Area Forecast Discussion
Issued by NWS State College, PA

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333 FXUS61 KCTP 182348 AFDCTP Area Forecast Discussion National Weather Service State College PA 748 PM EDT Wed Oct 18 2017 .SYNOPSIS... 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 on Thursday without significant moisture. 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. && .NEAR TERM /UNTIL 7 AM THURSDAY MORNING/... Temps now down to about normal maxes for today. Little change to the grids with little weather to speak of. Mins may near frosty levels in the Mid Susq and THV, but it will again be too spotty to warrant an advisory. Prev... 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 /7 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... Warm air, with maximum temperatures 5 to 10 degrees above normal, will continue through the weekend. A weak wave will push a front into our region. However the very weak front will be dry as the moisture starved system is coming into a dry air mass. Expect a bit more wind than today with the weak frontal surge. Rain chances through the weekend are near zero. The high pressure that will dominate the pattern through the weekend will finally shift off early next week. This will be a two pronged system with precipitation chances Monday through Wednesday. The best influx of moisture will be Tuesday as the long range guidance has the trough deepening over the Great Lakes region. Precipitation should continue into Wednesday. Cold air behind the low will finally filter down into the region through the latter half of next week with 850 mb temps around 0C Wednesday night. So expect temperatures to be back to around and slightly below normal for this time of year next week. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... 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 /00Z THURSDAY THROUGH MONDAY/...
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Expect VFR conditions overnight. Perhaps a little fog at IPT, left this in from the earlier fcst. Dry cold front moving across on Thursday. I did up winds some, given how winds picked up on Monday aft sunrise. Also have winds up some behind the cold front, given strong wind fields. High pressure builds in for Friday and lingers into the weekend. As the high builds in this weekend we could see an uptick in valley fog and fog over rivers and streams this weekend. Looks like the rain should hold off until early next week. Fly on! Outlook... Fri-Sun...Mainly VFR, with just some patchy AM valley fog. Mon...A chance of showers.
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&& .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/Dangelo SHORT TERM...Grumm LONG TERM...Ceru/Steinbugl AVIATION...Martin/Grumm CLIMATE...Steinbugl

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