Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 201043 AFDCTP Area Forecast Discussion National Weather Service State College PA 643 AM EDT Thu Jul 20 2017 .SYNOPSIS... Pennsylvania will be on the northern periphery of a subtropical ridge passing across the southern states through the weekend. A slow moving cold front will push through the area early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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09Z satellite loop showing fairly extensive valley fog across central Pa, which should burn off by 13Z-14Z based on trends of recent days and latest LAMP guidance. Main focus will then shift toward a potential MCS tracking across the Grt Lks toward northwest Pa. Latest convection-allowing model guidance, including NCAR ensemble and SPC SSEO support likely POPs across the northwest mountains during mid to late afternoon, with a diminishing chance of showers/storms as convection progresses southeast into the rest of central Pa this evening. Focus of the strongest tstorms may be just north of Pa at nose of anomalous low level jet. However, moderate CAPES and 0-6km shear of around 40kts are favorable for an organized severe weather threat across the northwest half of the forecast area late today. Other concern will be potentially dangerous heat indices across the Lower Susq Valley, where combination of heat and humidity should push heat indices to near 100F. Not sure we will achieve the criteria of widespread 100F for 2+ hours, so have held off on an advisory for now.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Both SPC SSEO and NCAR ensemble suggest a dwindling band of convection will push southeast across the region overnight, as best forcing ahead of shortwave shifts into New England and trailing low level jet sags south across Pa. Large scale subsidence and arrival of much lower PWATs progged for Friday, resulting in a mostly sunny day for most if not all of the forecast area. Have maintained just a slight chance of a lingering shower across Somerset county, which will remain on northern edge of ring of fire. GEFS mean 850 temps still around 17C-18C Friday, which should translate to max temps from the low 80s over the northern mountains, to the low 90s in the Susq Valley. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The Day 2 MRGL risk extends into west-central PA on the eastern extent of upstream organized convective zone. Over the weekend, pcpn pattern looks to reach a relative peak with max POPs based on multi-model blend. Exact timing and location of pcpn will depend on details not well resolved until the very short term time frame. Therefore the later periods will keep a 40-60 percent POP given lack of confidence in highlighting any specific areas/timeframe with concentrated pcpn potential. Medium range models generally agree that a continued/gradual weakening and east-southeast shift of the persistent central U.S. upper ridge can be expected with time, as shortwave troughing shifts slowly southeast out of the Canadian Prairie across the northeast quarter of the country by early next week. The associated cold front is progged by med range guidance to push slowing southeast through the forecast area early next week. Above average temperatures (+5-10 degree max T departures) should trend toward mid to late July climo numbers by next Tue-Wed. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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Satellite again showing fairly extensive valley fog across central PA (under a veil of thin cirrus) which should burn off by 13Z-14Z. Main focus will then shift toward a potential MCS tracking across the Great Lakes toward NW PA. TSRA probs become likely there by mid to late afternoon, with a diminishing chance of showers/storms as convection progresses southeast into the rest of central PA this evening. Focus of the strongest tstorms may be just north of Pa at nose of anomalous low level jet. However, moderate CAPES and 0-6km shear of around 40kts are favorable for an organized severe weather threat across the northwest half of the forecast area late today. In addition, isolated convection may develop over the Lower Susq around peak heating. Tonight, scattered convection over central mtns will be diminishing. Areas of valley fog will again become likely, with CIG restrictions poss over the NW. Isolated TSRA poss on Fri, with VFR otherwise. TSRA become likely again for Sat and Sun as humid airmass remains in place. .OUTLOOK... Fri...AM valley fog. Cig restrictions likely NW half. Isolated TSRA. Sat-Sun...AM valley fog poss. TSRA likely. Mon...AM valley fog poss. Scattered TSRA.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald/Steinbugl AVIATION...RXR

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