textproduct: State College

WHAT HAS CHANGED

*Lowered dewpoints and minimum RH this afternoon. *WPC added a level 1/4 excessive rain risk for Monday 7/27.

KEY MESSAGES

1) Pleasant/dry pattern continues into the last weekend of July. 2) Turning more humid with showers and storms next week. Perhaps a few strong storms with heavy rain at times.

DISCUSSION

KEY MESSAGE 1: Pleasant/dry pattern continues into the last weekend of July.

After a stormy period since last weekend, a really nice afternoon outside with clear skies and low humidity levels. PW values about as low as they get this time of year.

High pressure over the region will provide the area with another night with clear skies and cool temperatures.

Friday will feature another day of sunshine and low humidity.

While there could be a shower or storm over the region this weekend, the airmass remains rather dry. Main support for any activity would be across western sections on Sunday.

KEY MESSAGE 2: Turning more humid with showers and storms next week. Perhaps a few strong storms with heavy rain at times.

Weak systems dropping southeast next week will bring chances for showers and storms at times. Systems are rather weak and will be moving along, so timing would be a factor.

The other factor is that the higher dewpoint air is expected to be rather limited, mainly later on Tuesday.

Main timing for anything widespread would be late Monday night into early Wednesday.

More detail below.

The pattern looks increasingly unsettled Sunday into the middle of next week as upper troughing is carved out over the Great Lakes/Ohio Valley into the Mid-Atlantic and Northeast states.

Ample northern stream system energies set to dig into the upper trough position will support potential for strong storms and heavy rainfall. WPC introduced a broad level 1/4 marginal excessive rain risk for D5/Monday July 27 that covers most of CPA.

Severe storm potential could shift east/southeast on Tuesday. Confidence in where greater risk corridors may develop is low, and will largely be influenced by convective evolution in the Days 4-5/Sunday-Monday periods.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

VFR conditions are generally expected throughout the 06Z TAF package with high (> 90%) confidence at all airfields outside of BFD where some lower visibility restrictions will be possible in the 08-12Z Friday timeframe. Current ECONUS Nighttime Microphysics outlines the typical dendritic valley fog due to clear skies and calm winds despite the relatively dry air mass for this time of the year. Dewpoint depression at BFD remain stout at 2F; however, seeing increasing coverage of fog around the entire TAF site. At this time, the bulk of lower visibility restrictions will likely stay *just* outside of the terminal with some vicinity fog likely beginning to make way over the next hour or two. Recent GLAMP model guidance does outline IFR visibilities but could see MVFR being a slightly more likely outcome at this time given that visibilities appear to be verifying closer to the minimum HREF members as of 2AM. If this verifies, visibilities near-or-below 2SM will be possible between 09-11Z before rapid improvement towards VFR occurs by 13Z Friday.

After 13Z Friday, VFR conditions are virtually certain across all of central Pennsylvania's terminals. High clouds and light winds are expected throughout the day with some lower-level clouds progged by model guidance along the ridgetops, thus have outlined some scattered lower-level clouds at JST/AOO where this is most likely to be observed. Skies clear out with light winds trending towards calm towards the end of the 06Z TAF package, which will bring some potential for valley fog tomorrow night; however, signals appear to be more confined to NE PA.

Outlook...

Sat...Generally VFR conditions with low-end (< 20%) chance of an afternoon shower/storm across western sections of central PA.

Sun...Increasing chances of PM showers/storms, with some restrictions possible.

Mon-Tue...Restrictions possible in showers/storms.

CLIMATE

Multiple record low temperatures were set for July 23rd across central Pennsylvania:

* Altoona set a record low temperature of 47 degrees was set, breaking the previous record of 50 degrees set back in 1981.

* Bradford tied a record low temperature of 38 degrees which was previously set in 1981.

* Johnstown tied a record low temperature of 49 degrees which was previously set in 1983.

CTP WATCHES/WARNINGS/ADVISORIES

None.