Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 310945 AFDCTP Area Forecast Discussion National Weather Service State College PA 545 AM EDT SUN JUL 31 2016 .SYNOPSIS...
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The plume of deep moisture that brought numerous heavy showers and scattered thunderstorms to the region on Saturday, will slide into extreme Pennsylvania late this morning as a weak trough drifts across the state. Behind this first trough, another disturbance aloft and weak area of low pressure at the surface will drift northeast from the Ohio Valley...bringing scattered mainly afternoon showers and isolated thunderstorms. A slight chance of showers and isolated afternoon thunderstorms will continue on Monday as a pool of cooler air aloft moves over the warm and still rather humid air at the surface. Warm and dry conditions are expected for Tuesday and Wednesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Slowly northeastward drifting showers will be confined to mainly the northeastern one-third to one-half of the CWA for the rest of this morning as the axis of high...2 inch PWAT air and meso jet of 30-40kt southerly 850 mb winds drifts into far NEPA and Sern NY. A quasi-stationary sfc front was draped east-west along the entire length of Interstate 80 in PA at 0830Z. A 60-70kt upper level jetlet over the middle Ohio Valley will move northeast...dragging its thermally direct right entrance region over the frontal boundary (and plume of higher PWAT air across Eastern PA) this afternoon. This mesoscale area of lift and favorable convective parameters will help to spark scattered showers and isolated afternoon TSRA. Though basin average rainfl amounts are expected to be 0.20 or less today...highly localized one-inch amounts are still possible across the Susq Valley and points east by dusk. Areas of fog (and highly localized dense fog) will persist through 13z before dissipating to just some areas of 5-6SM haze later this morning...then 7-10SM this afternoon. Max temps this afternoon will be a few to several deg F warmer than Saturday in many locations...ranging from the u70s to around 80F across the Northern and Western Mountains...to the mid 80s in the Susq Valley.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
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Sfc frontal boundary sags Se across the state tonight. Any sctd evening showers (and a few isolated TSRA prior to 02Z) will end around or by after midnight across all but perhaps the far eastern part of our CWA. Areas of partial clearing...combined with light wind and still moderately high sfc dewpoints in the 60s will lead to areas of 1/2Sm fog forming late. Min temps early Monday will vary from the u50s in the perennial cold spots of the north...to the u60s in the SE valleys.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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Main upper level trough axis and pool of cool mid/upper level air drifts across the CWA Monday. Low-mid level lapse rates will increase to 6-6.5C/KM Monday afternoon...causing one final round of scattered showers and isolated TSRA (especially across the eastern half of the state)...before high pressure builds in from the west at the sfc and aloft for Tuesday and Wednesday with dry conditions and near to slightly above normal high temps. Short-wave energy over the upper Great Lakes Wednesday weakens and drops to the SE as large scale height rises push northeast and sharpen across that region. A second/minor upper ridge axis builds into Western PA by 12z Thursday. Any upstream convection from this aforementioned shortwave should dive mainly SSE toward the Mid Ohio Valley Wed night (with the eastern edge of the SHRA/TSRA possibly brushing the Laurel Highlands during that period. 30/12Z Nbm pops are in the 25-30 percent range across our western zones Wed night...while GMOS and Official NDFD grids are closer to 10 percent. ECMWF takes the bulk of any convection south across Ohio into WVA leaving PA dry for late Wed night through Thursday night. 31/00Z GFS/GEFS is weaker and further north with some convection over the southern and wrn mtns of PA. Stayed closer to the ECMWF solution with no POPs at this point. Both models agree on a more rigorous cold front dropping southeast toward PA on Friday. This will help surge the temperatures and humidity up ahead of it over central PA Friday. Right now the timing is such that late day convective storms will feed off the days heat and humidity and roll through late in the day into the overnight. Models bring the cold front southeast across PA overnight and then stall it near the Mason- Dixon Line for Saturday.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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Been updating TAFS quite a bit this shift. While most places have some fog, there is a lot variation in conditions. Expect things to improve some this afternoon. However there will be still a chance for a few showers and storms. Some fog is possible late tonight again. Conditions should improve for Tuesday into Wednesday, as weak high pressure builds southward from eastern Canada. OUTLOOK... MON...Am fog possible, then isold pm tsra impacts possible. TUE...Am fog possible. WED...No sig wx expected. THU...Isold pm tsra impacts possible western Pa.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Watson/Lambert AVIATION...Martin

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