Area Forecast Discussion
Issued by NWS State College, PA

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898 FXUS61 KCTP 181748 AFDCTP Area Forecast Discussion National Weather Service State College PA 148 PM EDT Wed Oct 18 2017 .SYNOPSIS...
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For the most part our weather will be dominated by a surface high and an upper-level ridge through late Sunday. A weak short-wave comes over the ridge Thursday. Our first real chance of rain will be early next week when a trough moves our way. By mid-week we could see some below normal temperatures with a deep trough just to our west.
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&& .NEAR TERM /THROUGH TONIGHT/... High pressure over us is weakening due to a wave in the northern stream. But the dry air is still in place so it is an outstanding day. Though I appear to be indoors. Used the blends which in some locations are a tad low for highs. Overnight another nice night the winds may increase above the PBL as the high retreats due to the wave. This will limit fog a bit more than early this AM. And there was not a lot of fog this AM. Nice overnight lows mainly 40s except for a few colder spots in rural areas to the south. Less wind south as high retreats. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The weak wave will push a front into our region, very weak front but our 850 mb temperatures should drop during the afternoon Thursday. Still a nice day as the front is moisture starved coming into a dry air mass. A bit more wind than today with the weak frontal surge. Warmer air is forecast to begin to move back overnight Thursday and Friday. Chance rain at this times is about 0. && .LONG TERM /SATURDAY THROUGH TUESDAY/... A strong upper level ridge of high pressure will support above average temperatures through the weekend. This will further add to the anomalous October warmth which should help to secure a spot in the top-10 warmest Octobers - if not top 5 or even #1. Both GFS and ECMWF ensemble systems continue to indicate a pattern flip by the middle of next week with a period of colder (near/below normal) temperatures starting around October 25th. The depth and longevity of the emerging upper trough and subsequent cooler pattern remains in question - so we will have to wait and see how much of a dent it can put in the strongly positive month-to-date departures from climatology. On the precipitation side, the prolonged dry spell ends early next week as a cold front moves across the Appalachians. Stream separation differences/closed low development in some of the deterministic models leads to increasing spread and thus uncertainty in the forecast details such as timing. The GOM will be open for moisture inflow northward ahead of the front. So will keep continuity and favor max POPs in the Monday night- early Tuesday timeframe. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... The overall period from this afternoon through Sunday looks like nearly ideal flying weather. High pressure weakens as a wave comes by Thursday. Then high pressure builds back in Friday-Sunday. So light winds most of the time and few clouds to talk about. As the high builds in this weekend we could see an uptick in valley fog and fog over rivers and streams. Looks like the rain should hold off until early next week. Fly on! Outlook... Wed-Thu...No sig wx expected. Fri-Sun...Mainly VFR, with just some patchy AM valley fog. && .CLIMATE... Month-to-date, October 2017 is the warmest October on record at Harrisburg and Williamsport. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...Steinbugl AVIATION...Grumm CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.