Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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833 FXUS61 KCTP 180755 AFDCTP Area Forecast Discussion National Weather Service State College PA 355 AM EDT Wed Sep 18 2024 .SYNOPSIS... A cut off upper low and weak surface reflection spinning over the Southern Appalachians this morning will drift slowly to the Northeast today before moving off the Mid Atlantic Coast Thursday into Friday. A ridge of high pressure at the surface and aloft will build East from the Ohio Valley for the upcoming weekend with generally dry conditions and daytime temperatures averaging several degrees above normal in most places. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MRMS and surface obs early this morning showed a few bands of light rain pushing NWWD across the CWA and dissipating as they approached the deeper/dry air in the lowest 7-8 kft AGL near and to the north of Interstate 80. We`re seeing a milder start compared to recent days with daybreak temps ranging from the low and mid 50s over the northern tier, to the low and mid 60s in the Lower Susq Valley. Another few rounds of rain are expected later this morning and this afternoon over the southern third of the state, where 2-3 tenths of an inch are possible by dusk. Locally higher amounts near 0.50 of an inch are possible over the southern tier counties, where some models indicate a bit of elevated instability and the potential of a deeper warm cloud layer and heavier showers in the 12-18Z time frame. Elsewhere across Central and Northern PA, rainfall amounts will be minimal, but widespread and generally thick mid level clouds will persist with a light East to ENE breeze. Afternoon highs today will be coolest (low to mid 60s) across the Laurel Highlands and mainly between 70-75 degrees over the remainder of the CWA. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... The weak surface low off of the NC coast is progged to drift northeast and out to sea tonight through the week`s end. This will cause the low level flow to gradually back from the ESE to the Northeast, allowing drier air to advect into the much of the CWA late today and tonight. An increasingly northerly flow should dry things out Thursday into Friday. However, a few bands of enhanced mid-level FGEN forcing just to the NW of the 1008 mb sfc low east of KACY will help to focus the best chc for rain near and to the SE of the I-81 corridor later tonight through Thursday night where an additional few tenths of rain are expected. Elsewhere, partial clearing of the mid and high cloud layer is expected with just a few sprinkles or a stray brief shower possible. Model RH profiles support an increasing amounts of sunshine Thursday into Friday across much of Central and NW PA. GEFS 850mb and surface temps indicate a return to above normal afternoon readings. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Higher confidence in dry wx/no rainfall particularly early in the period (through the upcoming weekend) thanks to deep layer ridge pattern at the sfc and aloft. While model variability remains elevated into next week, the ensemble means generally favor weak upper troughing centered around the Great Lakes which will support a marginal increase in rainfall/shower potential along/ahead of an approaching front by next Monday or Tuesday. Forecast max temps 75-80F peak +5-10F above mid/late September climo to start the weekend and trend modestly cooler to 65-75F (near the historical average) into early next week. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... MVFR ceilings across the Laurels (JST/AOO) could show slight hints of improvement over the next couple of hours through 09Z with HREF probabilities and GLAMP guidance both suggesting conditions resolving to low-end VFR near 08Z at AOO. Improvement will be short-lived; however, as ceilings are expected to tank towards IFR thresholds closer to sunrise (10-12Z) and continue through at least 16Z at AOO/18Z at JST. There is some uncertainty with regards there lower ceilings, so have these in the 06Z TAF package with moderate (~40-50%) confidence. MVFR ceilings are also expected to begin making way into MDT/LNS closer to sunrise, with the most reasonable timing near 10Z, although could realistically see these restrictions pushed back closer to the 11/12Z timeframe as guidance continues to slow low-level clouds (~1500ft AGL) into the LSV. Scattered -SHRA will also be possible mainly at JST/AOO/UNV, although have limited mentions as the bulk of shower activity has moved west of these airfields at this time. Recent GLAMP guidance and HREF probabilities continue to go heavy on visibilities ~1/2SM at BFD in the overnight period, and generally could see these coming to fruition given SKC/00000kt conditions over multiple hours, thus have offered up ~2hrs of increased restrictions in the 10-12Z timeframe. If ANY cloud cover gets into BFD over the next couple of hours, this will likely limit fog potential in the timeframe and BFD could escape with an hour/two with MVFR thresholds (10-12Z) or, even more likely, VFR prevailing throughout the overnight period. If fog does manage to develop, restrictions will be quick to resolve by 13Z with VFR prevailing throughout the daytime hours. After sunrise, improvement looks unlikely through 17Z at all airfields (minus BFD/IPT, who outside of the aforementioned fog restrictions at BFD will remain VFR overnight). Slow improvement is progged by the bulk of model guidance, with MDT/LNS first to resolve in the 16Z-17Z timeframe and JST/AOO resolving closer to 00Z Thursday as low ceilings slowly scatter out towards VFR. Outlook... Thu...MVFR cigs possible in the southern and eastern portions of the airspace. Fri-Sun...Valley fog in the morning; otherwise VFR/no sig wx. && .CLIMATE... The first day of Autumn 2024 (Fall Equinox) begins at 8:44 am EDT on September 22nd. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Fitzgerald/Steinbugl AVIATION...NPB CLIMATE...NPB