Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 180547 AFDCTP Area Forecast Discussion National Weather Service State College PA 147 AM EDT Fri Aug 18 2017 .SYNOPSIS... A cold front will move through the region Friday triggering showers and thunderstorms. The cooler air will be replaced by warmer air Monday into Tuesday as a ridge builds aloft. Another cold front should trigger showers around mid-week and the week should end on a cooler note. && .NEAR TERM /UNTIL 7 AM THIS MORNING/...
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There were a few thunderstorms were over south-central Pennsylvania at 930 PM. Some showers were present over northern and northwestern Pennsylvania. The HRRR pushes the area of shower to the west through the region by 4 AM. Rainfall amounts are generally light. Some hints in northwestern PA of some potentially stronger cells with rainfall potential of an inch in these stronger cells, should they develop. Many areas, especially in the southeast should remain rainfree overnight though patchy fog is possible.
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&& .SHORT TERM /7 AM THIS MORNING THROUGH 6 PM SATURDAY/... The HRRR goes to about 17Z and it shows a weak line of showers and thunderstorms across our southwestern counties northeast toward Tioga county. General concept is showers developing around 15-17Z Friday. The HRRR shows CAPE over 2400JKG-1 east of these showers and other NCEP models show over 1800JKG-1 of CAPE to the east. Thus have higher POPS in central to southeastern PA in the afternoon hours. Models indicated the potential for some strong to severe thunderstorms Friday afternoon and the potential for some locally heavy rainfall. Most models show mainly 0.25 to 1.00 inch of QPF but stronger cells could produce higher amounts. Most guidance shows the cooler drier air improving conditions in western PA in the late morning and early afternoon. The front should clear our southeastern counties in the 22Z to 03Z timeframe Friday evening. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Models imply a weak wave could trigger some light showers on Saturday evening. Sunday into Tuesday looks very dry. The next chance for widespread rain would likely be around Wednesday and possibly into Thursday as short-wave and cold front move into the region. At this time Wednesday has the higher probability of QPF then it dries out Thursday into Friday. The PW forecasts show low PW over the region Saturday to Tuesday then a surge of higher PW air Wednesday ahead of the front. Then the PW falls Thursday into Friday to below normal values. Temperature wise, the cool air should be replaced by warmer air by Monday afternoon and Tuesday should be even warmer still. The 850 hPa temperatures go above normal Monday evening and peak in the 16-19C range Tuesday afternoon. Tuesday could be quite hot. Good news is the 850 hPa temperatures fall Wednesday into Friday. Most guidance shows below normal 850 hPa temperatures by Friday with below normal PW values. The week as currently forecast should end on a cool dry note (like D sharp?). && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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A band of showers and a few thunderstorms is pushing across the area as of midnight. Some rotation on cell heading toward IPT. Strong southeast flow off the mountain south of IPT for a few more hours. Another area of showers and storms over far southwest PA. Expect this area to slowly work to the northeast and linger into at least into the mid to late morning hours. Skies should try to clear later today, but the cold front will be well to the west. Main concern is the very high dewpoints in place, one of the few times this summer. Main difference this event is that the low level winds shift to the south and southwest, unlike recent events, that seem to occur at the end of the week this season. For now, will use VCSH for the most part. Potential is there for storms with heavy rain and strong winds. Weekend not looking bad for a change. .OUTLOOK... Sat-Mon...No sig wx. Tue...SHRA/TSRA poss.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...Grumm/Lambert AVIATION...Grumm/Fitzgerald/Martin

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