Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 201133 AFDCTP Area Forecast Discussion National Weather Service State College PA 733 AM EDT Wed Sep 20 2017 .SYNOPSIS... A ridge of high pressure at the surface and aloft will extend across Pennsylvania through next Tuesday. This dominant weather feature will provide fair, warm and generally dry weather for this entire period. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Earlier clear skies and strong radiational cooling with light wind and moderately high sfc dewpoints in the 50s to lower 60s has set us up for another foggy morning throughout most of the central and northern valleys of the commonwealth. Temp/dwpt spread is now basically zero across most locations to the NW of the Interstate 81 corridor with temps in the l-m 50s across the mtns, and upper 50s to low 60s throughout the Central Mtns and Middle Susq Valley. Look for areas of dense fog to become fairly widespread for a few hours either side of daybreak today. The western influence of moisture from what is now tropical storm Jose (that`s parked about 250 miles south southeast of Islip Long Island) was seen in the form of bkn-ovc strato cu pushing slowly wwd across the Lower Susq Valley and Western Poconos. Fog early today will be minimized in those places due to the extent of cloud cover and still mild temps with a 5-8 deg F temp/dwpt spread. Min temps will be about 2-4F lower than early Tuesday over the northern half and similar to Tuesday across the the southern half - and notably milder than normal, especially in the cloud covered SE. After the fog burns off in the valleys late this morning, a spectacular Wednesday late morning and afternoon is on tap with abundant sunshine and just a few flat cu and thin cirrus to paint the otherwise azure blue sky. There could be a couple of showers off to our SW in a very weak and eroding trough, but only result for us will be potentially an increase in cloud cover over the Laurel Highlands. Mid afternoon Max temps will once again range from the upper 70s across the higher terrain of the north and west, to the lower 80s (and maybe a few mid 80s) in the southeast thanks to a milder start with the early morning cloud cover. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... The broken record continues for tonight and Thursday under the persistent ridge along the spine of the Appalachians. mainly clear skies, light wind and a slight bump up in sfc dewpoint will provide optimal conditions for another night of locally dense and fairly widespread valley fog. Low temps early Thursday should be 2-4 deg F milder than early Wednesday, and similar increases in high temps from the prior day are also expected with highs near 80F across the nrn and wrn mtns, and low to mid 80s elsewhere. Sky cover (after the dissipation of the morning fog) will be generally scattered with some flat afternoon cu and areas of thin cirrus. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... The overall pattern hasn`t changed much, there is a good overall consensus in the models for the end of the work week. For much of this period, a 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. The GEFS forecasts showed this feature as a closed 5880 m ridge over us with near +2 sigma above normal heights which will translate to well above normal temperatures. High temps from Friday through the weekend will be 10-15F above normal with little or no chance of rain until Monday at the very earliest. 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 /12Z WEDNESDAY THROUGH SUNDAY/...
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GOES-16 fog channel imagery shows widespread valley fog confined mainly to the west of the Susquehanna River. The outer edge of cloud shield associated with TS Jose is drifting over the southeast airfields and has precluded fog formation. Locally dense fog will produce local cig/vis AOB airfield minimums. Expect fog to dissipate through mid morning with VFR conditions this afternoon and evening. Persistence fcst favors more fog restrictions late tonight into Thursday morning. .Outlook... Thu-Sun...Patchy valley fog possible each morning. Otherwise VFR with generally light winds and minimal clouds.
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&& .CLIMATE... Astronomical Fall/Autumnal Equinox begins at 4:02 PM Friday September 22, 2017. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/RXR NEAR TERM...DeVoir/Lambert SHORT TERM...Lambert/RXR LONG TERM...Ceru/Gartner AVIATION...Steinbugl CLIMATE...

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