Area Forecast Discussion
Issued by NWS State College, PA

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970 FXUS61 KCTP 220331 AFDCTP Area Forecast Discussion National Weather Service State College PA 1031 PM EST Wed Feb 21 2018 .SYNOPSIS... An anomalous upper level ridge will remain parked off the southeast coast through the upcoming weekend. At the surface, a quasi-stationary front will oscillate in the vicinity of Pennsylvania through next Sunday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... A relative lull in the precip is expected the first part of the night, as dying cold front sags south of the state and high pressure and colder air mass settles in. MRMS RALA at 03Z showing just a few showers across southern Pa and the northwest mountains. Steadier/heavier precipitation will redevelop late tonight, as a weak wave along the stalled front ripples eastward toward Pa. Main forcing mechanism will be the strong frontogenetic forcing within right entrance region of Grt Lks jet streak. Band of precipitation over the Ohio Valley is lining up well with model 850-700mb fgen fields, which support the idea of the axis of heaviest precip moving across northern Pa between 09Z-18Z. Meanwhile, colder air will continue to filter into the region on northerly flow setting the stage for a wintry mix across northern PA Thursday. Based on model soundings and latest HREFV2, it looks like mixed precip to turn to snow around 12Z across the northern tier of counties. Further south, precip may initially begin as rain, but expect a transition to freezing rain over the high terrain along I-80 by around dawn. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... HREFV2 suggests a period of heavy snow is possible between 9am and noon along the NY border, as influx of anomalous PWATS combines with strong fgen forcing within jet streak right entrance region. Further south, a more shallow layer of cold air will result a fzra/sleet mix along and just north of I-80. Across the southern half of the state, model soundings support a mainly rain event. However, the ridgetops of the Laurels and central mountains are likely to be just cold enough for fzra through around midday. Based on model blended qpf, most likely snow accums range from around 3 inches along the NY border, to nothing from I-80 southward. Ice accums over most of northern Pa should average around a tenth of an inch. However, the higher terrain along I-80, where ptype should be primarily fzra, could see close to a quarter inch. Expect precipitation to taper off from west to east between 19Z-21Z, as low level jet and associated plume of deep moisture shifts east of the state. Residual low level moisture, combined with an upsloping easterly flow, is likely to yield lingering drizzle over much of the region into the evening with fzdz possible over the higher terrain of northern Pa. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Did not change much for Thursday night into Friday. New 12Z GFS numbers show some sites colder tonight and Thursday night and some warmer. Current fcst looks decent. While it could be a little cooler...we are colder than others by a tad...especially on Friday...so I did not want to go down more at this point. Weekend still looks similar to the last few days. Best chance for a warm up is Sunday...as system lifts to the north and west of central PA. This track is a little further west now...which would keep the heavy rain threat further away from our area. Depending on the mixing...more record highs could occur. Looks dry after Sunday evening. More information below. Forecast for Thursday into Friday looks cloudy and damp with periods of light rain/drizzle and areas of fog. The fog will be locally dense at times, especially on East-Facing slopes and ridgetops during the overnight and early to mid morning hours. Stalled out sfc front across the Virginias and Ohio River Valley and SW flow aloft will be the conduit for a few waves of low pressure to ripple NE along, and bring us this rather dismal weather. There is the potential for a significant change in practical weather...if frontal position changes north or south very much. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... A sharp cold front will continue to slide SE across the flying area with VFR dominating the warm air east of the front and MVFR/IFR with scattered rain and showers on the cold side of the front. Some drier air and improved conditions will move in this evening as the front settles south, but will be replaced by lowering ceilings once again between about 06-12Z as a new area of rain overspreads the region. Across the far north a wintry mix of freezing rain, sleet and snow is likely and could last into the early afternoon hours. An active second half of the week follows, as several weak waves of low pressure bringing bouts of rain, and even some light freezing precipitation to the north Thu into early Fri. Outlook... Fri...Widespread restrictions in periods of rain. Some improvement poss SW late. Sat...Rain remains likely. Widespread restrictions north, gradual improvement south. Sun...Widespread restrictions likely in periods of rain. Mon...No sig wx. && .HYDROLOGY... Recent rainfall and snowmelt has resulted in wet 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. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 1 AM to 4 PM EST Thursday for PAZ004>006-010>012-017-018-037-041-042. && $$ SYNOPSIS...Fitzgerald/La Corte NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Lambert/Martin AVIATION...La Corte/Gartner HYDROLOGY...

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