Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 300310 AFDCTP Area Forecast Discussion National Weather Service State College PA 1110 PM EDT Mon May 29 2017 .SYNOPSIS... A cold front over eastern PA will weaken and dissipate overnight. Another cold front will push toward the region Tuesday. Low pressure at the surface and aloft will stay centered near James Bay Canada through the rest of the week providing a period of slightly cooler than normal temperatures along with several chances for scattered showers and thunderstorms. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 10PM update... The meso anal shows the a weak front remaining stalled over my eastern zones extending from just west of IPT south to around Camp David MD. The low clouds and cooler marine air remain entrenched over the eastern zones. The HRRR suggests this boundary could even slide a bit to the west over the next few hours before washing out altogether in the strengthening SW flow after midnight. Upstream convection embedded in the broad cyclonic flow aloft could sneak a few showers/isolated thunderstorms into my western and northern zones overnight, but the majority of the region will remain dry and mild. Lows will average about 5-10 deg above normal. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Brief ridging will allow any popcorn sprinkles and light showers to clear over the western two-thirds of the CWA this evening, and residual moisture may lead to areas of fog, especially in the central valleys. The low level moisture and low stratus deck AOB 1000 ft AGL will push gradually westward across the Central Mtns and West Br Susq Valley and stay intact through early Tuesday. Mins tonight will dip into the 50s for most, as the dewpoints will be the bottom limit. A separate, weak sfc trough will be pushed into the area from the northwest tonight. 8H temps fall a bit over the NW. Heights fall just a little, too, so some precip is possible before sunrise Tuesday over the northwestern third of the area, but it should be light. The trough begins to catch the stalled trough over the eastern counties. The southerly or southeasterly wind will yield good convergence and will crank up some showers and thunderstorms. Have painted high POPs for the area, but the amount/severity of destabilization is in question with the clouds in the NE early in the day. NAM cranks out 1500joules of CAPE and LI drops to -2 or so in the mid-day and aftn on Tues. SPC marginal Risk of svr wx for Day 2 (Tues) is painted across our eastern half, focused on the peak heating time. Will continue to mention this in the HWO. Max temps across the region will range through the 70s, with the warmest readings once again in the scent mtns where 78-80F readings should occur. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... The long term period begins with a good consensus on the location and shape of the large upper level low over southern Canada. That low will dominate the weather pattern this week into next. As the low rotates it will bring successive short and long wave troughs through the Mid Atlantic region. These troughs will bring the possibility of precipitation, mainly Wednesday and Friday afternoon. This upper level low will also bring cooler northwesterly flow into central PA. That flow should keep temperatures around, to slightly below, normal. The next chance for significant precipitation will be Friday night into Saturday as that upper level low progresses eastward. The models begin to diverge on the position, timing and strength of the system. This decreases confidence. However, all models show a boundary that should set up through the keystone state. The main question is when will it progress through and how much moisture will be available for QPF when the corresponding cold front moves through Saturday. Current GFS brings precipitation through Saturday where the EC brings largest QPF Sunday. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... Some minor adjustments to 03Z TAFS. Activity to the southeast is south of our area, and showers to the west are weakening. Left shower out of BFD, that area north of PA now. For 00Z TAF package, did add brief tempo group for fog at UNV, AOO, and BFD, given wet ground. I did not make it too long, given short nights. Far eastern areas will likely see MVFR and IFR conditions tonight into Tuesday, given easterly flow. For Tuesday, expect most of the area to be VFR. For now, went with VCSH instead of any significant time or point with showers and storms. Dewpoints not real high, much lower than yesterday, and low level flow not real strong, hard to see much in the way of widespread storms with low CIGS etc. Best chance for a dry day will be Thursday. .OUTLOOK... Wed...Chance of showers. Thu...No sig wx expected. Fri...Chance of showers and thunderstorms. Sat...Still a chance of showers and thunderstorms. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Lambert LONG TERM...Ceru/Martin AVIATION...Martin

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