Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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823 FXUS61 KCTP 220536 AFDCTP Area Forecast Discussion National Weather Service State College PA 136 AM EDT Sun Sep 22 2024 .SYNOPSIS... A frontal system will fall apart as it moves through Central PA overnight accompanied by scattered showers and thunderstorms. Mostly cloudy, but rain- free weather returns for Sunday, before a slow-moving trough brings the next chance of rain from Monday through midweek. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Strong shortwave driving southward across the Lower Susquehanna River Valley maintaining deep convection well past the midnight hour, with marginally severe hail and wind gusts in excess of 45 kts within cells embedded within Cumberland, Dauphin, Lebanon, York and (soon to be) Adams Counties as of 0430Z. Once the aforementioned shortwave clears the PA/MD border, stable stratification arrives and activity will wind down after 06z. Heavy rain/flash flooding threat has diminished over the past 2 hours thanks to more progressive storm motion as the shortwave drops southeastward, while hail and wind gusts are still marginally severe for the next 1 to 1.5 hours. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... Forecast soundings indicate an upsloping southeast flow will result in persistent stratus and perhaps a bit of fog or drizzle over the central/east zones for Sun and Sun night. The cloud cover and flow off of the Atlantic should result in markedly cooler afternoon temps Sunday than on Saturday, with highs likely stuck in the 60s over the Central Mtns. Sun night looks mainly dry with prev anticipated forcing holding off a bit longer/later. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Surging PWATs with enhanced energy from an upper-level trough will bring about an unsettled pattern throughout much of the long-term period. Deterministic model guidance is in fairly good agreement that low-pressure stationed over the southern Great Lakes will bring about shower activity on Monday; however, model guidance has trended slower with the onset of rainfall and have chopped PoPs throughout the early period of the day as models tend to converge on a (slightly) slower progression. The best chances of showers will come across the Laurel Highlands during the late morning hours, continuing eastward throughout the afternoon/evening hours. Elevated instability will be highest across the western third of the area, so have limited mentions of storms to this area during the PM hours. Model guidance outlines another surface low-pressure system tracking northeastward across western portions of the Upper Ohio Valley and into southern Ontario Tuesday into 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 coupled with enhanced moisture, have retained likely PoPs in the Tuesday to Wednesday timeframe. Given PWATs in the 1.50-1.75" range on Wednesday, locally heavy rainfall will be possible and this has been outlined with marginal (level 1/4) risks in the D4 (W) and D5 (E) Excessive Rainfall Outlooks from the Weather Prediction Center. Impacts at this time look less likely at this time given ongoing dry conditions across especially SW PA where D2 drought conditions persist; however, any heavier rainfall in the preceding days could allow for slightly more impacts. As we shift into the later part of the week, slightly more model uncertainty with regards to low-pressure moving N/E of the area and how this will impact rainfall chances for Central PA. At this time, have capped PoPs at a chance for Thursday as the low-pressure system will be slightly closer to our eastern half, and capped at a slight chance for Friday, keeping close to NBM model guidance in this timeframe. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... 06Z TAFS sent. More in the way of weather than I expected when I came in early. Last of the storms now south of the TAF sites. Key to fcst seems to be having southeast flow of slightly higher dewpoints with a drier airmass building in from east. This happen a few weeks ago. Storms get caught in similar locations, most likely aided by terrain features. Anyway, main issue will be fog and low CIGS overnight. Expect conditions to improve during the day, but I did now bring conditions up too fast, given time of year. First day of fall today, so days are getting shorter with less intense sun to burn off fog and low clouds as fast as back in the summer. Setup for showers and storms similar to yesterday, but left mention out of the TAFS for now. Less chance today, as dewpoints fall off more. Also coverage of activity during the day time on Saturday was rather limited. Outlook... Mon-Thu...Scattered showers, restrictions possible. && .CLIMATE... The high temperature in Bradford on Friday set a new record high of 82 degrees. This broke the record of 81 degrees set in 1978 and 2016. The first day of autumn 2024 (Fall Equinox) begins at 8:44 am EDT on Sunday September 22nd. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Dangelo NEAR TERM...DeVoir/Dangelo/Gartner SHORT TERM...Dangelo/Gartner LONG TERM...Gartner/NPB AVIATION...Martin CLIMATE...Steinbugl/Martin/NPB