Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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276 FXUS61 KCTP 171115 AFDCTP Area Forecast Discussion National Weather Service State College PA 715 AM EDT Fri May 17 2024 .SYNOPSIS... A weakening cold front approaching from the Ohio Valley today and low pressure passing well to the south of us on Saturday will team up to bring us occasional showers later today through Saturday morning. A ridge of high pressure will build into the Commonwealth for Sunday through early next week, bringing warmer and drier conditions, followed by a return of showers and scattered thunderstorms for the middle of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A weak and nearly stationary north/south sfc trough extended from near KELZ to KUNV and KCBE early today and separated widespread stratocu clouds to the east from notably higher/thinner clouds to the west. early morning temperatures were highly uniform across the region and mainly between 55 and 60F. Clouds may be thin enough across the Susq Valley and points east for some breaks of sunshine during the 12-16Z period, before thickening layered clouds aloft spread in from the west this afternoon and evening. Nearly calm air with moderate dewpoints in the low to mid 50s will help to create some patchy valley fog across the south Central Mountains and into the Susquehanna`s West Branch Valleys through 13Z today. HREF and its high res members suggest that the onset of rain will likely (60-70 percent confidence) be late this Friday morning across the Western Mountains of the state, but should hold off until the mid to late afternoon hours across the Central Mountains and possibly won`t begin until early this evening over the Susquehanna Valley and points east. MU CAPE will be very limited today and generally below 500 J?KG across our far western zones and non-existent across the far east. Thus, previous thinking and our current inclusion of a SCHC for embedded TSRA with the showers across the Central Mtns late today and this evening may be overdone. Highs today will be around 70F across the Western Mtns and in the low to mid 70s across the Central Mtns and Susq Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... The axis of showers will continue to propagate slowly eastward tonight within an area of relatively high PWs of 1.2-1.5"and marginally unstable airmass (though again, the bulk of the instability will stay west of the Allegheny Plateau). Scattered to numerous showers will continue into Saturday as southeasterly flow helps keep overcast skies and cooler conditions in place. It will be cloudy, dreary and somewhat chilly Saturday, but the majority of the rain will occur in the morning in most places. HREF 48 hour Prob Matched Mean precip ranges from around 1 inch across the Western Mtns (with some higher point amounts) to as little as a tenth or so across the far east. WPCs MRGL Risk for excessive rainfall nips Somerset County for tonight and Saturday, but we don`t foresee even high end amounts of 1.5 inches causing any significant problems with flooding on even the smallest streams. Would need to see over 2.5 inches for any flooding issues to develop across the West. Temperatures on Saturday will top out in the 60s, though a classic cold air damming scenario could keep highs in the upper 50s in a few locations. Improving conditions are likely on Sunday as an area of high pressure over the northeast sags southward. This will promote some breaks in the clouds and a bit milder temperatures. Some uncertainty remains in how stubborn the clouds will be on Sunday, but Sunday looks much better than Saturday for outdoor plans and activities. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... *Drying trend with more sun and warmer temperatures Mon-Tue. Decent model and ensemble signal for dry weather and more sunshine leading to a seasonal warming trend next Monday- Wednesday as a potential cutoff low parks over the western Atlantic and high pressure builds overhead. Max temps are forecast to climb back into the 75-85F range through Wednesday. By the middle of next week, upper troughing will move across Pennsylvania and support a better chance for showers and thunderstorms. At the surface, there remains plenty of model uncertainty about the timing of a cold front. The mean timing is Wednesday afternoon, but individual models bring precipitation as early as Tuesday evening and as a late as Thursday morning. If the front moves through Wednesday afternoon or evening, it could produce the first threat for severe weather in some time. After the front moves through, considerable uncertainty exists in terms of how much and how frequent rain will be. Have kept a chance of showers in place through the end of the week. Fairly high confidence in temperatures being close to average in zonal flow. && .AVIATION /11Z FRIDAY THROUGH TUESDAY/... As the sun came up this morning, low clouds (IFR over the western highlands and generally MVFR elsewhere) were observed across central PA. At the same time, high clouds are streaming in from the Ohio Valley and overtopping the lower cloud deck. Ceiling bases with the low cloud deck should gradually begin to lift after sunrise. However, an approaching warm front will spread showers (and perhaps some thunder) and lowering cigs into the western half of PA during the afternoon and evening hours. Latest ensemble prob charts indicate an increasing probability of IFR cigs (50-70% chc) by late evening over the western highlands (JST, BFD). IFR conds will continue into the overnight across the western highlands, with cigs expected to drop to borderline IFR/MVFR late this evening into the overnight across the central mtns. The Susq Valley should see cigs drop to MVFR overnight. Periods of rain will continue into the overnight hours as well. Outlook... Sat...Restrictive lower ceilings and periods of rain continuing. Sun...Morning low cigs/fog possible. Mon...Patchy AM fog possible. Otherwise, becoming VFR. Tue...Predominantly VFR, w/ no sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Steinbugl NEAR TERM...Lambert/Banghoff SHORT TERM...Lambert/Steinbugl/Banghoff LONG TERM...Guseman/Banghoff AVIATION...Evanego