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Central PA - December 2013


PennMan

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Maybe something to keep in mind-the radar seems to be keeping the snow pretty far south over the Midwest. Indianapolis, for example, hasn't been in the snow shield yet and they were in a warning yesterday. If this continues, northern PA (northwest of the Coudersport/Clearfield line I mentioned earlier) may not see as much precip (therefore snow) as models have now, and the best action may be further south tonight.

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The low pressure wave riding along the front will cause it to stall for a time, meaning the snow line won't race east anymore after a point. But the low is forcing lift which is generating the enhanced precip.

Thanks JM and Djr. That makes sense and why LSV will be missing out on a couple of inches of snow.

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Maybe something to keep in mind-the radar seems to be keeping the snow pretty far south over the Midwest. Indianapolis, for example, hasn't been in the snow shield yet and they were in a warning yesterday. If this continues, northern PA (northwest of the Coudersport/Clearfield line I mentioned earlier) may not see as much precip (therefore snow) as models have now, and the best action may be further south tonight.

 

My uncle that lives in Paducah, KY was facing mainly an ice storm yesterday with up to a half inch of ice or so of freezing rain and some sleet/snow accums at the tail end. Was mainly sleet overnight and already flipped over to snow and PAH bumped them up to 4-8 inches. So it seems like the cold air is winning the battle more than had been originally expected. 

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The 12z Hi-Res NAM is ... a weenie dream come true?

http://www.meteo.psu.edu/~fxg1/NAMSFC4_12z/comploop.html

 

One thing is for certain, we will need those precipitation rates for a lot of people in Central PA and points south and east to get substantial accumulating snow. There is a warm nose initially (due to the shallow nature of the arctic air) but the endothermic cooling of melting snowflakes should help create an isothermal layer. The precipitation is probably all sleet/rain at 00z at State College but it switches over to snow between 00-01z when the heavier rates arrive (>= 0.1" liquid equivalent)

 

There is definitely the potential for some more intense mesoscale banding with this system. The 12z GFS has decent mid-level frontogenesis over central PA at 00z tonight. There is also some areas of negative EPV collocated with high relative humidity which may support the presence of some CSI.

 

Absolutely... additionally this is a favorable synoptic pattern (neutral temperature advection, jet forced ascent, frontogenesis) for a laterally quasi-stationary snowband that could train over the same region (along isentropes) over the next 6-12 hours. Thus, there will probably be a significant snowfall gradient between those who receive the highest amounts and those who don't receive much at all. Jaymes Kenyon has done some excellent work on this topic and this appears to be the ideal synoptic case for nearly stationary mesoscale snow bands.

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Prediction: MDT gets some pity ice tonight but not much more, points east just get rain. RDG might get a pity pellet or two as well. South and east of the MDT/RDG line, it'll just be rain.

 

Book it.

Caveat: I have no formal met training. However, I correctly predicted the sex of my son 4 months before we knew, so I'm pretty good at predicting the future.

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There is definitely the potential for some more intense mesoscale banding with this system. The 12z GFS has decent mid-level frontogenesis over central PA at 00z tonight. There is also some areas of negative EPV collocated with high relative humidity which may support the presence of some CSI.

This mechanism cannot be underestimated in terms of getting some surprisingly high snow totals.  

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This mechanism cannot be underestimated in terms of getting some surprisingly high snow totals.  

 

There is already some good evidence of banding upstream. Check out the band coming into Ohio just south of Dayton and going through Columbus... probably 1" per hour rates under that band.

 

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From MU's Eric Horst:

 

attachicon.gifspecialwxmap.jpg

 

 

Yeah, Eric called me just after I made that previous prediction post to hear what I had to say. He changed his original prediction (80' of snow, 102' of ice) to the quoted below:

 

 

Here in Lancaster, however, the near-freezing air won't arrive until after midnight and most of the steady precip will be gone by then. While I can't rule out a few wet flakes or sleet pellets after midnight, it's areas west of I-81 that have the best chance of seeing some accumulating snow and perhaps even a little ice

 

 

 

Kidding aside, he's usually right on for the Lancaster area.

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Yeah, Eric called me just after I made that previous prediction post to hear what I had to say. He changed his original prediction (80' of snow, 102' of ice) to the quoted below:

 

 

 

 

Kidding aside, he's usually right on for the Lancaster area.

Just in case some of y'all in my old stomping grounds do not have the link to his awesome discussions: http://snowball.millersville.edu/~cws/SpecialWeatherDiscussion.html

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The mixing line, per Intellicast's radar, is definitely further southeast from northern KY through PA and through southeastern MO and AR than the 12z Hi-Res NAM had modeled at this time.

I don't like using that radar-it usually shows it too cold at least in my area around NYC. However, it's a good sign that so many snow and sleet reports are showing up already near PIT.

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I don't like using that radar-it usually shows it too cold at least in my area around NYC. However, it's a good sign that so many snow and sleet reports are showing up already near PIT.

 

Ya, I agree. One should take the Intellicast radar's precip type with a grain of salt.

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FYI Sterling WFO went with a winter storm watch for all Mason-Dixon counties in MD west of the Susquehanna for Sunday/Monday.  Would not be surprised if CTP went the same later tonight once this storm clear their CWA.  I do not see an ice threat for Lancaster county...York westward.

Dr Greg Forbes posted on facebook the NWS forecast of probabilities of freezing rain Sunday morning to Monday morning... its not uploading here well from my phone but if I am reading it right has southeast PA in the 80%+ area

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