Area Forecast Discussion
Issued by NWS State College, PA

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342 FXUS61 KCTP 212045 AFDCTP Area Forecast Discussion National Weather Service State College PA 345 PM EST Tue Nov 21 2017 .SYNOPSIS... Pennsylvania will remain under a mean upper level trough through the week, with a succession of shortwaves and accompanying cold fronts pushing southeast across the state. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Warm daytime temperatures from the return flow and strong 850MB winds forming a low level jet will keep gusty winds across the region through the afternoon and early evening. The latest models have continued the warming trend with 12Z model soundings become well mixed through at least 850mb, so have increased daytime maxes by a few degrees accordingly. The latest CAMS show the mixing should continue until around 22 to 23Z. Latest satellite has bands of cirrus over the region. Mid to low level clouds will increase tonight as a cold front treks across the central Pennsylvania. There is a lack of a moisture with this system, however there remains impressive large scale forcing ahead of a potent mid level shortwave that should support a period of light rain beginning between 00Z to 03Z. That should change to snow across the northwest mountains after 06Z tonight. The GFS, NAM and EC all showing a band of 850-700mb fgen forcing within right jet entrance region, resulting in bulk of precip falling in colder air behind surface cold front. So even though latest models have around a tenth of an inch in moisture, it should be in the regions with the best forcing and colder air through the NW mtns. Given this, have increased QPF and snow amounts slightly. Expecting around an inch to an inch and a half through Warren and an inch through far western McKean. && .SHORT TERM /6 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/...
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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.
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&& .AVIATION /21Z TUESDAY THROUGH SUNDAY/... VFR will continue through the daytime as high pressure slides east of the Carolina coast. Gusty winds will continue through the daytime hours and will diminish between 22 to 00Z. Showers coming in from the west will bring down cigs and vsbys for a period between 03Z to 09Z behind frontal passage. There could be a brief period of rain just ahead of the front but will drop quickly to snow after 05Z. The main reductions will be at BFD and JST with improvements after 15Z. Outlook... Tue night-Wed...Rain/snow showers along and in the wake of a cold front. MVFR likely wrn 1/2. Thu-Fri...No sig wx expected. Sat...Chance of rain/snow showers. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald/Ceru SHORT TERM...Fitzgerald/Ceru LONG TERM...DeVoir AVIATION...Ceru/Gartner

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