Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220630 AFDCTP Area Forecast Discussion National Weather Service State College PA 230 AM EDT Sat Apr 22 2017 .SYNOPSIS... A stalled frontal system just to the south of the Commonwealth will keep the region flirting with clouds and precipitation into the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Meso anal shows northerly winds finally establishing across the entire CWA as the surface low over the Mid Atlantic settled slowly south. The rest of the overnight should remain dry with clouds returning from the southwest. Overnight lows in the 30s and 40s will average near normal over the north, and some 5-10 warmer than normal over the south. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... Latest HRRR is very aggressive returning the rain into the southern half of my CWA during the hours just after sunrise, and continuing well into the afternoon hours. I adjusted POPs up a bit to cover this, but I suspect they are still underdone. From about I-80 south it could be a rather chilly and wet Saturday with the driest weather indicated over the northern tier. Highs will average in the 50s, or some 5-10 deg cooler than normal for a change. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... 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 /06Z SATURDAY THROUGH WEDNESDAY/... Biggest concern during the predawn hours is the possibility of fog at LNS, where 06Z dewpoint depression stands at just 1F. A few breaks in the overcast could result in enough radiational cooling there to produce IFR visibilities between 07Z-09z. After 09Z, the arrival of drier air in the low levels, combined with increasing mid level cloudiness should result in a diminishing threat of low visibility. Elsewhere, no significant reductions expected this morning. Radar loop at 06Z does show an area of rain showers approaching from Ohio associated with an upper level disturbance. These showers will affect parts of central and southern Pa later this morning, but there should be enough dry air in the low levels to preclude significant CIG/VIS reductions. Any showers should exit southeast Pa by early afternoon. After that, a drier northerly flow should ensure widespread VFR conditions for the rest of the day through this evening. Outlook... Sun-Mon...No sig wx expected. Tue...Rain/low CIGs possible. Wed...AM Rain/low CIGs possible, mainly eastern Pa. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Dangelo/Gartner LONG TERM...Grumm AVIATION...Fitzgerald

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