Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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917 FXUS61 KCTP 182321 AFDCTP Area Forecast Discussion National Weather Service State College PA 721 PM EDT Tue Jun 18 2024 .SYNOPSIS... *Isolated strong/severe T-storms this evening *Long duration and potentially dangerous heat wave this week *Near-record high temperatures 90+ degrees into the weekend && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Aerial coverage of convection has begun to wane as of 23Z. However, the threat of a strong to severe tsra remains over the NW Mtns, where SPC mesoanalysis shows MLCAPES still near 2500 J/kg. Expect any remains showers/tsra to fade with loss of heating around sunset. It will be another warm and muggy night under the upper level ridge. Patchy late night valley fog seems a good bet, especially where rain fall earlier today. Latest NAMNest and SREF prob charts target the central mountains for the best chance of fog. See no reason to deviate from NBM min temps, which are in 65-70F range or generally +5-15F above average. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... Heat wave will continue through late week, as subtropical ridge remains parked over the Mid Atlantic region. Wednesday`s model 850mb temps are very similar to today, so expect highs once again ranging from the mid 80s over the highest elevations of the Alleghenies, to the 90-95F range in most valley locations. Lower pwats and somewhat lower afternoon dewpoints, especially over the Lower Susq Valley, suggest max heat indices will be in the 90s across the forecast area. Mid level temps warm a bit Wednesday, likely limiting diurnally-driven PM convection to the NW Mtns. Weak shear indicates convection will be of the pulse variety with little risk of organized severe weather. However, high pwats and instability indicate locally heavy downpours are possible, with a chance of localized 2-3 inch amounts based on the 12Z HREF. Surface front sinks south across the US/CN border on Thursday and will encounter a very warm/moist environment. Favorable timing with peak heating suggests scattered storms are likely with a MRGL risk SWO over the northern tier of central PA. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The heat and humidity will continue into Saturday, although we could begin to see some slight relief working into northeastern PA in the form of a backdoor cold front. It will be another hot day for much of the area though, and could easily see continuing to push the advy out into the weekend for much of the CWA. The proximity of the cold front will bring a slight increase in PoPs, esp across north-central and northeastern PA. Sunday into Monday should see the (slightly) cooler temperatures expand southward as a cold front crosses the area. This front will be accompanied slightly increased PoPs areawide Sunday into Monday. Any subtle cool down early next week looks like it will be short-lived, with heat building once again by midweek. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Hazy, hot and humid conds will be the rule across central PA for the next few days. Spotty storms will continue to pop up this afternoon with daytime heating, with the best chc of getting wet being over the higher elevations of the Allegheny Plateau. Brief reductions and gusty winds are possible in any storms, but this activity should be widely scattered. Added VCTS to JST, which already has some thunder nearby, with VCSH added to the remaining TAF sites outside of the Lower Susq Valley. Despite the spotty storms, most sites will be VFR for the majority of the day. Another warm and muggy night is in store, with any lingering showers/storms quickly diminishing as we lose the heat of the day. Patchy fog is once again possible in areas that see downpours today, but not confident enough to put it in any specific TAF sites yet. Outlook... Wed-Sun...Predominantly VFR, with continued heat and iso TSRA. Density altitude concerns possible. && .CLIMATE... A period of warmer than average temperatures is expected across much of central Pennsylvania through the end of the week, with record high temperatures at mutiple cities being challenged every day through Saturday. Two records were either set or tied for sites today: * A record high temperature of 92 degrees was set at Altoona today that ties the old record of 92 degrees set back in 1994. * A record high temperature of 90 degrees was set at Bradford today that breaks the old record of 87 degrees set back in 1993. The record high temperatures for some sites across central PA that could be challenged are outlined below: Jun 18 Jun 19 Jun 20 Jun 21 Harrisburg 97/1957 98/1994 98/1931 98/1923 Williamsport 97/2018 96/1929 101/1923 97/1933 State College 94/1923 94/1931 94/1953 94/1988 Highest Max Temperatures for Central Pennsylvania Observing sites for June (date of occurrance is in parentheses: State College 96 in 1952 (26th) and 1933 (29th) Harrisburg 100 in 1966 (27th), 1952 (26th), and 1934 (29th) Williamsport 104 in 1925 (5th) Altoona 97 in 1971 (28th) and 1953 (21st) Bradford 93 in 2022 (22nd) Longest run of consecutive days with max temp >=90 in June: State College 6 (24-29th 1966) Harrisburg 10* (19-28th 1943) Williamsport 9 (18-26th 1923) Altoona 8 (13-20th 1994) Bradford 0 (has not occurred since POR started at site in 1957) *Harrisburg had a run of 11 days with temperatures greater than 90 degrees that started on 26th and ended on July 6th in 1901. && .CTP WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM EDT Friday for PAZ004>006-010>012- 017>019-024>028-033>037-041-042-045-046-049>053-056>059- 063>066. && $$ SYNOPSIS... NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Steinbugl LONG TERM...Evanego/NPB AVIATION...Evanego CLIMATE...Evans