Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 170750 AFDCTP Area Forecast Discussion National Weather Service State College PA 250 AM EST Tue Jan 17 2017 .SYNOPSIS... A warm frontal system will push into the region from the Ohio Valley today, followed by a cold frontal passage tonight and early Wednesday. High pressure will follow and bring mainly dry conditions with temperatures several degrees above normal from the middle of the week into the weekend. && .NEAR TERM /THROUGH TODAY/... Regional 88D loop showing several areas of light-moderate rain moving east from the Allegheny Plateau to the Central Ridge and Valley Region at 07Z. Meso Obs showing numerous locations where the temp has dipped to 32F, which should result in some areas of light freezing rain and a few hundredths of an inch of ice accretion on untreated sfcs. An approx 2-3 hour break in the precipitation will occur over the Central and SW zones in the wake of this lead area of rain. Frequent periods of rain will persist across the NW mtns in closer proximity to the nose of a 50kt swrly LLJ and near the best LLVL theta-e convergence near the quasi stnry/warm frontal boundary. The axis of the relatively strong LLJ (and a distinct neg tilt trough axis at 850 mb) will lift NE across central and western PA late this morning and bring periods of light to mdt rain between 10Z-19Z today. Best freezing rain potential for Central and Northern PA (covered by the Freezing Rain Advisory) will be between 10Z-13Z which is unfortunately during the peaks hours of the morning commute to work and school. Surface T/Td spreads of 2-5 deg F will allow temps to wet bulb down by another deg F or two between 07-12Z. All of the latest model guidance continues to suggest that the main freezing rain threat will be over the higher terrain of northern Pa, with a diminishing risk in the valleys and across southern Pa. Will therefore make no changes to current Freezing Rain Advisory, but will monitor temps across southern areas for a possible expansion as current readings are mainly in the mid 30s with a few locations in the 32-33F range. . QPF will be light so amounts of ice are not expected to be significant, but as we have seen several times over the past few weeks, even a little ice on untreated surfaces can cause significant problems. A steadier rain will overspread the region from the west during the mid to late morning hours today, as the strongest low to mid level WAA accompanies passage of aforementioned low level jet. SREF and NAM both indicate the possibility of lingering icing through mid morning ((14Z) across the high terrain of northcentral and northeastern Pa (especially between KUNV and KIPT, and points to the north). The mid level shortwave and associated low level jet are progged to shift east of the area between 18Z-21Z, causing rain to taper to spotty drizzle. Surface warm front is progged to push into the Laurel Highlands during the afternoon, pushing temps into the 50s down there. Elsewhere, readings expected to top out in the 40s most places and the upper 30s over the Mtns north of Williamsport. Maintained POPs near 100 pct today based on the latest GEFS/SREF probs and overall favorable pattern of anomalous PWATS and strong lg scale forcing ahead of shortwave. Blend of model QPF ranging fairly close to a third of an inch through Today. && .SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/... Winds turn westerly behind the system by late tonight (west) and Wednesday (over the east) morning as flow turns more zonal, but with no real cold air is in sight. Low stratus and strato cu will combine with a westerly flow of the shallow cooler air to produce some light drizzle (across mainly the west-facing slopes and ridgetops of the Alleghenies) and also areas of ridge- top shrouding fog. Low temps early Wednesday will range from the mid 30s acrs the northern mountains, to the lower 40s in the south. The Wednesday morning stratus/stratocu layer will gradually dissipate during the mid to late afternoon hours, as a secondary cfront pushes through and is followed by enhanced deep-layer subsidence and drying, with only slightly cooler air in its wake. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Ridge re-establishes itself over the eastern U.S. for late in the week, as mild SW flow persists over the midwest. Guidance suggests energy will dive south along the west coast eventually helping to strengthen the building upper ridge over the east. We`ll be on the eastern side of this, so subtle shortwaves sliding into the Midwest will bring varying amounts of cloudiness to the west (less in the east) with low end chances for light showers. Another wave approaches/lifts into the OH valley late next weekend into next Monday. Again, temps could be marginal at the start of pcpn overnight Sunday for some ice or snow, but the bulk of pcpn looks to be rain at this point. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Widespread MVFR to IFR conditions expected through 17/06z TAF period with rain spreading from west to east across the airspace by later this morning. Pockets of -fzra remain possible at the northern terminals thru 15z but temps are marginal. Outlook... Wed...MVFR/IFR west; MVFR to VFR central-southeast. Rain showers west ending Wed ngt. Thu...No sig wx. Fri...Sub-VFR possible with rain moving SW-NE. Sat...No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... Freezing Rain Advisory until 10 AM EST this morning for PAZ004>006-010>012-017>019-037-041-042-045-046-049>053-058. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/Gartner AVIATION...Steinbugl

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