Area Forecast Discussion
Issued by NWS State College, PA

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093 FXUS61 KCTP 250327 AFDCTP Area Forecast Discussion National Weather Service State College PA 1127 PM EDT Wed May 24 2017 .SYNOPSIS... A storm over the TN valley will deepen and slide over PA on Thursday and up the New England coast Friday. Rain tonight and Thursday morning will be followed by scattered showers through Friday night. Saturday may be the best day of the weekend. The second half of the Memorial Day weekend looks wet with another storm system moving through the Great Lakes. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Showers have overspread the western half of central PA as of late evening and are rapidly spreading ENE across central VA. Eastern half of central PA will be raining in most areas by 06z...as secondary 850 mb jet lifting northward from the central and northern Virginia strengthens and focuses forcing over central and eastern PA. This feature becomes quite robust by 09-12z...strengthening to over 40 kts as the nose of the LLJ tracks northward through PA after 12z. This should support moderate rain arriving north of the Mason Dixon line between 09z and 15z...and current QPF amounts of near or slightly over 1 inch for my south central and central zones look good at this time. While the low levels remain quite stable. The steadiest rain will be crossing the Mason- Dixon line around sunrise... in conjunction with the aforementioned LLJ.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... The rain will lift up northward through the morning. However, it looks to stay cloudy for another few hours. The southerly flow is not all that strong and may not help to scour out the low clouds very efficiently. Showers may again develop - esp if there will be breaks develop in the south. These would then rotate north in the aftn. But, for most folks there will be a brief break of just cloudy during the morning in the south and midday central and elsewhere. Again, if the low clouds hang around too long, the arrival of the upper energy will not line up with sun/instability. May be able to make some points on MOS by keeping temps down a notch or two in the south. The sky cover forecast for Thurs is pretty bleak, so we will hold maxes below guidance a bit. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... The strong upper trough will consolidate low pressure at the surface over PA producing a rainy Thursday night before lifting it up the New England coast Friday. Broad cyclonic/northwest flow with additional shortwaves rotating around the departing upper low will keep showers in the fcst on Friday before precip winds down Friday night/AM Saturday. A lower-amplitude mid level flow pattern in the wake of the departing closed upper low will feature rising heights/weak ridging aloft into the weekend. The pattern will evolve into a broadly cyclonic flow regime by early next week with upper low spinning between the Great Lakes and Hudson Bay into midweek. There is still some uncertainty regarding the location and timing of shortwave impulses that could be a factor for convection on Saturday. Model and ensemble guidance still favoring locations to the south/west of Central PA so a dry start to the holiday weekend may be in store for the area. Model blend maintains the highest POPs on Sunday with a risk for thunderstorms as well as a frontal system slides through. Another round of showers (storms SE) possible for Memorial Day, with sct showers poss lingering Tue into Wed as the parade of shortwaves around the trough continues into midweek. && .AVIATION /04Z THURSDAY THROUGH MONDAY/...
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MVFR/IFR ceilings have advected into most of the flying area as of 11PM, and conditions will continue to deteriorate as the rain overspreads the region. MVFR/IFR conditions will continue into the morning in the south and perhaps well into the afternoon in the north. Breaks associated with the dry slot will develop in the south in the morning as the steady rain pulls away. This will set the stage for some modest instability to develop leading to the chance for a thunderstorm in the afternoon. .OUTLOOK... Fri...Scattered showers with MVFR ceilings, mainly over western terminals. Sat...Mainly VFR with scattered rain showers. Sun...Reduced conditions with scattered showers/thunderstorms associated with a cold front. Mon...Mainly VFR with scattered showers/thunderstorms.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Steinbugl NEAR TERM...Dangelo/DeVoir SHORT TERM...Dangelo LONG TERM...RXR/Steinbugl AVIATION...La Corte

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