is not actually the old eta, though it evolved from it in some regards (and may share some commonality).

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Good post.  I pretty much agree.  I'm not sure I trust the SREF with a system having such a tight gradient. 

 

Wes,

 

Agreed.  The SREF mean is obviously going to spread out the 0.10", 0.25", and 0.50" a bit more.  Moreover, with the "new" SREF, we're swapping out all those old ETA and RSM members with WRF members, which could tell a pretty interesting story once the 21Z SREF comes in (after what we've seen with the 18Z NAM).

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No...im not in the predicting business..i do get the sense you like being right though and i definitely know you love snow

 

I have had my heart broken too many times..I would be HAPPY to be wrong and to get a snowstorm...when it comes to snow I couldnt care less about being right if it means snow...I have a lot less ego than you think....But I do have experience....and there is no way to "spin"  the wettest and coldest model which already has a cold and wet bias swinging wildly in 6 hours to being the driest and furthest south..it is bad...

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Folks,

 

A few things I noticed while at work today, some of this you probably already know (knew):

 

1) The 12Z NAM was the most robust with the liquid equiv...0.50 to 0.75 through the DC metro region, though not all of it snow.

2) GFS was slightly drier (closer to 0.5 for DCA), though with the NAM, both NCEP runs were clearly wetter than the non-NCEP suite.

3) EC/UKMet/CMC at 12Z were all drier for the DC metro region, i.e. less than a quarter inch.

3) The 15Z SREF was consistent with the 09Z version, perhaps a smidge wetter for DC, though still more like in a 0.25 to .50 inch, or lighter than the 12Z NAM/GFS.

 

Now, this was most notable:

 

ALL the high-resolution runs at 12Z, which included the NCEP WRFs (ARW and NMM), NAM CONUS-nest, the NSSL WRF, SPC WRF, and the SSEO mean noted a much TIGHTER pcpn gradient on the northern side -- giving DCA more or less the shaft with a tenth of an inch or less of liquid equivalent pcpn -- while much higher QPF remained over central and srn VA.  What was alarming to me was that the NAM's own CONUS nest version (4km) was remarkably different from the parent 12km run with the moisture gradient on the northern side.  That's never a comforting sign.  It's almost as if the higher res runs were trying to resolve the strengthening deformation (frontogenesis) better, and in doing so, yielded a tighter moisture gradient N-S, thereby drying out the DC area.  Take it FWIW...though I'm hearing (though have not yet seen) the 18Z NAM went farther south with the more appreciable QPF.

 

Very, very high-bust potential forecast either way, because obviously not all the QPF farther south (into cen VA) would be all snow.  Still, that part of the world (EZF-RIC) would stand the best chance on getting in on the deformation axis steadier snows after 21Z or so, to a point where 35-36F can quickly cool to 32-33F.  Looks to me like the event late last year in which the RIC area got 4-6" or so, while little if any fell in the DC area.

 

This is a pretty good analysis.  Makes me wonder all the more whether LWX perhaps jumped the gun a bit in extending the watch farther northeast into the metro DC area.  Clearly southwest of here has a much better chance.  But could they have waited until the late evening forecast on whether or not to push it up this way?  On the other hand, I can see the concern over the timing and getting some kind of notice out that would get peoples' attention.  I guess there were already arguments on this earlier this afternoon when the watch came out.

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