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
660 FXUS61 KCTP 271514 AFDCTP Area Forecast Discussion National Weather Service State College PA 1114 AM EDT Fri Sep 27 2024 .SYNOPSIS... *Cloudy and humid with periods of rain and mild nights for the last weekend of September; rain continues to start October *The heaviest rain is expected Sunday and Monday over south central PA which should be largely beneficial *A shift toward drier/cooler weather is possible by the end of next week/first weekend of October && .NEAR TERM /UNTIL 8 PM THIS EVENING/... A few peaks of sun along the PA/NY border early this morning; otherwise a cloudy last Friday of September with waves of rain and pockets of drizzle expanding from south to north across CPA this afternoon into the evening. Updated POPs to reflect the latest MRMS radar trends with ongoing light rain over the southern tier lifting north of the PA Turnpike to JST/AOO/MDT line at 15Z. Other area to monitor will be the ridgetops along the southern Laurel Highlands where wind gusts 35-40 mph are expected. Can`t rule out gusts reaching advisory criteria with blended HREF/NBM probabilities a shade over 50/50. Will insert into HWO for now and consider matching PBZ with an advisory for later today. Despite the extensive cloud cover, max temps in the 65-75F range are near to even a few degrees above daily climo for this time of year. It will also feel quite humid especially over the southern half of the forecast area with Td 65-70F. && .SHORT TERM /8 PM THIS EVENING THROUGH SUNDAY/... Showers should remain off and on throughout the night as moisture getting pulled into what`s left of Hurricane Helene (which will be wobbling westward into the lower OH valley). The true tropical moisture plume will be pulling out to the east and leave PA in a general light rainfall. There is a sliver of neg LIs aloft per NAM and GFS. So a TSRA cannot be ruled out (20pct chc), mainly in the central counties. The risk for any 40KT gusts should be over by midnight as the lljet passes. Again, too low of a prob to make a wind advy at this point. Temps only drop 5-6F in most places tonight. Saturday, we should see the bulk of the showers/light rain lift northward through the day, and perhaps drop southward again as the night starts with some ridging trying to develop overhead. Sat should be a little milder than today. By Sunday, the heavily-modified remnants of Helene will have combined with a deep upper low to our southwest. This upper low will be nosing into PA on Sunday. Height falls and moisture from the Atlantic will lead to an increase in rainfall, mainly in the south. Sunday should be a cool day with highs only in the 60s under thick clouds. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Complex pattern early next week. Hard to see much widespread dry weather prior to later Wed. There has been a lot of spread on the large scale pattern lately. More information below. An upper-level low over the Ohio Valley will 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. High pressure building in behind the front will bring drier weather and cooler temperatures for the end of the week. Highs will generally be in the 60s with overnight lows in the 40s. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... A slow moving cold front has become practically stalled-out and draped east/west just south of the I-80 corridor early today. Low level moisture ahead of the front, combined with nocturnal cooling and an upsloping easterly flow, should help to maintain IFR/LIFR cigs across the southern half of PA through 12-13Z today. Ensemble prob charts indicate a 60-80pct chance of IFR cigs across the southern half of the state, with a 80-90pct along the ridgetops. Cigs across the north are generally MVFR with VFR Vsbys thanks to the weak push of drier air from the NE behind the front. Conditions should improve further today with respect to CIGS, which should lift into the high MVFR/VFR range. Weak diurnal heating/mixing and mixing of some drier air above 5 kft AGL should result in modest improvement in cigs through the day today, with most locations in the MVFR category by afternoon and possibly VFR at the Susq Valley airfields. Moisture steaming upslope into the CWA from the SE and indirectly related to the remnants of Hurricane Helene will start to overrun the aforementioned stalled-out frontal boundary lying across Southern PA this later today and tonight, leading to deteriorating conditions in the form of light rain and lowering cigs. CIGS will dip back into the IFR to low MVFR range around or shortly after dusk today across the north. Model soundings and ensemble prob charts indicate IFR/LIFR conditions will become likely over the Central Mtns by the evening hours. The arrival of a core of relatively strong winds aloft will likely result in LLWS criteria late today through early today, mainly across the Southern PA Airfields. Confidence is about 70 percent for this to occur in the valley airfields and about 90 percent at KJST. Outlook... Sat-Sun...Low cigs/drizzle likely, mainly Central Mtns during the AM. Mon-Tue...Rain/low cigs likely, especially Central Mtns. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Steinbugl SHORT TERM...Dangelo LONG TERM...Martin/Bauco AVIATION...Lambert/Fitzgerald