Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240213 AFDCTP Area Forecast Discussion National Weather Service State College PA 1013 PM EDT Sun Jul 23 2017 .SYNOPSIS...
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A frontal boundary will remain in the vicinity of Pennsylvania through Monday, touching off scattered to numerous showers and strong thunderstorms, some with heavy downpours through late tonight and early Monday morning. Another round of showers and thunderstorms is expected on Monday before high pressure builds into the region by the middle of next week. Some of the storms on Monday may make damaging winds and large hail. A cold front will likely push southeast in the state toward the end of next week.
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&& .NEAR TERM /UNTIL 8 AM MONDAY MORNING/...
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Tweaking the FFA area based on current radar and trends observed. Specifically, a vort max and it`s forcing over wrn PA is going to ramp up and expand the heavy rainfall over the north and central - but especially so over the Mid-Susq valley. As it slides eastward overnight, it will at first enhance the lift, but also should kill things off as the negative influence of the western side of the short wave trough moves across. Prev... Heaviest convection waning over the east, but moisture remains very high. Flooding in Middletown is pretty bad at this hour, but may start to improve shortly without current rainfall. However....... Convection over the N is along a wind shift boundary and most is sliding to the south. Convection over SWrn PA is looking like it will collide with that boundary. Most CAMs do pump up convection over the central counties - and the cells just to the S of UNV and IPT are evidence that it is still unstable in some small degree. Thus, will have to continue to watch for flash flooding. The wettest areas and the most likely areas to see heavy rain later tonight are in the FFA already. Will see if we can`t trim it back a bit from the earlier expansion, but likely no trimming done before we can see where the next few hours takes us. Prev... Ridging aloft with deepest layer moisture pooled to the south of quasi-stationary front draped across central PA this afternoon. Still sufficient moisture for isold to sct coverage of showers and now isold tstorms tracking into the Laurel Highlands. Boundary layer winds still extremely weak, so the main threat from any of these slow movers is a locally heavy downpour through late afternoon. NCAR ensemble CAPEs still pointing toward near 2000 J/kg values and although speed shear is a bit lacking for a hail threat late this afternoon and early evening. By early to mid evening, however, increasing large scale forcing ahead of approaching upper trough should will support increasing coverage of showers/ thunderstorms with more organized and possibly training clusters of storms expected. CAMs have been latching onto this idea since the overnight, and painting 2-4" amounts over portions of the middle to lower Susq River Valley. Some of these areas have 3 hr FFG values as low as 1.5". Coordinated a FF Watch for my east central and southeast Counties with BGM and PHI...focusing on the evening to overnight timeframe for greatest heavy rainfall threat (running from 21z through 09z Mon). Lesser threat of severe given absence of boundary layer winds, but some storms could produce strong downbursts as well from impressive water loading. Locally heavy rain and FF threat lasts into the pre dawn hours, especially middle to lower Susq. which CAMs suggest will see multiple rounds/clusters with potentially heavy rainfall.
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&& .SHORT TERM /8 AM MONDAY MORNING THROUGH 6 PM MONDAY/... Upper trough will pivot through on Monday, bringing a good chance of additional showers/storms to northeast Pa, while large scale subsidence in its wake is likely to suppress convection across the southwest part of the state. With the exception of northeast Pa, Monday should feature more sunshine than today, as much lower PW air finally flows into the region. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Not a lot of change from yesterday. Still going mainly with dry conditions Tuesday into Wed. Did lower temperatures a degree or so on Tue, given concern for some clouds and lack of real strong cool push. Also models show pair of weak lows just inland from the south shore of the lower Great Lakes, not sure what to make of this. A strange summer lately. Still expecting showers and storms on Thursday into the first part of Friday, with the next cold front. Went with mainly dry conditions after early Friday. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... At 00Z the latest radar has showers and thunderstorms moving through eastern PA bringing heavy rain. These are exiting the region but will bring -SHRA with VCTS to IPT through 01Z. The next line is approaching from the west along a boundary which will reach JST with possible -TSRA between 02Z to 03Z. These will slide along the southern tier of counties and have timed them through the TAFs. Latest short term models are showing the precipitation should exit the region between 09Z to 11Z. Expect cigs and vsbys to drop to IFR and LIFR shortly after due to low stratocu and valley fog. The restrictions should lift between 12Z to 14Z. Another round of showers and thunderstorms are possible tomorrow afternoon due to another trough moving through the mid Atlantic. Expect showers and thunderstorms west to east after 19Z. Tonight, restrictions return in wake of trough axis, with IFR conditions likely in the north and east, and MVFR in the central mountains. .OUTLOOK... Tonight...Cig restrictions likely. Scattered TSRA/SHRA. Mon...AM restrictions likely. Scattered TSRA. Tue-Wed...AM restrictions north/west. Otherwise no sig wx. Thu-Fri...Chance of afternoon TSRA/SHRA. && .CTP WATCHES/WARNINGS/ADVISORIES...
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Flash Flood Watch until 6 AM EDT Monday for PAZ006-010>012-028- 037-041-042-045-046-049>053-056>059-063>066.
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&& $$ SYNOPSIS...DeVoir NEAR TERM...Dangelo SHORT TERM...DeVoir LONG TERM...Martin AVIATION...DeVoir/Ceru

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