textproduct: State College

WHAT HAS CHANGED

Highlighted wind and frost/freeze risks in the HWO and Key Messages.

KEY MESSAGES

1) Big temperature swing ahead

2) Windy and wet end to the week with first flakes

3) Frost and freeze conditions this weekend

DISCUSSION

KEY MESSAGE 1: Big temperature swing ahead

Max temperatures are projected to challenge daily records Tuesday and Wednesday. Highs in the 70-85 range are 10 to 20 degrees above the historical average for mid October.

Contrast the early week record-challenging warmth with much colder air coming on the horizon for the weekend. The difference between max temps Tuesday vs. min temps Sat/Sun will be 40 to 50 degrees. Even more impressive will be the difference between max temps Tuesday vs. minimum wind chill values which could reach 50 to 60 degrees for some locations.

KEY MESSAGE 2: Windy and wet end to the week with first flakes

Little to no rain is expected through midweek. The most likely period of widespread wet weather comes late in the week between Thursday night and Friday as an amplified upper trough crosses the Great Lakes and spins up a deep sfc low in the Gulf of Maine into the Canadian Maritimes. While broader in overall coverage, late week rainfall amounts will be on the light side ranging from around 0.50 inch in the NW Alleghenies to 0.10 inch in the Lower Susquehanna Valley.

Gusty winds up to 40 mph are forecast on the backside of the deep low and will deliver much colder air spilling downwind of the Great Lakes this weekend. This pattern will be favorable for lake effect rain and possibly snow showers later Friday into early Saturday over the higher elevations. NBM data even suggests a minor snow accum (<0.5 inch) is possible in the NW mtns and highest ridgetops/summits in the Laurel Highlands.

KEY MESSAGE 3: Frost and freeze conditions this weekend

Freezing temperatures and frosty conditions are forecast into and over the weekend. Friday night will be a wind driven freeze likely confined over the NW mtns; Saturday and Sunday nights look more conducive for a traditional radiational cooling frost/freeze setup. Aside from being on the chilly side of mid October climo, the upcoming weekend will be fair and dry.

AVIATION /18Z MONDAY THROUGH SATURDAY/

Gradual improvements to VFR continue across central Pennsylvania this afternoon as post-frontal stratocumulus slowly mix out. Around 00Z, most of the area should have recovered to VFR, though areas of fog and low stratus are likely to develop tonight, particularly across the Northern Tier (KBFD) and on the windward side of the Alleghenies (KJST). The GLAMP is optimistic, having prevailing VFR overnight for all forecast terminals except KBFD, though I leaned towards the more pessimistic HREF/REFS guidance with hints of VCFG/SCT003 for most. With that said, downsloping may keep KAOO free of fog or low stratus concerns, as shown by the LAMP/HREF/REFS.

Overnight fog and low stratus will have mixed out regionwide by 15-16Z Tuesday as south/southwest flow picks up to 10-15 kts ahead of a progressive low pressure system sliding across the Great Lakes. Scattered showers, and perhaps a few thunderstorms (MUCAPE of around 500 J/kg), may move across the Northern Tier (KBFD) during the morning and afternoon as the system passes by. Little to no precipitation is expected elsewhere across our area, partly due to upper-level suppression under the right-exit region of a jet streak.

Outlook...

Wed...Restrictions from low ceilings and -SHRA possible as the front moves southward across the Commonwealth.

Thu...A period of VFR is favored behind the front, with a chance for restrictions and -RA later on Thursday as the front oscillates back northward.

Fri...Scattered -SHRA and isolated -TSRA could bring restrictions across the region with cold FROPA. W-NW winds may gust to around 25 kts behind the front.

Sat...Localized restrictions possible early due to post-frontal stratocumulus and lake-effect -SHRA/-SHSN, primarily across the Northern Tier. Otherwise, VFR prevailing with NW-NNW wind gusts to around 25 kts possible regionwide.

CLIMATE

Daily record high temperatures for October 13th and 14th:

MDT 85/1954 | 85/1975 IPT 83/1954 | 84/1975 AOO 82/2024 | 80/2021 BFD 78/1969 | 79/1975 STC 82/1930 | 84/1897

CTP WATCHES/WARNINGS/ADVISORIES

None.