Area Forecast Discussion
Issued by NWS State College, PA

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740 FXUS61 KCTP 301825 AFDCTP Area Forecast Discussion National Weather Service State College PA 225 PM EDT SAT JUL 30 2016 .SYNOPSIS... A plume of deep moisture on the west side of the subtropical ridge will produce showers and thunderstorms over the region into early Sunday. A weak trough will push the deep moisture to our east Sunday. Behind this system it will slowly dry out. A ridge building to our west early next week will work its way eastward producing some hot weather later in the week. This surge of warm air appears to be just ahead of what could be a real cold front and a real break from the warm weather we have had for the past month. && .NEAR TERM /UNTIL MIDNIGHT TONIGHT/... Radar shows several areas of rainfall over the region. An east-west band along the weak frontal boundary is over the northern tier counties. Some locally heavy rainfall in this boundary with 1-3 inches as it drifts slowly to the northeast this afternoon. There is a band moving across central regions which is producing 1-2 inches based on STA and MRMS data. To the east some scattered showers area ahead of this and another area of rain is to our west still. The air mass is very moist with 1-2SD above normal PW values and dew points in the east are in the 70s. Cores of heavy rain are possible. Along the northern tier counties dew points are still in the low to mid 60s. The HRRR implies these 3 features move slow east (northern band drifts northeast). The HRRRV1 and V2 imply that the stuff in central PA might develop into moderate to severe convection as it moves into southeastern areas. Some runs now show linear and possibly bowing segments this afternoon from Franklin County east. Areas under these bands could see moderate to heavy rainfall and embedded thunderstorms of course. Put moderate RW and thunder with heavy rain in the grids 17 to 03Z. && .SHORT TERM /MIDNIGHT THROUGH 6 PM SUNDAY/... The NCEP HRRRV2 appears to get 80 percent of the rain out of our area by about 0500 UTC. Rain should taper off west to east this evening and tonight with most of the steady rain to our east a few hours either side of midnight. The larger scale models still have moisture lingering and a slow drying trend. Thus they still produce afternoon convection and nearly all have some QPF. Kept PoPs lower than the model blends as they have a significant wet bias. But heating Sunday will likely produce at least a chance of showers and thunderstorms. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Short-waves sweeps to the coast but broad upper level trough lingering across PA. The main trough axis lies through Central PA by 12z Monday and slowly progresses east through the day. With the trough and cyclonic flow aloft scattered showers/isolated thunderstorms are possible with best chances over the eastern counties in the afternoon. High pressure builds in Monday night and everything begins drying out. For Tuesday into Wednesday a sharp upper level ridge is to our west over the Great Lake region with the trough now off the coast, dry NW flow and surface high pressure across the region. Short-wave weakens the ridge into Thursday. ECMWF takes this south across Ohio into VA leaving PA dry. GFS is weaker and further north with some convection over the PA mountains which it moves east across PA through Thursday night. 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. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Showers and thunderstorms are slowly moving across central Pennsylvania and there is a weaker line of showers near the New York border. Showers and thunderstorms will lower ceilings and visibilities to IFR at times. Some of the storms in southern PA will have heavy rainfall at times with them. There could be some winds shear near the storms and the outflow from the storms. Overnight the rain and shower activity diminish. Rapidly in the 00 to 03 UTC range. But the moisture air with recent rainfall favors fog and patch dense fog in valleys. Lots of IFR after midnight. Fog burns to haze early Sunday mainly VFR and MVFR by mid-morning. Could be showers/thunderstorms in the afternoon Sunday. Far fewer than today. OUTLOOK... SUN- MON...Morning fog restrictions, then scattered showers and isolated thunder. TUE- WED...Mainly VFR, but with morning fog restrictions. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...Watson AVIATION...Grumm is the U.S. government's official web portal to all federal, state and local government web resources and services.