textproduct: State College

WHAT HAS CHANGED

* Flood Watch refined for Somerset Co

KEY MESSAGES

1) Flooding possible across southwestern PA into the afternoon

2) Seasonably cooler and tranquil/pleasant weather conditions forecast Thursday through the last weekend of May

DISCUSSION

KEY MESSAGE 1: Flooding possible across southwestern PA into the afternoon

Convection is bubbling up all along the srn border counties at this time. Some of the echoes are rolling west to east, and some have more of a northeasterly drift to them. Shortwave trough moving through OH/WV is kicking off an area of thunderstorms. These storms could deposit heavy rain in the Laurels/south- central mountains. The FFG averages about 1"/hr for that area. The soil is moist and base streamflows are certainly higher than just a week ago, but not especially high. Much of the guidance pushes the convection to our S in the early-mid afternoon. We have pulled the end time of the flood watch back to 20Z (4 PM) in a nod to that consistent trend in the model guidance.

While there is very light wind in the lowest 10-15kft on latest model soundings for JST today, the 6km bulk shear is close to 40KT. If deep convection can tap the deep shear, some wind damage could occur. SPC has nudged the MRGL risk into 4 of our SWrn counties for today. The threat would be highest if storms can happen in the afternoon with heating peaked because the clouds and early day rainfall should present a challenge for thick CAPE to develop and be realized.

So, there is both a heavy rain/flooding and limited severe weather threat for a small part of the CWA today. The colder, drier air moving down from the north today/tonight should end these threats - but could make a couple of showers/storms as it passes through the central mountains later today.

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KEY MESSAGE 2: Seasonably cooler and tranquil/pleasant weather conditions forecast Thursday through the last weekend of May

A mainly-dry cold front delivers cooler and drier/less humid air for Thursday followed by high pressure through late week. Reinforcing troughing over the Northeast should result in near to below normal temperatures (seasonably cool) and low precipitation chances for the last weekend of May.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

A broad area of convergence associated with a slow moving warm frontal boundary near the Pennsylvania/Maryland border will be the focus for rain through the rest of the morning and into the early afternoon. Showers may make it as far north as UNV, though JST, AOO, MDT, and LNS are most likely to see rain today. Some of the rain could be heavy at times, potentially leading to brief visibility restrictions. Thunder cannot be ruled out, but timing and placement remains uncertain so we'll keep it out of the TAFs for now.

Anywhere that sees rain today has the potential to see ceilings and visibility drop to MVFR or IFR at times, but confidence on prolonged restrictions is low.

Conditions will return to VFR by mid afternoon across all of Central PA and the bulk of the shower activity should shift south of all TAF sites. A cold front will cross the region during the evening and into early Thursday morning, but any showers look to be very isolated along this feature. Winds will flip around to the northwest behind the front and a much drier airmass will move into Pennsylvania.

Outlook...

Thu-Sun...VFR with no significant weather expected.

CTP WATCHES/WARNINGS/ADVISORIES

Flood Watch through this evening for PAZ033.