Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 170541 AFDCTP Area Forecast Discussion National Weather Service State College PA 141 AM EDT Thu Aug 17 2017 .SYNOPSIS... Warm air will surge into our region Thursday ahead of an approaching cold front. Showers and thunderstorms are likely Thursday into Friday ahead of the front. Cooler drier should improve our weekend weather. A ridge builds in early next week and we should warm up before another northern stream cold front triggers showers again and ushers in cooler drier around mid- week. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... GOES-16 advanced microphysics shows it is mostly clear over the region to night. Deep clouds are well to west over IL-IN and into western OH. Clear skies and retreating surface high we should fade away fast and clouds will come into the west toward morning. This will produce some areas of patchy fog mainly near water bodies. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM FRIDAY/... Used latest National Blend of Models in these grids minor tweaks for timing of showers/thunderstorms. We rely on larger scale models which over do light QPF in instability situations so tempered the POPS down a tad. But general trend is a good start to the day with increasing chance of showers and thunderstorms west to east as the day goes on. Overall a warmer day with more humidity. Highs mainly in the 80s with upper 70s in the northern and southwestern mountains. Chance of rain and thunderstorms increases in the evening and overnight hours as a deep cyclone moves into the western Great Lakes. In the GEFS the 0000 to 1200 UTC Friday timeframe is the wettest period. Strong southwesterly flow and above normal PW implies good chance of convection and some areas could see locally higher QPF amounts than depicted in the grids. Due to high PW and clouds it will be a warm overnight. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The GEFS and CMCEFS suggest our PW values drop during the day Friday back to normal as the front is forecast to push to our east. This means improving weather from morning to afternoon. Lowering POPS over time. We should remain relatively dry as the PW values stay near normal until perhaps Tuesday. This said there are hints of a weak wave and scattered showers perhaps Sunday. Tuesday could be rather warm as there is a surge of above normal 850 hPa temperatures and PW values above normal. Not surprisingly the GEFS shows higher POPS Tuesday afternoon into Wednesday with the wave and front. We should enter the second half of the weak in a cooler and drier air mass as currently forecast. And thus in the grids. Bottom line in this period the NCEP guidance suggests low probability of significant QPF. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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Some fog possible late. 06Z TAFS sent. Earlier discussion below. VFR continues late this evening and into the overnight hours with high pressure and large-scale subsidence overhead. Fog impacts are again expected to develop late and continue into Thursday mid-morning - after which much of the day on Thursday should be VFR. Scattered showers will pop up Thursday afternoon in the west and south and move northeastward. The coverage of these showers before 18Z is too low to even mention PROB30s for any site in this package. However, Thursday afternoon into Friday evening hold a much more widespread chance of thunderstorm impacts as a warm front lifts across the area and a cold front follows 24 hours later. .OUTLOOK... Thu night-Fri...SCT-NMRS TSRA impacts likely. Sat-Mon...No sig wx.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Grumm SHORT TERM...Grumm LONG TERM...Grumm AVIATION...Martin/RXR

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