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Central PA & the fringes - January 2015 Part III


WmsptWx

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Thanks! At least it doesn't appear to be much ice.

Seems that this season you can't really put much faith in anything out past 15 hours - especially with this one. Looks to be a very tricky forecast for precip type.

 

What a great year to finally decide to try and get familiar with the models. Have always relied on others to comment and post about them. So now that I'm looking at the Euro and GFS for myself, am finding little accuracy beyond telegraphing something is coming.

 

Totally realize the fun is in looking out 240 hours to see what may be coming along and then eagerly anticipating each successive model run to fully enjoy the roller coaster ride. But will probably end up just going back to letting the "advance scouts" herald impending Armageddon and only pay close attention to the HRRR. Much less stressful. :)

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After reading the Model diagnostics from WPC, they seem to be siding with the Euro and GFS as the best representation of the upper level flow coming into the west coast and approaching the east coast by tomorrow. Each model is starting to hone in on the best axis of precipitation for the Northeast and it looks like the first round will be too far to the north to affect the Commonwealth with any substantial precipitation. The best frontogenesis looks to setup in southern NYS with a good axis of precipitation breaking out ahead of the warm frontal boundary lifting off to the north. The northern tier of PA could see a brief period of snow followed by a change to mixed precipitation as the mid levels go above freezing for the entire region. 

 

The second wave, or main area of low pressure will be what affects the region on Sunday night into Monday. The low pressure will traverse east across the plains tomorrow and make its way toward the east coast. Guidance shows the surface low advancing southeast once it reaches the Ohio Valley and will transfer its energy to the Mid Atlantic coast. At that same juncture, there will be an cold frontal boundary pushing back south across the northern tier into CPA during Monday morning. How far south this boundary makes it and how quickly will determine how much snow will fall across the state. The entire state will be located in the left exit region of the main jet core on Monday morning which should provide enough upper level divergence to breakout another steady precipitation shield starting in WPA and advancing eastward. The best area of lift coupled with the frontal boundary looks to remain along the I80 corridor and to the north. To the south in the LSV, it might be too late for any significant accumulation (4+"), but some areas if they get a small banding structure could receive a coating-2" with the max potential located around northern Dauphin, Perry and Cumberland counties. The areas of the best combination of lift and timing associated with the frontal boundary look decent for 1-4" with NE PA being in line for 3-6+" based upon a longer duration of QPF from the overrunning feature and developing coastal. Don't be shocked if counties like York and Lancaster get the short end of the stick once the energy transfer begins to take place since historically this is where the precip gets split up due to a Miller B type transfer.

 

With that being said, here are my ideas for snowfall accumulation for parts of the forum:

 

UNV: 1-4" 

IPT: 1-4"

THV: T-1"

LNS: T-1"

ABE: C-2"

Poconos: 2-4"

AOO: C-2"

JST: 1-3"

AVP: 2-5"

Far NE PA: 3-6"

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Looks like the 18z suite (NAM and GFS ticked north again.

 

I agree with the NAM ticking northward a bit, but it was too amplified to begin with the main low pressure and height falls downstream per WPC. It's come more in line with the GFS and Euro from this afternoon. The GFS may have ever so slightly ticked north, but the QPF expansion on Monday afternoon/evening actually looks better than its previous run. Just splitting hairs at this point. I think the main depiction is starting to appear right before our very eyes.

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I agree with the NAM ticking northward a bit, but it was too amplified to begin with the main low pressure and height falls downstream per WPC. It's come more in line with the GFS and Euro from this afternoon. The GFS may have ever so slightly ticked north, but the QPF expansion on Monday afternoon/evening actually looks better than its previous run. Just splitting hairs at this point. I think the main depiction is starting to appear right before our very eyes.

 

I think ultimately what will determine whether or not some of us have salvage a half decent accumulating snowfall from what is generally a tough setup in our position is how fast things cool enough to allow snow to fall. 850 temps start pretty marginal and eventually cool enough to snow with the 850 low meandering overhead. GFS snowmaps have been particiularly adamant about keeping anything accumulating in far NE PA and the somewhat colder Euro allows for that second region of snowfall to blossom across the middle of the state. It's going to be pretty close, and a likely messy transition period. Probably going to be some ice to be had as the below freezing temps will be first bleeding in at the surface and 925 levels.  Any potential noteworthy snow accums would certainly favor the north central/NE/ and perhaps the higher Laurels portions of PA. I could see it going either way at this point...ending up as a mostly rain to perhaps snow showers type deal for most or a quicker transition and perhaps thump of wet snow. 

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Ehhh comparing the profiles they're about the same.

 

 

 The GFS may have ever so slightly ticked north, but the QPF expansion on Monday afternoon/evening actually looks better than its previous run. Just splitting hairs at this point.

 

 

Not really

 

 

Yeah, I was actually implying that the snow shield ticked north. I should have been clearer.

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I think ultimately what will determine whether or not some of us have salvage a half decent accumulating snowfall from what is generally a tough setup in our position is how fast things cool enough to allow snow to fall. 850 temps start pretty marginal and eventually cool enough to snow with the 850 low meandering overhead. GFS snowmaps have been particiularly adamant about keeping anything accumulating in far NE PA and the somewhat colder Euro allows for that second region of snowfall to blossom across the middle of the state. It's going to be pretty close, and a likely messy transition period. Probably going to be some ice to be had as the below freezing temps will be first bleeding in at the surface and 925 levels.  Any potential noteworthy snow accums would certainly favor the north central/NE/ and perhaps the higher Laurels portions of PA. I could see it going either way at this point...ending up as a mostly rain to perhaps snow showers type deal for most or a quicker transition and perhaps thump of wet snow. 

I think your analysis is right on. With the temps up the next couple days I just cant see any real threat of accumulating snow until possibly late Mon afternoon/evening. Looks like plenty of cold air to follow for the upcoming week.  Any other snow possibilities for us after Monday???

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