Area Forecast Discussion
Issued by NWS State College, PA

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847 FXUS61 KCTP 301141 AFDCTP Area Forecast Discussion National Weather Service State College PA 741 AM EDT THU JUN 30 2016 .SYNOPSIS... High pressure is overhead today. A cold front will move east across the state on Friday followed by another high pressure area which will cover the region for most of the holiday weekend. A chance of showers is in the forecast for Monday (Independence Day) as low pressure approaches from the Ohio Valley. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... No real changes to the forecast other than to remove fog from many areas. Dewpoint dropped 10+ degrees at KBFD overnight. Haven`t see a 40 dewpoint reading in a while. prev... High pressure and subsidence will keep it dry today. Humidity will drop into the 30-40 percent range. A very weak short wave trough will move overhead this morning/early afternoon leading to some high-level clouds. Enough moisture may be present to allow sct cumulus to form this afternoon, especially in the south-central mountains. POPs will stay unmentionable as nothing should grow tall enough to rain. A light west wind will turn to the south. Deep mixing will help temps rise 4-8F higher than Wednesday`s numbers. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... A cold front will be moving through the Upper Great Lakes tonight. Light southerly winds over PA should keep min temps 5-10F milder than Thurs morning. Deep layer moisture will increase but PWATs don`t get too far above one inch by Friday afternoon. The best PWATs will be in the eastern third to half of the area. The upper trough axis and cold front will swing through late-day or early night on Friday with the cold front ushering in another very dry airmass from the Canadian plains. The NAM and GFS both pop up some isolated showers over the south- central and southeastern counties later tonight and move them NE. But, the airmass is still pretty dry tonight and any showers might have a tough time reaching the ground. But, the right entrance region of a jet max will provide a positive environment for some lift and showers in the SE. Will call for scattered-30 POPs late tonight in the SE. As the moisture increases on Friday and an advance/lee trough develops the coverage of showers and some thunderstorms will increase slightly for the daytime in the east. The cold front will be arriving just after peak heating in the NW. It will also be working on pretty dry air until it gets east of State College. Will keep POPs lower in the west but increase them through the day. NAM generates more showers than other models as the really dry moves in during the evening. Have allowed for this possibility and lingered 20-30 pops through midnight. It should be dry after that. Winds never get strong, but deep layer shear increases - especially in the east. CAPES getting 1000-1500 range in the northeast/Poconos could make a couple of stronger storms there in the afternoon/evening. SPC DY2 outlook has introduced a MRGL risk into the eastern counties. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Refined POPs a bit on the 4th and 5th based on a slightly better consensus amongst the models that low pressure could slide into the Ohio Valley and end up bringing some showers/storms to (mainly the southern half of) the forecast area. The GFS is slower, pinching off a closed 5H contour for a brief time to our west. This causes it to be slower with the potential precip arrival and would keep the 4th and fireworks time dry. This is still 4-5 days out, so.... prev... The front shifts off the coast with high pressure and abnormally dry airmass moving into Central PA for the weekend. What appeared to be a fairly predictable/confident forecast in dry weather lasting through the 4th of July has begun to degrade with recent deterministic model runs showing increasing differences in shortwave details from the Central U.S. into southeastern Canada. More specifically, the 29/12z GFS and CMC show a northward trend or shift in the stationary boundary located along/north of the I-70 corridor with pcpn arriving in western PA around the time fireworks are getting underway. The 29/00z ECMWF keeps the boundary and bulk of associated pcpn further south of the Mason Dixon line along the I-64 corridor. Given the increasing model differences, will utilize a blend of the latest guidance with the previous forecast which increases POPs a bit over the southern counties around Mon-Tue but still keeps continuity for a mainly dry and seasonable Holiday weekend. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... High pressure and associated dry air mass over Pennsylvania should ensure widespread vfr conds and light wind today. OUTLOOK... Fri...Sct tsra impacts possible...mainly east. Sat and Sun...No sig wx expected. Mon...Slight chance of pm showers/reduced cigs. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Dangelo/Steinbugl AVIATION...Fitzgerald

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