435 FXUS61 KCTP 300127 AFDCTP Area Forecast Discussion National Weather Service State College PA 927 PM EDT Sun Oct 29 2023 .SYNOPSIS... Low pressure over the Ohio Valley will track south of Pennsylvania tonight into early Monday. Surface ridging will briefly build into the area Monday night and Tuesday, then a cold front will sweep across the region Tuesday night, with upper level troughing lingering over Pennsylvania into Wednesday. High pressure over the Midwest is then expected to build into the east coast by late next week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Central PA is in a lull in the rain late this evening between one wave of low pressure, which is pushing off of the Mid Atlantic coast, and another approaching from the Ohio Valley. However, plenty of low level moisture and an upsloping easterly flow is resulting in areas of drizzle and ridgetop fog. Increasing isentropic lift ahead of the approaching low will lead to rain spreading back into Central PA late tonight/Monday morning. Multi model and EFS mean additional QPF is between 0.25 and 0.50, focused mainly across Central and Northern PA, with the southern tier likely receiving near or just under 0.25 inch as a result of the low pressure center passing nearly right over southern PA. Nearly steady temps are expected overnight, with lows ranging from the low 40s over the N Mtns to the mid 50s in the south. Widespread ridge shrouding fog (near the base of the strong llvl inversion related to the shallow cool airmass that has advected into the region) could impact travel where roads cross the higher terrain. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... The steady rain should taper off by around midday Monday, as the the second wave of low pressure passes east of the state. However, fgen forcing beneath the right entrance of a jet streak over the Grt Lks appears likely to keep skies mainly cloudy with lingering afternoon showers focused primarily where the northwest flow is forced over the Allegheny Plateau. Deepening cold air advection then starts in earnest by Monday afternoon and spreads the much colder air over the Great Lakes across PA through the aftn and evening. The arriving airmass should be cold enough to generate lake effect Monday night. However, surface ridging and associated low inversion heights should limit activity to only scattered rain/snow showers over the NW Mtns, with little if any snow accums expected. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Skies may clear a bit later in the day on Monday, before an upper level trough lifts across the region later Tuesday. The airmass is quite cold at low levels, but time of day on Tuesday will allow for some rain to mix in. Better chance for mainly snow will be early Wed. As noted above, not the best set up for upslope, lake effect precipitation. The upper level trough shears out, instead of digging, which will limit the snow and rain. Adjusted POPS and weather some to fit in areas that normally get upslope and lake effect precipitation. After early Wednesday, looking at high pressure building in to support a west to southwest flow of moderating air into central PA into the end of the week. Next chance of showers would not be to late in the weekend. Also of concern is freezing temperatures for our southeast part of the CWA. First night of concern is Monday night, larger concern is Tuesday, Wednesday, and Thursday night. While days will moderate, nights are long, so loss of wind is the key factor. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... IFR to LIFR conditions will affect central Pennsylvania through the night and into the first half of Mon 30/OCT. A wave of low pressure is moving northeast along a frontal boundary that stretches right across PA. Either side of this boundary will see a steady rain overnight. South of the boundary (possibly up to KAOO) will see dewpoints jump into the upper 50s. As the wave slides northeast of the area later Monday AM, cold air advection will help conditions improve through MVFR to VFR on an increasingly gusty northwest wind. Gusts should reach 20-25kts through the afternoon hours Monday. There may be an isolated -SHSN over the far northwest (KBFD) by the end of the forecast period. Outlook... Tue...Evening rain/low cigs poss SE PA. MVFR with scattered snow showers over the Northern and Western Mtns. Wed...AM low cigs possible W Mtns and SE PA. && .CLIMATE... The high temperature at Harrisburg on Saturday was 81F. This broke the record high for the day of 80F which was set back in 1984. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Lambert/Fitzgerald LONG TERM...Martin AVIATION...Tyburski CLIMATE...