Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 201823 AFDCTP Area Forecast Discussion National Weather Service State College PA 223 PM EDT Sun May 20 2018 .SYNOPSIS...
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A weak cold front will settle south of the area by this evening followed by drier air that will finally work into the region. During the day Monday, this same old frontal boundary will lift back northward as a warm front. Showers and scattered thunderstorms will accompany the front as it lifts north across the Commonwealth.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Satellite shows brightening skies, but with plenty of post frontal strato-cu over northern areas. The HRRR doesn`t make me optimistic for these clouds to mix out in time to bring much sunshine before the afternoon is over. Over the SE, still ahead of the weak front, a few showers are developing. They are still fairly squat and despite the RAP showing max CAPEs in excess of 1000J, lapse rates are not very impressive so we expect little more than some brief showers and maybe a rumble of thunder. The HRRR shuts things down fairly quickly after about 5PM. High pressure over the Upper Midwest/Northern Great Lakes will build SE and moves across Pennsylvania late tonight and Monday morning with fair/dry weather, lower humidity and light wind helping to yield cool temps. Recent rains have left conditions moist, so some late night fog looks like a fair bet. Lows tonight will vary from the upper 40s across the Northern Tier of PA to the lower 60s in the Southern Valleys.
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&& .SHORT TERM /MONDAY/...
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The gift that keeps on giving in the form of our cold front, will start to make a return Monday as a warm front. The first showers could reach my SWRN Laurel Highlands zones by mid day, but more likely we will see the chance for showers ramp up from SW to NE as the afternoon progresses. Ensembles show the PWATs starting to creep up and 12Z guidance shows some erosion in the stability, so thunderstorms will be possible. Highs should be relatively pleasant topping 70 everywhere. That`s a few degrees warmer than normal for the time of year.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... After being suppressed to our south early next week, the chances for showers will increase once again Monday as moisture on the northern periphery of the subtropical ridge creeps back into the region as an old frontal boundary lifts to the NE as a warm front. Diurnal nature of convection will bring mention mainly over the SW third of CWA for mainly afternoon showers /thunderstorms. Interestingly, GFS indicating a ribbon of drier air sliding across the north (ahead of moisture return) just off the surface that should mix down midday over the northeast and could drop dewpoints into the lower 40s at KIPT for several hours. Numerous showers along with a few thunderstorms will bring a few to several tenths of an inch of rainfall to much of the region Monday night into Tuesday before drier air makes a push in from the NW starting Wednesday. Tuesday looks potentially cooler than current guidance with clouds/showers around, esp over the southern half of CWA. So undercut MOS by a couple degrees. From there it looks like the period form Wednesday through Friday will feature some rare (of late) rain-free conditions, before the chance for a pop-up shower or storm becomes returns for Sat. Temps look to climb into the 70s each day, with Saturday the warmest as high range from the mid 70s to the lower 80s. The coolest morning will be Friday with valleys of the northern mountains dipping into the mid 40s. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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The cold front seems to be getting absorbed in the lee side trough over the lower Susq Valley. RAP shows some CAPE over the SE and a few showers/storms starting to fire in the marginally unstable airmass. The SERN terminals will have the highest chance of seeing brief reductions associated with the passing convection. BFD is holding onto a MVFR ceiling, but all other airports are VFR and should continue into the evening. Partial clearing tonight combined with light winds and residual low level moisture from recent rains will produce fog/visibility impacts Monday morning. Outlook... Tue-Wed...Variable conditions with showers and thunderstorms mainly in the afternoon/evening. Thu-Fri...AM Fog. Otherwise VFR/no sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...Lambert/RXR AVIATION...La Corte

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