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Central PA - Winter 2020/2021 Part 2


MAG5035
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The 12z Euro did tick slightly southeast with the snow line compared to the 6z run for Tuesday.

For example, at 6z Harrisburg had 1.4 inches of snow by the end of Tuesday and now at 12z, it had 2.2 of snow.

It seems subtle, but still time to pull the 6 inches of snow from State College & Selinsgrove down to the Harrisburg area with the track depicted.

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What’s the temp showing on the euro the night before storm? During storm? What time is it suppose to start? Most important is how long is duration? Is this 1” going to come in a 6 hr period or 24 hours? If it’s the latter and you have generators I’d advise to test them and fuel up.


.

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8 minutes ago, Jns2183 said:

What’s the temp showing on the euro the night before storm? During storm? What time is it suppose to start? Most important is how long is duration? Is this 1” going to come in a 6 hr period or 24 hours? If it’s the latter and you have generators I’d advise to test them and fuel up.


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Here is a snapshot of 4am Tuesday with surface, 925, 850 & 700mb temps for 4am as well.

This is very close to a better front end thump of snow for the Harrisburg and I-81 areas and north west from there. A small shift will make all of the difference.

Here is the surface precip type map for 4am and the surface temps.

 

53230B52-FE16-4E5A-888D-2A1DD35AF168.png

13662567-FA39-4D79-A43F-F453E24DD3E9.png

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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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13 minutes ago, Blizzard of 93 said:

Long range NAM....is like....never mind!

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. 

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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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