textproduct: State College

WHAT HAS CHANGED

* Tweaks to match near term radar and sky trends.

KEY MESSAGES

1) Showers/storms affect some of the area tonight as a warm front lifts across the state.

2) Severe thunderstorm risk for Wed night/Thursday 6/17-18, with a gusty westerly gradient wind of 30-35 mph in the afternoon across the NW half of the state.

DISCUSSION

KEY MESSAGE 1: Showers/storms affect some of the area tonight as a warm front lifts across the state.

Storms associated with the advance of an upper trough and warm front are starting to impact the NW mtns. Some gusts into the 30+KT range have been noted across wrn PA. Lightning is decreasing slightly as the cluster of storms moves into the CWA. Cannot see any significant downdraft potential from these storms, but a gust to 40KT across Warren/McKean/Elk Cos is possible.

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KEY MESSAGE 2: Severe thunderstorm risk for Wed night/Thursday 6/17-18, with a gusty westerly gradient wind of 30-35 mph in the afternoon across the NW half of the state.

Latest model guidance is a bit concerning regarding the potential for an Eastward/SEWD moving MCS late Wed night and Thursday AM. The area most prone to seeing this will be the NW Mtns of PA where a surge of llvl moisture and warmer temps will lead to at least several hundred J/kg of MU CAPE - mainly across the NW half of PA.

We'll be monitoring the potential timing for severe weather closely. It could be one of those rare nights where the number and timing of storms makes it a rather noisy night to sleep undisturbed.

The severe threat shifts to the southeastern half of the CWA for Thursday, though there still remains some uncertainty regarding how much the airmass will be able to recover behind any morning convection and cloud cover.

The nose of a very strong, 40-50 KT swrly 850 mb jet 50+ KT at 700 mb (both being 3-4 sigma on the standardized anomaly scale), the the left exit region of a 100 KT 250 mb jet and PWATS around 1.5 inches (with the potential for a narrow tongue of an EML surging east ahead of a strong sfc cold front) will create a favorable synoptic setup for severe weather (High Cape Low shear Environment).

Another notable weather factor for the bulk of the daylight hours Thursday will be the likelihood of 30-35 kt gradient, westerly wind gusts focused mainly across the NW half of the CWA.

AVIATION /01Z WEDNESDAY THROUGH SUNDAY/

VFR conditions will continue through the 00Z TAF period with scattered clouds around 5000 feet likely sticking around through the rest of the afternoon and early evening. Winds will be light out of the south- southwest into the evening, before becoming variable at less than 5 knots for tonight. Mid and high clouds increase from west to east overnight ahead of a low pressure system that will track well to our north. This system will bring a few showers and possibly even a thunderstorm to northern PA into the morning along a shallow warm front. The best chance for rain will be at BFD and IPT, though a few showers may make it as far south as JST, AOO, and UNV. Prob30s have been mentioned at sites with the highest confidence. Some guidance shows additional showers developing around MDT and LNS, though confidence is very low on this outcome.

Scattered to broken clouds between 5000 and 10000 feet will stick around through Wednesday morning, though rain becomes less likely after 14Z. Winds will be out of the southwest around 10 knots with gusts of 15 to 20 knots possible by late morning. Additional widely scattered showers may develop during the afternoon, but most TAF sites are expected to remain dry at this point.

Outlook...

Wed...Higher chances for -SHRA/-TSRA, restrictions more likely late. High probability (90+ percent) for LLWS Wed night into Thursday morning as the axis of an anomalously strong south/southwesterly LLJ slides east across the Commonwealth.

Thu...Restrictions possible in -SHRA/-TSRA.

Fri...Showers ending.

Sat-Sun...Chance of afternoon showers and thunderstorms over the north and west.

CTP WATCHES/WARNINGS/ADVISORIES

None.