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Central PA & the fringes - January 2015 Part III


WmsptWx

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Don't pay attention to the snow maps, they might count sleet as snow accumulation. Look at soundings instead and the track of the 850 low. The warm nose looks to be above 850mb, so looking at that level might be deceiving. It might be below zero at 850 but above at 750 and 800mb, meaning sleet.

 

Due to the lack of a closed 700mb low its doubtful that we would be dealing with a warm nose in that region and indeed, a look at the cross section product accupro has indicates that temps are quite safe above 800mb. Ran a cross section from KPIT to KABE (Allentown) with the 0z NAM and the "warm nose" resided from the surface (in SW PA to about 825mb..with 900mb on down being below freezing from the Laurels east. Temps in the warm nose are def less than 2ºC and likely not even 1ºC.. which would probably be barely enough of a column to support snow at heavier rates. The flat track of the storm system doesn't inspire much of a drive of warm air aloft out ahead of the 850 low. I think the bigger problem with the 850 low tracking over PA (esp southern tier) is the fact that the best forcing is going to be north.. and thus the best precip. The rule of thumb, or at least one of them to go by is the potential of heaviest snowfall is 90nm to the left of the track of the low. Not to mention if the surface low moves over PA that will likely minimize or shut precip off anyways... but perhaps not before a front end thump, as is suggested by the GFS by getting those higher snow amounts into the Sus Valley. 

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Not a disaster on the 0z suite tonight but definitely still keeps us further north sweating.

 

I suppose I agree, however usually with these events there is a recorrection within 36-60 hours the opposite way after trends stop. Hoping that the models tomorrow tick south, any further north and I'll be eating crow with my statement I made earlier.  :axe:

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After taking a look at the Euro run, there is strong agreement between the Op, Control and Ensemble mean. They each take the track of the low from the far SW corner of PA to just off the southern tip of NJ. Snow maps for the Op, control and mean had MDT area between 6-8 inches. Amounts of around 10 inches were about 50 miles to the north. I agree that a shift of 50 miles or so south would certainly help, especially for us in the LSV area, but I like our chances as of now.

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Looks like a mix or changeover at hr54 on the 6z GFS.


Date: 54 hour AVN valid 12Z MON 2 FEB 15

Station: 40.80,-75.96

Latitude: 40.80

Longitude: -75.96

-------------------------------------------------------------------------------

LEV PRES HGHT TEMP DEWP RH DD WETB DIR SPD THETA THE-V THE-W THE-E W

mb m C C % C C deg knt K K K K g/kg

-------------------------------------------------------------------------------

0 1000 -19

SFC 962 288 -0.2 -0.3 100 0.1 -0.2 89 6 276.0 276.6 274.9 286.6 3.90

2 950 394 0.3 0.2 99 0.2 0.3 107 10 277.5 278.2 276.0 288.7 4.07

3 900 828 1.0 0.9 99 0.1 0.9 175 19 282.5 283.3 279.1 295.2 4.53

4 850 1288 1.0 0.9 99 0.1 0.9 215 34 287.2 288.0 281.7 300.8 4.80

5 800 1775 -0.4 -0.5 100 0.1 -0.4 231 43 290.7 291.5 283.0 304.1 4.62

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LATEST MODEL SIMULATIONS AND ENSEMBLES CONTINUE TO SHOW VERY HIGH

POTENTIAL FOR HEAVY SNOWFALL AND MIXED PRECIPITATION (SOUTH) TO

IMPACT CENTRAL PA SUNDAY NIGHT THROUGH MONDAY. LATEST ECMWF

SOLUTION DEPICTS A MILLER-B TYPE SFC LOW EVOLUTION...WITH PRIMARY

LOW TRACKING TO SOUTHWEST CORNER OF PA BY 12Z MON...WHILE

SECONDARY FORMS OVER THE DELMARVA AND SCOOTS RAPIDLY OUT TO SEA BY

MONDAY AFTERNOON. THIS WILL PRODUCE A PERIOD OF MODERATE TO HEAVY

SNOWFALL ACROSS MOST OF CENTRAL AND NORTH CENTRAL PA...WHILE A

MIX AND CHANGEOVER TO SLEET AND FREEZING RAIN IS LIKELY ALONG AND

SOUTH OF THE TURNPIKE.

A WINTER STORM WATCH CONTINUES IN EFFECT FOR ALL CENTRAL PA

WPC FORECAST IS WEIGHTED HEAVILY IN THE FINAL GRIDDED SNOW/ICE

ACCUMULATIONS...AS BEFORE. CONFIDENCE IS NOW 80% OR GREATER FOR 4

INCHES OR MORE OF ACCUMULATION IN 24 HOURS BY 12Z MON OVER ALL BUT

THE SOUTHERN 1/5 OF CENTRAL PA WHERE MIXTURE IS EXPECTED. KEEPING

RECENT INCONSISTENCIES IN MIND...DO ANTICIPATE SOME CHANGES

REGARDING NUMBERS AND LOCATIONS OF SNOWFALL TOTALS...BUT WITH

UPPER WAVE OVER BC NOW ONSHORE AND PRESUMABLY BETTER INITIALIZED

THAN SOLUTIONS FROM 48 HOURS AGO...CONFIDENCE HAS MARKEDLY

INCREASED FOR AN IMPACTFUL WINTER STORM TO VISIT THE COMMONWEALTH

SUNDAY AFTERNOON THROUGH MONDAY.

http://forecast.weather.gov/product.php?site=CTP&issuedby=CTP&product=AFD&format=CI&version=1&glossary=1&highlight=off

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thanks PA.  

 

after reading CTP's update, and living here all of my life, a growing part of me thinks those of us in the "lower 1/5" that they reference, stand a shot at a mix....to dryslot, then back to snow.  seen this show before.  As much as i want pounded like those 25 miles north of me...ughh, I'd take that.  Just dont want the ZR.  We should be getting to a point where the north trend stops and we see how far south it ticks to a final solution.

 

Nut

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After reading all the posts after 2:00am and seeing Voyager's 6Z GFS map I was pretty disheartened, however CTP's snowfall map perked me back up.  I think the concensus at this point is for close to 6" in and around my area which would be a complete victory if that were to be realized.

 

We still have 24 hours of model runs before the first flake begins to fall.  Remember what happened with the blizzard last weekend.  Things can change in a hurry, so I will hold out hope.  I'm fine with sleet but would really prefer a minimum of freezing rain.  The one benefit to ZR, if we can keep it to less than 0.05" would be that it would put a nice crust on top that seals it up and prevents a huge amount of blowing snow after the storm.  It also melts a lot slower if that glaze is on top.

 

I bottomed out around 12 degrees earlier and am up to 18.6 now.  Dew Point creeping up from zero earlier now at +5F.

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