Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 051958 AFDCTP Area Forecast Discussion National Weather Service State College PA 258 PM EST Mon Dec 5 2016 .SYNOPSIS... A storm system will move in from the Gulf Coast states and bring another period of a wintry mix of precipitation to the region Tuesday and through the first half of Tuesday night. Much colder air will move in after a cold front passes on Wednesday. The end of the week will feature a prolonged bout of lake effect snow and much- below normal temperatures. && .NEAR TERM /THROUGH TONIGHT/... Generally cloudy skies but due to the breaks and some welcome sunshine, temperatures are in the upper 40s to low 50s through the southern half of the state. The northern half of the state remains generally overcast and in the mid to upper 30s. Generally high pressure and cloudy but fair weather will continue through the first half of the overnight period. Some clearing could help lower temperatures tonight but overnight lows should be in the mid 20s to low 30s across the region. && .SHORT TERM /TUESDAY/... A low pressure system with some moderate upper level forcing will be moving into the region tomorrow morning. The high pressure bubble that will be over the region today will move quickly to the northeast. A low will move into the OH valley late Tuesday with the earliest bands of precipitation from this storm reaching southwest PA by Tuesday morning. The most difficult part of the forecast is the p-type. The latest NAM brings in precipitation between 12Z to 15Z with some warm air advection aloft. However evaporative cooling should take the warm air advection quickly down to the wet bulb which should switch the precipitation type to snow. So there remains the threat of freezing rain/sleet through the Laurels with generally a wet snow/rain event through the rest of the region. There is still a slight chance for some mixed precipitation through the Lower susquehanna but given marginal temperatures and quickly cooling mid levels have left the area out of the advisory for now. Have the advisory with freezing rain for the Laurels but as the region warms during the daytime a rain/snow mix will intrude and switch to snow as the day continues. Since any snow falling will be fairly wet, accumulations are tricky. The Central mountain temperatures and through the northeast should be cold enough for a couple inches to be probable. At this time, we will keep the 12-24 hr forecast snow amounts around 1-2" with the highest amounts over the NC mtns. So tomorrow will be fairly wet with slippery roads. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Tuesday night will be the end of the precip from the next big thing. Precip should be tailing off and will effectively stop before the cold air and front passes late Tues night and Wed morning. A brief snow squall is possible with the frontal passage. Winds will get more gusty, too. 8H temps late Wed will be -6C NW to +1C SE. This is right about normal for mid- Dec, so will paint the maxes as almost exactly climo. High pressure nosing in from the southwest for a brief time on Wed/Night will keep it generally fair. But a few SHSN may occur in the extreme northern tier due to W winds. The coldest air does not arrive until Friday. The cold advection will kick off a LES event which will last into the weekend. 1000-500H thickness drop below 520dam - a pretty good indicator that most locations won`t get to freezing during the days Friday and Sat. Many in the N/W will not get to 25F. Wind chills will be near zero in the Laurels. Just the SE valleys could make ol Frosty to sweat briefly in the aftn. Sometime in the weekend an upper level trough (Montana Clipper?) will cross the Upper Great Lakes and may produce more-widespread snow. The POPs will be highest across the north for now as the flow is zonal/flat and little moisture will be added to the system && .AVIATION /17Z MONDAY THROUGH FRIDAY/... After a period of tranquil weather this afternoon and through most of the overnight period another system will slide overhead tomorrow morning. This system will bring periods of precipitation with -FZRA/IP possible to JST and maybe AOO. So expect MVFR to IFR cigs and VSBYS to overspread the region after 12Z tomorrow. With 12Z to 15Z for BFD, JST and AOO, 15Z to 18Z for the rest of the TAF sites. Given the low level jet accompanying this system, gusty winds will be probable with LLWS possible at JST and MDT after 15Z. Cig and vsby restrictions should continue through the first half of Tuesday night before slowly lifting into Wednesday. Mon afternoon/evening...No sig wx expected. Tue...Mixed precip/low CIGs possible, especially late. Wed...Lingering low CIGs possible. Thu...Mixed precipitation event - low CIGs possible. Fri...Blustery and much colder with NW mtn and Laurel Highland restrictions in SHSN and areas of enhanced Lake Effect Snow. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Dangelo/Ceru AVIATION...Jung/Gartner

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