textproduct: State College

WHAT HAS CHANGED

* Level 2/4 excessive rainfall risk expanded to cover most of central PA

KEY MESSAGES

1) Scattered to numerous severe thunderstorms are expected this afternoon through the evening

DISCUSSION

KEY MESSAGE 1: Scattered to numerous severe thunderstorms are expected this afternoon through the evening

Thunderstorms are expected to develop ahead of an eastward- moving cold front across the Ohio Valley and along a pre- frontal trough crossing the CWA between roughly 2-9PM. No changes were made to the level 3/5 enhanced risk area from SPC for day 1 with swaths of damaging wind gusts remaining the primary hazard. Diurnal heating within cloud breaks, combined with upper 60s to lower 70s dewpoints, will support moderate surface-based instability across the broad pre-frontal warm sector. The most favorable overlap of this instability and 40-50 kt of effective shear is expected to foster a mix of organized clusters and supercells that should evolve and spread eastward through the day. Severe hail and a few tornadoes will also be possible with any sustained supercells. The enhanced level 3/5 risk favors a higher confidence/coverage in severe storms with a few significant severe storms possible reaching intensity levels (75+ mph wind gusts and/or EF-2 tornado) we may only experience 1x or 2x/year.

WPC has expanded the level 2/4 excessive rainfall outlook to cover the majority of the CWA. However, despite plenty of juice and high PWATs supportive of locally intense rain rates, overall confidence is low/limited by the lack of a hires model signal and relatively fast/progressive storm motions. Opted to pass on a FF watch for this cycle and allow the dayshift to reassess or issue a more short-fused/targeted watch.

Rain showers linger tonight into Wednesday particularly downwind of Lake Erie and over the higher elevations, but for the most part we anticipate a multi-day drying trend with near to slightly below normal temps and comfortably low humidity from midweek into the last weekend of July.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

A few areas of low ceilings this morning with some showers already developing over the Allegheny front. Clouds and precipitation activity will only increase throughout the day ahead of an approaching cold front.

Conditions will waffle between MVFR and VFR through the morning as -SHRA pop up ahead of the main area of precipitation. The area has been placed in an enhanced risk for severe storms through the afternoon hours. However, confidence on the exact time of any storm passing over an individual airport is only about 20% at this time. Hence VCTS was added for the afternoon time frame with the expectation that timing will be narrowed down as we move closer to the event. In any case, plan for +TSRA to dot the state through the afternoon into evening with the usual suspects of wind shear, turbulence, heavy rain, and the potential for hail (especially aloft where it hasn't had time to melt on its way down).

In the wake of the storms this afternoon expect low ceilings to stick around for MVFR to IFR across the entire area leading into Wednesday.

Outlook...

Wed...Periods of lingering showers possible Wednesday morning as the frontal boundary exits the state.

Wed afternoon-Sat...Good VFR conditions expected.

CTP WATCHES/WARNINGS/ADVISORIES

None.