Area Forecast Discussion
Issued by NWS State College, PA

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509 FXUS61 KCTP 211448 AFDCTP Area Forecast Discussion National Weather Service State College PA 1048 AM EDT Thu Sep 21 2017 .SYNOPSIS...
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A ridge of high pressure at the surface and aloft will stay anchored across the Lower Great Lakes, Ohio Valley and Northeastern States through at least Tuesday. This will continue of dry and unseasonably warm weather to Pennsylvania.
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&& .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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Fog almost gone except for the very deepest valleys of the north and SWrn Somerset Co. Low clouds are trying to slide in from BGM`s CWA, but these should get eaten up by the sun and daytime mixing. Otherwise, the most cu will be found across the far southern tier near MD. The mixing won`t be very deep as the subsidence inversion continues to lower. Will keep POPs at zeroes. Prev... Latest GOES 16 10.3-3.9 UM fog channel shows dendritic valley fog pattern expanding throughout the NW mtns and Laurel Highlands attm, while most of the Central Ridge and Valley Region and Susq Valley is still holding onto a deg F or two T/Td spread with just some patchy lighter fog. Valley fog in these latter noted areas will thicken-up throughout the valleys containing larger rivers and streams between 09-10Z. The fog will once again be locally dense through 13Z then dissipate quickly. Low temperatures around sunrise will vary from the lower-mid 50s across the northern and western mtns, to the lower-mid 60s in the southeast metro areas. 07Z run of the RAP shows nil sfc based cape across much of the CWA later this morning and this afternoon, suggesting that any cur will be vary flat and sparse at best. Otherwise, expect just some patches of cirrus/cirrostratus (on the western periphery of what was once Hurricane Jose) to occur across the eastern half of the state. Max temps this afternoon were nudged toward the slightly warmer NBM and will range from the upper 70s to around 80F across the Laurel Highlands and Northern Mtns, to the Lower-Mid 80s across the Middle and Lower Susq Valley.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM FRIDAY/... Ridge holding strong for tonight. Look for areas of fog to form again in the early morning hours on Friday, followed by almost a repeat of today (Thursday) cloud, temp, and wind-wise here in Central PA and surrounding locations. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... For this weekend and early next week, the pattern remains stable as a building ridge continues to stifle any convection. Weak flow at night should allow for valley fog to form nightly and to greet morning commuters. The overall consensus in the models through the weekend is for the 590 dam closed 500 hPa high will drift slowly out of the midwest states, and become centered over western PA by late this weekend through early next week. Ensemble temperatures are in general consensus and high temps through the weekend will be 10-15F above normal with little or no chance of rain until Monday at the very earliest. There are hints that what was left of Jose could bring moisture and thus some rainfall through Monday into Tuesday. However there continues to be model variability so have only chance POPS. Lows early each morning will be consistently in the mid and upper 50s across the northern and western mtns, to lower 60s in the larger SE metro areas. Min temps may cool off slightly for this weekend thanks to deep dry air and a light N to NW llvl flow of drier dewpoint air at the sfc. && .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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VFR has returned to all terminals. Valley fog will redevelop each overnight for the next 5+ days lingering through 13-14Z each morning. Some morning fog may briefly impact the higher elevation terminals (BFD/JST) in the west. Otherwise, VFR should rule most of the area as high pressure remains stuck overhead. .Outlook... Sat-Mon...AM valley fog. Otherwise VFR.
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&& .CLIMATE...
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Astronomical Fall/Autumnal Equinox begins at 4:02 PM Friday September 22, 2017.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ross/Lambert NEAR TERM...Dangelo/Lambert SHORT TERM...Ross/Lambert LONG TERM...Lambert/Gartner AVIATION...Dangelo/Martin CLIMATE...

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