Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 281150 AFDCTP Area Forecast Discussion National Weather Service State College PA 750 AM EDT SUN AUG 28 2016 .SYNOPSIS... A warm front over western Pennsylvania will push east into the region this morning...followed by the passage of a weak cold front tonight and Monday morning. This pair of frontal systems will bring scattered showers and thunderstorms to mainly the northwest half of the state this afternoon and tonight. Another period of warmer than normal and mainly dry weather will follow for Monday into early Wednesday. A stronger cold front will move southeast across the commonwealth Wednesday followed by a refreshingly cooler airmass with low humidity Thursday through Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Tranquil conditions prevail across the region early this morning with moderate sfc dewpoints in the low-mid 60s and just some areas of mid and high clouds (mainly across the northwest third of the state. The current sfc dewpoints will mark the low temp in many locations. Some locations across the northern mtns could see some localized low clouds and patchy fog for an hour or two around sunrise. A few stray showers could brush the far nw zones during the mid to late morning hours thanks to the combination of the warm front over that region (and enhanced uvvel over the boundary) and theta-e advection focused near the nose of a 30 kt swrly LLJ. Will have to monitor the situation for potential isolated...strong to svr tsra across the central and nrn mtns of the state this afternoon and early evening. Very warm air aloft (8-9C at 700 mb) during the day today may make it hard to fire up many showers or storms. However...a ribbon of 1.5-2 inch PWAT air...the approaching warm/cold frontal tandem...and an elongated mid/upper shear axis will combine to bring a band of 1500-2500 j/kg sfc-based cape and sfc-6km wsw bulk shear of around 25-30 kts across NW PA later today and this evening. SPC has expanded their Marginal Risk for SVR slightly south and east today to cover practically all of the nrn mtns...and a smaller portion of the central mtns today...within the fairly narrow warm sector. Gusty (and highly localized damaging) westerly winds will accompany some of the stronger storms in the 18Z Sunday - 01Z Monday period in the MRGL Risk area. Above normal temps will continue today with similar maxes (or perhaps just a few deg f lower than Sat`s across the Susq Valley). Highs expected to range from the mid 80s (mtns) to near 90F in the Lower Susq Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... The weak cold front slowly sags SE through the state tonight and Monday. Best LLVL forcing/warm advection and cyclonic/convergence LL flow (via a 1-2 sigma 850 mb jet) will move off to the north of PA by tonight. This (along with increasing blyr stability) will support a quickly diminishing threat for showers/tsra after 03Z Monday. Close proximity of the front near or just south of the Mason/Dixon Line Monday afternoon and the tail end (RR Quad) of an 80-90kt upper jet will provide ample llvl convergence and broad, gentle uvvel aloft to produce isolate shra and tsra Monday afternoon in far souther PA. Lows tonight will range through the 60s, and high temps Monday will vary from near 80F across the NW Mtns, to near 90F in the southern valleys. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... The extended period looks like it will feature a transition from a persistent upper-level ridge over the eastern United States to a weak upper-level trough by mid to late week. As a result, above-normal temperatures through the Tuesday-Wednesday timeframe will transition to near or a little below normal by the end of the period. A weakening cold front will push slowly SE through the Commonwealth tonight and early Monday Sunday night into Monday morning accompanied by isolated to scattered showers/thunderstorms. The frontal boundary is expected to wash out near or just south of the Mason/Dixon line during the day Monday. Abundant low-level moisture, mesoscale convergence and some orographic lift/heating via the east to NE low level flow regime across the mountains of SW PA will focus the best chance for showers and scattered thunderstorms there Monday afternoon. Monday night through Wed morning looks to be dry with generally light wind and just the possibility of patchy early morning valley fog. Medium range guidance agrees with a second-stronger cold front pushing SE across the area Wednesday afternoon or early Thursday, with a renewed chance for showers and thunderstorms. This front will be followed by a cool-down for the end of next week. Max temps should be mainly in the 70s Thursday into the weekend over the northern and western higher terrain, with low to mid 80s elsewhere as an upper trough amplifies from central Quebec...to the Mid Atlantic Piedmont. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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Local visibility restrictions in BR/FG will give way to VFR by 13z. Scattered TS are forecast to develop across the NW 1/2 of the airspace this afternoon ahead of a weak boundary pushing southeast from the Lower Great Lakes. Showers may continue along the boundary into the evening as it sinks southward toward the MD border. Light winds and high boundary layer moisture could result in some low cigs and fog after midnight into early Monday morning. Outlook... Mon...VFR. Isold PM TS possible southern 1/4 airspace. Tue...Patchy AM fog, then VFR. Wed...Sct PM TS impacts possible. Thu...No sig wx expected.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Watson/Lambert/Martin LONG TERM...La Corte/Lambert AVIATION...Steinbugl

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