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
592 FXUS61 KCTP 260325 AFDCTP Area Forecast Discussion National Weather Service State College PA 1125 PM EDT Tue Jun 25 2024 .SYNOPSIS... A cold front will push southeast across the region Wednesday night, followed by high pressure building in Thursday and Friday. A relatively zonal flow will remain in place through early next week, with a cold front passage either late Saturday or early Sunday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Late evening water vapor loop shows a potent shortwave tracking well north of PA through the St Lawrence Valley. Satellite loop at 03Z shows cumulus with decent vertical development along the trailing low level jet from Northwest PA through the southern tier of NY state. Warm advection along this feature could potentially produce a shower/tsra across the N Mtns late this evening. Otherwise, tonight looks quiet with varying amounts of mid and high level cloudiness overspreading the state ahead of an upstream trough over the Plains. An active southwest breeze will draw steadily rising dewpoints into the region tonight, resulting in much warmer conditions than last night. See no reason to deviate from NBM mintemp, which range from the mid 60s over the NW Mtns, to the low 70s in the Lower Susq Valley. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY NIGHT/... Diurnal heating of an increasingly moist/unstable airmass, combined with falling heights ahead of the upstream trough, will result in developing convection during Wed afternoon. A ribbon of relatively strong mid level winds of 40-50kts, combined with progged moderate instability across Central and Southern PA, suggests organized convection and locally severe weather can be expected across this part of the state Wed PM. Some of the latest model guidance suggests an eastward-moving MCV could result in a batch of strong-severe convection across Southern PA in the 16Z-21Z time-frame, with diminished potential in the rain-cooled air behind it. However, wouldn`t place too much weight on this right now, as the strongest shear should be in the late afternoon to early evening timeframe. Some of the 12Z HREF members indicate UH values >150 across Southern PA in the early evening, which is supportive of supercells. Latest ensemble plumes indicates most likely aerial average rainfall Wed PM will be around a half inch. However, isolated amounts around 2 inches appear likely based on the latest HREF and a combination of moderate instability and +1-2SD pwats. Thicker clouds will likely cap temps to the upper 70s across the NW Mtns Wed, while a decent amount of sun is anticipated across the southeast counties based on model RH profiles. 850mb temps support highs as warm as the low 90s across the Lower Susq Valley. The combination of heat and humidity should result in heat indices peaking in the mid 90s in that part of the state. Dwindling convection from northwest to southeast is anticipated Wed night, as the upper trough and associated cold front work through. Large scale subsidence and the arrival of much drier air behind the exiting cold front should then result in fair and seasonable conditions Thursday. Surface high pressure building over the region should result in fair and cool weather Thu night. Fair and slightly warmer conditions are likely Friday, as low pwats persist over PA and a return southerly flow develops as the surface high passes off the coast. && .LONG TERM /SATURDAY THROUGH TUESDAY/... Latest medium range guidance is showing an unusual lack of spread among its members, all of which track a surface low north of PA Saturday, with a trailing cold front coming through Sat night into early Sunday. The lack of spread with regards to timing of the front, combined with progged GEFS pwats of +2-3SD, supports an increasing confidence in showers/tsra Saturday. A leading warm front could produce showers/tsra as early as Friday night and a slowing cold front could cause convection to linger into Sunday, mainly over the southeast counties. However, ensemble plumes indicate the most widespread convection should occur Sat afternoon and evening. There is some potential for severe wx Saturday PM, as decent mid level flow overspreads an increasingly moist warm sector. Ensemble plumes currently indicate moderate capes in the 1000 J/kg range and model 0-6km shear is in the 35-40kt range. If the cold front slows enough, severe wx would also be possible across the eastern edge of the forecast area Sunday PM. Latest EPS and GEFS both support fair weather with near to slightly below normal temps and low humidity early next week associated with high pressure building east from the Grt Lks. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... High confidence in VFR flying through the evening into the first half of tonight/06Z Wed. Uncertainty ramps up overnight into early Wednesday morning with potential for showers and t-storms moving into the airspace from the north/west. Can`t rule out some cig restrictions in the 06-15Z window based on the latest probabilistic guidance, but the overall pattern/low level flow don`t provide a strong enough signal to maintain in TAFs outside of KBFD. A 40kt low level jet from 230-260 degrees will maintain LLWS at KBFD between 00-06Z. There remains some timing uncertainty for the widespread convection expected to initiate on Wednesday. Showers are likely to begin kicking up before 18Z in western PA before overspreading to the east and strengthening through the afternoon. A few of these storms could be strong to severe with any impacted TAF site likely to see high wind gusts and low visibility. The best chance for strong storms will be between 18Z Wednesday and 00Z Thursday. Outlook... Wed...Thunderstorm impacts likely. Thu-Fri...Generally VFR. Sat-Sun...Thunderstorm impacts possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald AVIATION...Steinbugl/Bowen