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Central PA & Fringes - December-January 2014-15


djr5001

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Huh?

 

The Sunday night/Monday clipper is much stronger and more moist on the 12z Euro than it was on the 00z Euro. It's got a swath over >0.35" amounts for most of north-central PA.

meant weaker compared to 12z run of GFS sorry... this run of GFS develops a sub 1000mb low that tracks across PA with a more organized cluster of moisture which would make it stronger and with more available moisture than the clipper yesterday compared to the 12z euro run which is not as strong of a low with moisture a little bit disorganized... but yes text output still has roughly .25-.35" qpf over most of the region

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meant weaker compared to 12z run of GFS sorry... this run of GFS develops a sub 1000mb low that tracks across PA with a more organized cluster of moisture which would make it stronger and with more available moisture than the clipper yesterday compared to the 12z euro run which is not as strong of a low with moisture a little bit disorganized... but yes text output still has roughly .25-.35" qpf over most of the region

When I was at MU, Eric Horst always taught us that you want the clipper to pass along the I-70 corridor in Maryland to give the best snow for all of Central PA (This is Rt. 6 south to the Mason-Dixon).  

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Could you elaborate on the 12Z Euro for the LSV for both Saturday and Monday?

 

DJR might have been referring to just the LSV region with that post, but I certainly am not sure.

 

It's definitely a bit lighter down there, but I think it's still in the 0.15-0.25" range and plenty cold. And you guys get more with the Saturday storm, too.

 

 

meant weaker compared to 12z run of GFS sorry... this run of GFS develops a sub 1000mb low that tracks across PA with a more organized cluster of moisture which would make it stronger and with more available moisture than the clipper yesterday compared to the 12z euro run which is not as strong of a low with moisture a little bit disorganized... but yes text output still has roughly .25-.35" qpf over most of the region

 

Sure, but the 00z Euro was an almost non-event, so I think the 12z Euro is a huge improvement. It's much more in line with the GFS now that it was before.

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Mallow, any chance the clipper gets going sooner for us?

 

You mean purely timing-wise? I think most aspects of the clipper are still subject to decently large swings, as the energy associated with it is still over the North Pacific. It doesn't reach the coast (near the panhandle of Alaska) until late Friday night, and models will probably be pretty fluid with the strength, track, and timing until Saturday.

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Mallow while you're here, what are the biggest bust potentials with the clipper? Track too far south? Limited development?

 

One of the most consistent things in the ensembles/models seems to be the track. It seems embedded within fast flow around the base of the longwave trough, so although the track could shift a decent bit, it won't go all the way down to, say, North Carolina.

 

I think limited/late development is the biggest risk. That's the biggest difference between the models with low precip (e.g. the Canadian) and those with higher precip (like the GFS).

 

EDIT: Actually after a second look, I think the two go hand in hand. Later development seems to imply a further south track, as well. What seems to be the biggest factor is whether the vort-max becomes more spread out and digs deeper, or is more consolidated and digs less.

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One of the most consistent things in the ensembles/models seems to be the track. It seems embedded within fast flow around the base of the longwave trough, so although the track could shift a decent bit, it won't go all the way down to, say, North Carolina.

 

I think limited/late development is the biggest risk. That's the biggest difference between the models with low precip (e.g. the Canadian) and those with higher precip (like the GFS).

 

EDIT: Actually after a second look, I think the two go hand in hand. Later development seems to imply a further south track, as well. What seems to be the biggest factor is whether the vort-max becomes more spread out and digs deeper, or is more consolidated and digs less.

 

Redevelopment off the coast would be something that could prolong and maintain precip all the way across PA as well, esp further east across the Sus Valley. I agree that the track of this should stay pretty firm, but we'll have to watch the subtle shifts that will likely come into play with later runs. That will determine where the heavy swath comes across PA, whether it's along or above I-80 or along the turnpike, etc. As Joe alluded to in the previous page, ideally you want a track of one of these things just barely south of PA. 18z NAM's positioning is an example of a great track.  GFS has the track just a hair north going through the state, and the Euro is south of PA with more of a poorly defined low. 

 

Also, this clipper is progged to be quite strong right now.. if it ends up that way it might be the rare clipper that needs winter storm warnings for the axis of heaviest snow. 

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Redevelopment off the coast would be something that could prolong and maintain precip all the way across PA as well, esp further east across the Sus Valley. I agree that the track of this should stay pretty firm, but we'll have to watch the subtle shifts that will likely come into play with later runs. That will determine where the heavy swath comes across PA, whether it's along or above I-80 or along the turnpike, etc. As Joe alluded to in the previous page, ideally you want a track of one of these things just barely south of PA. 18z NAM's positioning is an example of a great track.  GFS has the track just a hair north going through the state, and the Euro is south of PA with more of a poorly defined low. 

 

Also, this clipper is progged to be quite strong right now.. if it ends up that way it might be the rare clipper that needs winter storm warnings for the axis of heaviest snow. 

 

I find it interesting that the GFS is basically giving UNV about 0.8" of precip between Saturday and Monday night. That's quite a bit for being on the far northwestern side of storm 1, and for storm 2 being a clipper. As you note, the clipper is unusually deep.

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I find it interesting that the GFS is basically giving UNV about 0.8" of precip between Saturday and Monday night. That's quite a bit for being on the far northwestern side of storm 1, and for storm 2 being a clipper. As you note, the clipper is unusually deep.

 

It would be just what the doctor ordered in this winter where we just haven't been able to amplify and phase in southern stream waves without the -NAO blocking and get the bigger storms.

 

Speaking of storm 1... models look slightly better this afternoon at getting precip into PA coverage wise, specifically the Euro, UKMET, RGEM, and now the 18z GFS (edging the .1-.25" zone to the AOO-UNV-IPT corridor). Euro had a broader field of 850mb negative u-wind anomalies (easterly fetch), with less than -1 st deviations over about the southeast half of the state. That's much deeper into PA than yesterday's 12z run but way weaker overall, as yesterdays bomb had a much more intense and compact presentation. The overall problem with getting a more widespread precip field into PA despite a generally favorable track is the presence of the Canadian low above the lakes instead of a high that would promote a much stronger and longer fetch off the Atlantic. It's looking like the top end is going to end up being an advisory event in the Lower Sus valley and a general 1-2 maybe getting back to the aforementioned AOO-UNV-IPT. 

 

Some intermediate models for posterity:

 

18z RGEM 39hr (12z was similar)

post-1507-0-53640500-1421973575_thumb.gi

 

12z UKMET 42hr

post-1507-0-80406600-1421973589_thumb.gi

 

12z UKMET 48hr

post-1507-0-13214600-1421973609_thumb.gi

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This storm just doesn't seem to be one for anybody outside New England overall...the 95 cities might luck out a bit on the front end but any decent precip seems to be on the slop side anyway.

Based on the pattern we've been in, I'll take nickel and dime events any day of the week, as it sounds like better times may be coming.  i didn't expect to go from nothing to everything in a week or two.  as long as we're heading in a better direction I'll take it.

 

Nut

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RGEM for Saturday storm

 

 

rgem_asnow_eus_15.png

 

Was just about to post on it being a good hit, didn't have this snowmap though. Wow I'd take that and run. The low stays inland through far SE VA and stays right on the coastline up thru NJ then heads just off the southern New England coast. Perfect C-PA track and we need a perfect one in this setup to score the widespread decent snows in most of our region. We'll see if the rest of the 0z obliges. I had personally tabbed this 0z cycle as one that should largely get things roughly settled in on precip shield placement...or I would hope so anyways. 

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Was just about to post on it being a good hit, didn't have this snowmap though. Wow I'd take that and run. The low stays inland through far SE VA and stays right on the coastline up thru NJ then heads just off the southern New England coast. Perfect C-PA track and we need a perfect one in this setup to score the widespread decent snows in most of our region. We'll see if the rest of the 0z obliges. I had personally tabbed this 0z cycle as one that should largely get things roughly settled in on precip shield placement...or I would hope so anyways. 

 

Thanks for your thoughts as always MAG.

 

Things seem to be looking better so far tonight... hope it holds.

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