Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271856 AFDCTP Area Forecast Discussion National Weather Service State College PA 256 PM EDT Thu Jul 27 2017 .SYNOPSIS...
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A cold front over the lower Great Lakes early this afternoon will drift southeast and cross the state tonight and Friday morning. The front will stall along the Maryland border for Friday and an unusually strong wave of low pressure for mid summer will form and move east along this boundary, pulling abundant moisture up and over the front from the south. Heavy rain is expected later Friday into Saturday, especially across the southern tier of PA. A much cooler airmass will overspread the commonwealth over the weekend. Temperatures this weekend will be more like mid fall than mid summer.Dry and warmer conditions will return to the area early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SPC cut back on the outlook for this aft. Updated HWO. Some heating in the local area and points west, but stronger wind fields to the northeast. Thus cut back more on POPS through tonight. Minor adjustments to temperatures etc.
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&& .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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Did cut back POPS some early Friday. Models still show several sfc lows and QPF max with each. Behind this, a digging upper level low to follow and result in deepening. Not clear how all this will phase and how much rain will fall. For now went with a flash flood watch southern PA starting at 18Z. Some plumes very wet. Key will be how convection over the plains this afternoon comes into play. Models been showing several sfc lows and the upper lvl low digging for several days now, thus after touching base, went with a flash flood watch. Watch extends out to 18Z Saturday, later shift can push it further out in time and space. Did not go as far north as Lycoming County, very wet there, but QPF is fcst to be lower. Still have to watch how the moisture is advected up the mid Susquehanna Valley, the mountain range to the south of IPT often has a large influence on things. Only adjusted max temperature a little on Friday. Later starting time of the heavy rain may allow high temperatures to be not that cold. Main concern would be on Saturday. More info. below. Max temps Friday and Saturday will almost certainly be several Deg or more lower than most MOS guidance given the widespread light to moderate rain and a trajectory of the anomalously strong llvl wind from the New England Coast in contrast to the Mid Atl Coast.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/... The trough rounds the base of a long-wave trough after it passes our longitude, and clears things out nicely. This should happen sometime Sat (most likely waiting until the afternoon or early evening in the southeast). Will linger POPs in the S for the day Sat, but go very dry and sunny/clear for the next 2-3 days. Scattered diurnal convection may then start to pop up - esp in NY state Tues/Wed. But, the risk of a shra/tsra in PA is very low until at least Wed as the humidity rises back to more- August like values. Highs Saturday will be only in the l-m 60s across the northern and wrn mtns, and a few spots may stay in the upper 50s. Temps should sneak into the lower 70s across the Susq Valley. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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Still some lower CIGS across the east. Clearing across the west, with VFR conditions. Not much on the way of showers on the radar. Perhaps a shower in a few spots into early this evening. Expect some fog and haze later tonight again. Widespread showers and storms with heavy rain expected later Friday into Sat. .OUTLOOK... Friday night-Sat...Scattered SHRA north with more numerous and heavier SHRA/TSRA across the south. Sun...More shower activity possible. Mon-Tue...No sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES...
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Flash Flood Watch from Friday afternoon through Saturday afternoon for PAZ024>028-033>036-056-057-059-063>066.
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&& $$ SYNOPSIS...Lambert/Martin NEAR TERM...Martin SHORT TERM...Lambert/Martin LONG TERM...Lambert AVIATION...Ross/Martin

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