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Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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684 FXUS61 KCTP 270746 AFDCTP Area Forecast Discussion National Weather Service State College PA 346 AM EDT Thu Jun 27 2024 .SYNOPSIS... *Showers and thunderstorms with locally heavy rainfall will settle southward to the Mason Dixon line by midnight. *Partly to mostly sunny and less humid Thursday and Friday *Return of summertime heat+humidity will fuel thunderstorms for the last weekend of June; seasonably cooler & dry start to July && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 5H trough axis moving into central PA late this evening with good dry punch reaching into western PA and 40+ kt 850 mb jet driving sfc cold front across the region. Fairly long lived MCV tracked across the Pittsburgh metro area into the Laurel Highlands through the mid evening hours producing persistent velocity couplets and a developing linear squall line that has pushes into the South Central Mountains by 02z. Some discreet cells ahead and south of the aforementioned convective line have also been producing locally strong wind gusts, and we`ll continue to watch these marginally severe storms for the next few hours until they clear southern and southeast portions of the Lower Susq River Valley by 06z. Earlier question about how much recovery would occur over southern half of central PA has been answered, with the consensus winning out that it would be hard to destablize sufficiently to support widespread severe convection. Still, marginal cells and bowing line segments will still be watched as the 40+ kt 850 mb jet drives the cold front southeastward through 06z, producing heavy downpours, wind gusts over 40 mph in areas and still the threat of isolated damaging wind gusts. Showers and isold tsra should move through southern PA through late tonight with decreasing activity after midnight. Even with the heavy downpours, the rest of tonight`s rainfall falls into the beneficial category for central and south central PA where many areas throughout the southern tier have been bone dry in recent weeks. Thus, runoff and flash flooding concerns are very low. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/... Large scale subsidence and the arrival of much drier (less humid) air behind the exiting cold front will lead to fair and seasonable conditions Thursday. Surface high pressure building over the region should result in fair and cool weather Thu night with valley fog formation likely given air/water spreads 20-30 degrees. Partly cloudy and slightly warmer conditions are likely Friday, as low pwats persist over PA and a return southerly flow develops as the surface high passes off the coast. Latest model data suggests some showers and storms may develop Friday night over the western portion of the forecast area. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Latest medium range guidance is showing an unusual lack of spread among its members, all of which track a surface low north of PA Saturday, with a trailing cold front coming through Sat night into early Sunday. The lack of spread with regards to timing of the front, combined with progged GEFS pwats of +2-3SD, supports an increasing confidence in showers/tsra Saturday. A leading warm front could produce showers/tsra as early as Friday night and a slowing cold front could cause convection to linger into Sunday, mainly over the southeast counties. However, ensemble plumes indicate the most widespread convection should occur Sat afternoon and evening. There is some potential for severe wx Saturday PM, as decent mid level flow overspreads an increasingly moist warm sector. Ensemble plumes currently indicate moderate CAPE in the 1000 J/kg range and model 0-6km shear is in the 35-40kt range. If the cold front slows enough, severe wx would also be possible across the eastern edge of the forecast area Sunday PM. Latest EPS and GEFS both support fair weather with near to slightly below normal temps and low humidity early next week associated with high pressure building east from the Grt Lks. A seasonably cool and dry start to July! && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Widespread low stratus has developed across northwestern PA including the Alleghenies. IFR conds are likely at BFD and JST, with LIFR possible between 09z and sunrise. Downslope flow and some wind will probably keep IPT/UNV/AOO from getting as bad (low) of conditions overnight. But, some IFR is possible at those locations, too (less than a 50% chc), and fog can not be ruled out at MDT and LNS if the midlevel clouds move out before sunrise. All TAF sites will be VFR by mid morning Thursday. Winds will remain from the NW with gusts generally less than 20 kts. Outlook... Fri...Generally VFR. Sat-Sun...Thunderstorm impacts possible. Mon...Generally VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Steinbugl NEAR TERM...DeVoir/Steinbugl SHORT TERM...Lambert/DeVoir/Fitzgerald/Steinbugl LONG TERM...DeVoir/Steinbugl AVIATION...Dangelo/Colbert