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Central PA & Fringes - Fall 2014


Eskimo Joe

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I have you seen them? what do you consider middle finger LSV looks good?

Its when eastern PA gets heavy precip from the coastal storm and western PA gets heavy precip from the upslope and any lake effect and upper low effect but central PA gets downsloped. That's why it's important that the upper low goes through VA and closes off over DC or the Delmarva, or else this is a bunch of wind and some showers and snow for most of this thread. The Euro today was promising so hopefully that trend wins out.
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Its when eastern PA gets heavy precip from the coastal storm and western PA gets heavy precip from the upslope and any lake effect and upper low effect but central PA gets downsloped. That's why it's important that the upper low goes through VA and closes off over DC or the Delmarva, or else this is a bunch of wind and some showers and snow for most of this thread. The Euro today was promising so hopefully that trend wins out.

Actually, most of the time we have a situation that the primary transfers to the coast, we get screwed...either by a changeover, or the storm drying out..a notable exception was 2/10/10

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0Z Nam breakdown for KCXY (verbatim):

 

0Z - 6Z Tuesday -- Very light precip with probably snow/sleet mix begins; only 0.04" liquid

6Z - 12Z -- Warming tongue with above 0C filters in between 900 - 1000mb; Surface around -2C goes up to just below 0C; moderate freezing rain falls during this period with 0.40" liquid accumulation

12Z - 18Z -- Surface up to 800mb all above 0C to around +2C; freezing rain to rain with accumulation of 0.30"

18Z - 0Z (Wednesday) -- surface up to 875mb still above 0C; 850 on up to 800mb just beginning to go negative; moderate rain has fallen with 0.35" accumulation

0Z - 6Z Wednesday -- Column from 925 down to surface cooling to just above 0C; rain (95%) at beginning changing to snow (5%) at end with accumulation of 0.23"

6Z - 12Z -- all layers below 0C except at the surface with +0.5C; accumulating snow has begun with 0.31" of liquid (probably around 2" snow?)

12Z - 18Z -- surface has risen to +1.5C; additional accumulation of up to an inch of snow; liquid accumulation of 0.10"

18Z+ only very minor amounts of additional snowfall of less than 0.5" as storm departs

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Actually, most of the time we have a situation that the primary transfers to the coast, we get screwed...either by a changeover, or the storm drying out..a notable exception was 2/10/10

Western PA often gets upslope or lake enhanced snow showers behind storms like these which downslope east of the Allegheny and Laurel highlands. It's not the same as the Nor'easter but it's an OK consolation prize.
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According to Bufkit for the 0z NAM, it looks like a period of light ZR for Harrisburg that continues from 3-9z on Tuesday with 0.117" precip fallen. It has surface temperatures around 27-29 at the start and slowly moderating to above freezing (albeit barely) by morning on Tuesday, but that's when the heaviest precip begins to fall. The temperatures moderate to the mid-upper 30's for most the day on Tuesday, then crash down below freezing for the remainder 0.15" precip overnight on Wed. It is definitely a touchy situation as areas just north of there will be a little colder and could hang on to ZR longer. That's just from looking at one model run. Hope that helps

 

The 0z NAM to me untrained eye looks like a significant bordering on destructive ice storm for Harrisburg,

Please tell me I'm wrong.

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What a crazy day. I've been following here and there today after watching football and doing school work. This storm is going to be a doozy as far as precipitation totals go. The area of upper level diffluence seems to be best aimed at EPA into the Poconos region on northward into the lower/mid Hudson valley. My feeling is this will still be an elevation dependent event for many. Places in PA above 1000' look to see some frozen precip out of this for the majority of the storm and places 1400'+ will see a lot of snow. You have to ignore snow maps of any kind at this point (or ever for that matter) because they can't see the complete elevation picture. The thermal profiles for this storm will be marginal to start, but once the storm cranks and the 500 mb low closes off, the thermal structure for areas that were borderline would improve and switch back over to frozen. The only thing is, there is going to be one hell an easterly fetch with this storm in some areas, although I think it stays off to our north for the most part. Those easterly winds will torch the mid levels and kill any chance of frozen precip for a period in areas in eastern PA and NJ. I think areas away from the coast in CPA and along/west of the 81 corridor can stay basically all frozen and accumulate snow and maybe some sleet at the height before thermals improve. If the Euro has its way, the UL energy will meander for 36-48 hrs before exiting, so that would prolong a period of upslope snow in the higher terrain and provide snow shower chances for the entire state due to little vorticies from the UL piece sticking around and providing just enough energy to spark some snow showers. One thing is for sure, it sure looks cold and will feel like Christmas for a good portion of this week if that happens.

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Euro east per New England thread.

The system overall looks to be kicked east and close off late, which would be bad news for you guys on this run. 

 

If the system doesn't close off over the DC area or northern Delmarva, I wouldn't count on a lot of precip west of I-81 at max. You guys need the mid level lows to close off to force the Atlantic jet to back into PA. Otherwise the storm matures too late and it's an upstate NY and NNE snow event.

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Euro east per New England thread.

 

It did bump east a tad but the precip extent of the deform in PA is not as robust as the 12z run. Fades a bit more before closing off further north so backlash is negligible this go-around in the central counties as well.  The south central counties do get an initial period of precip (approx 0.1-0.3") at the hour 36 frame, but the focus shifts more to the eastern 1/4 of PA after that with the deform band. Models are starting to zero in with the track, but still plenty of questions with regards to extent and placement of the deform shield and of course precip types. The 0z suite does seem to renew the focus on NE PA and northward for the best chance of snows over maybe getting central PA involved with an earlier close off of the storm. Will have to see how Euro ensemble and 03z SREFs look later on. SREFs have been very wet QPF wise and seemed to factor into WPCs snow probs given how far west they had their snow axis. I would imagine that they will eventually start reflecting what the other guidance has eventually. The 21z suite had about a 1" QPF mean at State College. 

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Wow, after a big 12z run too.

It should be mentioned that the Euro ensembles are still very bullish on this storm with 8.5" mean over 51 members in State College. What concerns me is that not many of them show the initial heavy burst that the 12Z Euro operational showed yesterday. The 8.5" occurs over a prolonged 72 hour period which makes it very unlikely IMO that we would ever see 8.5" on the ground. In any case, I like the update WPC maps. I think they capture the uncertainty/potential with this storm:

 

http://www.wpc.ncep.noaa.gov/pwpf/wwd_accum_probs.php?ftype=probabilities&fpd=72&ptype=snow

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