Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220141 AFDCTP Area Forecast Discussion National Weather Service State College PA 941 PM EDT Thu Sep 21 2017 .SYNOPSIS... A ridge of high pressure at the surface and aloft will stay anchored across the Lower Great Lakes, Ohio Valley and Northeastern States through at least Tuesday. This will continue of dry and unseasonably warm weather to Pennsylvania. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Thin high clouds associated with Jose have covered much of the eastern half of PA this evening as it continues to churn well off of the southeast New England coast. Aside from these high clouds, the only other sensible weather will be fog developing again overnight, mainly in the valleys. Going with just a deg or two cooler tonight than last night, as the drying of the airmass today may allow things to cool off just slightly more tonight. The subsidence inversion height is lowering slightly hour by hour, so mixing during the day on Fri should not be as deep as today. This might make reaching today`s maxes a little challenging, but it is tough to go away from a persistence forecast in this ever-so- stagnant pattern. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Ridge, ridge and more ridge. The subsidence inversion height is lowering slightly hour by hour, so mixing during the day on Fri should not be as deep as today. This might make reaching today`s (thurs) maxes again a little challenging, but it is tough to go away from a persistence forecast in this ever-so- stagnant pattern. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... For this weekend and early next week, the pattern remains stable as a building ridge continues to stifle any convection. Weak flow at night should allow for valley fog to form nightly and to greet morning commuters. The overall consensus in the models through the weekend is for the 590 dam closed 500 hPa high will drift slowly out of the midwest states, and become centered over western PA by late this weekend through early next week. Ensemble temperatures are in general consensus and high temps through the weekend will be 10-15F above normal with little or no chance of rain until Monday at the very earliest. There are hints that what was left of Jose could bring moisture and thus some rainfall through Monday into Tuesday. However there continues to be model variability so have only chance POPS. Lows early each morning will be consistently in the mid and upper 50s across the northern and western mtns, to lower 60s in the larger SE metro areas. Min temps may cool off slightly for this weekend thanks to deep dry air and a light N to NW llvl flow of drier dewpoint air at the sfc. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/...
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Light wind will allow valley fog to form across northern Pa overnight. Model guidance and persistence forecasting indicate KBFD is very likely to experience IFR/LIFR conditions early Friday morning. Further south, model guidance suggests a veil of high clouds may become thick enough to temper the radiational cooling and fog potential. However, based on falling temps and dewpoint depressions this evening, believe a period of IFR/LIFR conditions is likely at KIPT and possible (~50 pct) at KUNV/KAOO around dawn. The odds of of significant reductions at KJST/KLNS/KMDT appear very low. Any early fog should burn off between 13Z-15Z, then model data supports a near certainty of VFR conditions and light wind everywhere for Friday afternoon, as high pressure remains over the region. .Outlook... Sat-Tue...Patchy AM valley fog possible.
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&& .CLIMATE... Astronomical Fall/Autumnal Equinox begins at 4:02 PM Friday September 22, 2017. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...DeVoir SHORT TERM...Dangelo LONG TERM...Lambert/Gartner AVIATION...Fitzgerald CLIMATE...

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