Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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349 FXUS61 KCTP 180913 AFDCTP Area Forecast Discussion National Weather Service State College PA 513 AM EDT Thu Jul 18 2024 .SYNOPSIS... - The cold front will continue to trek across central PA tonight along with a band of mainly stratiform rain showers. - Patchy fog is possible tonight mainly across the NW mountains and Allegheny Front. - High pressure will build in from the Great Lakes on Thursday and bring mainly fair weather with seasonable temperatures through the end of the week. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... A cold front, which lies across the N Mtns at 07Z, will press southeast across the forecast area early this morning. There is strong large scale forcing ahead of the associated upper trough. However, SPC mesoanalysis indicates virtually no instability, so expect nothing more than an isolated shower across the southern half of the forecast area during the pre-dawn hours. Valley fog appears likely to remain confined to the Alleghenies, with a decent pressure gradient keeping breeze up further south and east. Temperatures are on track to bottom out from the mid 50s in the coolest valleys of the NW Mtns, to around 70F across the Lower Susq Valley. && .SHORT TERM /8 AM THIS MORNING THROUGH FRIDAY NIGHT/... The cold front is progged to exit the southeast corner of the forecast area by noon, with a much drier northwest flow ensuring fair weather the rest of the day. Upstream satellite imagery and model soundings indicate cirrus will continue to stream into PA ahead of the upper trough approaching from the Grt Lks. Therefore, partly sunny wording should suffice for most of the region. Model soundings indicate mixing this afternoon to 800mb, where model temps support highs from the mid 70s across the N Mtns, to the mid and upper 80s in the Lower Susq Valley. A bit of high cloudiness could linger into this evening over the eastern counties, then mainly clear skies are anticipated with the passage of the upper trough. The arrival of surface ridging and an associated low-pwat airmass should result in the coolest night we have seen a quite a while. The weakest gradient and most efficient radiational cooling is anticipated over the NW Mtns, where we have slightly undercut NBM min temp guidance. Air/water temp differences of >25 degrees should result in patchy late night fog in the deep river/stream valleys of the Alleghenies. Fair and seasonable conditions with light winds are expected Friday, as high pressure ridge remains over the state. An approaching warm front is likely to spread increasing clouds into at least Southern PA Friday night, but the odds of any rain look slim. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... On Saturday, there could still be enough moisture working into the state from the south that a shower or two could develop over the SE and/or ridge-and-valley region if the ridge tops can help nudge the moisture high enough. It`s only worth a 20pct chc at this point based both on coverage and probability. This is the only mar in an otherwise stellar weekend forecast. During the early part of the new week, the humidity levels will creep back up as the deep upper low over ern Canada slides a little more to the east and the Bermuda High pushes moisture farther to the north and into the state. The stationary boundary to our south may struggle to move northward, so we`ll keep the increase in precip chances slow for the time being. Overall, we will see muggy nights again by mid week and a gradual increase in cloud cover and PoPs. By Wed, PoPs get close to 70pct. Confidence is higher than normal in the extended pattern. Of course, confidence is lower on the day- to- day details. But, normal diurnal trends in convection have been leaned on for most of the long range. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... Post cold frontal upslope IFR to LIFR CIGS and MVFR to VFR Vsbys will occur across the NW Mtns and Laurel Highlands early this morning (through 12-13Z), while generally MVFR cigs with VFR vsbys will be found across much of the Central Ridge and Valley region of the state As vertical mixing deepens around and after 13Z today, much drier air will transported from aloft will erode the clouds leaving excellent vsby and mainly varying amounts of high level, cirrus and cirrostratus clouds for the late morning and afternoon hours. SCT-BKN but shallow VFR (3500-400 FT AGL)stratocu clouds will form across the northern and western Mtns later this morning and continue this afternoon. Outlook... Fri-Mon...AM valley fog. Otherwise, no sig wx/VFR. && .CLIMATE... The max temperature hit 100 degrees at Harrisburg yesterday 7/16. The last time KMDT hit 100 was back on July 19, 2020. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Bowen NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Bowen LONG TERM...Dangelo/Gartner AVIATION...Lambert CLIMATE...Steinbugl