textproduct: State College

WHAT HAS CHANGED

Minor changes to the rainfall forecast for the rest of today.

KEY MESSAGES

1) Drying out for Wednesday, but rain chances return to end the week.

2) Increasing heat risk to end June and start July.

DISCUSSION

KEY MESSAGE 1: Drying out for Wednesday, but rain chances return to end the week.

Steady rain over southeast PA will gradually come to an end through the afternoon and evening as a wave of low pressure riding along a slow-moving cold front moves away from the region. High pressure building in behind this system will provide dry weather on Wednesday with mainly clear skies along with temperatures in the 70s and low 80s.

The next chance for rain will come Thursday evening into Friday as a couple of upper level disturbances move overhead. The best forcing with these systems look to pass to our north, so the highest chances for any showers or thunderstorms looks to be across the northern half of Pennsylvania. Most guidance shows another shortwave tracking farther to the south Friday night into Saturday which will bring another round of showers and thunderstorms to parts of central PA. Locations along and south of I-80 appear favored to see the most rain from this system.

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KEY MESSAGE 2: Increasing heat risk to end June and start July.

A major pattern change over the Pacific Northwest and Intermountain West this weekend will likely result in a downstream upper ridge developing over the eastern U.S. by early next week. Blended ensemble guidance driving the prototype probabilistic heatrisk is confirming the signal for a heatwave to end June and start July. CPC has placed a 20-40% slight risk of extreme heat over CPA from 6/30-7/6 with higher chances in the 40-60% range in southeast PA. There is still quite a bit of spread in ensembles regarding the placement of the upper level ridge, but there is increasing potential for high temperatures to exceed 90 degrees over a large portion of the area towards the end of the forecast period. With humidity also expected to be on the rise, we may see heat index values approach 100 degrees. Depending on the exact positioning of the ridge, there may also be some potential for showers and thunderstorms to develop each afternoon in northwest flow aloft.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

The low cloud deck causing restrictions this morning is pivoting off to the east with only MDT and LNS still firmly experiencing MVFR restrictions and light showers as of the 18Z update. They both should be seeing improving conditions likely within the next 1-3 hours as the precipitation moves out of our area. Conditions look to be mainly VFR with scattered cumulus as the main clouds behind this cloud shield.

Calm winds and clear skies may lead to areas of fog and low stratus forming across western PA between 07z-12z Wed, with probability of IFR conditions still around 30 pct at BFD and 10-20 pct chc at the other airfields. Have put TEMPO groups into JST and BFD for visibility restrictions to highlight most confident timing of fog development.

Outlook...

Wed...Mainly VFR, dry conditions expected.

Thu...Restrictions possible in another round of showers and storms late.

Fri-Sat...Restrictions possible in additional showers and storms.

Sun..Mainly VFR, dry conditions prevail.

CTP WATCHES/WARNINGS/ADVISORIES

None.