Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
409 FXUS61 KCTP 230106 AFDCTP Area Forecast Discussion National Weather Service State College PA 906 PM EDT Sat Jun 22 2024 .SYNOPSIS... *Ongoing heat wave peaks this weekend with some relief in sight for Monday *Severe thunderstorm risk will ramp up over the weekend with scattered damaging winds most likely Sunday afternoon/evening *A shorter duration summertime hot spell will precede a round of t-storms into the middle of the last week of June && .NEAR TERM /UNTIL 7 AM SUNDAY MORNING/... Convection grew rapidly. A few larger ones have made damage and marginal to barely severe hail. Reports numerous over Lycoming Co, and forthcoming in LSRs. Most storms have tamed down, but lingering boundaries and high CAPE will continue to allow convection to pop thru the rest of the evening. Cells in PBZ and LWX`s areas are drifting slightly N of E as the steering flow becomes a bit more SWrly. Later convection should not hold the punch of the most recent stuff as temps/CAPE lower. No worries for flooding despite the convection in the east rolling over some of the wetter ground in the CWA. The cells are moving along nicely. Prev... Convective temps were realized early this afternoon off of the higher terrain with isolated coverage of shra and a few rogue storms, mainly along the Erie Lakeshore and over the Pocono Plateau. Unlike previous days, today`s lower DCAPEs are not producing sufficient cold pools to initiate subsequent convection along outflows, so most of what forms over western and central PA rains out and decays, with the trend on regional radar mosaic for dying cells at mid afternoon. Looking at forecast soundings, a fair amount of CIN below 5k feet may also be to blame for this, with cool pools being too shallow to overcome this here in the mid afternoon hours, but with additional surface heating by late afternoon, we could see true surface based convection materialize that can last longer and produce outflows strong enough to initiate secondary convection. We shall see...it`s very warm aloft and it`ll be hard to generate much more than heavy downpours from the cells that do generate this afternoon into this evening. Record daily and even all- time monthly high temperatures will be challenged this afternoon with fcst maxT between 90-100F. Heat index values reaching high- end advisory levels and push warning criteria ~105F in portions of the mid and lower Susq Valley. Major to locally extreme heat risk impacts are likely to affect health systems, heat-sensitive industries, and some infrastructure along with anyone without effective cooling and/or adequate hydration. The early season heat persisting over multiple days with light wind, limited cloud cover, and warm overnight temperatures will exacerbate heat stress. If you have plans to be outside, drink plenty of water even if you are not thirsty and have options for getting relief (shade or AC) from the heat. The lack of rain combined with the prolonged heat is also contributing to rapid onset drought risk in some areas. Isolated evening t-storms should dissipate by late tonight. Warm and muggy overnight with low temps peaking in the upper 60s to mid 70s or +15-20F above the historical average for mid June - providing little to no relief from the daytime heat. && .SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... Looking ahead to Sunday, bulk shear increases and a front will enter the picture to potentially focus stronger storms to break the heat. SPC Slight risk still stands for Sunday. The breakdown of the upper ridge continues on Sunday with upper trough base moving from the Great Lakes into the Northeast accompanied by stronger low/mid level flow overspreading a moderately unstable environment. Trailing cold front and prefrontal boundary should help to trigger scattered t-storms by the afternoon with potential for organized cells/clusters to produce damaging winds. WPC has maintained a MRGL risk ERO for Sunday over the Alleghenies given ribbon of higher pwats along the cold front, but forward progression will be limiting factor concerning flooding potential. Recent dryness has caused a large increase in FFG over most of CPA with the lowest values in the northern tier. The projected instability and available moisture should support local 1-2 in/hr rates in stronger storms, but overall flood risk is low. Storms should weaken moving to the southeast later Sunday night. The 500mb trough swings through on Monday while sfc dewpoints fall into the 50s. There could be another round of scattered showers/t-storms, but with drier boundary layer and and PW air mass working into the area, signs point to a General thunder day for most. High pressure arrives by Monday night and will provide a mainly clear and comfortable night with valley fog and low temps dropping back closer to climo for this time of year in the 55-65F range. && .LONG TERM /TUESDAY THROUGH SATURDAY/... A warming trend emerges on Tuesday as surface high pressure builds across the Mid-Atlantic. Despite the warm-up into Tuesday, MaxTs in the lower 90s across portions of the Lower Susquehanna Valley will be the ceiling in this forecast cycle, where 10-20% of ENS members outline temperatures exceeding 90F during peak warming hours with less than 10% of GEFS members outlining temperatures exceeding 90F. Surging PWATs ahead of a sfc cold front begin to enter central Pennsylvania late Tuesday evening into Wednesday morning, where chances of precipitation return to the area. Deterministic model guidance has notably shown less coverage in precipitation Tuesday evening, and have limited PoPs towards the northern tier where the best moisture and forcing will be available. PoPs will begin to expand areawide through Wednesday, especially during the afternoon/evening hours where the best daytime heating will be available ahead of the cold front. Mild conditions and drier air will return for Thursday in the wake of the cold front and continue through Friday, with MaxTs closer to seasonal averages for the end of June. Looking into Saturday, considerable deterministic model spread begins to bring uncertainty into the forecast with some potential for diurnally driven showers/storms possible across the area. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... As of 01z, all TAF sites were VFR. The only remaining thunderstorms are along a line from just north of KSEG to east towards KEWR in New Jersey, and expected to dissipate by 06z. There remains some persistence in LLWS potential at BFD in the 10-14Z Sunday timeframe low-level winds increase ahead of an approaching frontal boundary. Despite the persistence in some model guidance, lower confidence coupled with the marginal nature of LLWS parameters limits mention in the TAF for this cycle. The next batch of SHRA/TSRA will begin to form during the early afternoon hours on Sunday ahead of a cold frontal passage. Guidance (GLAMP/HREF/RAP) have shown some potential for SHRA in the 15-17Z Sunday timeframe at BFD/AOO/UNV. Later in the afternoon (mainly after 18Z), there is higher confidence in SHRA/TSRA impacts at airfields across central PA with continued daytime heating ahead of the front. Outlook... Mon...Predominantly VFR, with brief restrictions possible in scattered SHRA/TSRA as a cold front crosses the area. Tue...VFR, no sig wx expected. Wed...Restrictions possible in TSRA. Thu...AM SHRA/TSRA with restrictions possible, drying out late. && .CLIMATE... A heat wave will continue through the weekend with near-record temperatures forecast in some locations on Sunday. Daily record highs for Sunday June 23: 6/23 State College 91 (1966) Harrisburg 97 (1965) Williamsport94 (1923) Altoona 90 (1994) Bradford 86 (2013) The following records have been set during this stretch of heat: MDT: * A record high temperature of 99 degrees was set at Harrisburg, PA on Saturday, Jun 22, breaking the old record of 97 degrees set in 1988. IPT: * A record high temperature of 98 degrees was set at Williamsport on Friday June 21st, breaking the old record of 97 degrees set in 1923 and tied in 1933. BFD: * A record high temperature of 89 degrees was tied at Bradford on Friday June 21st, tying the record set in 2022. * A record high temperature of 90 degrees was set at Bradford on Thursday June 20th breaking the old record of 88 degrees set in 2012. * A record high temperature of 88 degrees was set at Bradford on Wednesday June 19, breaking the old record of 87 degrees set in 1987. AOO: * A record high temperature of 96 degrees was set on Saturday, Jun 22, breaking the old record of 91 degrees set in 1988. Highest Max Temperatures for Central Pennsylvania Observing sites for June (date of occurrence 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) /current streak=1/ Harrisburg 10* (19-28th 1943) /current streak=6/ Williamsport 9 (18-26th 1923) /current streak=6/ Altoona 8 (13-20th 1994) /current streak=6/ Bradford 1 (23rd 2024) /current streak=1/ *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 Sunday for PAZ028-036-049>053- 056>059-063>066. && $$ SYNOPSIS...DeVoir/Steinbugl NEAR TERM...DeVoir/Dangelo/Steinbugl SHORT TERM...DeVoir/Steinbugl LONG TERM...NPB AVIATION...Colbert/NPB CLIMATE...Evans/Steinbugl/Colbert