Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 222153 AFDCTP Area Forecast Discussion National Weather Service State College PA 553 PM EDT Sun Oct 22 2017 .SYNOPSIS... Low pressure over the Mississippi Valley will track northward through the Great Lakes late Monday and Tuesday. A trailing cold front will push through Pennsylvania Monday night into early Tuesday. An upper level trough will then swing through Pennsylvania Wednesday and Thursday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Ridging at the surface and aloft will remain along the east coast tonight, ensuring a continuation of fair weather across the area. A southerly breeze, combined with a thin cirrus shield, should result in a milder night than those recently. A blend of latest model guidance supports overnight lows between 50-55F. Although there should be enough of a breeze to preclude fog issues over the bulk of central Pa, a weaker gradient across southeast Pa could lead to some fog across the southeast part of the forecast area early Monday morning. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... 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. Short to mid range models continue to narrow in on the timing of the approaching system. 12Z GEFS and NAM are in fair agreement on precipitation reaching Western PA and the Alleghenies late tomorrow afternoon. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... 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 south central 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. Another chance for precipitation will arrive at the end of the period when a cold front is anticipated next Sunday, bringing rain showers to the region. && .AVIATION /22Z SUNDAY THROUGH FRIDAY/...
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Just some mid and high clouds on this nice late fall afternoon. 21Z TAF set sent. Will look at the low cld situation more later, when I do the 00Z TAFS. Earlier discussion below. Guidance continues to show risk for low clouds and fog developing late tonight into early Monday morning across the eastern 1/3 of the airspace - and have increased and spread MVFR/IFR restrictions through the eastern and central TAF sites. Have kept restrictions until around 14Z. LLWS is possible at JST/AOO and BFD but it is marginal as strongest low level jet is above 2KFT. So have left it out of the TAFs for now. 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. Fri...Mainly VFR.
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&& .CLIMATE... Month-to-date, October 2017 remains the 2nd and 3rd warmest on record at Williamsport and Harrisburg respectively. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald/Lambert NEAR TERM...Fitzgerald SHORT TERM...Lambert LONG TERM...Lambert/Gartner AVIATION...Ceru/Martin/Steinbugl CLIMATE...

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