Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 182031 AFDCTP Area Forecast Discussion National Weather Service State College PA 431 PM EDT Fri Aug 18 2017 .SYNOPSIS... A cold front will move through late 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. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Radar shows the line of showers and thunderstorms pushing across Lancaster county. Only a few isolated showers behind the line. GOES-16 shows another nice area of cool stable air near the NY border behind the showers which moved across the northern tier. Based on HRRR and radar the watch for the southeast has a shorter shelf life than advertised. We may drop soon. Enhanced words in zones and grids reflect the watch in the southeast. Most areas will see steady improvement this evening to include a lowering of the dew points! Enjoy! Some patchy fog will develop after mid-night.
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Minor update with new data focusing showers in the afternoon. No other significant changes. Previous: The high pressure moving in finally clears everyone out in the morning. Any low clouds in the NW will dissipate nicely with the sunshine. The trouble there is that the lingering moisture, the passage of the upper trough and enhancement from a potent short wave coming around the base will meet up at peak heating. These factors and the wind field will generate multiple showers in the NW half of the area in the aftn. Some of these will make some good gusts - and some could get severe. A little small hail is also possible with colder air aloft than today. SPC does have that area in a MRGL risk for severe wx. The showers/storms will struggle to get past the Allegheny Front (roughly IPT-UNV- AOO line). Max temps will be right near normals.
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&& .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... The mid range models are all in good agreement on the timing and strength of the passing shortwave Saturday night. Once that passes, the heights will rise and become quasi-zonal. This will bring fair weather to the region Sunday through Tuesday. Dry westerly flow will also bring warm summertime temperatures with Tuesday continually trending warmer. 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 /21Z FRIDAY THROUGH WEDNESDAY/... Storms all over the radar scope at 19z SE of UNV-IPT-AOO. Just a spot of showers in the N east of BFD. That spot is probably along the real cold front as there are lower dewpoints immediately to the west of it. Additional storms are possible in the west and central counties late this aftn, but most locations will remain dry and VFR. A final push of drier air will move through this evening and early tonight. Thus, a few shra 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 it has rained and had clearing, but little time to dry. 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... Mon...No sig wx. Tue-Wed...SHRA/TSRA poss. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Grumm/Dangelo SHORT TERM...Grumm/Dangelo LONG TERM...La Corte/Ceru AVIATION...Dangelo is the U.S. government's official web portal to all federal, state and local government web resources and services.