Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 031131 AFDCTP Area Forecast Discussion National Weather Service State College PA 731 AM EDT Mon Aug 3 2020 .SYNOPSIS... An upper level trough over the midwest will push slowly east over the next few days. This weather feature will help to steer tropical storm Isaias north along the east coast today and Tuesday. A widespread heavy rain is expected tonight through Tuesday across the eastern Third to half of the state. High pressure is likely to build in from the Great Lakes the second half of the week. However, a stalled frontal boundary will linger just south of Pennsylvania. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 09Z surface analysis shows a weak, stalling front stretching from Southern NJ to Central VA. low level moisture streaming NNE along the spine of the Central Appalachians and Allegheny Plateau was producing widespread stratocu and altocu clouds and nothing more than a brief light shower possible this morning. 8/3 00Z HREF and latest runs of the HRRR suggest that showers will spread into the Scent Zones and Lower Susq Valley (along with the far NW part of our CWA) between 21-23Z today. Given the meager amounts of CAPE (though high amounts of Precip Wtr between 1.5-2.0 inches across the SE third of the state) there will be occasional moderate showers at times. Min temps to start today will be from the upper 50s in the normally cooler areas of NW PA and 65-70F across much of the central and eastern ridge/valley region. Highs this afternoon will be in the upper 70s over the northern and western mtns and generally the low to mid 80s elsewhere. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Focus will shift to potential heavy rainfall impacts associated with TS Isaias later tonight into Tuesday. The latest blended QPF from WPC/NBM indicates 2-4" are possible across the eastern/southeastern zones through Tuesday night with higher amounts possible closer to the I-95 corridor. The axis of heaviest QPF has shifted a little to the west with the recent guidance blends/WPC. Continued with the same areal coverage of the flash flood watch from tonight through Tuesday evening in collaboration with WFOs LWX and PHI. Fortunately, we are going into this event with relatively dry ground in most places - although the eastern part of the CWA has been the "wettest" relative to moderate drought locations in the central and western parts of the CWA. Some locally heavy rain in this area was also observed last night and early this morning. High rainfall rates, however, could work against the dryness. Latest ECENS and NAEFS support fair and seasonable conditions Wednesday, as a cold front behind Isaias is progged to move east of forecast area by dawn. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Medium range guidance is in decent agreement later this week, all of which indicate a pair of shortwaves affecting the region Thursday and Friday, spawning waves of low pressure along stalled frontal boundary running from the Ohio Valley to Mid Atlantic. Will maintain just a slight chance of showers along the southern tier for the first wave Thursday, then a better chance of showers with the stronger wave Friday. Latest ECENS and NAEFS show high pressure and drier air mass working into the state next weekend. Have therefore undercut the NBM and Superblend POPs, but retain mention of widely scattered diurnal convection. Temperatures should begin near seasonal normals Thu-Sat, then expect a return to above normal temperatures by late next weekend, as surface high passes east of Pa and return southwest flow ensues. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... 12Z TAFS sent. As of 6 AM, most of the lower clouds are out of the area. Nice sunrise. Still some lake effect showers along the NY border. Expect winds to shift more to the southwest, and CIGS to lift by mid morning. For now, went with a dry fcst for most of the day. Low level moisture less than on Sunday, and we had very little activity after sunrise yesterday. Also no one feature to focus widespread showers on. The main concern will be the potential for heavy rainfall impacts associated with TS Isaias later tonight into Tuesday evening. Outlook... Tue...Moderate to heavy rain with MVFR/IFR restrictions likely across the central and eastern airspace. Wed-Thu...Trending drier/VFR with just an isolated shower or t-storm possible. Fri...Local impacts from sct showers/tstms. && .CLIMATE... July 2020 was a remarkably warm and dry month in Central PA. *Average Temperature* -Warmest month on record at Harrisburg & State College (82.2F at MDT, breaking the old record of 81.8F set in July 1999; 77.0F at STC, breaking the old record of 76.5F set in 1955). -T-3rd warmest month at Williamsport (78.2F, tied with July 1921 and behind 1955 with 79.1F and 1901 with 78.9F) *Average Maximum Temperature* -3rd warmest month on record at Harrisburg (92.2F behind 1999 with 93.5F and 1966 with 93.2). -5th warmest month on record at Williamsport (90.0F; record of 93.0F set in 1955 with other warmer Julys in 1988, 1934, and 1921). *Average Minimum Temperature* -Warmest month on record at Harrisburg & State College (72.2F at MDT, shattering the old record of 70.7F last year; 67.5F at STC, breaking the old record of 66.6F set in 2012) -2nd warmest month on record at Williamsport (66.4F behind 1901 with 71.1F) *90 degree days* -2nd most on record at Williamsport with 19, behind 1955 with 25. -T-2nd most on record at Harrisburg with 22, behind 1966 with 23 and tied with 1999. *Precipitation* -Driest July since 2007 at Williamsport (1.86") -Driest July since 2002 at Harrisburg (1.35") -5th driest July at State College (1.38") && .CTP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from this evening through Tuesday evening for PAZ035-036-056>059-063>066. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert/Steinbugl LONG TERM...Fitzgerald AVIATION...Martin CLIMATE...

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