Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220740 AFDCTP Area Forecast Discussion National Weather Service State College PA 340 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 TODAY/... A few speckles on radar continue to slide eastward. The rest of the overnight should be rain-free - but not very dry. The high dewpoints out there now will mean that a good supply of moisture will be in place in the low levels as the cold front over the Upper Midwest nears late today. PWATs rise above 2" and the the trough aloft will dig hard with 5H height falls of 12dam over the next 24 hrs. The storms over IN/IL/MO are along a strong short wave trough. Ol` fashioned extrapolation puts those storms/showers associated with the forcing into our NW zones during the middle of the morning. Most models do bring in some SHRA before noon in the NW while the rest of the area cooks under the power of our nearest star. No moon in the way to cool us down in the middle of the day today. By the middle of the afternoon, CAPEs poke above 1000 J/kg, by sunset some places may be closer to 2000 than 1000. Effective shear climbs into the 35-45KT range. The hodograph looks like an open parachute and will create a threat of supercells and all that is bad about them. SPC paints the threat for tornadoes higher over our NE zones today. The EHI and Sig Tor parameter are highest/worst in the far NW in the early aftn and then again in the far SErn zones just before/around sunset. LCLs will be low in the NW ~1500ft coincident with the high EHI, but will be >2500ft later in the day over the SE. Also, CAPEs will be lower in the NW, but much higher (perhaps as high as 3000 J/kg) in the SE. In between the NW and SE maxima things look they would be organized into more-linear storms with the predominant threat wind damage. Will carry catg POPs for the day over the NW and central zones, but keep them lower than 80 in the SE, since the storms may not get there/develop overhead until close to or after sunset. Maxes will be very warm for this time of year with maxes 5-10F above normal. && .SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/... On-going convection will be entering the SE third of the area around 00z per most guidance. Some cells may pop up ahead of the main area/line of storms due to the very high CAPEs - but some mid-level capping/lapse rates will try to suppress deep convection as long as it can. Will make high-likely to lower categorical POPs for the SE half of the area after 00z, but kill most of the convection around midnight. The real cold front will likely move through in the middle of the night, so some SHRA may linger behind the main show. The front should clear the area before sunrise. Dewpoints will be crashing in the wake of the cold front. Mins will be in the m50s in the NW, but still in the l70s SE. Some instability under the upper trough and with a lake breeze could pop some SHRA close to the lower lakes and drift would bring them south. Will keep POPs below mentionable except in the NW 3 zones. Maxes on Wed will be near normal in the east/valleys, but about 5F below normal in the mountains. && .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 /07Z TUESDAY THROUGH SATURDAY/... Only a few showers left across the far northeast now. 06Z TAFS adjusted and sent. Areas of fog beginning to develop, with a few areas of LIFR already being reported at KIPT. Overnight, expect widespread MVFR fog, with areas of IFR/LIFR visibilities and ceilings. 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. .OUTLOOK... Wed...AM low cigs BFD/JST, otherwise VFR. Thu-Sat...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...La Corte/Lambert AVIATION...Jung/Martin

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