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Central PA - Winter 2020/2021 Part 2


MAG5035
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4 minutes ago, Bubbler86 said:

Yea, its very weak but if you notice the SLP in the gulf just sort of hangs around while the precip cuts off up north a bit after 48.  On 57 it shows the low in SC and 3 hours later it is off NJ and scoots out to sea.  I guess the point of my post is that this is not a typical Gulf low and that this really is a bit of a hybrid  overrunning situation with potential big changes last minute.  

 

image.png.5462273de80697097988b7cc0e788aff.png

 

Again, I think we are dealing with subtle details. This is definitely an overrunning event with a coastal component that could produce or not. If the coastal component produces it than prolongs the event and not a quick hitter type of form that Horst was saying. 

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10 minutes ago, paweather said:

Again, I think we are dealing with subtle details. This is definitely an overrunning event with a coastal component that could produce or not. If the coastal component produces it than prolongs the event and not a quick hitter type of form that Horst was saying. 

LOL.  Discussing the details is why I am here.    

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thru 60 GFS ticks southeast w/ best accums but gives LSV the wiggle room it needed for tomorrows north jog.  If this look holds tonight, I'm thinking this one is a safe bet for down here in southern pa.  540 came south a bit as well.  Little colder is nice and needed and might help w/ ratios a bit.  

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4 minutes ago, pasnownut said:

thru 60 GFS ticks southeast w/ best accums but gives LSV the wiggle room it needed for tomorrows north jog.  If this look holds tonight, I'm thinking this one is a safe bet for down here in southern pa.  540 came south a bit as well.  Little colder is nice and needed and might help w/ ratios a bit.  

The GFS just gave the MA their model of choice to bitch about if it falls apart. 

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3 minutes ago, Bubbler86 said:

The GFS just gave the MA their model of choice to bitch about if it falls apart. 

Icon verbatim was a nice 2 part deal....I like it.  Not sure if I believe but man do I like.  Blizz's heads gonna get stuck walkin thru the door cause this is his storm.

 

 

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27 minutes ago, Bubbler86 said:

@Cashtown_Coop, a pic my wife just took coming down Old Pen Mar road just out of one of the curves....White Tail Resort in the distance.

 

 

penmar.jpg

I was over your way earlier at Penn National golf course looking at some equipment for sale.   Even in mt alto you have a nice view over to the Tuscarora ridge 

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1 hour ago, Bubbler86 said:

Yea, its very weak but if you notice the SLP in the gulf just sort of hangs around while the precip cuts off up north a bit after 48.  On 57 it shows the low in SC and 3 hours later it is off NJ and scoots out to sea.  I guess the point of my post is that this is not a typical Gulf low and that this really is a bit of a hybrid  overrunning situation with potential big changes last minute.  

 

The bigger concern I have for especially the LSV wrt to some mixing later in the storm deals with the mid-level features at 850 and 700mb. The 850 low and 700.. trough are based west of the area. Fortunately these features are weak because a more dynamic phasing storm would assuredly be cutting west given 500mb positioning of the mean trough still over the middle of the country into Texas. Here's the 500mb mid-storm via the Euro. You wouldn't think at first glance CTP (or southern PA here in the Euro's case) is in the midst of getting a significant snowfall but thats the magic of when the features below 17k feet (500mb) are at least somewhat favorable and there's cold air. This isn't the first time we've played this game this winter either. 

ecmwf-deterministic-namer-z500_anom-3692800.thumb.png.f12271133dc5dd0db21d32a515aded39.png

 

Now going to show what the latest 3k NAM had with it's mid level features. The NAM is definitely on the most amped side of guidance, but same general idea is applying to the other guidance as well. 

850mb heights/wind 

nam-nest-east-z850_speed-3671200.thumb.png.c6bb079086ddd952636f3620d99f8cc9.png

 850 temps

nam-nest-east-t850-3671200.thumb.png.dd0149f698ebd6eea6f57d7e266e7aec.png

First off, you can see the big difference between this one and the last storm... where the 50-60kt+ jet is nosed over SE VA and the Delmarva instead of right directly over PA like last night. There is some southerly flow into PA (enhanced a bit on the west side of the Laurel's) but not the major jet that torches the layer.  That big arrow i drew doesn't show it well but the streamlines show that flow turning back a bit toward a due southerly flow over the Delmarva keeping the 0ºC line somewhat close. But overall, that level is okay for us but we don't want to slow down and amp this storm up much more or your going to direct that southerly flow more towards southern/southeast PA. 

Now 700mb winds/heights

nam-nest-east-z700_speed-3671200.thumb.png.1db0b38104453bfaa41782b741ab539f.png

700mb temps

nam-nest-east-t700-3671200.thumb.png.1d1d890bcb248947ad1307eb32bef936.png

This is the level (and possibly somewhat between the 850 and 700mb) that I'm most concerned about for mixing here in our region. You can already see why the NAM has so much sleet as a pretty strong 700mb jet runs through the Mid-Atlantic into PA.. There's going to be some significant WAA in that layer either way (which could cap snow ratios to a degree) but that 0ºC line is teetering near the LSV at 48 when the bulk of the precip is happening. Above 0ºC 700mb air does work into roughly the SE quarter of PA by hr 54.  Now as I said..the NAM is generally the most amped with the features I pointed out right now, but consider where we ended up last night. WAA aloft ended up being so strong that even the counties in the north that we're supposed to still 6+ of snow at the beginning of yesterday ended up not seeing anywhere near that.

Now let me add the disclaimer that this event should drop some nice snow up front for everyone. With that said, obviously my concern is more robust warming aloft than even the NAM has modeled... especially at 700mb considering how far west the low feature is. You get that sneaky thin area up somewhere between 700-800mb of above 0ºC air and suddenly your pinging away. So def something to keep in consideration. 

 

 

 

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Temps already back to 24°F here with some fluffy upslope snow showers starting to get things covered up again.

Spent enough time above freezing this morning that ice is mostly off the trees. Was hard to measure. I called it about a half inch of sleet which combined with the freezing rain made quite the ice layer on the snow. Actual ice accrual on trees and such looked fairly similar to the mostly ZR event I got at the end of December (which I measured 0.2”). 
 

Snowpack avg depth after the ice is about 8-9” with as low as 4” and as high as over a foot. 

B25E6A12-6605-4130-8EBC-2A97501EAB00.thumb.jpeg.542c5c8317c827d040bc9f404b7e8880.jpeg


 

 

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