Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 210258 AFDCTP Area Forecast Discussion National Weather Service State College PA 958 PM EST Tue Feb 20 2018 .SYNOPSIS... An anomalous upper level ridge will remain parked off the southeast coast through the upcoming week. At the surface, a dying cold front will push southeast across the area late Wednesday, then stall in the vicinity of Pennsylvania late this week into the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... The last of the scattered showers associated with low level jet over the eastern Grt Lks are lifting north of the border, so will remove mention of rain for the rest of the evening. Will reintroduce a slight chance of showers toward dawn over Warren County associated with approaching cold front. A very mild February night is in store for the area within broad southwest flow circulating around Bermuda high. Mostly clear skies and light wind will likely result in areas of fog tonight over the eastern portion of the forecast area, where low level cool air wasn`t completely scoured out today. Dewpoint depressions already quite low at 22Z in some spots, so expect patchy fog to form this evening and become more widespread late tonight. Mins will range from the middle to upper 50s across the west, and lower to middle 50s central and even some upper 40s likely over portions of the Susq River Valley. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... The warmth continues into Wednesday, with a spring like start to the day. Areas of fog especially east will give way to mixed clouds and sun with near- record to record high temps across much of portions of Central and Western PA. A weakening area of showers will accompany a cold front dropping across the commonwealth Wednesday, beginning mid to late morning NW and reaching into the Lower Susq. by evening. This will hold down highs over the northwest, but allow another day of 60s and 70s elsewhere. Showers will accompany the front later Wed morning (NW) and during the afternoon and evening elsewhere across the Central Mountains, then Lower Susq Valley. Considered thunder possibility but instability appears absent this go around. Colder air to come Wednesday night thanks to strong 1040 mb high pressure buildings eastward from the Midwest. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Did not change a lot for the period Wednesday night into Friday. Current fcst looks good. Potential for a significant change in practical weather...if frontal position changes very much. Some downward adjustments made earlier today on ice amts. My main change was to add additional grids. Still looking like another warm up on Sunday. Potential for some heavy showers across the west...but several days out. Still looks dry behind the front Sunday Night...so I took out the showers of the fcst after 06Z Monday. Left Monday into Tuesday dry...weak system fcst to cut under the ridge...but not seeing much moisture with this. More information below from earlier shifts. *Periods of rain with a several hour period of icing from freezing rain expected late Wed night through Thur morning. brief interval of mixed precip possible Wed. night- AM Fri. A light accumulation of snow could precede the freezing rain across the Northern Mountains early Thursday. *Pattern favors above average temperatures this weekend into next week The cold front will become quasi stationary near the MD line Wed. night. The wavy frontal boundary will bring periods of rain into the weekend, with several (to as much as 8) hour period of mixed wintry precip likely across mainly the Central and northern mountains Wed. night and Thu morning, thanks to an increasing and moderately strong northerly, 1000 mb Ageostrophic flow that will serve to pump shallow/sub-freezing air south into the region. Confidence is moderate with respect to the exact ptype details (and the location and amount of fzra). However, there is at least some risk for a light snow and/or ice accumulation. We`re in good agreement with WPC`s Winter Weather graphics ATTM, with a coating to 2 inches of snow possible at the onset across parts of northcentral and NW PA, before a changeover to sleet and or Freezing Rain. Another round or two or rain is likely over the weekend. We will need to monitor the potential for flooding especially across south- central PA where the ground is very saturated from previous rain/snowmelt and streamflows are well above normal. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
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Patchy fog to form again overnight at most airfields under clear skies and generally calm to light southwesterly winds. Over the eastern airspace expect thicker fog/ low ceilings to redevelop / move back into the Susq Valley from the east into Wed morning where a tongue of higher surface dewpoints exists. VFR conditions should return to the region later Wed morning. An exception will be over the NW mtns as a sharp cold front will spread rain and restrictions in from the NW, with restrictions possible in the afternoon/evening into the central mountains. That will be followed by several weak waves of low pressure bringing bouts of rain for the second half of the week, and even some light freezing precipitation Thursday morning. Outlook... Wed...Restrictions from fog early then likely in rain showers mainly NW half. Thu...Widespread restrictions in rain south/wintry mix north. Fri-Sun...Widespread restrictions in periods of rain.
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&& .HYDROLOGY... Recent rainfall and snowmelt has resulted in very saturated soil and well above normal streamflows across much of the area especially south-central PA. Rainfall of 0.50 to 1.00 inch is forecast between Wednesday and Thursday night, with additional rainfall likely into/over the weekend. River flood potential (including small streams, creeks and tributaries) is above normal and we will continue to monitor the risk in the coming days. && .CLIMATE... Looks like some sites at or above record highs for today. CLI data will be out by 530 - 6 PM. See CLI data for more details later this aft. Record highs for selected sites for Tuesday and Wednesday February 20th and 21st: MDT: 72/1930;71/1997 IPT: 67/2016;69/1930 BFD: 58/2016;64/1997 AOO: 62/2016;71/1997 && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Fitzgerald NEAR TERM...DeVoir/Fitzgerald SHORT TERM...DeVoir LONG TERM...Lambert/Martin AVIATION...DeVoir HYDROLOGY... CLIMATE...

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