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Central PA - December 2013

PennMan

By PennMan,
in Upstate New York/Pennsylvania

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JamieOber

JamieOber

Posted
Posted

For UNV 18z NAM Cobb data has 0.63" of ZR after a lot of rain. The soundings themselves don't agree with this, but it is a very marginal setup.

My guess is that the immediate State College area gets rain to sleet to a little snow at the end. We tend to change over to sleet earlier than expected with these situations, but hang on to the warm layer longer than expected.

Link is here if you want to check out the closest location to you: http://www.meteor.iastate.edu/~ckarsten/cobb/cobb.php?model=namm&site=kunv

I am trying to remember any rain to sleet events here...I can't come up with any. But memory tend to be bad for weather so I am likley forgetting. Do you have any analog examples of similar events?

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MAG5035

MAG5035

Posted
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GFS has the 850-700mb warm layer but it's more on par with the Euro with how warm it is. Likely a sleet becoming a highly marginal snow profile for the central places.

 

Snow map indicates the 6 inch line running from roughly Johnstown to State College to Scranton. 3 inch line runs very close to the 6 northeast-ward from western MD to Sunbury(ish) to Hazelton. Harrisburg between the 1 and 3 inch lines, not much southeast from that. Wish I could just post the dang map haha. IPT within an area of 8-10", PIT within an area of 10-12". This assumes 10:1 ratio and to be honest, if this were to come to fruition... I would take about 20-30% off of snow totals in especially the areas that are in the axis of heaviest snowfall. Any prolonged sleet will obviously knock things down but the warm layer of temps right around 32ºF from roughly 850 to 700mb is going to yield to poor snow growth and probably some riming of flakes. Very close and complicated situation, 0z suite of models should be fun tonight. 

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KPITSnow

KPITSnow

Posted
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Might take a crack at one once I see the 0z suite and at least the 21z Baby NAMs.

Mag, I'm extemely confused. Almost every model is showing a warning level event for kpit, but not even an advisory? Is there something I am missing, or are they just that gunshy after the last event here?

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MAG5035

MAG5035

Posted
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Mag, I'm extemely confused. Almost every model is showing a warning level event for kpit, but not even an advisory? Is there something I am missing, or are they just that gunshy after the last event here?

 

This is a tough forecast, and a little bit of temp difference either way could mean either a pretty big snowfall or more of a mess that doesn't amount to very much.  I'm sure NWS PIT and CTP are probably factoring the NAM and SREFs pretty heavily into their forecasts, which have been the most pronounced with the warm layer that could make for more of a prolonged sleet profile and confine heavier snows to NW PA. These borderline profiles can still light up a snowfall map, so one must be cautious as to not get too crazy with potential accumulations. With that said, I am kinda surprised that more of Pit's CWA doesn't at least have advisories. 0z model suite will probably go a long way to determining if things need expanded, especially if they continue the trend of being slightly cooler. 

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heavy_wx

heavy_wx

Posted
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Nan looks way better for most of us. Any mets want to interpret for a weenie like me?

 

The 00z NAM does look like it brings the frontal boundary a bit farther south. It's still very marginal for areas along a line intersecting Altoona and Williamsport and too warm farther southeast. There looks to be about 0.25" QPF for UNV after the time temperatures from 850 to 700 mb get below or at freezing. There would probably be a good chance of sleet mixing in at State College and other valley locations. It will be easier to tell however once the bufkit profiles are available.

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Mallow

Mallow

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The 00z NAM does look like it brings the frontal boundary a bit farther south. It's still very marginal for areas along a line intersecting Altoona and Williamsport and too warm farther southeast. There looks to be about 0.25" QPF for UNV after the time temperatures from 850 to 700 mb get below or at freezing. There would probably be a good chance of sleet mixing in at State College and other valley locations. It will be easier to tell however once the bufkit profiles are available.

 

You're basically assuming none of the stuff that falls between hrs 21-24 is snow in State College. I think most of it is. I think the cooling in that layer and the heavier band of precip arrive at the same time.

http://www.meteo.psu.edu/~fxg1/ETANE9_0z/etaloop.html

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NortheastPAWx

NortheastPAWx

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You're basically assuming none of the stuff that falls between hrs 21-24 is snow in State College. I think most of it is. I think the cooling in that layer and the heavier band of precip arrive at the same time.

http://www.meteo.psu.edu/~fxg1/ETANE9_0z/etaloop.html

In all fairness to him the precip maps do say rain.

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heavy_wx

heavy_wx

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Posted

You're basically assuming none of the stuff that falls between hrs 21-24 is snow in State College. I think most of it is. I think the cooling in that layer and the heavier band of precip arrive at the same time.

http://www.meteo.psu.edu/~fxg1/ETANE9_0z/etaloop.html

 

The 00z NAM keeps a layer between 800 anfd 750 mb above freezing until 00z Saturday. Temperatures in the column fall quickly between 23 and 00z and the model produces 0.11" QPF during that time which can probably be assumed to be all snow. However, at 01z Saturday, temperatures at around 750 mb rise just above freezing so there would have to be at least some sleet mixing in during that hour. QPF during that hour is also 0.11". The column then cools again below freezing and puts out another 0.18" of QPF as snow.

 

post-869-0-26218000-1386308282_thumb.png

 

This depiction by the 00z NAM is the coldest run so far even though it still keeps the warm tongue of air near enough to KUNV to bring in mixing concerns.

 

The 00z GFS actually is a bit warmer, keeping temperatures between 850 and 750 mb above freezing until 03z. It puts out 0.34" QPF between 00z and 03z. Some of that is not going to be snow because part of the profile is above freezing at 00z. You can't really tell how much of course, since the time resolution of the model is only every three hours. The model also puts out another 0.07" after 03z as snow.

 

post-869-0-85675100-1386308912_thumb.png

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