Area Forecast Discussion
Issued by NWS State College, PA

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457 FXUS61 KCTP 221004 AFDCTP Area Forecast Discussion National Weather Service State College PA 604 AM EDT Sun Oct 22 2017 .SYNOPSIS... A large area of high pressure centered off the New Jersey coast will bring spectacular Autumn conditions today through much of Monday, to enjoy the near peak color of the fall foliage. A high-amplitude and deepening, cold upper trough will become located across the eastern U.S. during the Wednesday and Thursday timeframe. This weather feature will be preceded and accompanied by rain that could be heavy at times late Monday into Tuesday. There is also a chance that a narrow band of gusty thunderstorms will develop and push east across the state along a cold front during the day Tuesday. Brisk and colder weather will follow for Wednesday afternoon through Thursday with the likelihood of the first snowflakes of the season across the Northern and Western Mountains of Pennsylvania. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Today will be a near carbon copy of Saturday temp-wise, though the southerly breeze will likely increase by 5 kts or so, into the 8-10 kt range with gusts into the mid-upper teens. Variable amounts and thickness of high clouds (cirrus/cirrostratus) will also spread across the Commonwealth by this afternoon, and will persist through tonight. The high clouds today will likely dim the sun at times. Max temps today will be very uniform (71-75F), within a degree or two of Saturday`s high and the Nat`l Blend of Models forecast temps for this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Areas of stratus will advect north and westward beneath the rather widespread cirrostratus layer expected tonight. Thanks to the cloud cover, low temps tonight will be in the low-mid 50s, or a good 10-15F above normal lows. An upper level trough low swinging through the upper midwest will absorb a closed upper low over the lower Mississippi valley during the day Monday. This will bring an extensive plume of moisture into the state from the south. The south to Serly llvl flow will freshen by about 10 kts during the day Monday and bring with it areas of low clouds (stratus/Stratocu) and perhaps some patchy drizzle across the central third of the state. Max temps Monday should be about 3-4 F lower than those of today for everyone except those in the Lower Susq Valley. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Models have converged to indicate the center of the significant rainfall event occurring later Monday night through Tuesday evening when widespread rainfall amounts of 1-1.5 inches is anticipated. As the cold front works slowly east across the Commonwealth Tuesday into Tuesday evening, SFC-850 mb LIs go slightly negative across parts of southcentral PA and the Susquehanna Valley. In addition to the expansive shield of moderate to briefly heavy rainfall rates, the pattern appears favorable for a Narrow Cold Frontal Rainband - NCFRB (with brief gusty winds) to push through as well. By Thursday, 850 mb temps drop below zero which will bring a relatively chilly day with scattered rain showers which may mix with a snowflake or two over the higher elevations. However, this cooler stretch will be short lived as heights and 850 temps rise quickly into next weekend. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/... Patchy fog is possible early this morning across the eastern 1/3 of the airspace - otherwise VFR conditions and light winds will continue to dominate the aviation forecast into tonight. Guidance is indicating risk for MVFR/IFR conditions developing late tonight into early Monday morning across the eastern airspace and will address this with the 22/12z scheduled TAF issuance. Outlook... Mon...AM low cigs/fog possible eastern 1/3. Showers advancing into the airspace Monday night with lowering cigs/vis and LLWS. Tue...LLWS/gusty/heavy showers in the morning. Sharp FROPA and windshift. Improving conditions by afternoon. Wed-Thu...Sct showers and low cigs possible KBFD/KJST. && .CLIMATE... Month-to-date, October 2017 was the warmest October on record at Harrisburg and Williamsport several days ago. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Martin NEAR TERM...Lambert/Martin SHORT TERM...Lambert/Martin LONG TERM...Lambert/Tyburski AVIATION...Fitzgerald/Steinbugl CLIMATE...

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