textproduct: State College

WHAT HAS CHANGED

* No sig changes

KEY MESSAGES

1) Becoming noticeably less humid through the day today with cooler air settling in for tonight.

2) Rain returning by Sunday, heavy at times.

3) Rainy pattern continues into much of next week.

DISCUSSION

KEY MESSAGE 1: Becoming noticeably less humid through the day today with cooler air settling in for tonight.

With the cold front now pushing into the southern tier, high clouds are peeling off to the south. However, moisture remains trapped in the boundary layer resulting in widespread stratus and a few areas of fog. Dewpoints range from the upper 60s to the low 70s in these predawn hours. Showers are expected to remain isolated at best. A north breeze with gusts up to 20 mph will advect a cooler and drier air mass, with temps and dewpts in the 40s for central PA by late tonight. Patchy valley fog is possible early Saturday morning. Most, if not all of Saturday will be dry.

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KEY MESSAGE 2: Rain returning by Sunday, heavy at times.

Periods of potentially heavy rainfall are expected Saturday night into Sunday. Both NAEFS and ECMWF SATs show at least 90th percentile PWs returning to the region, which is supportive of at least a marginal excessive rain signal. A surface low expected to track over the Great Lakes will usher in this moisture and more than enough forcing for widespread precipitation. A few to several hundred J/kg of MUCAPE should support some heavier downpours, but little to no CAPE above the -10C level suggests the lightning threat will be limited. Most likely rainfall amounts with the Sunday system are 0.50-1.50".

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KEY MESSAGE 3: Rainy pattern continues into much of next week.

PoPs are progged to drop into the 30-40 pct range on Monday as high pressure wedges in from the north. However, the jet stream will remain active and amplified with Pacific disturbances moving across the nation. By Tuesday, most guidance has a slow moving trough in the Ohio Valley advecting warm air above a wedge of cool sfc air in place from the aforementioned high pressure system. This setup may linger for a few days, with up to several inches of rainfall possible through the week. The cold air damming will also result in high temps only in the 50s to low 60s.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Overnight mid-level clouds increasing from north to south ahead of an upper level wave. VFR conditions expected to remain in place throughout the night, because valley fog formation seems unlikely to impact any TAF sites due to a dry air mass and increasing clouds.

In the morning hours, winds will shift to the east, as the high pressure system moves off to the east. Low-level clouds will begin to build over the area during the afternoon though we should remain under VFR conditions as any clouds look to be scattered between 4000 and 5000 feet.

Tomorrow evening, warm air advection (WWA) increases ahead of an approaching low pressure system, with chances of rain/showers increasing through the evening and overnight hours. MVFR-IFR ceilings are favored with the onset of these showers as low- level moisture increases. Borderline LLWS conditions are possible as 925 mb winds build to around 170deg/35kts later Saturday evening into early Sunday morning, with LLWS mentions possible areawide if projected wind shear values increase from current guidance (25-30 kts).

Outlook...

Sunday-Wednesday...Periods of rain/storms with MVFR likely (70%) and IFR possible (30%) for short periods.

CTP WATCHES/WARNINGS/ADVISORIES

None.