Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 181504 AFDCTP Area Forecast Discussion National Weather Service State College PA 1104 AM EDT Fri Aug 18 2017 .SYNOPSIS...
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A cold front will move through the region today. An upper trough will move across the area on Saturday. Temperatures will stay above normal but rise even higher each day through Tuesday as a ridge builds aloft. Another cold front should trigger showers around mid-week and the week should end on a cooler note.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Broken area of rain is now becoming more showery and a line is forming to the west of JST/FIG. Instability back in the clear-er air over the NW is also firing up a sct line of shra which may produce TS soon. Some pockets of heavy rain are possible as PWATs/dewpoints are very high - some of the highest of the summer in many places. Temps aloft are very warm but the temps aloft should be cooling slightly this aftn and, as is happening in the NW, thunder is possible in most places. Timing still looks very solid with the storms/rain pushing out of the SE by 21Z, and only a sct shra/tsra in the nrn mtns after that but well before midnight. Prev... With the front passing off to the east this evening, the bulk of the overnight hours will be dry, with the best chance for a lingering shower after dark being over the far eastern areas. Cooler and drier air will seep in overnight. Lows will drop back into the upper 50s to mid 60s.
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&& .SHORT TERM /SATURDAY/...
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High pressure will nose into the state to start the day with fair-dry conditions. However a potent shortwave rotating through the base of the long-wave trough passing overhead will bring a renewed threat for scattered showers and perhaps thunder back into the forecast area during the afternoon. The timing is almost perfectly lined up for daytime heat and the short-wave trough forcing. Dewpoints should be around 60F by that time. Saturday`s highs will range from the mid 70s north to mid 80s south which will average a couple of deg either side of normal.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... After the shortwave moves through the area by later Saturday, heights aloft are forecast to rise and become quasi-zonal. Sunday into Tuesday looks warm and dry, with Tuesday even ending up hot over most of the area. A new shortwave moving through SRN Canada will an bring an increasing chance for rain, possibly as early as Tuesday afternoon over western sections of the forecast area. There are differences in timing of the rain with the ECMWF suggesting it holds off until Tuesday night. Blended MOS POPs show a small chance of showers moving into western sections Tuesday afternoon, but the highest POPs are reserved for the overnight. Cyclonic flow aloft will then dominate the flow pattern through Thursday. The cool air aloft will help trigger a few mainly diurnal showers Wednesday and Thursday. The showers will tend to favor northern and western higher elevations. Temperatures will be significantly cooler for the second half of the week. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/...
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Almost solid area of showers/rain running right thru the central part of the area from SE to NW is sliding only slowly to the east. Breaks in the sky cover will allow it to get unstable and make sct-nmrs TSRA this aftn. Reductions to MVFR are likely and some IFR is possible through early aftn in BFD, and 20z in the central terminals, and 22z in MDT/LNS. A final push of drier air will move through this evening and early tonight. Thus, a few shra/tsra are possible in BFD between 23z and 02z - but the other terminals should stay dry this evening and tonight. Fog is possible for most of the area tonight, but more so in the SE where the dry air arrives later. Lower clouds should form over the NW mtns tonight, but these should stop around the old AOO-UNV-IPT line. An upper level trough and rather strong forcing passing directly overhead in the cooler air aloft could make sct shra/tsra across the northern third/half of PA on Sat aftn. Much drier air will make for a mainly-VFR Sun-Mon with only valley fog in the AM a potential issue. .OUTLOOK... Sun-Mon...No sig wx. Tue...SHRA/TSRA poss.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/La Corte NEAR TERM...Dangelo SHORT TERM...La Corte LONG TERM...La Corte AVIATION...Dangelo/Martin

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