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Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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918 FXUS61 KCTP 270208 AFDCTP Area Forecast Discussion National Weather Service State College PA 1008 PM EDT Wed Jun 26 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 THURSDAY 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 gustts. 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 THURSDAY 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 capes 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 /02Z THURSDAY THROUGH MONDAY/... Storms that moved across northern and central sections of the state have exited to the east. However, southern PA is still relatively unstable and additional storms are moving through PIT now and LBE soon. The storms are expected to hold together at least until they get into JST and perhaps AOO. The wind gusts across the PIT metro area are into the 30s and 40s. So, we have pegged the gusts at 35KT at PBZ for 1 hr (roughly 02-03Z) and 25KT about an hour later at AOO. These storms could weaken some as they move to the east, but will hold together until they get close to MDT/LNS. Winds behind the storms will get light over the NW and (rather widespread) fog and/or stratus is expected to develop in the Alleghenies. We have brought BFD and JST into LIFR around 06-08Z time frame, with these conditions lasting past sunrise at those sites. Downslope 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 - but only a 50% chc at this point. It has rained, but the wind won`t be as light at those 3 locations. The rain ending later at MDT and LNS will give them a 30% chc at fog bad enough to get to IFR. But, the wind/downslope will keep us from mentioning IFR at those 2 locations overnight/early AM. The wind picks up in the morning everywhere, and ends any flight category reductions at all sites, slowest over JST, of course. VFR then rules thru the end of the TAF period. 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/Fitzgerald/Steinbugl AVIATION...Dangelo