Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 140452 AFDCTP Area Forecast Discussion National Weather Service State College PA 1152 PM EST Wed Dec 13 2017 .SYNOPSIS... An Alberta Clipper will track across southern Pennsylvania overnight. Behind this system, a ridge of high pressure will slide across the region Thursday and Thursday night with cold but mainly dry conditions. Another clipper will move north of the region overnight Friday and Saturday morning with limited moisture. High pressure will build across the area early Sunday with a brief moderating trend. A series of cold fronts will move across the area late Sunday into Wednesday. Windy and colder temperatures will follow for Tuesday into Wednesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... An Alberta Clipper, located over northwest Ohio at 03Z, will streak ESE through southern PA overnight and off to our east by early Thursday. An impressive mid level jet streak is progged to dive through the Ohio Valley and just south of the MD border overnight, placing the region in the favorable left front quadrant of the jet. The low level response will be a strengthening southerly flow and a period of strong warm advection and isentropic lift centered over central PA. Light snow has overspread nearly the entire forecast area at 03Z and expect strongest WAA at nose of low level jet to move from the Laurel Highlands at 03Z to the Susq Valley around 05Z-06Z. Many areas will likely see snow diminish after 06Z, as low level jet shifts east. However, 00Z HREFV2 suggests a moist upslope flow into the the Laurels/Central Mtns should keep the accumulating snow going in that area until almost dawn. As expected with a clipper, model omega/temp time-sections indicate fairly high snow/water ratios. Close to 20:1 expected across northern Pa, where max lift if progged to occur within the best dendritic growth zone. Across the southern counties, indications are for slightly lower ratios with some riming likely based on profiles of temp and lift. Model blended qpf, including contributions from latest HRRR and 00Z runs of the HREFV2/NAM, support storm total snowfall ranging from less than an inch from Chambersburg and York southward, to around 6 inches across Cambria and southern Clearfield counties. Considered upgrading to an warning for Cambria, didn`t see much to be gained by upgrading one county for what would be a borderline, low end warning. Strong wind gusts across southwest Ohio have caught my eye this evening. Although not anticipating the 47kts observed at KILN, do expect winds to become gusty late tonight across portions of Somerset County, as this area briefly breaks into the warm sector south of sfc low. Bufkit soundings support gusts to around 25kts down there by around 09Z. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... The snow should have ended by dawn over nearly the entire region, as fast-moving clipper passes off the NJ coast. High pressure will build in during the day leaving little more than some scattered snow showers over NWRN sections and possibly the Laurel highlands. Highs ranging from the upper teens across the northern tier to around freezing in the far SE will average about 10-15 deg colder than normal. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... A few snow showers for Thursday evening, then clearing and quite cold conditions for overnight under the center of high pressure. Min temps will vary from the single digits over the NW mtns, to the teens throughout the Susq Valley and Southern Tier. A mid level wind max will drop southeast Friday night and early Saturday. Some snow showers expected, mainly across the west. I did up POPS some. For the first part of the weekend, did lower temperatures some more. Still looking mainly dry later Saturday into the first part of Sunday. A complex pattern will prevail after Sunday, with some energy from the southern branch of the westerlies becoming more active. Moisture from the Gulf of Mexico will be limited, with a ridge in place. Expect colder and more in the way of wind by later Tuesday into Wednesday. Overall, minor changes to the package. && .AVIATION /04Z THURSDAY THROUGH MONDAY/...
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* Cloud/Ceiling info will be missing at KBFD until new part can be installed * Light to moderate snow occurring at all TAF sites attm, causing widespread IFR and MVFR cigs and vsbys. These conds will continue for the next several hours into the early overnight. Surface low responsible for the snow is forecast to move to eastern PA by around 12Z/sunrise Thursday. The snow will taper off quickly in the pre-dawn hours with rapid improvement setting in as the storm moves east of the area. The higher elevation terminals could remain MVFR for a good part of Thursday, but elsewhere airports should become VFR by mid morning and continue throughout the day. Outlook... Thu-Sat...Scattered snow showers and local restrictions NW/Laurels. Sun-Mon...Mainly VFR.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 8 AM EST Thursday for PAZ004>006- 010>012-017>019-024>028-033-034-037-041-042-045-046-049>053- 056>059. && $$ SYNOPSIS...Fitzgerald/La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Martin AVIATION...La Corte/Gartner

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