Area Forecast Discussion
Issued by NWS State College, PA

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950 FXUS61 KCTP 260839 AFDCTP Area Forecast Discussion National Weather Service State College PA 439 AM EDT Sat May 26 2018 .SYNOPSIS... Summer-like warmth and humidity is in store for the Memorial Day holiday weekend as the Bermuda high sets up off the East Coast. The influx of humidity will lead to an almost-daily chance for showers and thunderstorms, especially across the southern half of the state. The moisture from Subtropical Storm Alberto could affect the region toward the end of next week. && .NEAR TERM /THROUGH TONIGHT/... A small but intrepid cluster of showers and the thunderstorms is trekking ENE out of the Laurels. Meso anal shows some moisture convergence and some small measure of elevated instability, but a large scale feature driving these storms is hard to find so confidence in how far east they can manage to go before pooping out is low. The latest HRRR tracks them across about the southern half of the CWA through dawn so I adjusted the near term POPs to account for this. Once we are done with the nocturnal convection, the day should start dry in most areas before we start to deal with more general pop-up convection with the afternoon heating. The SREF is characteristically very wet for the second half of the day, as is the GFS MOS. I used the blended MOS which shows the best chance of a shower/storm over the Mason-Dixon line counties with lesser chances over central and northern areas. Hard to get much more excited than that given the weak forcing aloft. Highs will be in the 80s region-wide, and we could scrape 90 over the SE. Dewpoints will start to creep into the noticeable range to make the first weekend of the traditional summer feel the part. A dying shortwave will move through the state overnight with more scattered showers and thunderstorms. One flavor of the SPC HREF shows a fairly significant MCS moving across, but the bulk of the guidance is less organized so I kept with the idea of mainly disorganized convection. Temperatures and dewpoints in the 60s overnight will feel rather clammy. && .SHORT TERM /SUNDAY/... Sunday will be another warm and humid day with convection tending to cook up with afternoon heating. With rising upper heights and weak warm advection aloft, I once again wonder if the model POPs are a tad high. However with cyclonic flow aloft and PWATs on the order of +1 to 3 sigma, it does seem likely that showers and storms will impact at least some outdoor holiday activities. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... While a pop-up shower or thunderstorm cannot be ruled out, Monday and Tuesday look relatively dry as we come under an elongated ridge aloft that will connect from the upper Midwest to the off the eastern seaboard. By Wednesday a deep southerly flow becomes established as the remnants of Alberto get pushed north on the western periphery of the Bermuda ridge. GEFS shows PWATs surging back to +2 to 3 sigma Wednesday night into Thursday. If such a scenario plays out, we could see tropical downpours as Alberto gets absorbed into the upper trough that will be approaching from the Midwest. Overall the upcoming week looks to be warmer than normal and it will be on the humid side. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... A few showers over southwestern PA and western MD as of 1 AM. 06Z TAFS sent. Earlier discussion below. VFR will continue with only some widely scattered valley fog. Have mentioned VCSH at JST for part of overnight as showers creep northeastward along the western front. Otherwise the sky will stay mostly clear. High pressure offshore will pump the temps and humidity up Sat and Sun. The likelihood of TS/SHRA increases on Sat and Sun. The more-likely places will be the southern half of the state. But, a stray shower is still possible in the north. Timing the convection will be difficult without a clear forcing mechanism, so scattered VCSH for the later afternoon hours in many TAFs which can be refined moving forward. Outlook... Sun-Wed...Mainly VFR with scattered showers/thunderstorms. && .CLIMATE... It has been a wet May across much of the region. As of Midnight, Williamsport rainfall for the month has been 7.05 inches. This is the 6th wettest May on record, and we still have a few days to add to the total. The wettest May was 1919 with 9.91 inches of rainfall. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...La Corte AVIATION...Martin/RXR CLIMATE...

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