Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 171155 AFDCTP Area Forecast Discussion National Weather Service State College PA 755 AM EDT Sun Sep 17 2017 .SYNOPSIS... A weak upper level low pressure system will bring a slight chance of showers today before a large ridge of high pressure will dominate our weather for much of the work week. Temperatures this week will run well above average. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Showers increasing in coverage across eastern Lancaster and Lebanon County and updated POPS there. With another morning of mild and humid conditions, widespread fog with patchy dense fog is forming. The fog will dissipate by mid morning, followed by sunny and mild conditions into the early afternoon. With a weak upper level trough in the area, isolated/scattered afternoon showers are possible in the midst of some modest afternoon instability. Surface based LI`s will be slightly lower and Capes a bit higher Sunday afternoon which could lead to a better chance of a rumble of thunder in some spots. Expect max temps from the upper 70s over the higher terrain, to the low and mid 80s in the Susq Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Surface High pressure ridge holds tough tonight and Monday bringing mainly dry weather and pleasantly warm temps with very light wind. Min temps will range from the upper 50s across the nrn and wrn mtns, to the lower and mid 60s in the metro areas of southeastern PA. High temps Monday will feature a very tight temp range in the Mid to Upper 60s. Fog could once again become quite thick between 5 and 8 am. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... For much of this period, a 500 hPa ridge will dominate our weather. The ridge will be reinforced with Hurricane Jose forecast to remain far enough offshore to just bring some high clouds to the eastern half of the area. As Jose moves away heights will rise and this should further dry us out for the latter part of next week. The GEFS forecasts a closed 5880 m ridge over us with near +2 sigma above normal heights by next Friday and Saturday which will translate to well above normal temps. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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The main issue this morning (and similar to early Saturday) will be the coverage and thickness of Valley Fog. Current sfc T/Td spread is 1 Deg or less, and vsbys should stay quite low in locally dense fog (particularly in the deeper valleys) for the next few hours, thanks to very weak llvl flow and shallow verticaly mixing. On other area of concern is assoicated with a small area of MDT-HVY slow-moving showers (across our SE zones of Lebanon and Lancaster couunties) that were occuring beneath a weak upper low that will be meandering slowly to the E or NE the next few days. The only clouds noted above the locally dense valley fog this morning was a layer of high-based stratocu and alto cu clouds across the Susquehanna Valley. Conditions will improve to mainly vfr for this afternoon and evening, before sliding back down to mvfr at most TAF sistes tonight. .Outlook... Mon...Areas of A.M. fog. Mainly dry with VFR conditions. Perhaps an isolated afternoon shower. Tue-Wed...Mainly dry with patchy morning fog. Otherwise primarily VFR conditions. Eastern areas may see NE winds 10-20 mph as main impacts from Jose remain off to our east. Thu...No sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ross NEAR TERM...Ross/Fitzgerald SHORT TERM...Ross LONG TERM...Ross AVIATION...Lambert/Martin

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