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
945 FXUS61 KCTP 252305 AFDCTP Area Forecast Discussion National Weather Service State College PA 705 PM EDT Wed Sep 25 2024 .SYNOPSIS... Damp and unsettled weather will persist into Thursday, with perhaps a brief break Thursday night into early Friday. A stationary front draped across the Mason-Dixon Line will bring an increasing chance of showers for late Friday and into the weekend. A steadier period of rain is possible over parts of Central Pennsylvania Saturday night or Sunday as the weakened moisture remnants of Helene very slowly pull away from the region. && .NEAR TERM /THROUGH THURSDAY/... Easterly ageostrophic flow and western Atlantic component being overrun by moisture WSW flow at 850mb and above, yielding dense low clouds cover and widespread drizzle and patchy light rain this evening. Current conditions will persist for most of tonight and Thursday, as central PA remains sandwiched between an upper- level trough crossing New England and upper low centered over the Lower Ohio Valley. Blanket of clouds will keep overnight temperatures mild, with lows in the upper 50s to mid 60s running about 15 degrees above normal for late September. Thursday should be a bit milder than the past few days, with highs expected to reach the 70s areawide. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... The upper-level trough over New England will pull off the Atlantic Coast Thurs night into Friday, while the remnants of Hurricane Helene become wrapped up in the upper low over the Lower Ohio Valley. At the sfc, a stationary front will become draped across southern Pennsylvania. We will have to see how the remnant moisture from Helene interacts with the stationary front. The presence of this front could keep showers in the forecast into this weekend, esp across southern PA. Temperature-wise, the days will see temperatures fairly close to average, while clouds will keep nighttime temperatures well above average for early fall. There is still some uncertainty in regards to how Helene will impact central Pennsylvania, mainly dependent on interactions with an upper-level low stationed across the eastern Tennessee Valley. Deterministic model guidance has outlined that the bulk of rainfall will stay west of the area while a rather narrow, negatively tilted upper-level ridge holds strong from the Great Lakes through the Upper Ohio River Valley. Given the uncertainty with regards to upper-low interactions, did not deviate much from continuity and NBM guidance this cycle. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... An upper-level low over the Ohio Valley will likely drift east across the Commonwealth into the beginning of next week, keeping rain chances around through at least Tuesday. Uncertainty begins to increase towards the middle of the week as a northern stream shortwave tracks near the region, bringing a cold front along with it. The timing of this feature is a little unclear with some ensemble members showing the front tracking through early Wednesday morning while others show a later frontal passage. Moisture appears to be limited ahead of the front and the best forcing looks to remain to our north, so widespread rainfall does not appear likely at this point. Most guidance shows high pressure building in behind the front which will bring drier weather and cooler temperatures. By Wednesday, expect high temperatures in the upper 50s and 60s and lows mainly in the 40s. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... IFR ceilings are expected to persist through the rest of the day and into Thursday morning along with scattered showers and potentially a thunderstorm. Model soundings support widespread ceilings below 500 feet overnight at all airfields, and the HREF suggests a 30 to 40% chance of fog developing across the northern half of Central PA. Ceilings may slowly rise into Thursday afternoon with most guidance showing MVFR ceilings in the northwest after 15Z while the rest of the airfields likely remain IFR. Scattered showers will continue into the early afternoon. Outlook... Thu...AM low cigs/chc showers, mainly early. Fri...Patchy AM valley fog possible N Mtns. Chance of showers/low cigs across the south. Sat-Mon...Chance of low cigs/showers, mainly across the south. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Evanego NEAR TERM...DeVoir/Evanego SHORT TERM...Evanego LONG TERM...Bauco/NPB AVIATION...Bauco