textproduct: State College

WHAT HAS CHANGED

* Extreme Heat Warning upgrade for Fulton, Franklin, Perry, and Cumberland Counties

KEY MESSAGES

1) Breakdown of early July heat wave promotes an increased risk of damaging thunderstorm wind gusts and potential flash flooding through Independence Day weekend

DISCUSSION

KEY MESSAGE 1: Breakdown of early July heat wave promotes an increased risk of damaging thunderstorm wind gusts and potential flash flooding through Independence Day weekend

Final day of heat headlines with max heat indices reaching 100-110 degrees to the east of the Allegheny Plateau. The breakdown or ending process of heat waves is often marked by bouts of severe weather - and that will likely hold true through the July 4th holiday weekend.

Clusters of storms are projected to develop through the weekend in a very moist, unstable, modestly sheared environment and will have the potential to produce localized to perhaps widespread damaging wind gusts - especially of they can grow upscale and sustain strong cold pools. A threat for heavy to excessive rainfall will also be in play given high pwats and efficient rainfall/hourly rates.

SPC and WPC outlooks were largely unchanged for this cycle.

AVIATION /15Z SATURDAY THROUGH WEDNESDAY/

For the 18Z TAF package, main change is to slow down the start time of showers and storms. This based on a similar pattern to what we had yesterday. Also lower dewpoints and more of a NW wind so far today. Yesterday storms fired up across the north during the early to mid afternoon hours, and stayed northeast of MDT and LNS.

Another set of storms moved eastward into central PA toward UNV by late evening.

The airmass so far today has dewpoints lower than the last few days. Maybe not a huge factor for humans, but storms are happy with the more humid airmass, thus a slight change in moisture can lead to large changes in the outcome.

The other change was to add more detail later tonight into Sunday, where some fog and lower CIGS possible, mainly in spots like BFD and IPT and in areas that get some rain.

Lower CIGS Sunday could occur and linger behind the front if widespread showers form early enough, before heating takes hold. Poor conditions could occur from time to time right into Tue, before some improvement by mid week.

Outlook...

Mon-Tue...Restrictions possible in A.M. fog and P.M. T-storms. Wed-Thu...Improving conditions expected.

CLIMATE

Williamsport tied their record max 7/3/26 (100F in 1966).

Record maxes for the next few days:

Station/Date...07/04...07/05 MDT.............104.....102 IPT.............100.....100 AOO............. 97......94 JST.............100.....101 BFD..............91......91

CTP WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM EDT this evening for PAZ019-025>028- 034-045-046-049>053-058. Extreme Heat Warning until 8 PM EDT this evening for PAZ035- 036-056-057-059-063>066.