608 FXUS61 KCTP 160535 AFDCTP Area Forecast Discussion National Weather Service State College PA 135 AM EDT Thu May 16 2024 .SYNOPSIS... * Mostly rain-free and seasonably warm weather Thursday into Friday with patchy fog overnight. * Wet, cloudy, and cool conditions return for Saturday, as has become tradition. * Trending warmer and dry early next week with showers and storms making a comeback by midweek. && .NEAR TERM /UNTIL 10 AM THIS MORNING/... A stationary boundary is draped across eastern Ohio, northwest PA, and upstate New York this evening and is focusing a band of showers along its axis. SPC Mesoanalysis indicates 100 to 250 J/kg of MUCAPE in northwest PA will dissipate over the next few hours, which will correspond with showers tapering off by midnight (if not sooner). The main forecast problem tonight is how much clearing builds in and subsequently how much fog develops. The boundary layer is sufficiently moist area wide and winds will go virtually calm, so any clearing will almost certainly result in patchy fog formation. Latest hi-resolution guidance indicates clouds may stay in place across southeast PA closer to the parent surface low and lingering cloudiness is expected near the aforementioned stationary boundary. The sweet spot for fog may end up being across the central mountains region. A safe bet seems to be including patchy fog potential for most locations outside of the Lower Susquehanna Valley owing to either radiational fog development OR persistent low clouds at higher elevations. Lows by daybreak will generally be in the 50-55 range for most locales. As discussed previously, the cloud cover forecast looms large in determining how cold it gets tonight. If clouds do clear out, isolated minimum temperatures dipping into the 40s are not out of the question. && .SHORT TERM /10 AM THIS MORNING THROUGH FRIDAY NIGHT/... *1 dry day for most on Thursday before cloudy/wet pattern resumes Friday Areas of low clouds and fog are likely to persist through Thursday morning before breaking for some sunshine through the afternoon. Fair weather cumulus will be abundant across Central PA later in the afternoon. Ridging, particularly aloft to the west of a stacked low offshore the Mid Atlantic coast, combined with lower PW air directed into the region via northerly low level flow favors decreasing/lower POPs and a welcomed dry day for most locations. Hires model data does suggest a stray diurnal/instability or terrain induced rain shower or t-storm cannot be ruled out, especially along and west of the Allegheny Plateau tomorrow afternoon near quasi- stationary front/low level convergence zone. Highs should reach the 70-75F range across most of CPA with downside risk to hold in the 60s in the eastern portion of the Lower Susq where low clouds could hang on for most of the day nearer to the surface low pressure system. The mean low level flow turns back to the east/southeast Thursday night into Friday. This should result in low clouds, patchy fog and a relatively mild Thursday night into Friday AM before a cloudy and slightly cooler end to the week. Large scale forcing downstream of mid/upper trough moving into the Ohio Valley combined with building instability banked along and west of the Alleghenies favors highest POPs across the western and southwestern portions of the CWA Fri- Friday night. Consensus of guidance brings showers and storms to western PA early Friday afternoon and the rest of the Commonwealth during the afternoon and evening. Lows continue to trend above mid- May climo in the 55-60F range Friday night into AM Saturday. QPF totals through Friday night (ending 12Z Saturday) range from ~0.10" in the southeast to ~0.50" across parts of the western mtns. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... *Cloudy & wet start to the weekend; marginal improvement Sunday *Drying trend with more sun and warmer temperatures Mon-Tue Low pressure tracking to the south of PA combined with plenty of easterly flow will translate into another cloudy and wet Saturday with highs in the 60s. The cold air damming pattern presents high confidence in temperatures ending up lower than guidance, and highs in the upper 50s to low 60s may be a more reasonable expectation for what feels like an unending stretch of miserable Saturdays in Central PA. The departing low will slowly exit stage right as high pressure builds into the area. This will mean low clouds likely stick around early Sunday, but conditions should gradually improve/dry out by Sunday night into Monday. Highest uncertainty in the forecast at this time is if Sunday stays cloudy/cool/rainy or if a bit of sunshine can peek through and help temperatures rebound to seasonable levels. Regardless of the details, POPs will trend lower through the weekend and highs will recover by at least 5 to 10F on Sunday compared to Monday. Decent model and ensemble signal for dry wx and more sunshine leading to seasonal warming trend next Monday-Wednesday as a potential cutoff low parks over the Carolinas and high pressure builds overhead. Max temps are forecast to climb back into the 75-85F range. We have the greatest confidence for 2 consecutive dry days (Mon & Tue) with the next frontal system projected to arrive around midweek. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... It is a tricky overnight for aviation forecasting. We're seeing fog form quickly where skies are clearing, but there are patches of 3-5 kft cigs drifting across Central PA that are temporarily working against the formation of fog. It looks like IFR vsbys/cigs should eventually win out across much of the central mtns (AOO, UNV, IPT) and the western highlands (JST, BFD). However, the Lower Susq Valley may see just enough of a northerly sfc breeze to inhibit the formation of fog, and have kept them VFR through the TAF period. Model guidance indicates any fog will mix out 12Z-14Z. Confidence in VFR conditions is high for most of the region the remainder of Thursday. However, can't completely rule out (30-50% chc) lingering MVFR stratocu over NW PA (KBFD) into this aftn. Outlook... Fri...AM fog possible Central Mtns. Otherwise, becoming VFR. PM showers/reductions possible western half of PA. Sat...Rain/low cigs likely, esp in the morning. Low cigs could linger over the Laurel Highlands into the evening. Sun...AM low cigs possible. Mon...Patchy AM valley fog possible. Otherwise, becoming VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Banghoff NEAR TERM...Banghoff SHORT TERM...Steinbugl/Banghoff LONG TERM...Steinbugl/Banghoff AVIATION...Evanego