Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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843 FXUS61 KCTP 072223 AFDCTP Area Forecast Discussion National Weather Service State College PA 623 PM EDT Sun Jul 7 2024 .SYNOPSIS... * Dry and seasonably hot today with more comfortable humidity * Increasing heat and humidity returns for early this week with max heat index values around 100 in parts of south central PA again Monday through Wednesday * The best chance of rain/t-storms will be later Wednesday as deep, tropical moisture from Beryl is funneled north from the Gulf coast states && .NEAR TERM /THROUGH MONDAY/... High pressure across the Ohio Valley into western PA making for a dry and seasonable early July afternoon. Expect cumulus clouds to continue with peak heating today, along with some cirrus streaming in from the southwest. Very Warm to hot temps in the low 80s to low 90s are expected this afternoon with plenty of sunshine and more comfortable dewpoint temperatures. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/... Another mainly clear night with patchy to areas of valley fog across northern PA as the center of high pressure slides overhead. Minimum temperatures tonight look similar to those on Sunday morning, bottoming out around 60 in the northern tier to 70 near the Mason-Dixon line. Diurnally driven, albeit isolated, showers and thunderstorms are possible on Monday afternoon with the easterly/southeasterly flow on the back side of the departing high bringing an increase of low level moisture/humidity back to central Pennsylvania. Heat index values are likely to approach 100F again on Monday afternoon in south central to southeast PA where a Heat Advisory has been hoisted. Increasing clouds are likely Monday night as a result of the combination of wind flow and positive moisture flux. As a result, lows on Monday night will be a bit milder in the 65-75F range (+10-15F above climo), making it feel quite muggy once again as dewpoints remain in the same range. Fog will be possible in locations that get rain, but clouds and southeast flow should limit radiational cooling and the extent/thickness of the fog. Lowered shower/storm chances for Tuesday given neutral to positive height tendencies as the remnants of Beryl and a mid- latitude trough slowly phase in the Mississippi Valley. Will still see some terrain-induced storms pop along with additional convection along outflow boundaries, but large scale forcing looks negligible at this time. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... As we move into the middle of the week, guidance depicts a pattern of unsettled weather with southwesterly flow bringing a plume of tropical moisture. The latest forecast cone from NHC brings the center of Beryl through the Ohio Valley as it weakens to a post-tropical depression and gets absorbed by a midlatitude trough. Even if the remnant circulation passes well to our west, the gradient between the low pressure system and strengthening high pressure over Bermuda will result in a conveyor belt of deep tropical moisture with PWAT progged to exceed 2.00 inches over much of central PA between Wed afternoon and Thursday. Also of note, the GFS is showing the freezing level between 13-15kft Wed-Thu, suggesting efficient warm rain processes. The highest PoPs look to be Wednesday afternoon into Wed night, although we will likely see continued chc/slight chc PoPs right into next weekend (peaking with the daytime heating each aftn/eve). A reasonable worst case scenario for 24 hr rainfall is 2.00-2.50 inches from Wed-Thu afternoon, as per the NBM 90th percentile. Not surprisingly, given the tropical nature of the airmass, WPC has painted a slight risk for excessive rainfall over some of northern Pennsylvania. Farther south, where conditions over the past few months have been much drier, any rainfall coming this week will largely be beneficial. In terms of heat and humidity, the extended period looks to feature a continuation of the warm and humid weather we`ve been seeing recently. Heat index values will have a shot at the low 100s again Wednesday in the lower Susq valley, especially if clouds/precip hold off until later Wed afternoon or Wed night. A shot of somewhat less humid air (upper 50s to low 60s dewpoints) appears likely behind the remnants of Beryl late Thursday into Friday across western zones, but the tropical moisture will be slow to move out of the east. && .AVIATION /22Z SUNDAY THROUGH FRIDAY/... High pressure will provide widespread VFR conditions today, with a light westerly wind about 5 kts expected. Scattered high level clouds and fair weather cu are expected, but beyond that mostly sunny skies are going to be prevalent. Mostly clear skies tonight will provide effective radiational cooling for much of central PA. Patchy fog is once again possible across the NW airfields. BFD will likely see visibility restrictions during the early morning hours on Monday, and vsby restrictions can not be ruled out at other airfields such as IPT. After Mon morning fog dissipates, the rest of the day looks VFR with sct to bkn cu forming between 3500 and 5000 ft. Outlook... Tue...Scattered mainly afternoon showers/storms, otherwise VFR Wed-Thu...More numerous SHRA/TSRA causing restrictions Fri...Scattered mainly afternoon showers/storms, otherwise VFR && .CLIMATE... A prolonged stretch of very mild nights is in store thanks to anomalous moisture in Central PA. The following minimum temperatures records are in jeopardy of being tied or broken at Harrisburg and Williamsport this week. HARRISBURG WILLIAMSPORT DATE HIGHEST MIN T YEAR HIGHEST MIN T YEAR July 9 76 1994 July 10 77 1993 74 1925 July 11 76 1989 72 1910, 1921 July 12 75 1911, 2011 The duration of warmth may also end up being notable. Harrisburg has not dropped below 70 degrees since July 3rd. Here are the longest stretches with temperatures at or above 70 on record at Harrisburg. # OF DAYS DATES YEAR 17 7/19-8/04 2020 13 8/16-8/28 2021 13 7/13-7/25 2010 12 7/18-7/29 2022 12 7/17-7/28 1999 12 7/20-7/31 1940 11 8/04-8/14 1977 10 8/10-8/19 2016 10 7/14-7/23 2013 10 7/21-7/30 1898 9 12 times, most recently 7/7-7/11/2020 .................................................... 4+ 7/04-?? 2024 && .CTP WATCHES/WARNINGS/ADVISORIES... Heat Advisory from noon to 8 PM EDT Monday for PAZ036-056-057- 059-063>066. && $$ SYNOPSIS...Guseman/Lambert NEAR TERM...Guseman/Lambert SHORT TERM...Guseman/Lambert LONG TERM...Evanego/Colbert AVIATION...Colbert/Bowen CLIMATE...Banghoff