textproduct: State College

WHAT HAS CHANGED

* Increased rainfall amounts slightly through the weekend.

KEY MESSAGES

1) Noticeably cooler into Memorial Day weekend with temperatures challenging record low maximums on Saturday.

2) Widespread soaking rain dampers outdoor plans and activities to start Memorial Day weekend.

DISCUSSION

KEY MESSAGE 1: Noticeably cooler into Memorial Day weekend with temperatures challenging record low maximums on Saturday.

Mainly clear skies and light winds have allowed for temperatures to fall into the upper 30s across northern PA this morning as high pressure builds into the region. While temperatures likely won't fall to much farther from their current values before sunrise, some patchy frost is possible in the coldest locations.

Model data shows the anomalous high pressure channeling southward down the east side of the Appalachians, setting up a classic cool wedge/cold air damming (CAD) pattern into Memorial Day weekend. We continue to reiterate a bearish outlook for daytime temps Fri-Sun with record challenging low maxes on the table for Saturday (see climate section below).

850 mb show a highly anomalous V-component (wind from the SSE) at 18Z Sat with Standardized Anomalies of +3-4 St deviations over Central and NW PA, while winds around 925 mb highlight negative U anomalies of the same magnitude (from the ESE).

This will create an expansive llvl CAD regime with strong moisture advection aloft, leading to steady light to moderate rain/drizzle. The moderately gusty east/southeast wind will make it feel downright dreary/raw, unseasonably chilly and pretty miserable for this time of year - especially for outdoor activities Friday afternoon through Sunday morning.

The 2-3 day cool stretch will certainly be noticeable following an early summerlike surge, but won't have staying power with temperatures forecast to moderate and trend above normal into the middle of next week.

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KEY MESSAGE 2: Widespread soaking/beneficial rain dampers outdoor plans and activities to start Memorial Day weekend

Mainly dry conditions will continue through the morning before rain gradually spreads northward this afternoon (beginning mainly after 19-20Z near and to the north of I-80, and possibly not until near or shortly after midnight near the PA/NY border) The rain will continue through the day on Saturday, with the steadiest rain expected during the late morning/early afternoon as a 40 to 50 knot low-level jet moves over the region.

Expect widespread 1-2" rainfall totals which will be very beneficial for D1-D2 drought areas in the far southern tier into the LSV. Anomalous upslope east-southeasterly flow may result in locally higher rainfall amounts approaching 3 inches across portions of south-central PA. The precip pattern transitions from steady rain/drizzle to more of a showery/low chance thunder regime for Sunday as the best forcing moves away from Pennsylvania. Another round of steady rain is possible Sunday night into Monday morning as another disturbance approaches from the west.

AVIATION /09Z FRIDAY THROUGH TUESDAY/

Low clouds will surge northward today, bringing MVFR restrictions to AOO and JST, then UNV, MDT, and IPT. Eventually all airfields will be restricted by this evening. Widespread stratiform rain showers will accompany the lowering ceilings and will bring reduced (MVFR to IFR) visibilities.

There is a signal for gusty southeasterly winds at KJST and KBFD today, with gusts 20 to 25 kts. Although gusty winds are also possible at KLNS and KMDT, clouds/rain should keep the airmass stable and prevent winds from mixing down consistently. By 12Z Saturday, all airfields should have at least MVFR restrictions,

Outlook...

Fri...Restrictions likely with rain moving in from south to north, lasting into Fri night.

Sat...Widespread IFR/LIFR restrictions in steady rain

Sun...Minor improvement to MVFR/IFR restrictions as rain tapers off

Mon...IFR/MVFR early, then MVFR in light rain showers

Tue...Continued MVFR restrictions with scattered showers, especially south

CLIMATE

Daily Record Low Maximum & Forecast Temperatures for May 23:

LOCATION RECORD (YEAR) FORECAST HIGH Harrisburg 54 (1982) 54 Williamsport 57 (1982) 53 Altoona 52 (2005) 51 Bradford 45 (1963) 49 State College 53 (1968) 51

CTP WATCHES/WARNINGS/ADVISORIES

None.