Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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970 FXUS61 KCTP 232225 AFDCTP Area Forecast Discussion National Weather Service State College PA 625 PM EDT Mon Sep 23 2024 .SYNOPSIS... An amplifying upper level trough and slow moving frontal system will bring showery conditions to Central Pennsylvania through at least Wednesday, along with a few rumbles of thunder. As such, it will be cloudy and cool through midweek. The latter part of the week looks milder with at least partial sunshine expected late this week and into the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Just a few breaks in the clouds have opened over the Laurels and Warren Co this aftn. We shouldn`t see this improvement spread much farther eastward since the flow is still E/SE in llvls and continues to be highly influential. Despite the building ridge aloft, the clouds should spread back to the west and reclaim their previously held territories. The clouds will keep the temps from going more than 5-10F lower than current values. PoPs will be in the 30-60pct range for most, mainly kept lower than categorical because the precip will be very light and disorganized. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Good surge of moisture and forcing comes across the CWA in the afternoon and evening Tuesday. Some instability will be present in the west, so the slight chc T will be retained there. SPC even touches Somerset Co with a MRGL risk of svr wx. Similarly, the ERO is also a MRGL risk - and only in Somerset Co. The showers/thunder should really not be enough to drop enough rainfall to generate flooding there since it has been so dry. The rain today (Mon) was barely enough to get water to the soils. Maxes will be just 5--8F above nighttime lows. Any breaks in the clouds in the AM will close up. Tues night is mainly rain, Basin averages thru the next 36 hrs will be 0.25-1", and will be welcome rainfall in many areas. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Model guidance outlines another surface low-pressure system tracking northeastward across the Great Lakes and into southern Ontario on Wednesday, with slightly more moisture and lift available as the warm front aligns itself north-to- south across west-central PA. Given slightly better lift with this low- pressure system overhead coupled with enhanced moisture, have retained likely PoPs on Wednesday with highest chances during the late morning to early afternoon hours. Heavy rainfall threats look less robust compared to previous forecast cycles; however, some instability will allow for thunderstorms across the Laurels, brining some potential for locally heavy rainfall, with maximum totals ~0.50" on Wed. Lingering showers across mainly E PA will continue into Thursday before a brief reprieve in rainfall Thursday evening and into Friday morning. Rainfall chances begin to increase as Friday morning progresses with the potential remnants of PTC9 approaching the area. There is still some uncertainty in regards to how PTC9 will impact central Pennsylvania, mainly dependent on interactions with a trough stationed across the eastern Tennessee Valley. At this time, deterministic model guidance shows modest agreement in the bulk of rainfall keeping south of the area; however, given uncertainty have not deviated much from NBM guidance this cycle. If precipitation manages to make way into central Pennsylvania in the Friday-Sunday timeframe, highest chances (25-35%) will be across S/W PA along the Laurels with a SChc (15-25%) progged west of the Susquehanna Valley. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... The combination of a moist southeast flow off of the Atlantic Ocean and a stalled warm front near the PA/OH border will result in persistent stratus and patchy drizzle across Central PA through Tuesday. VFR conditions are noted at 21Z at KJST in the vicinity of the warm front, where the low level flow has shifted to the west. However, models all indicate this boundary will retreat westward, with a moist southeast flow and low cigs redeveloping this evening at KJST. The passage of a weak upper level disturbance will produce a few showers across the region this evening, then the approach of a more important disturbance will spread additional showers into Western PA late Tuesday. Upsloping flow should yield the lowest cigs along the spine of the Appalachians tonight and Tuesday, where LIFR/IFR cigs are very likely based on current conditions and model output. Further east, the cigs are expected to be borderline IFR/MVFR at KIPT and trending to MVFR at KMDT/KLNS after tempo IFR conditions this evening. Outlook... Wed...Low cigs/showers likely. Improving conditions possible W Mtns Wed PM. Thu...AM low cigs/showers likely. Fri...No sig wx expected. Sat...Chance of low cigs/rain Laurel Highlands. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...NPB AVIATION...Fitzgerald