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
105 FXUS61 KCTP 272301 AFDCTP Area Forecast Discussion National Weather Service State College PA 701 PM EDT Thu Jun 27 2024 .SYNOPSIS... *Seasonable end to the week with comfortable humidity *Return of heat+humidity fuels T-storms this weekend *Cooler & dry start to July; heat & T-storms by the 4th && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 645 pm update... The diurnal cumulus field is fading fast this evening with the loss of daytime heating in a dry air mass. This will lead to a clear and refreshingly cool night for late June. As indicated in the previous discussion, good radiational cooling conditions overnight should lead to the development of river valley fog, especially across northern PA and across the Alleghenies. Lows by daybreak will range from the mid 40s across the northern tier, to the upper 50s over portions of south- central PA. Previous discussion... Cu will crumble this evening setting up a refreshingly cool and mainly clear night across central PA. Low pwats and favorable radiational cooling pattern supports trending below the 50th percentile NBM with relatively chilly min temps in the mid 40s across the northern tier. Beneath dome of 1020mb high pressure, synoptic conditions support fog formation late tonight into early Friday morning in the river/stream valleys across the western and northern Alleghenies. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... AM fog will dissipate quickly after sunrise Friday. Expect partly cloudy and seasonably comfortable conditions with highs 75-85F. An increasingly strong southerly llvl return flow develops into Friday night as the aforementioned surface high shifts eastward off the New England coast. Latest model data suggests 30-40kt LLJ from the south-southwest will drive some showers and elevated t-storms over west central PA late Friday night into early Saturday morning. The belt of strong 850mb flow will transport rich low level moisture (dewpoints in the upper 60s to lower 70s) northeastward along/ahead of a cold front this weekend. PWAT values are forecast to reach 1.5-2.5 inches on Saturday or +2-3SD. The anomalous deep layer moisture will support risk of heavy to potentially excessive rainfall. WPC currently has a broad MRGL risk, but the setup will likely yield an upgrade to SLGT risk particularly where FFGs are reduced. Although mid lvl lapse rates may remain weak, high dewpoints and diurnal heating should fuel at least moderate buoyancy by mid/late afternoon. The projected instability and deep shear profiles support a conditional risk of strong to severe storms. SPC has most of the area in a MRGL risk for D3, but their discussion suggests a categorical upgrade/expansion of SLGT risk (just to the west) is possible in subsequent outlooks. The influence of early day clouds/waning overnight convection could be a limiting factor. Convection should decrease in coverage and intensity into Saturday night, which will be warm and muggy with lows 65-75. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Latest model consensus shifts primary t-storm/svr wx risk to the southeast on Sunday with max POPs across the far southeastern portion of the forecast area. Highs on the last day of June are fcst to reach the low 90s in the lower Susquehanna Valley with max heat index values approaching 100F in some locations. There is high confidence that July will start relatively cool and dry with near to slightly below normal temps and low humidity lasting through early next week -- thanks to another seasonably strong high pressure system. The pattern for the first week of July is almost a repeat of 6/25-6/29 with comfortable days and cool nights followed by a ramp in heat and humidity driving max temps and chance of t-storms higher by the 4th of July. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... For the 00Z TAF packege, looking at mainly clear skies overnight, as high pressure builds into the area. As I mentioned on the late afternoon update, I added a TEMPO group for fog at BFD late, as low temperatures drop to or just below the expected dewpoint. Friday looks like a dry day at this point, with a southerly flow of air and just a few clouds. More in the way of adverse weather for the weekend, as a warm front lifts northward, followed by a cold front on Sunday. Outlook... Sat-Sun...Widespread showers and thunderstorm with impacts possible. Mon-Tue...Dry weather with VFR conditions. && .CLIMATE... Through 6/26, June ranks as tied for the second warmest on record at Harrisburg. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Jurewicz/Steinbugl SHORT TERM...Steinbugl LONG TERM...Steinbugl AVIATION...Martin CLIMATE...Steinbugl