Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 221413 AFDCTP Area Forecast Discussion National Weather Service State College PA 1013 AM EDT Sat Apr 22 2017 .SYNOPSIS...
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A frontal boundary will remain stalled out just to the south of the state. An upper level cut off low will form over the Tennessee Valley late this weekend, and could end up bringing a storm up the East Coast in the first part of the upcoming week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Radar mosaic shows several bands of light-mdt rain showers streaming to the NE, and covering approximately the SE half of our forecast area. The showers were being generated by a broad area of mid-level FGEN forcing and uvvel beneath the thermally direct/RE region of a 95-105 KT upper jet core draped from the Ohio River Valley to central New York at midday. High res models agree very well with what we`re seeing on regional radar loops late this morning, that being that the NW edge of the showers will be gradually shifting to the SE through the midday and afternoon hours, and becoming confined to the region near or to the SE of I-81 after 18Z. Expect additional rainfall to average between 0.05 and 0.15 of an inch across the SE half of the CWA for the rest of the day, with nothing more than a late morning sprinkle from the gradually lifting and SE drifting mid level cloud deck over the northern mtns. Temps will only get near 50F in the higher elevations. We may touch 60F in a few spots - with the best chance for that probably in the EC zones.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
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Rain is expected to press to the south of the Mason-Dixon line very early this evening. It should remain dry - even in the south - for the rest of the weekend. Temps will get pretty chilly Sunday morning, especially in the mountains. Much of the area will be into the U30s and L40s. However, it will probably get below freezing in the mountains - most of the NW third to half of the CWA. Wind will be calm or light/northerly. Much of the area will clear out. 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. Subsidence will lead to plentiful sunshine on Sunday. Temps should rebound nicely with almost all of the area back into the 60s.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... There is a better-than-normal agreement between the models on timing and positioning of the cut-off low ref`d below. Rain will likely spread up the coast and into the area Monday into Tuesday, but may not make the western counties wet at all. Have bumped POPs up 10-20pct over the eastern half for that period. Prev... The period of Sunday 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. 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. Sunday weak high pressure and low moisture values should provide for a relatively nice day. We will be well north of the frontal boundary. Monday the low to our south begins its slow journey towards the Carolina coast. Our PW values come up and the threat of QPF in the GEFS/SREF and CMCE show increased chance of light rain overnight Sunday into Monday. Best chance of rain should be in southeastern PA. 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 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. Thus 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 added 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 /14Z SATURDAY THROUGH WEDNESDAY/...
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Radar loop at 14Z showing several bands of showers covering the SE half of the state, and shifting gradually to the east. There should be enough dry air in the low levels to preclude significant CIG/VIS reductions. No worse than MVFR CIGs expected late this morning at KBFD and KJST, with VFR CIGs but brief 4-5SM MVFR vsbys at KMDT and KLNS during the late morning through mid afternoon hours. Generally VFR will occur elsewhere at airfields across the NW half of PA this afternoon. Any showers should exit southeast Pa by early evening. After that, a drier northerly flow should ensure widespread VFR conditions tonight. Outlook... Sun-Mon...No sig wx expected. Tue...Rain/low CIGs possible. Wed...AM Rain/low CIGs possible, mainly eastern Pa.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Lambert NEAR TERM...Lambert SHORT TERM...Dangelo LONG TERM...Grumm/Dangelo AVIATION...Lambert/Fitzgerald

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