textproduct: State College

WHAT HAS CHANGED

*Flood Watch expanded across the southern tier of central PA

KEY MESSAGES

1) Locally significant flash flooding possible across portions of south central PA this afternoon and evening

2) Unsettled weather continues into the first half of the weekend.

DISCUSSION

KEY MESSAGE 1: Locally significant flash flooding possible across portions of south central PA this afternoon and evening

Showers and thunderstorms are increasing in coverage this afternoon across southern PA. Rainfall rates of 2-3"/hr are likely at times, leading to 2-4" of rain with locally higher amounts possible.

Synoptic ascent associated with shortwave lifting E/NE out of KY is working in tandem with RRQ of a modest jet streak aloft robust thermodynamics reflected by PWs measured via the 12Z soundings that are near previous daily records (2.17" at IAD) and a ribbon of MLCAPE already reaching 1000+ J/kg (2000 J/kg within clearing sky conditions). MRMS hourly rainfall have been above 1 inch in some areas, indicative of the impressive heavy rain environment in place. Earlier this morning, rainfall rates of ~1.5"/hr where achieved via ground truth report from broadcast media partner - so rates >2" should be easily attainable given the time of day and copious amount of moisture available. WPC excessive rainfall outlook continues to favor a "high-end" level 2/4 flash flood risk over the southern tier of central PA where locally significant/urban flash flooding is possible.

KEY MESSAGE 2: Unsettled weather continues into the first half of the weekend.

Additional showers and thunderstorms are expected on Friday ahead of a cold front that will slowly cross the region into Saturday. Isolated flash flooding will be the primary concern as the environment will still be supportive of very heavy rainfall. A few showers remain possible on Saturday across the southern half of the area as the cold front will be very slow to move to our south. Sunday looks like a much drier day as the front finally moves off to the south and a strong ridge develops over the middle of the country.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

VFR flying across south central PA may be interrupted and restricted by showers and thunderstorms through 00Z Fri. Storms will be capable of torrential rainfall likely resulting in IFR/LIFR visibility. Gusty winds are also possible.

In the wake of this storms, partial clearing along with residual low level moisture from recent rainfall and light/variable wind may lead to areas of fog and low stratus developing late tonight into early Friday morning. Expect sub-VFR restrictions to improve to VFR by Friday afternoon with more scattered showers and storms possible.

Outlook...

Sat...Reduced chance and more limited coverage of PM showers/t-storm.

Sun-Tue...Mainly VFR/no sig wx.

CTP WATCHES/WARNINGS/ADVISORIES

Flood Watch until midnight EDT tonight for PAZ033>036-056-057- 059-063>066.