Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 260940 AFDCTP Area Forecast Discussion National Weather Service State College PA 540 AM EDT FRI AUG 26 2016 .SYNOPSIS... A large ridge of high pressure at the surface and aloft will build over the Mid Atlantic Region through the upcoming weekend, bringing a string of warm and dry days. A weak front will try to push southeast across the state Sunday night into Monday morning and could be accompanied by a shower or thunderstorm. Another period of warmer than normal and dry days will follow for Monday, Tuesday, and possibly Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Last vestige of convection (just ahead of a weak pre-frontal trough) were exiting our far SE zones at 09z. Plenty of convective debris mid/high level cloud cover across the Susq Valley and points east (and quite extensive strato cu across the nrn and wrn mtns of PA), will combine with high sfc dewpoints in the upper 60s to lower 70s, and light wind across the central two-thirds of the CWA to bring a warm/muggy start to the day today. Expect to see just some patchy fog through the mid morning hours in areas that received some of the heavier rain Thursday evening (which is across the NW Mtns and Laurel Highlands). Temps will struggle to dip into the mid 60s across the mtns... and will start out in the 70-75F range throughout the Susq Valley. For later this morning and this afternoon...PWATs that were close to 2 inches last evening and early today...will decrease to less than 1.5 inches across much of the state...but will still linger close to 1.75 inches right along the Mason-Dixon line. There...sfc based cape should climb to 1300 j/kg or higher between 18-23Z today
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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Ridging during the day today will maintain quite warm temperatures aloft (plus 7-9C) Combine this with a lack of noticeable, organized Theta-E convergence and minimal mesoscale upward Vertical Velocity, and we`ll see a great limitation to the threat of convection. Slightly less surface moisture will make things feel more comfortable, though temperatures will once again top out well above average. Sfc high will slide right over the region tonight, resulting in a fair and mild night. Will have to watch for the possibility of patchy valley fog over the northern mtns late.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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A weak cold front will bring the chance for a few showers or thunderstorms late Sunday into Monday morning. Otherwise, Medium Range Guidance is in good agreement in keeping an anomalous ridge aloft in place over the region Sunday...into the early days of next week. This will assure we remain warmer than normal with daytime highs in the mid to upper 80s, low to mid 90s over southeastern areas, at least into Tuesday. By mid week week, weak troughing rippling through southern Canada and the Great Lakes is made to erode the northern portion of the northeastern ridge a bit, but only to the extent that upper heights and temperatures fall back closer to normal values. The NAEFS and GEFS end up carving out a weak mean trough by the end of the week, but once again heights and temps are forecast to be near seasonal norms so it should remain quite pleasant with the biggest chance being a break in the humidity. Chances for rain will be generally limited to scattered diurnal convection each day, but with warm air aloft the chances should remain small in the absence of well defined forcing. There is a period later Sunday into Monday morning as we come under the northern edge of the subtropical ridge and a weak cold front approaches, which could be the first hints at the development of a more significant MCS upstream. But with such a strong ridge aloft it`s hard to be confident at this range. Main item of difference is the tropical system the ECMWF blows up over the southeastern Gulf of Mexico early next week that the GFS doesn`t do much with at all. Both model suites agree with the northern stream trough mentioned above to be enough to keep any possible tropical developments well south of the local area.
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&& .AVIATION /09Z FRIDAY THROUGH TUESDAY/... Isolated TS impacting KMUI/KMDT/KLNS 08-09z. No additional TS expected today. The main concern will be low cigs over the western 1/3 of the airspace, as weak upslope flow combines with high boundary layer moisture. The light westerly wind should limit fog formation and visibility restrictions, thus favoring low cigs. It should also allow for VFR to prevail east of the Alleghenies due to opposite downslope effect. Diurnal mixing and increasing surface wind from 270-320 degrees will spell improvement to VFR by mid morning. VFR continues through tonight with some local restrictions in fog possible early Saturday morning. Outlook... Sun...scattered TS northwest 1/3 airspace in the afternoon. Mon-Tue...low chance of TS. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...La Corte/Lambert AVIATION...Steinbugl

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