Area Forecast Discussion
Issued by NWS State College, PA

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662 FXUS61 KCTP 251957 AFDCTP Area Forecast Discussion National Weather Service State College PA 357 PM EDT Thu May 25 2017 .SYNOPSIS... Mostly cloudy skies with scattered showers will persist into the evening hours. A few strong thunderstorms are possible, mainly across south- central and southwestern PA. Scattered showers will linger into Friday followed by a period of mainly dry conditions Friday night into Saturday. Showers and thunderstorms will likely impact the area Sunday into Memorial Day. Today will be the coolest day this week with temperatures rebounding through the holiday weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Back end of double barreled surface low pressure system will lift north through the area overnight. Sfc cyclonic flow under cold upper core aloft will support scattered rain shower into the early overnight, especially western sections early this evening. Srn third to half of the CWA remains in a Marginal outlook for severe thunderstorms through this evening. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
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Broad cyclonic/west-northwest flow on southern end of exiting upper trough will support terrain-enhanced showers on Friday before precip winds down Friday night/AM Saturday.
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&& .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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A lower-amplitude but moderately strong westerly (zonal) mid level flow will set up in the wake of the departing upper trough with modest height rises/weak will ridging aloft into the weekend. A warm front is progged to extend east from surface low in the western Ohio Valley to the mid-Atlantic coast on Saturday. Central PA should reside on the north/east fringe of high instability convective corridor/MCS type pattern expected to evolve from the central and southern Plains to the southern mid- Atlantic coast into Saturday night. The greatest risk for scattered thunderstorms remains over the SW 1/3 of the CWA which is consistent with previous fcsts. SPC has introduced a MRGL risk into this area for D3. The remainder of the area should see a mainly dry start to the holiday weekend but will maintain slight chance POPs. The large scale pattern will evolve into a broadly cyclonic flow regime by Monday with upper trough parked over the Great Lakes and southeast Canada into midweek. The aforementioned warm front will lift north across the area on Sunday followed by a series of weaker cold front associated with shortwave trough rotating around parent upper low centered to the south of Hudson Bay. Ensemble blend still supports max POPs on Sunday/Sunday night into Monday with some additional shower opportunities into midweek as series of shortwaves rotate around mean upper trough. Temps should average pretty close to normal/seasonal to close out the month of May.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... Primary surface low pressure (995 mb) was located over Ohio early this afternoon and is nearly stacked with its parent upper low. A few disturbances rotating around its base will lift northeast twd Pennsylvania last this afternoon and evening...returning a couple of rounds of showers (and isolated-sct TSRA across the SW third- half of the state after 20Z). Widespread IFR/low MVFR cigs will continue across Central Pa and the Susq Valley through the mid-late afternoon, with gradual improvement across at least the western TAF sites as an Occluded front lifts NE across that region with some drier air aloft in its wake along with a gradual veering of the wind to the southwest, then west at KJST,KAOO KUNV and KBFD late this afternoon and this evening. The drying aloft, and some breaks in the dual-multi layered cloud deck, will help to create some MDT instability for the chc of a TSRA. Mentioned VCTS at KJST, KAOO and KUNV, in the 21Z-00Z period. MVFR to IFR cigs will likely linger in many locations tonight with vsbys dipping back to MVFR at most TAF sites. Cooler air advecting in aloft, combined with deep moisture and a favorable westerly upslope component over the Western Mtns and Laurel Highlands will lead to periods of LIFR/VLIFR cigs and IFR to ocnl LIFR vsbys at KJST and KBFD. Across eastern Pa, light wind, wet ground and light winds could result in areas of LIFR fog forming late tonight. After some areas of low cigs and fog early in the day Friday, the afternoon will feature mainly vfr cigs with brief mvfr to ifr cigs and vsbys in isolated-scattered showers...mainly after 16Z. Moist WNW upslope flow continues across the western mtns with the best potential for IFR in sctd showers. .OUTLOOK... Fri...AM low cigs/showers likely BFD/JST. Sat...AM fog possible BFD. Sun...Showers/reduced cigs possible, esp Sun night. Mon and Tue...AM low cigs poss west. Sct PM tsra impacts poss east. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Gartner NEAR TERM...Gartner/Steinbugl SHORT TERM...Steinbugl LONG TERM...RXR/Steinbugl AVIATION...Lambert

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