textproduct: State College

WHAT HAS CHANGED

* Lowered temps Saturday by 5F across much of Central and Eastern PA, pegged sky cover at 100 pct and removed the mention of thunder under llvl CAD regime with periods of steady light to moderate rain and drizzle in between.

KEY MESSAGES

1) Showers likely and a thunderstorm possible Friday (Central and NW Mtns).

2) Periods of rain area-wide Fri night-Sat night does not look heavy. Sunday now looking dry.

3) Several more shots at rain follow for the new week.

DISCUSSION

KEY MESSAGE 1: Showers likely and a thunderstorm possible Friday (Central and NW Mtns).

Sfc warm/Q-stnry front extended from KYNG to KIDI and SE to around KHGR at 18Z Thu.

This boundary will be lifting northward through the western and southern counties of PA as a warm front on Friday, and will help to generate scattered SHRA/TSRA, mainly in the afternoon near and to the west of RT 219 where MU CAPE of up to around 750 J/KG is possible based on the latest HREF.

Most models produce convection, and confidence is high. Clearfield county (and points just to the North and East (along a fairly sharp, quasi-stnry 925-850 mb boundary) seems like it would be the most-likely place to get 2 or more SHRAs.

PWAT barely gets near 1" by the end of the day. Best instability will be around there. Point amounts may near 0.25", but chc for more than that is very low. Light easterly wind to the east of the warm front could keep the temps there down 4-7F vs Thurs.

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KEY MESSAGE 2: Periods of rain/drizzle area-wide Fri night-Sat night does not look heavy. Sunday now looking dry.

Main change for this period was to lower temps (by about 5 deg F) acrs central and eastern parts of the CWA within a regime of low-level CAD.

MCS looks likely to drop down from the Upper Great Lakes Friday night, but the 8H jet looks weak. Timing looks more-solid, now, with the bulk of the rain in the second half of Fri night and early Sat. Some models/members linger precip much of Sat with the big upper low over nrn New England retrograding/wobbling westward slightly. Energy dropping southeast could still provide enough lift to trigger sct SHRA/TSRA Sat - mainly in the east.

There could be a little briefly heavy rain from TSRA, but the overall QPF for Fri night into Sat night is 1" or less. Everything is grown across the southern 2/3rds of the CWA. Even the N is seeing a little color on the hills. Therefore, there is no threat for flooding. Overall, Sat looks 10F cooler than Fri on the whole, with the E cooler (50s) vs W (60s).

Upper ridging builds in on Sun with a drying trend continuing amongst the preponderance of solutions. Lag is about the only thing keeping a 20 PoP in for Sun for now. Overall, it looks like the sky will brighten Sun with maxes in the 60s.

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KEY MESSAGE 3: Several more shots at rain follow for the new week.

Upper low to our NE finally slides east and allows a brief visit from dry weather later Sun-Mon. The upper ridge is weak and breaks down quickly, though and moisture from the west rolls in Mon night/Tues. The pattern looks favorable for at least two shots of rain with two cold fronts mid-week. Timing and details are uncertain, though. Neither front looks like a significant transition, and temps stay seasonable. Many places in Central PA would welcome additional rainfall, esp the S.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

VFR is likely to prevail through 00Z Saturday with flight restrictions limited to SHRA across Central PA tomorrow morning & afternoon.

Clouds will increase between 02Z-07Z Friday as a shortwave approaches from the northwest, with conditions remaining dry through the night. An initial round of scattered showers is expected between 12Z-17Z Friday along a narrow NNW/SSE boundary over Central PA (closest to KBFD/KIPT/KUNV), where milder/moist air from the southwest meets & rises over cooler/drier air from the northeast. Most of these showers will move across the drier side of this boundary, with VFR favored for these showers given low-level dry air (T/Td spreads around 10 degrees C).

A second round of scattered showers will develop across this boundary in the afternoon (18Z-24Z), driven by instability developing on the mild/moist side (HREF mean SBCAPE around 500 J/kg). Visibility restrictions will be more likely with these showers given the diurnally driven instability in place, with brief gusty winds also possible given the inverted-V profile in place (primarily KJST/KAOO/KUNV). For our other sites, spottier shower coverage is expected due to greater distance from the frontal boundary & less moisture being available on the drier side, though visibility restrictions to 5-6SM are possible. Moreover, a few thundershowers may develop given the instability, though the low-topped nature of these showers (HRRR modeled cloud top temperatures warmer than -30 degrees C) precludes TSRA mentions at this time.

Outlook...

Sat-Sun..Periods of rain with MVFR to IFR conditions.

Mon...VFR likely.

Tue...VFR early, with restrictions west to east as ceilings lower and showers move in.

CTP WATCHES/WARNINGS/ADVISORIES

None.