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Central PA - 2012 wanes

NortheastPAWx

By NortheastPAWx,
in Upstate New York/Pennsylvania

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Jim Marusak

Jim Marusak

Posted
Posted

have to admit, i've been stuck here in the mid-west pattern for a while but just am looking back in NEPA for the folks, now that I have the time to after working 12 straight.

have the NAM and GFS been running as warm in northeast and north-central PA on a run-to-run basis with this thing? or is this a one-run anomaly and i should go with a more canadian regional/euros solution for this? and how have the 850's been trending up here for this event? catch me up to speed real quick.

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Jim Marusak

Jim Marusak

Posted
Posted

^ Not like the 2007 V-Day storm with 13" of snow and 4-5" of sleet which froze under temps <5°F! That pack stuck around until late March.

that was a total CF, i remember that one because to most people i knew i was saying 12 or so" of snow, then all of a sudden, about 6 hrs early, i started hearing sleet at the house in honey pot, and saw the freezing rain way too early into reading and the IP way too early into the i-78 corridor.

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Jns2183

Jns2183

Posted
Posted

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD

1121 PM EST TUE DEC 25 2012

VALID DEC 26/0000 UTC THRU DEC 29/1200 UTC

STORM MOVING ACROSS THE SOUTH AND EAST

======================================

PREFERENCE: NON-NAM COMPROMISE WITH AVERAGE CONFIDENCE

INITIALLY, THE 00Z NAM APPEARS TO BE 2-3C TOO WARM WITH ITS 850

HPA FREEZING LINE ACROSS VIRGINIA/MARYLAND AND THE UPPER OHIO

VALLEY. THE 00Z GFS PROBLEMS ARE CONSTRAINED TO A 2-3C ERROR IN

THE UPPER OHIO VALLEY. THESE 850 HPA TEMPERATURE ERRORS HAVE

POSSIBLE IMPLICATIONS FOR THEIR FORECAST WINTER WEATHER

PRECIPITATION TYPES EARLY ON. SEE WINTER WEATHER

GRAPHICS/PRODUCTS FROM HPC AND LOCAL FORECAST OFFICES FOR MORE ON

SNOW/SLEET/FREEZING RAIN EXPECTATIONS WITH THIS CYCLONE.

DURING THE SHORT RANGE PERIOD, THE 00Z NAM BECOMES A SLOWER THAN

THE REMAINDER OF THE GUIDANCE WITH THE SYSTEM MOVING THROUGH THE

NORTHEAST FROM LATE THURSDAY ONWARD, AND LIES NEAR THE SOUTHWEST

CORNER OF THE 12Z GLOBAL ENSEMBLE SPREAD WITH ITS ASSOCIATED

SURFACE LOW POSITION FRIDAY MORNING. TREND-WISE, THE GUIDANCE HAS

STRENGTHENED THIS SYSTEM OVER THEIR PAST DAY OF RUNS, BUT THE NAM

HAS STOPPED TRENDING QUICKER/NORTHEAST. WITH THE 21Z SREF/18Z

GEFS/12Z ECMWF ENSEMBLE MEANS SUPPORTING THE QUICKER NON-NAM

CONSENSUS, THE PREFERENCE IS FOR A NON-NAM COMPROMISE HERE WITH

AVERAGE CONFIDENCE CONSIDERING ITS PROGRESSIVE NATURE.

...MODEL TREND GRAPHICS AT www.hpc.ncep.noaa.gov/html/model2.shtml

...500 MB FORECASTS AT www.hpc.ncep.noaa.gov/h5pref/h5pref.shtml

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Jim Marusak

Jim Marusak

Posted
Posted

The NAM and GFS both had initialization errors with their 850 temperatures being to warm. The NAMs was more significant I believe. . The GFS error was more up in the OH valley.

it definitely looks way warm at 850 at AVP in both models, ~ +4C at AVP at the peak with the NAM and the GFS compared to say 0C that I could estimate off the canadian. that would explain it a lot if the initalization was that bad. was it a bad RAOB upstream that caused it, convective contamination from down south, or just a bad smoothing job?

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jm1220

jm1220

Posted
Posted

Wow...guess that could skew things. Off quite a bit.

Mixing oftentimes makes it north of where predictions have it in these kind of mid level WAA events. The most obvious example is VD 2007 when most of PA mixed, but just prior to the storm progs only had mixing up to maybe Rt. 22. I remember seeing the mix line charging north through JST/AOO and knew we were cooked in State College. We had about a foot of cement at the end of it. We had stinging sleet and temps in the teens. Wicked.

I would expect mixing of some sort to make it to I-80 before the storm's done, but hopefully most of the precip is done by then.

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Jns2183

Jns2183

Posted
Posted

I've heard convection with the NAM and upstream with the GFS. Neither I feel handled the strength of the storms in the south this evening particularly well. I'm located just west of Harrisburg and I'm starting to fear a nasty ice storm here. The temperature is 29 and falling in Camp Hill with a dew point of 20. Winds are just slightly the NNE (10 degrees) and the barometer just stopped rising just after midnight. That high pressure is doing a number here.

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Jim Marusak

Jim Marusak

Posted
Posted

Mixing oftentimes makes it north of where predictions have it in these kind of mid level WAA events. The most obvious example is VD 2007 when most of PA mixed, but just prior to the storm progs only had mixing up to maybe Rt. 22. I remember seeing the mix line charging north through JST/AOO and knew we were cooked in State College. We had about a foot of cement at the end of it. We had stinging sleet and temps in the teens. Wicked.

I would expect mixing of some sort to make it to I-80 before the storm's done, but hopefully most of the precip is done by then.

this may be one where everyone in here may have to be a bit of a mesonet point for p-type to see the final verdict. because that's exactly how the calls had to be changed on the VD-2007 storm. and unfortunately, the signals weren't timely enough with the PennDot district in charge of the I-78 corridor, and they needed to get people out of their cars with the National guard.

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Jim Marusak

Jim Marusak

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Posted

I've heard convection with the NAM and upstream with the GFS. Neither I feel handled the strength of the storms in the south this evening particularly well. I'm located just west of Harrisburg and I'm starting to fear a nasty ice storm here. The temperature is 29 and falling in Camp Hill with a dew point of 20. Winds are just slightly the NNE (10 degrees) and the barometer just stopped rising just after midnight. That high pressure is doing a number here.

hopefully they can get that corrected for the 06Z run, that should be initalized soon. because if not, I may start to wonder if that modified 3dvar they're running for initialization is really part of the problem.

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MAG5035

MAG5035

Posted
Posted

Final call map on the storm, no major changes.

post-1507-0-07117200-1356501923_thumb.gi

Evened the 6" line out a bit in eastern PA so it is running pretty much right thru Scranton attm. Million dollar question is how much mixing gets into this region, if NE PA manages to stay all snow, they're going to get the 10-14 forecasted further west. It continues to be American vs foreign guidance in that regard with NAM/GFS and co. continuing to ram mixing up into NE PA. I left the line over Scranton/WB as they will likely be a couple inches either side of 6" (aka 4-8 inches). 3 inch line unchanged except for shrinking the SW PA hole a bit. Widened 10-14" zone in the north.

That's interesting about the model initialization errors on the 850 temps... certainly something to monitor. I've not really liked the NAM's warm take on this system since this event has gotten into its range. The GFS is a little better but still kind of warm for this setup with a high to the north and sufficient CAD. I think alot of mixing that occurs will be in the form of sleet in C-PA, with liquid mainly relegated south and east of Harrisburg. I don't really see a deep push of very warm air at the lowest levels. Very highly anomalous easterly 850 winds were cited as possible cause of warming that particular layer enough to mix in some of the area. I'm beginning to think this is going to be like our cutter event bout 5 days ago in that the main bulk of precip comes in a major slug a bit ahead of the low. I just wonder if it outruns enough to be able to thump more snow in Sus Valley places before mixing and/or changing.

Euro is coming in cold again btw by looks of text data. Gonna be very interesting to see if it ends up winning this thermal battle. My map will be too low amount wise in alot of the southeast if these colder Euro runs straight up verify.

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2001kx

2001kx

Posted
Posted

Final call map on the storm, no major changes.

post-1507-0-07117200-1356501923_thumb.gi

Evened the 6" line out a bit in eastern PA so it is running pretty much right thru Scranton attm. Million dollar question is how much mixing gets into this region, if NE PA manages to stay all snow, they're going to get the 10-14 forecasted further west. It continues to be American vs foreign guidance in that regard with NAM/GFS and co. continuing to ram mixing up into NE PA. I left the line over Scranton/WB as they will likely be a couple inches either side of 6" (aka 4-8 inches). 3 inch line unchanged except for shrinking the SW PA hole a bit. Widened 10-14" zone in the north.

That's interesting about the model initialization errors on the 850 temps... certainly something to monitor. I've not really liked the NAM's warm take on this system since this event has gotten into its range. The GFS is a little better but still kind of warm for this setup with a high to the north and sufficient CAD. I think alot of mixing that occurs will be in the form of sleet in C-PA, with liquid mainly relegated south and east of Harrisburg. I don't really see a deep push of very warm air at the lowest levels. Very highly anomalous easterly 850 winds were cited as possible cause of warming that particular layer enough to mix in some of the area. I'm beginning to think this is going to be like our cutter event bout 5 days ago in that the main bulk of precip comes in a major slug a bit ahead of the low. I just wonder if it outruns enough to be able to thump more snow in Sus Valley places before mixing and/or changing.

Euro is coming in cold again btw by looks of text data. Gonna be very interesting to see if it ends up winning this thermal battle. My map will be too low amount wise in alot of the southeast if these colder Euro runs straight up verify.

nice write up mike...been waiting for it.

but your just teasing me now with that 10"-14" line being so close :P

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jm1220

jm1220

Posted
Posted

I've heard convection with the NAM and upstream with the GFS. Neither I feel handled the strength of the storms in the south this evening particularly well. I'm located just west of Harrisburg and I'm starting to fear a nasty ice storm here. The temperature is 29 and falling in Camp Hill with a dew point of 20. Winds are just slightly the NNE (10 degrees) and the barometer just stopped rising just after midnight. That high pressure is doing a number here.

It's a possibility-a lot of times cold surface air is hard to scour out from the Susquehanna Valley. The low looks like it will track roughly along I-95, so lower level warmth could win out. But I would say a lot of slop-sleet and then freezing rain, for many of you guys.

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