textproduct: State College

WHAT HAS CHANGED

* Lowered Thursday's dewpoints with dry air above a weak inversion. * Potential for faster timing with the exit of the main batch of showers Saturday morning/midday based on 12Z Model Consensus, though would like to see 2 cycles in a row better supporting this trend.

KEY MESSAGES

1) Trending warmer Thursday and Friday.

2) Wet start to the weekend.

DISCUSSION

KEY MESSAGE 1: Trending warmer Thursday and Friday.

For tonight clear to partly cloudy with patchy fog late, mainly across the NW Mtns and portions of the mid and lower Susq Valley.

Thursday looks dry and much warmer, jumping about 10F over Wednesday. Everyone but the far NErn mtns will be in the 70s. An 80F is not out of the question close to the MD border. This warmth and associated deep mixing should help dewpoints/RHs get a little lower than NBM guidance. Min RH should be close to 30 pct if not lower Thurs. NAM is an outlier with much higher dewpoints and cloud cover and slightly cooler temps in the west. Have discounted for now. The front that passed through late Wednesday will return northward over western PA on Friday.

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KEY MESSAGE 2: Wet start to the weekend.

The lift over the front and daytime instability will generate sct SHRA/TSRA in the western half of the CWA on Friday. The cold air tries to hang on over the east and may even back in a bit as the upper low over New England presses southward along the coast. This will keep the warm front in place or nudge it to the west as a backdoor cold front.

The energy diving down from the N/NW and perhaps an enhanced LLJet will bring in more moisture, and generate more SHRA/TSRA Fri night. Sat looks pretty wet for everyone with numerous SHRA/TSRA. QPF in the 0.5-1.00" range is a solid forecast for many Fri night and Sat. Recent runs continue to trend faster with the exit of precipitation on Saturday. If the trends continue/persist, Saturday could end up not being a total washout.

Some model divergence is seen for Sunday, though. Confidence is low in how fast the precip moves through. So, Sunday may hold sct SHRA, and PoPs in the 20-35% range are being kept for the time being.

Next storm system approaches for Tues, resulting in a medium confidence and medium to high PoPs. Will leave those high PoPs in for now, but model/EPS difference exists on evolution of the storm/mass fields.

AVIATION /01Z THURSDAY THROUGH MONDAY/

VFR conditions prevail tonight and should be the primary condition across the area through the end of the TAF period. Overnight (after 06Z), fog development becomes a concern due to largely cloud- free skies and light winds, particularly across the southeastern airfields (KMDT/KLNS) and near KBFD.

For KMDT/KLNS, light easterly flow on the backside of the low pressure that brought us rain showers earlier today will keep low-level moisture in place, increasing the chances for visibility restrictions due to mist/fog. Confidence for fog (around 30%) is higher at KLNS given their proximity to the coast, with less confidence at KMDT.

In addition to fog potential at the aforementioned airfields, upslope winds at KJST may contribute to low clouds developing after 06Z, with restrictions to IFR favored (60% chance) at the site. Any restrictions will improve by mid morning with light winds and mostly sunny skies expected areawide.

Outlook...

Fri...Light rain possible. VFR to MVFR.

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

Mon...Mainly VFR, decreasing ceilings later in the day.

CLIMATE

A handful of record lows were set/tied on Tues morning (April 21st):

Harrisburg's 29 broke the previous record of 30 degrees set back in 1956.

Altoona's 24 broke the previous record of 26 degrees also set back in 1956.

Williamsport tied it's record of 25 degrees set back in 1925.

CTP WATCHES/WARNINGS/ADVISORIES

None.