Area Forecast Discussion
Issued by NWS State College, PA

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453 FXUS61 KCTP 280641 AFDCTP Area Forecast Discussion National Weather Service State College PA 141 AM EST Tue Feb 28 2017 .SYNOPSIS... Return flow around high pressure off the mid-Atlantic coast will bring milder air into the region through the middle of the week. Low pressure will move across the Ohio Valley and track north of Pennsylvania midweek, bringing a rainy period followed by a potent cold front late Wednesday. Much colder air is in store for late week, with sub-normal temperatures likely over the weekend. && .NEAR TERM /UNTIL 7 AM THIS MORNING/... Spinkles moving north of the arewa. Little to no wind around but clouds abound. There is clearing right along the Mason-Dixon Line and this might work north a few inches. But, clouds from earlier upstream convection moving in now. They are higher clouds, though, and not as likely to re-radiate a significant portion of the terrestrial longwave radiation. Will therefore hold forecast temps as is across most of the area, but nudge them down a hair in the far south. && .SHORT TERM /7 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... Low pressure deepening over the upper midwest Tuesday will push a warm front into the state bringing showers and perhaps a thunderstorm or two late day or Tue night. Overall, precip will be on the light side during this period. Temps on Tuesday will be another 10F higher than today thanks to the warm advection and morning sunshine - especially in the south. Readings climb back into the 50s north/60s south. A very mild night in store for Tue night as warmer air surges in from the SW ahead of a potent low pressure system - keeping lows in the 50s most locales. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Severe thunderstorm risk is the primary focus on Wednesday with another strong cold front impinging on a convective environment characterized by unseasonably warm temperatures, above normal PW, relatively low instability and very strong low-to-mid tropospheric winds. There is still some uncertainty in the details such as timing and whether CAPE can be realized due to preceding clouds/pcpn. Despite depicting clear potential for strong to severe storms given high shear/low cape scenario, there is still room for adjustments as models begin to converge on a consensus solution. The key message is preparation for what could evolve into another damaging thunderstorm wind event. The threat and risk information have been communicated through the HWO and social media/decision support channels with updates coming tomorrow morning with the Day 2 SPC outlook. It will turn noticeably colder Wednesday night into Thursday as strong NWLY post-frontal flow directs colder air into the area. Widespread 30-35 mph wind gusts are probable with 40+mph gusts possible on the Laurel ridges. The surge of CAA will bring snow showers downwind of Lake Erie into the NW Alleghenies/Laurels with minor accumulations (<1 inch) forecast Wed. night into Thursday morning. A broad trough remaining over the Northeast U.S. on Friday will push off the coast by the beginning of the weekend. A clipper system associated with the final piece of shortwave energy embedded in the trough may bring a mix of snow and rain Thursday night into Friday with a light accumulation possible. The mean 500mb flow is fcst to flatten out a bit over the weekend with temperatures moderating nicely to above average after bottoming out on Friday. Overall, the pattern looks fairly quiet over the weekend and into early next week with another strong frontal system possible by March 7-8. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Mainly mid level clouds across the region as of midnight. Some lower clouds at BFD. 06Z TAFS sent. Earlier discussion below. Weak shortwave has now weakened and slid off to the northeast. Showers and patchy drizzle are pretty much over for the night, as radar showing just minor returns in the northeast...likely not producing any sensible weather at the surface. All locations now back to VFR conditions. As a warm front approaches Tuesday, expect lowering conditions, with showers moving into the west during the later afternoon. Some restrictions in ceilings and visibilities are expected late (after 20z) in the western airfields. Outlook... Wed...Rain showers/Sub-VFR reductions. Breezy. LLWS likely. Chance of thunderstorms. Wed Night...Strong FROPA early with gusty winds/tstms. Thu-Fri...Sub-VFR likely west in sct snow showers. NW winds. VFR elsewhere. Sat...No sig wx. && .CLIMATE... With only one more day left in meteorological winter (Dec+Jan+Feb), it seems that we are currently running as the 4th-warmest winter at both Harrisburg (tie) and Williamsport. Today should be another above-normal day, which may push Harrisburg up to 3rd place, and Williamsport may get nudged up to a tie for or even an outright 3rd place. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/RXR NEAR TERM...Dangelo SHORT TERM...RXR LONG TERM...Steinbugl AVIATION...Jung/Martin CLIMATE...Dangelo is the U.S. government's official web portal to all federal, state and local government web resources and services.