Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220034 AFDCTP Area Forecast Discussion National Weather Service State College PA 734 PM EST Tue Nov 21 2017 .SYNOPSIS...
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A very dry period is in store after a weak, dry cold front passes through overnight and early in the morning. High pressure will then hold until another cold front with meager precipitation rolls through in the middle of the Holiday weekend. After that, high pressure will build back in for several more days.
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&& .NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
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Sky has cleared for the moment, but the front and associated clouds are on the way in from the NW. The wave rolling along the east coast is also moving steadily this way. The timing of precip onset is right around midnight in Warren County, but it will take another 6 hours to get near to the Allegheny Front. By the time it gets there, the moisture will be drying up almost completely. The precip should only take an hour or so to turn from the initial rain to snow. Initially warm ground may make for icy patches on the roads as the melted snow freezes up later in the night. Going accums looks fine at just 1.5" or less in the far NW. Temps have dropped off very quickly at THV and MDT where it is in the 30s. CXY hanging in at 48F, but MDT only 39F. Gotta love micro climate. Expect anything that falls from the sky in the SE overnight to be trying to work down from far aloft and also to be liquid with dewpoints in the 30s. Keeping the POPs less than 30pct there, but decent frontogenesis aloft around 8H could make a stripe of very light rain for a few hours.
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&& .SHORT TERM /7 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... As the front moves eastward through Pa early Wednesday the bands of rain/snow should diminish as it pushes southeast. The HREFV3 data supporting only slight chance of measurable precip southeast of the Allegheny Plateau. However, incipient secondary low off the Mid Atlantic coast could clip the southeast counties with a period of rain Wednesday morning. The brief period of lake effect snow showers Wed morning will end by mid to late Wednesday morning as the approach of high pressure and falling inversion heights should result in minimal accums early in the day across the western mountains. For most of central Pa, Wednesday should be dry and breezy with temps below normal. GEFS mean 8h temps between -4C and -9C should translate to highs from the low 30s across the high terrain of northwest Pa, to the upper 40s across Lancaster Co. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... High confidence a period of fair and seasonable weather for Wednesday night through Friday, thanks to high pressure tracking from the GLAKS to the mid Atlantic region. Moderating temps for Friday into Sat as return SW flow arrives ahead of a fast moving cold front tracking from the northern Plains to the ern GLAKS by Sat morning. A light mix of RW/SW is possible along the PA/NY border with the front, followed by post frontal lake effect regime Sat PM through Sunday. Fair weather arrives for all Sun night through Tuesday with strong high pressure rebuilding across the region. There remains to be fairly good agreement in the large scale features this weekend through early next week. Initially below normal temperatures early next week will moderate as return SW flow reaches the region Tuesday ahead of another approaching cold front for Tue night-Wed. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Weak band of showers pushing into NW Ohio early this evening, but airmass over central PA on the dry side. Thus other than the BFD and JST TAF sites, hard to see nay rain and snow showers with reduced cigs later tonight and early Wed. Gusty downslope winds at IPT for several more hours. Left some fog in at MDT and LNS late tonight, based on earlier TAF packages and latest guidance. Not sure this will happen, given the low dewpoints, but left in for now, may take out later. Overall pattern favors no big weather systems into the upcoming weekend, but frontal passages with limited moisture every few days. Outlook... Thu-Fri...No sig wx expected. Sat...Chance of rain/snow showers. Sun...Chance of snow showers across the NW in the morning. Otherwise no sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo/Fitzgerald/Ceru LONG TERM...DeVoir AVIATION...Martin

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