textproduct: State College

WHAT HAS CHANGED

* Forecast overwhelmingly consistent.

KEY MESSAGES

1) Trending warmer through the week with a few chances for showers.

DISCUSSION

KEY MESSAGE 1: Trending warmer through the week with a few chances for showers.

A weak warm front will move into western NY, western PA late today. A few showers will be possible, but with the no real moisture feed from the gulf, amts will be light.

The front slips to southern PA late Wednesday, so there will be a drying trend into Thursday.

Thursday looks rain-free as high pressure noses down from Canada.

A pattern change has shut down the high end severe weather pattern for central PA for now. Typical of spring and fall, looking at cutoff lows. By late week, we are between one low to the west, and one near the coast. Complex pattern, forecast could change some over the next several forecast cycles.

Overall a cooler pattern than what we have had the last 6 weeks. May has feature cold conditions the last few years, including last May.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Widespread VFR flying continues this afternoon and into the evening hours, with restrictions not expected until closer to the ~03/04Z Wednesday timeframe based on recent runs of model guidance. The bulk of model guidance has trended slightly back on timing with low-level dry air in place. Recent model guidance looks to be tracking fairly well with recent observational trends, thus is seems reasonable to trend rainfall chances back slightly for the 18Z TAF package. Increasing odds of sub-VFR flight categories are expected across the area, mainly in the 06-12Z timeframe as rain gradually overspreads the area with HREF probabilities of MVFR ceilings generally over ~60-70%, thus high confidence in all airfields experiencing some period of sub- VFR conditions into the early morning hours. These conditions are likely to continue through 18Z Wed at most airfields based on recent GLAMP/NBM model guidance; however, some slight improvement cannot be ruled out in the 15-18Z Wed timeframe.

LLWS concerns are in play overnight, despite not being outright mentioned in the 18Z TAF package, especially across our southern airfields (JST/AOO/MDT/LNS). Recent NBM model guidance looks to have trended back slightly and favors less LLWS mentions while NAM model guidance does seem to indicate this potential as fairly consistent from the previous TAF package. Confidence remains lower (~20-30%) in LLWS criteria being met due to this slight trend back and differences in model guidance; however, there is a non-zero chance for LLWS at the aforementioned airfields, generally between 03-12Z Wed.

Outlook...

Thu...VFR. Partly cloudy and rainfree.

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

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

CLIMATE

Preliminary data outlines that multiple record low temperatures have been set and/or tied this morning across central Pennsylvania for April 21st:

Low temperature this morning of 29 degrees in Harrisburg will break the previous record of 30 degrees set back in 1956.

Low temperature this morning of 24 degrees in Altoona will break the previous record of 26 degrees set back in 1956.

Low temperature this morning of 25 degrees in Williamsport will tie the previous record of 25 degrees set back in 1925.

This data is preliminary, the evening climate will be issued near 5 PM this evening which will provide more official data.

CTP WATCHES/WARNINGS/ADVISORIES

None.