textproduct: State College

WHAT HAS CHANGED

* No significant changes.

KEY MESSAGES

1) Big temperature swing ahead with record challenging warmth followed by major cooldown this weekend

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

DISCUSSION

KEY MESSAGE 1: Big temperature swing ahead with record challenging warmth followed by major cooldown this weekend

Abundant sunshine and gusty southwest breeze fueling record challenging warmth this afternoon across central PA. It's an OcTOASTer pattern for sure. The unseasonably mild temperatures continue tonight with min temps +20 to +25 degree above climo in the upper 50s and lower 60s.

In stark contrast to the summerlike conditions this afternoon, a major cooldown is looming for the end of the week into the weekend. The temperature difference between highs today and minimum wind chills Saturday morning will be 50 to 60 degrees! For example, the most extreme case would be around Bradford, PA with a drop from 78F this afternoon to a wind chill of 18F Saturday morning.

Friday night could be a wind-driven, advective cold freeze situation (no frost due to gusty winds) across parts of the Alleghenies, with a more traditional frost/freeze pattern setting up for Saturday and Sunday nights.

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

Latest HREF/REFS bring some rain showers from northern Ohio across the southwest part of the forecast area on Wednesday. Spotty rain chances should be largely confined to the southern tier Wednesday night into early Thursday. Total QPF through 00Z Friday ranges from a couple of hundreths across the Endless Mtns/NEPA to 0.25-0.50" in the Laurel Highlands.

An amplified upper trough will cross the Great Lakes Fri-Sat and spin up a deep sfc low near the Canadian Maritimes. This system will bring widespread rain/showers Thursday night into Friday before transitioning to a lake effect/enhanced precip pattern Friday night into early Saturday. Total QPF from 00Z Friday to 00Z Saturday ranges from around 0.75" in the NW mtns downwind of Lake Erie to <0.10" in the southern tier valleys to the east of I-99 and south of the PA Turnpike.

Gusty winds 35-45 mph are forecast on the backside of the deep low and will deliver much colder air downwind of the Great Lakes this weekend. The shot of colder air will allow for rain to mix or changeover to snow showers Friday night into Saturday morning across the higher terrain along the Allegheny Mtns. Any minor accum (<0.5") would have to occur overnight and be limited to non paved surfaces.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

VFR conditions prevail this evening with the main near-term concern overnight (through 12Z Wednesday) being the low-end potential for a shower at BFD/JST/AOO along with LLWS. Recent model guidance has trended slightly downward with shower potential with low-level dry air still in place across the region as of 00Z. At this time, low (~10-20%) confidence on any showers at these airfields so have limited mentions in the most recent forecast. HREF still outlines some potential for TSRA; however, this threat will likely be limited to JST in the 11-13Z timeframe but confidence with respect to the thunderstorm potential remains too low to include in the 00Z TAF cycle. In terms of LLWS, fairly high (~70-80%) confidence in LLWS thresholds being met at JST/BFD/AOO as a 40-50kt LLJ continues over northern/western Pennsylvania. Slightly lower, but still notable, concerns at UNV/IPT overnight so have also continued mentions with moderate (~50-60%) confidence overnight. At this time, all LLWS mentions have been taken out prior to sunrise as the LLJ becomes weaker closer to 12Z and LLWS mentions are less likely to be met across the board.

In terms of precipitation potential between 12Z Wednesday and 00Z Thursday, have made wholesale changes with the 00Z TAF cycle given slightly lower/higher confidence in certain timeframes of the forecast. Between 12Z-18Z Wednesday, fairly high confidence in more widespread SHRA expanding across all of the western terminals (BFD/JST/AOO) with some question marks on the extent eastward towards UNV/IPT. Given this, have made more robust mentions in SHRA in this timeframe at our western terminals given higher (~50-70%) confidence while still highlighting this potential at UNV/IPT/MDT/LNS where confidence in rainfall tomorrow morning/afternoon falls closer to the ~30% mark this evening. There does remain some elevated instability so an isolated thunderstorm will be possible; however, with expansive cloud cover and given that recent HREF guidance shows declining probabilities, have decided to nix TSRA mentions at BFD/JST/AOO/UNV during the morning hours. There will be a slight window at JST/AOO where there could be a couple hours of relatively dry conditions before rain filters back into the airfield based on more recent CONSShort/HREF model guidance, thus have also outlined this but timing is still uncertain.

Outlook...

Thu...Morning rain across S PA moves northward throughout the afternoon and evening hours. Restrictions possible.

Fri...Higher chances of SHRA with isolated TSRA. Restrictions increasingly likely.

Sat...Lingering SHRA across N/W PA with some -SHSN mixing in early Saturday morning. Restrictions likely at airfields that mix over to SHSN. Precipitation tapers off by sunrise, VFR prevails with gusty winds.

Sun...AM fog possible; otherwise, VFR conditions prevail.

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 State College COOP (7AM-7AM)

CTP WATCHES/WARNINGS/ADVISORIES

None.