Area Forecast Discussion
Issued by NWS State College, PA

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341 FXUS61 KCTP 222339 AFDCTP Area Forecast Discussion National Weather Service State College PA 739 PM EDT Sat Apr 22 2017 .SYNOPSIS... A frontal boundary will remain stalled out just to the south of the state throughout the remainder of the weekend. An upper level cut off low will form over the Tennessee Valley and could end up bringing a return to wet weather for the first part of the upcoming week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Radar mosaic shows the last of the showers exiting my SERN zones, and the near term guidance suggests that further rains associated with the boundary south of the border will remain over VA through Sunday. Breaks in the overcast are developing over the north and the improving sky conditions will continue to spread south overnight. Temps will get pretty chilly Sunday morning, especially in the mountains. Much of the valley areas in Central and Southern PA will see the mercury fall into the U30s and L40s. However, it will probably dip into the upper 20s in the perennial cold spots near Bradford, and between 30-35F over the rest of the NW third to half of the CWA. With clearing skiers the wind will be calm or light/northerly. The average date of the last spring freeze has passed for the SE third of the area, and there could be some frost in the ridge and valley region (between UNV and MDT). Will hold off on any mentions of frost in the wx grids/zones for now. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... Subsidence will lead to plentiful sunshine on Sunday. Temps should rebound nicely with almost all of the area back into upper 50s and lower 60s. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... The period of Sunday night to Wednesday will be dominated by the flow around a slow moving cut-off low which eventually will pass to our south and east. This system will bring clouds and light rain to the parts of our region for several days. The models are in fair agreement on timing and position of this low. Bands of precipitation should begin to streak through the region, mainly the east Tuesday morning. Timing and position of the low will change whether or not different portions of central Pennsylvania get precipitation. Have increased POPS for eastern PA. The gradient will be tight on any precipitation amounts. Once this system goes by large scale retrogression will put our region on the western edge of a relatively strong 500 hPa ridge and it will get warm fast. It should feel like summer by next Thursday. The potential for rain will be higher in southeastern PA and much lower in northwestern PA. Rainfall will likely be very light and the best chance for measurable rainfall will be in southeastern PA. Enjoy the mostly cloudy and relatively cool weather while it lasts. As the 500 hPa low fills and the attendant moves to our northeast the chance of rain should fall off Wednesday into Wednesday evening. Our 850 hPa temperatures will rise rapidly Wednesday and it should be noticeably warmer Wednesday relative to Monday and Tuesday. Thursday into Saturday the 850 hPa temperatures will be well above normal, mainly in the 14 to 16C range and we will be on the western edge of a rather impressive early season subtropical ridge. The GEFS and GEFSBC show a closed 5880 m ridge along the VA/NC/SC coast with +2 sigma height anomalies by Fri-Sat. Thursday through at least Saturday should be very warm and humid. We should have several days with high temperatures well into the 80s. Any precipitation after Wednesday will likely be in a more summer-like atmosphere so have kept thunder in all forecasts beyond Wednesday. The ridge will likely continue retrograding. If the NEAFSBC and GEFSBC are correct we could be looking at our first enduring period of warm weather from this coming thursday into the following week. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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Still a wave over the TN Valley, which will keep some clouds across the region tonight. 002 TAFS adjusted some. Earlier discussion below. Most areas VFR now with mid and high clouds. Low levels quite dry, thus rain not making it to the ground. Still some patchy rain across the far southeast for a few more hours. 21Z TAFS adjusted for the above conditions. Skies should clear out overnight, as the upper level trough moves east of the area. Airmass is quite dry, thus not expecting fog at this point. Sunday should be a nice day with dry conditions. Some patchy light rain could push back to the north later Sunday Night into Monday, as a complex storm system forms across the southeast states. Some rain could get into central areas on Monday, and perhaps into northern PA Monday Night. Potential for a wet day on Tuesday, as a complex low lifts northeast along the coast. Improving conditions for Wed. Showers and thunderstorms spreading eastward, along and ahead of a cold front on Thursday. Outlook... Mon...Patchy rain spreading slowly northward. Tue...Rain/low CIGs likely. Wed...Improving conditions. Thu...A chance of showers and Thunderstorms.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...La Corte/Lambert SHORT TERM...Lambert LONG TERM...Dangelo/Ceru AVIATION...Martin

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