Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 241938 AFDCTP Area Forecast Discussion National Weather Service State College PA 338 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/... Low clouds have clogged up the skies in the southwest on deep ESE flow. Diurnal cu are expanding across the rest of the area, and will put a halt to our warming. These cu will likely just turn to a lower deck of stratus. The light rain over PBZs area will continue to stream over Warren Co for another hour or so. But, a break will then occur until the short wave trough over KY lifts and sends the showers currently over the Hatfields and McCoys up toward the Laurels. Will leave out the mention of thunder for tonight, but there may be a rumble. It is going to be pretty stable with all the low clouds. Forecast precip amounts remain on track with the 0.75-1 inch numbers advertised for a while. Recent runs of the numerical guidance incl SREF show a slight uptick to a general/widespread 1 inch with 1.2 on the high end. The end of the steadier rain will be crossing the Mason-Dixon line around sunrise. && .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 guid a bit. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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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.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... Cu thickening over most of the area due to heating of the day where sun dominated earlier. Winds will be gusty through the first part of the night. The rain will become more organized through the evening and spread SW-NE unevenly. Everyone will drop to IFR somewhere between 03 and 08Z as the rain and fog bring vis down concurrently with the clouds lowering to IFR. There is a very brief period in the middle of the night when there could be some LLWS, but there should be gusty sfc winds coincident with the passage of this low-level jet feature. So, will leave out the mentions of WS at this point. IFR cigs and vis will continue into the morning in the south and perhaps well into the aftn in the north. Breaks may begin to appear in the S in the morning a few hours after the steady rain pulls away to the north. So, there is a small chc for TS in the aftn across the S as the upper low and cooler air aloft will contribute to instability on Thurs. The sfc and upper low both cross the area Thur night. This will keep sct SHRA going. The NW cyclonic flow will generate additional SHRA all of Fri in the western terminals. Some of those SHRA may extend into the rest of the area. .OUTLOOK... Sat...SCT SHRA NW. VFR elsewhere. Sun...Reduced conditions with scattered showers. Mon...Occnl SHRA/TSRA. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Steinbugl NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...RXR/Steinbugl AVIATION...Dangelo

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