Area Forecast Discussion
Issued by NWS State College, PA

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882 FXUS61 KCTP 221458 AFDCTP Area Forecast Discussion National Weather Service State College PA 1058 AM EDT Tue Aug 22 2017 .SYNOPSIS... A strong cold front will move through the region late today and early tonight. Much cooler and drier conditions will return for the second half of the week. Temperatures will average a few degrees below normal highs starting tomorrow and lasting into early next week. && .NEAR TERM /THROUGH TONIGHT/... New motor in KCCX is being installed. Key forecast issue is the timing of the line(s) of convection with the front to our west. Ahead of the front it will be mostly sunny through some haze and very warm. The CAPE is high in the warm air but not as high closer to the front as forecast by the HRRR as the front enters western PA this afternoon. Most HRRR cycles and the NCAR 3km EFS shows a line with bowing segments moving across NW PA this afternoon. A stronger line should form mid-afternoon if these models are correct and it should be near the middle of PA around 4-6 PM and keep tracking to the east. The main line in the HRRR exists the southeast in the 9 to 10 PM range. Our region is in an enhanced risk for severe weather this afternoon and evening. Strong thunderstorms with gusty winds and even the possibility of isolated tornadoes. Behind the line the PW values and thus humidity drop rapidly. We should dry out and cool off nicely overnight into Wednesday morning. && .SHORT TERM /WEDNESDAY/... Wednesday will be noticeably drier as the PW values crash to -1 sigma below normal after being well +1 to +2 sigma above normal. It will also be significantly cooler. The 850 hPa temperatures fall to near normal Wednesday and will fall below normal overnight Wednesday into Thursday. Chance of rain will be quite low, close to 0. The GEFS in 3-hour increments clearly shows all the QPF to our east after about 09Z Wednesday. The cool air aloft will likely produce some cumulus in the mountains during the afternoon hours. Should be a spot on day. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... An extended period of early autumn-like weather starts Wednesday and lasts into the upcoming weekend as an anomalously deep sfc low/upper trough slides east across southeastern Canada. Daytime high temps will be about 5-7 Deg F below normal across the Western Mtns on Wednesday, though still just slightly below normal across the SE zones prior to the arrival of the deeper/colder air for the latter part of the week. GEFS mean 850 mb temps will dip about 2-3 deg C in all locations for Thursday-Sunday, leading to max temps averaging 5-10 F below normal (with min temp departures about 10-13F below normal Friday-Sunday) as a large Canadian High Pressure area pushes SE across the Glakes Region and becomes centered over the NE states. Lows Fri/Sat/Sun mornings with high centered overhead will be dipping into the l-m 40s over the Northern Mountains (and deeper valleys of the Central Mountains) and solidly into the 50s elsewhere. Some of the perennial cold spots near and to the east of KBFD could see readings of 38 or 39F. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... Updated TAFS as all sites are not VFR. Some haze had some sites slow to come up this AM. Longer nights and very humid air mass. Tweaked timing a few hours for arrival of thunderstorms this afternoon and evening. All the models show a line of late afternoon thunderstorms moving across the State. These will be large and strong thunderstorms. Check the radar before takeoff this afternoon and evening as these storms will develop and move quite fast. Morning fog gives way to VFR conditions later this morning, but widespread TSRA expected during the afternoon and evening, as a strong cold front moves into the area. Potential for strong to severe wind gust. Conditions will improve after early Wednesday morning, as cool Canadian high pressure builds into the area. .OUTLOOK... Wed...AM low cigs BFD/JST, otherwise VFR. Thu-Sat...No sig wx expected. && .EQUIPMENT... KCCX is inoperable. It likely has a bad motor in the pedestal. Techs continue to assess the root of the problem. Return to service time is unknown. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Grumm SHORT TERM...Grumm/Dangelo LONG TERM...La Corte/Lambert AVIATION...Grumm/Martin EQUIPMENT...

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