####018006029#### FXUS61 KCTP 040653 AFDCTP Area Forecast Discussion National Weather Service State College PA 253 AM EDT Sat May 4 2024 .SYNOPSIS... -Noticeable cool down over the weekend with overcast skies and periods of rain -Remaining unsettled next week with a gradual warming trend && .NEAR TERM /THROUGH TODAY/... Radar loop at 03Z shows dwindling, diurnally-driven convection over the NW Mtns. The focus for the rest of the night shifts to the potential of additional showers linked to a mid level vort max lifting into Southwest PA from the Ohio Valley. Surging pwats, combined with the arrival of this feature will bring an increased chance of showers over primarily the southwest portion of the forecast area late tonight. An increasingly moist east/southeast flow off of the Atlantic, combined with upslope flow, will likely yield developing stratus along the spine of the Appalachians late tonight. Low temps will be above early May climo and range between 45-55F from the southwestern Poconos/Coal Region to Warren County. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... Model guidance supports developing rain Saturday across Central PA from south to north ahead of an upper level shortwave lifting out of the Tennessee Valley. The associated southerly low level jet and plume of higher pwats overrunning a dome of cool/stable air across Central PA should result scattered showers giving way to a steady rain early Sat morning over the southern tier counties and by late in the day over the northern tier. The upper level shortwave should begin to lift out of the area Sunday, resulting in rain tapering off from west to east. Scattered late day convection appears possible late Sunday over the Allegheny Plateaus associated with an approaching warm front over Western PA. Ensemble plumes support rain totals by late Sunday in the 0.5 to 0.75 inch range for most of the area. Hires models show CAD pattern firmly entrenched over CPA Saturday, and therefore we continued to trim max temps vs. NBM, due to thick cloud cover, easterly flow and arriving rain. We have blended the cooler NAM surface temps with those of the NBM, resulting in expected max temps in the mid to low 50s for much of the area. No risk of thunder on Saturday, so removed from wx grids and changed character of precip to rain from showers. Sunday looks to be another cool day for May, due to a persistent southeast flow off of the Atlantic. However, a slight rebound is expected over the western counties, due to rain tapering off the chance for a bit of afternoon brightening. Subsidence behind the departing shortwave should result in a mainly rain-free Sunday night. However, a lingering upsloping southeast flow will likely yield lingering low clouds/patchy drizzle. Fcst lows Sunday night are +10-15F above climo for early May in the 50-60F range. && .LONG TERM /MONDAY THROUGH FRIDAY/... Monday should feature much warmer and drier weather, as high pressure builds southeast from the Grt Lks behind a Sunday night cold/occluded front passage. However, the approach of an upper level shortwave appears likely to produce scattered PM convection in the vicinity of the stalled front along the Mason Dixon Line. Highest POPs are placed over the southern tier, with only slight chc POPs across the north. The return of sunshine and 850mb temps near 12C translates to expected highs in the 70s most places. Upper level ridging over PA indicates warm and generally dry conditions are likely Tuesday. However, a warm front lifting out of the Ohio Valley could result in increasing clouds with a PM shower/tsra, primarily across the southwest counties. The bulk of medium range guidance supports a very warm Wednesday with scattered convection, as the area briefly breaks into the warm sector ahead of a cold front pushing in from the Grt Lks. Model consensus supports a better chance for a more widespread rainfall Thursday, associated with a deepening upstream trough and wave of low pressure riding along the stalled cold front just south of PA. The surface low and deepest moisture is progged to shift east of the area by Thursday night. However, falling heights ahead of the upper trough will likely support scattered, diurnally-driven convection Friday, along with a downward trend in temperatures. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... As of 0630 UTC Sat, MVFR cigs have moved into the Laurels (JST and AOO) as well as portions of south central PA (CXY and THV). The low cigs will continue to expand over the next several hours, with the remaining TAF sites likely dropping to MVFR or lower by daybreak. Confidence in MVFR cigs after 11z is lowest at LNS, where much of the hires guidance shows LNS on the eastern periphery of the MVFR cloud deck. IFR conds are likely to develop first across the western airfields (BFD, JST, and AOO between 10z and 15z Sat) and then expand eastward through the day. Confidence is low in the exact timing of the low cigs. Periods of light rain will continue through the day. Southeast winds of 5-15 kts will continue through the TAF period, with gusts up to 25 kts. LLWS may become a concern from 00z-18z Sun as a southerly LLJ develops with 2kft winds 35-45 kts, strongest through north central PA. The LLJ will also produce the most widespread and heaviest rainfall during this period. Outlook... Sun...Widespread restrictions due to low cigs. SHRA likely with a slight chance of TSRA. Areas of fog poss Sun night. Mon-Wed...AM fog/clouds poss. PM -SHRA possible areawide. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl/Bowen NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Bowen LONG TERM...Fitzgerald AVIATION...Colbert/NPB