Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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453 FXUS61 KCTP 260107 AFDCTP Area Forecast Discussion National Weather Service State College PA 907 PM EDT Tue Jun 25 2024 .SYNOPSIS... High pressure will drift off of the Mid Atlantic Coast tonight, allowing increasing moisture to return to the region. Heat will build again by Wednesday leading to a chance of thunderstorms by late in the day and Wednesday night as a cold front pushes through the state. Dry weather with comfortable humidity on Thursday and Friday will be followed by another cold front late Saturday or early Sunday of next weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Early evening water vapor loop shows a potent shortwave tracking well north of PA through the St Lawrence Valley. Visible satellite loop at 00Z shows cumulus with decent vertical development along the trailing low level jet from KERI to KBUF. Warm advection along this feature could potentially produce a shower/tsra across the NW Mtns late this evening. Otherwise, tonight looks quiet with varying amounts of mid and high level cloudiness overspreading the state ahead of an upstream trough over the Plains. An active southwest breeze will draw steadily rising dewpoints into the region tonight, resulting in much warmer conditions than last night. See no reason to deviate from NBM mintemp, which range from the mid 60s over the NW Mtns, to the low 70s in the Lower Susq Valley. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY NIGHT/... Diurnal heating of an increasingly moist/unstable airmass, combined with falling heights ahead of the upstream trough, will result in developing convection during Wed afternoon. A ribbon of relatively strong mid level winds of 40-50kts, combined with progged moderate instability across Central and Southern PA, suggests organized convection and locally severe weather can be expected across this part of the state Wed PM. Some of the latest model guidance suggests an eastward-moving MCV could result in a batch of strong-severe convection across Southern PA in the 16Z-21Z time-frame, with diminished potential in the rain-cooled air behind it. However, wouldn`t place too much weight on this right now, as the strongest shear should be in the late afternoon to early evening timeframe. Some of the 12Z HREF members indicate UH values >150 across Southern PA in the early evening, which is supportive of supercells. Latest ensemble plumes indicates most likely aerial average rainfall Wed PM will be around a half inch. However, isolated amounts around 2 inches appear likely based on the latest HREF and a combination of moderate instability and +1-2SD pwats. Thicker clouds will likely cap temps to the upper 70s across the NW Mtns Wed, while a decent amount of sun is anticipated across the southeast counties based on model RH profiles. 850mb temps support highs as warm as the low 90s across the Lower Susq Valley. The combination of heat and humidity should result in heat indices peaking in the mid 90s in that part of the state. Dwindling convection from northwest to southeast is anticipated Wed night, as the upper trough and associated cold front work through. Large scale subsidence and the arrival of much drier air behind the exiting cold front should then result in fair and seasonable conditions Thursday. Surface high pressure building over the region should result in fair and cool weather Thu night. Fair 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. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Predictability begins to wane by this weekend regarding the timing/amplitude of the shortwave trough expected to move from the Great Lakes region into the Northeast/New England. There is some potential for stronger deep-layer flow to overspread an increasingly moist warm sector, but details regarding the surface pattern remain uncertain, and rather warm temperatures aloft could limit destabilization potential. Some potential for strong to locally severe storms could evolve on Saturday ahead of a cold front from the Ohio Valley into parts of the Northeast. WPC has also suggested the potential for a marginal to slight risk of locally heavy/excessive rainfall on Saturday with pwats surging to +2SD above normal. The timing of the main synoptic cold front on Sunday is also uncertain with some potential for a secondary strong/svr tstm risk. Confidence is significantly higher concerning the arrival of another refreshing Canadian high pressure system directing a comfortable (less humid) airmass into CPA for early next week...a seasonably cool and dry start to July! && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... High confidence in VFR flying through the evening into the first half of tonight/06Z Wed. Uncertainty ramps up overnight into early Wednesday morning with potential for showers and t-storms moving into the airspace from the north/west. Can`t rule out some cig restrictions in the 06-15Z window based on the latest probabilistic guidance, but the overall pattern/low level flow don`t provide a strong enough signal to maintain in TAFs outside of KBFD. A 40kt low level jet from 230-260 degrees will maintain LLWS at KBFD between 00-06Z. There remains some timing uncertainty for the widespread convection expected to initiate on Wednesday. Showers are likely to begin kicking up before 18Z in western PA before overspreading to the east and strengthening through the afternoon. A few of these storms could be strong to severe with any impacted TAF site likely to see high wind gusts and low visibility. The best chance for strong storms will be between 18Z Wednesday and 00Z Thursday. Outlook... Wed...Thunderstorm impacts likely. Thu-Fri...Generally VFR. Sat-Sun...Thunderstorm impacts possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/DeVoir NEAR TERM...Fitzgerald SHORT TERM...DeVoir/Fitzgerald LONG TERM...Banghoff AVIATION...Steinbugl/Bowen