Area Forecast Discussion
Issued by NWS State College, PA

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828 FXUS61 KCTP 260205 AFDCTP Area Forecast Discussion National Weather Service State College PA 1005 PM EDT THU AUG 25 2016 .SYNOPSIS...
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Thunderstorms should diminish as they move to the east overnight, but will still make much of the area wet. A seasonably warm and humid late- summer weather pattern will continue across Central Pennsylvania into next week.
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Tiny, discrete supercells have now merged into one big bow echo which should be accellerating through the CWA shortly. An MCV seems to be forming in the central part of the bow. Weakening is still forecast, but some CAPE above 1000 Joules is still available to the east of the bow. EHI just above 1 in the swrn part of the CWA. The shear along the southern fringe of the bow might still make some rotation in any cells which can form away from the bow and also at the tail end of the bow - much like just happened north of PIT. Will follow the HRRR timing as it seems to have a really good handle on current development/convection. It develops the cold pool (if 72/70 can be considered cold) and accellerates the bow thru the central mtns. Prev... Current radar mosaic over the NW seems rather benign at this time. However, there have been a few cells with 50kft+ tops and persistent rotation. So far, those nastier cells have stayed away from the CWA. Have refined the timing just slightly with this update. But, the main shot of precip is associated with a short wave trough that is moving through wrn NY and wrn PA. Dewpoints ahead of the line/s of showers are still in the l70s, and inflow/source dewpoints are in the m70s from SWrn PA. Thus, these showers (and the few tsra) should continue for a little while, but near-term models still indicate significant weakening/scattering as it moves through the c mtns. Prev... HRRR runs show convection entering nw cwa this evening. A few of these storms will be quite strong with frequent lightning...gusty winds and brief heavy downpours accompanying them as the move east and southeast. Convection will weaken after sunset with loss of heating...somewhere close to Centre County and points north south...likely not making it much further east. After convection diminishes look for another warm and humid night.
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&& .SHORT TERM /8 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Ridging will bring warm temperatures aloft to limit threat of convection. Slight less surface moisture will make things feel more comfortable though temperatures will once again top out well above average. Sfc high will build over the region Friday night, resulting in a fair and mild night. Will have to watch for the possibility of patchy valley fog over the northern mtns late. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Medium range guidance is in good agreement in keeping an anomalous ridge aloft in place over the region 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. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... VFR conditions continue this evening across Central Pennsylvania. Broken convection in far northwest Pennsylvania and Southwest New York slowly making progress towards KBFD. Included mention of VCTS in KBFD from 01z to 03z. Short range models continue and try and carry convection into Central Pa this evening, with activity reaching a KIPT-KUNV-KJST line between 03z and 05z. At this point, have held off mention of SHRA/TSRA in any of the other TAF locations...because of lower confidence /30 POPs/. Will continue to monitor evolution of activity for possible inclusion in TAFs. For Friday, some morning restrictions should give way to VFR conditions. Outlook... Fri...Morning restrictions in fog and lower ceilings, then VFR. Sat...Patchy morning fog...otherwise VFR. Sun...Mainly VFR...but isolated TSRA western 1/3 airspace in the afternoon. Mon-Tue...Isolated/Scattered thunderstorms possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ross NEAR TERM...Ross/Dangelo SHORT TERM...Ross LONG TERM...La Corte AVIATION...Jung is the U.S. government's official web portal to all federal, state and local government web resources and services.