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
520 FXUS61 KCTP 231829 AFDCTP Area Forecast Discussion National Weather Service State College PA 229 PM EDT Mon Sep 23 2024 .SYNOPSIS... An amplifying upper level trough and slow moving frontal system will bring showery conditions to Central Pennsylvania through at least Wednesday, along with a few rumbles of thunder. As such, it will be cloudy and cool through midweek. The latter part of the week looks milder with at least partial sunshine expected late this week and into the weekend. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... The steadiest rain is pushing out of the NW mtns, but a good mid-level short wave trough/MCV is moving across LE. This feature will probably create sct, weak/light convective rainfall across the entire area this aftn and evening. The best slug of rain should diminish as it tries to push more east. But, still end up making 0.05-0.50" of rain. Temps change little for the rest of the day with the clouds hanging tough. Prev... Clouds continue to increase, lower and thicken this morning from west to east with light rain breaking out over much of the Alleghenies here in the predawn hours. The approaching sfc frontal system is running into CAD in place over Central PA so eastward progression of precip will continue to be a chore. Still, moisture transport aloft is continuous this morning and will win out, with light rain/showers eventually spreading through the most of central PA through mid morning. It should then be showery throughout from the late morning through late afternoon hours with a rumble or two of thunder possible thanks to some elevated instability. but there might be a thunderstorm or two, more probable in the SW than E. Temps on Monday won`t go more than 10F above the morning numbers, and highs will range from the low to mid 60s in most areas, but perhaps near 70F across the Lower Susq Valley. && .SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY NIGHT/... First surge of light rain/showers peters out somewhat by this evening with a relative lull in the activity seen for several hours tonight. Another minor surge of WAA and moisture aloft arrives in the Laurels before sunrise Tuesday with increasing POPs again at that time. Given recent dryness, no flooding concerns for tonight`s rainfall which should average from a third to half inch in most basins. Cloudy and unsettled conditions prevail through Tuesday evening with continued rain/shower chances, especially central and western areas in best proximity with frontal forcing. There can also be rumbles of thunder from time to time, but not much beyond that. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Model guidance outlines another surface low-pressure system tracking northeastward across the Great Lakes and into southern Ontario on Wednesday, with slightly more moisture and lift available as the warm front aligns itself north-to- south across west-central PA. Given slightly better lift with this low- pressure system overhead coupled with enhanced moisture, have retained likely PoPs on Wednesday with highest chances during the late morning to early afternoon hours. Heavy rainfall threats look less robust compared to previous forecast cycles; however, some instability will allow for thunderstorms across the Laurels, brining some potential for locally heavy rainfall, with maximum totals ~0.50" on Wed. Lingering showers across mainly E PA will continue into Thursday before a brief reprieve in rainfall Thursday evening and into Friday morning. Rainfall chances begin to increase as Friday morning progresses with the potential remnants of PTC9 approaching the area. There is still some uncertainty in regards to how PTC9 will impact central Pennsylvania, mainly dependent on interactions with a trough stationed across the eastern Tennessee Valley. At this time, deterministic model guidance shows modest agreement in the bulk of rainfall keeping south of the area; however, given uncertainty have not deviated much from NBM guidance this cycle. If precipitation manages to make way into central Pennsylvania in the Friday-Sunday timeframe, highest chances (25-35%) will be across S/W PA along the Laurels with a SChc (15-25%) progged west of the Susquehanna Valley. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... MVFR-to-IFR conditions are generally expected over the next 24 hours across central Pennsylvania, although some scattering out of the lower-level cloud deck possible across the Laurel Highlands (JST/AOO) in the near-term (through 20Z) portion of the TAF package. As the evening progresses into the overnight period, there is moderate-to-high (60-70%) confidence in prevailing IFR conditions across much of the area. Low-level cloud decks ~300ft AGL are expected to impact all of the western airfields (all minus MDT/LNS) with moderate (~60%) confidence in the 03-13Z timeframe, with slight differences in onset/lifting of restrictions. After sunset, expect western airfields to prevail IFR through 18Z Tuesday, although there is slightly lower confidence in the 15-18Z Tuesday timeframe. For the LSV airfields (MDT/LNS), there is some uncertainty with regards to the eastward extent of low-level ceilings impacting the airfields after 22Z Monday. At this time, the bulk of model guidance suggest MDT is more likely to experience restrictions with HREF guidance pushing towards 40-50% probabilities in IFR ceilings throughout the overnight period, thus have slightly higher confidence in IFR conditions prevailing. At LNS, slightly lower probabilities and a combination of GLAMP/RAP model guidance outlines low-end MVFR as the more likely outcome after 22Z Monday; however, ceilings/visibilities will be very borderline in the 06-13Z timeframe. At this time, have outlined MVFR ceilings given lower probs of IFR ceilings and sticking closer to GLAMP guidance given uncertainty. Outlook... Wed...Chc/Likely SHRA with some TSRA possible. Thu...Lingering/scattered showers possible E PA. Fri-Sat...Scattered SHRA S/W PA; otherwise, trending drier. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Lambert/DeVoir/Dangelo SHORT TERM...Lambert/DeVoir/Dangelo LONG TERM...NPB AVIATION...NPB