Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 171108 AFDCTP Area Forecast Discussion National Weather Service State College PA 608 AM EST Sat Feb 17 2018 .SYNOPSIS... Low pressure, located over the southern Mississippi Valley early this morning, will track northeast to the Mid Atlantic coast by this evening. An anomalous upper level ridge will build off the east coast next week, with a dying cold front pushing into the state on Wednesday. && .NEAR TERM /THROUGH TONIGHT/... All short term models tracking southern plains shortwave and associated surface low northeast to the southern Virginia by late in the day, then off the Delmarva Peninsula this evening. A quick shot of warm advection/isentropic lift ahead of this system will bring a period of snow to the forecast area this afternoon and evening. An examination of model soundings indicates an all snow scenario, with just a slight chance of a change to rain over southern York/Lancaster counties. Based on ensemble qpf, have expanded advisory into the Middle Susquehanna Valley and tweaked snowfall amounts, generally 2-4 over southern Pa and 1-2 in the north. The heaviest snow is likely to fall roughly between 22Z-02Z, as jet entrance region lifts over the area. 00Z HREFV2 indicates a brief period of 1+ inch/hour rates is possible during this time frame over the Lower Susq Valley, where local amounts of 4-6 inches appear possible. Early sunshine will fade fairly quickly behind lowering/thickening cloud cover today. However, diurnal heating is likely to push readings into the upper 30s across the Susq Valley. Expect temperatures to drop quickly to around freezing as snow arrives and not diminish accums significantly. Expect snow to taper off between 00Z-03Z, as low pressure passes off the Delmarva. However, much lighter orographic snow is likely to linger over the Alleghenies until after midnight. && .SHORT TERM /SUNDAY/... High pressure will build over the region on Sunday, supplying fair and mild weather. Model soundings indicate some early stratocu over the Alleghenies. Otherwise mostly sunny skies expected. Mixing down ensemble mean 925mb temps of around 0C translate to expected max temps from the upper 30s over the high terrain of the Alleghenies, to the mid 40s over the Susq Valley. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Guidance continues to show a building anomalous upper ridge along the east coast next week. A period of rain appears likely Monday, as surface warm front lifts slowly through the area. After that, model guidance indicates central Pa will break into the warm sector with record high temps possible Tue/Wed. Ensemble mean 850 temps progged around 12C. Both 00Z ECENS and NAEFS indicate a dying cold front will push through the region Wed PM, accompanied by a chance of showers. A period of drier and slightly cooler conditions appear likely Thursday, then a renewed chance of rain Friday, as stalled front returns northward. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... High pressure over the region bringing light winds and predominantly VFR conditions - except for an area of pesky MVFR stratucu over western PA extending into JST. This finger of clouds should continue to recede with JST becoming VFR shortly after sunrise. Much of the day Saturday will be VFR, though mid/high clouds will thicken ahead of an approaching weather system. Winds will be from the south and increase to around 10 mph by midday, with some gusts to 15-20 mph generally across the western half. A fast-moving weak low pressure area will zip across the southeast states and off the mid Atlantic coast by Saturday evening, and local impacts will be reductions to MVFR then IFR conditions as light snow spreads in during the mid/late afternoon and persists through the evening. The biggest impacts will be across the southern tier and across the Lower Susq Valley from about 20z through 04z/Sun. Fast-moving nature of the system will bring improving conditions after midnight Sunday with SREF predicting much of central and eastern sections reaching VFR by 12-15z/Sun. Western areas will continue to see reductions from upslope flow/scattered light snow showers into midday Sunday. Winds turn to the west late Sat night and become breezy into first half of Sunday, especially along the spine of the Appalachians with ridgetop winds increasing to 20-25 mph with gusts to 30 mph. Elsewhere, speeds closer to 15 mph will be common. Winds lessen through Sunday afternoon. Outlook... Sun...Clearing, but A.M. restrictions west. Mon...Restrictions return, esp northern half, on Monday in periods of rain. May start as a short period of wintry mix. Tue-Wed...Restrictions likely in rain showers, mainly NW. Elsewhere, occasional restrictions possible, though much of the period may end up being dry with decent conditions. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 4 PM this afternoon to 2 AM EST Sunday for PAZ027-028-050>053-056>059-063>066. Winter Weather Advisory from 2 PM this afternoon to 4 AM EST Sunday for PAZ024-033. Winter Weather Advisory from 2 PM this afternoon to 11 PM EST this evening for PAZ025-026-034>036. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald AVIATION...RXR

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