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Central PA - Winter 2020/2021 Part 2


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Good post in the Mid Atlantic thread by the great @Bob Chill on the pattern this week:

It's a long ways away and future changes will keep coming. Any run that shows the knife edge within a reasonable distance is a net positive. Who knows what we'll be looking at in a few short days. Real cold is nearby. Lots of precip is overhead. I'm not jumping to any conclusions yet. We've trended the wrong way a lot last few weeks. Now that it's ugly instead in the mid range, maybe... just maybe the trend works the other way. 

After what we've all experienced since mid/late Jan, I'm def not spiking any footballs before the short range starts agreeing... and even then....

 

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I especially like this part of Bob’s post.

“Any run that shows the knife edge within a reasonable distance is a net positive. Who knows what we'll be looking at in a few short days. Real cold is nearby. Lots of precip is overhead. I'm not jumping to any conclusions yet.”

This situation is too close to call until the storm is on our doorstep in terms of precip type.

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Well we don’t have a low bombing out to give us a 3sd+ easterly fetch. We have a gulf moisture laden storm running head first into an artic dome, being reinforced by a high pressure, with us right on the boundary. Said Storm pinballs under us cause it’s not displacing that cold. This area will hold on to low level cold damn well. Now the 700/850 are just slightly above 0 if at all, and the 925 & surface seem below O. I think like Mag said before that would scream sleet. So why are the physics of the Euro spitting out freezing rain? Did anyone look at the skew-t on pivotal for the 4am? Is there a sneaky warm thin layer on there that isn’t being depicted on the 925/850/700?


.

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30 minutes ago, Jns2183 said:

Well we don’t have a low bombing out to give us a 3sd+ easterly fetch. We have a gulf moisture laden storm running head first into an artic dome, being reinforced by a high pressure, with us right on the boundary. Said Storm pinballs under us cause it’s not displacing that cold. This area will hold on to low level cold damn well. Now the 700/850 are just slightly above 0 if at all, and the 925 & surface seem below O. I think like Mag said before that would scream sleet. So why are the physics of the Euro spitting out freezing rain? Did anyone look at the skew-t on pivotal for the 4am? Is there a sneaky warm thin layer on there that isn’t being depicted on the 925/850/700?


.

The 12Z NAM 84 Hr has it above freezing from 725 down to the the surface at MDT.  That's a pretty thick no freeze zone.  

 

23 degrees and light rain over here.  Amazingly the roads are not too bad.

 

 

 

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CTP afternoon disco talks about a sharp snow to rain gradient between 1-80 and 1-81 with only a brief period of freezing rain expected for first storm.   
 

 Models are coming to a consensus on
general gist of this system, with significant snowfall
accumulations (>6" possible) primarily north of I-80 and a
wintry mix over to rain in SE PA. There is the chance for a
brief period of freezing rain in the far SE zones Tuesday
morning, but amounts seem to not be too significant at this
time. Models have been trending warmer, so this is an area to
watch. Expect a tight gradient between the heavier snow amounts
and areas with no snow, but some uncertainty exists in where
this gradient will set-up. This could mean the difference
between little to nothing or several inches of snow for areas
between the I-80 and I-81 corridors, so we will keep an eye on
model updates and the pattern in the gradient
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Winter Weather Advisory

URGENT - WINTER WEATHER MESSAGE
National Weather Service State College PA
307 PM EST Sat Feb 13 2021

PAZ017-018-024>026-033>036-056>059-063-140815-
/O.CON.KCTP.WW.Y.0013.000000T0000Z-210214T1300Z/
Clearfield-Northern Centre-Cambria-Blair-Huntingdon-Somerset-
Bedford-Fulton-Franklin-Perry-Dauphin-Schuylkill-Lebanon-
Cumberland-
Including the cities of DuBois, Clearfield, Philipsburg,
Johnstown, Altoona, Huntingdon, Mount Union, Somerset, Bedford,
McConnellsburg, Chambersburg, Newport, Harrisburg, Hershey,
Pottsville, Lebanon, and Carlisle
307 PM EST Sat Feb 13 2021

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 8 AM EST
SUNDAY...

* WHAT...Light freezing drizzle with patchy light snow and
  sleet. Ice accumulations of a light glaze, and snow and sleet
  accumulations of less than an inch.

* WHERE...Portions of central Pennsylvania.

* WHEN...Until 8 AM EST Sunday.

* IMPACTS...Plan on slippery road conditions.

* ADDITIONAL DETAILS...Bridges and elevated road surfaces will
  be most likely to have ice accretions.
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1 hour ago, Jns2183 said:

Well we don’t have a low bombing out to give us a 3sd+ easterly fetch. We have a gulf moisture laden storm running head first into an artic dome, being reinforced by a high pressure, with us right on the boundary. Said Storm pinballs under us cause it’s not displacing that cold. This area will hold on to low level cold damn well. Now the 700/850 are just slightly above 0 if at all, and the 925 & surface seem below O. I think like Mag said before that would scream sleet. So why are the physics of the Euro spitting out freezing rain? Did anyone look at the skew-t on pivotal for the 4am? Is there a sneaky warm thin layer on there that isn’t being depicted on the 925/850/700?


.

Great post...this is very close, especially for the Harrisburg area.

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13 minutes ago, Cashtown_Coop said:

CTP afternoon disco talks about a sharp snow to rain gradient between 1-80 and 1-81 with only a brief period of freezing rain expected for first storm.   

Here is that part of the CTP discussion:

“Expect a tight gradient between the heavier snow amounts and areas with no snow, but some uncertainty exists in where this gradient will set-up. This could mean the difference between little to nothing or several inches of snow for areas between the I-80 and I-81 corridors, so we will keep an eye on model updates and the pattern in the gradient.“

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5 minutes ago, Bubbler86 said:

You must have been blocking all the model verification posts down on the MA board.  84 Nam is > 12 hour Euro right now.    But the reason I posted it is I only had access to soundings GFS and Nam and I went with the better model. 

There is absolutely no way the NAM is better than the Euro.... ever!

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2 minutes ago, Blizzard of 93 said:

I don’t trust the 6 hour NAM....let alone the 84 hour....Remember the Wednesday 18z run that gave us 6 to 8 inches of snow that was beginning within a few hours?Most of the LSV ended up with 2 or 3 inches.

The Euro is not quite what is used to be...but it is still the best around....buy a long shot.

I remember the 0z GFS that you posted hours later that gave Carlisle 9" of snow that night. NAM has been doing better than given credit for. It has serious issues just like every other model. I'm waiting patiently for my 40 something inches the Euro was giving me earlier this week.

Only post I will make on this. 

Let's hope this week trends better.

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5 minutes ago, Cashtown_Coop said:

The nam short range “it’s wheelhouse” has sniffed out trends before the big boys caught on.  It’s been decent this year IMO 

True. I just think when you look at this week overall every model is all over the place. 18z ICON is a rain storm for the LSV Monday/Tuesday. 

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2 minutes ago, Itstrainingtime said:

I remember the 0z GFS that you posted hours later that gave Carlisle 9" of snow that night. NAM has been doing better than given credit for. It has serious issues just like every other model. I'm waiting patiently for my 40 something inches the Euro was giving me earlier this week.

Only post I will make on this. 

Let's hope this week trends better.

Exactly...I couldn’t believe how the models bumped totals Wednesday afternoon and evening as the storm was beginning, only to see much less verify by the next morning.

Also, yes, all of the major ensembles earlier this week we’re producing large amounts of snow day after day, run after run. Things have deteriorated the last couple of days, but we still have to get to game time on Tuesday & Thursday to see what will verify.

60 hours is an eternity in this pattern with so much on the table. There is much to still be decided.

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6 minutes ago, Blizzard of 93 said:

I agree, but the long range NAM... please...

There is no long range Nam.  It's the Nam.  It goes to 84 hours.    The Nam at 12Z was a compromise between the all rain GFS and the Frz Euro so its soundings are just as valid as any other model.    The question was why was the Euro not showing sleet and if anyone had more soundings from the Euro and I pointed out that the Nam was above freezing for just over 700 the whole way to the surface.  That is a long way for sleet to survive so the Euro may have been similar. 

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Just now, Bubbler86 said:

There is no long range Nam.  It's the Nam.  It goes to 84 hours.    The Nam at 12Z was a compromise between the all rain GFS and the Frz Euro so its soundings are just as valid as any other model.    The question was why was the Euro not showing sleet and if anyone had more soundings from the Euro and I pointed out that the Nam was above freezing for just over 700 the whole way to the surface.  That is a long way for sleet to survive so the Euro may have been similar. 

The NAM at 18z was a big dry slot mess. 

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