textproduct: State College

WHAT HAS CHANGED

Minor changes to the timing of precip Thursday-Saturday.

KEY MESSAGES

1) After a dry and pleasant day today, rain chances return Thursday with periods of rain through Saturday.

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

DISCUSSION

KEY MESSAGE 1: After a dry and pleasant day today, rain chances return Thursday with periods of rain through Saturday.

High pressure sliding from the Ohio Valley into the Mid Atlantic today will support mainly clear skies along with low humidity. Temperatures will generally be near to slightly below climo, with highs in the 70s and low 80s. Winds will be light from the NW with gusts to 15 mph.

The next chance for rain will come tomorrow (Thursday), with chc PoPs arriving in our NW zones by early afternoon, and pushing south and eastward through the later afternoon and evening as an upper trough moves across the southern Great Lakes. With the best forcing passing to our north, the highest chances for heavier showers or thunderstorms looks to be across the northern half of Pennsylvania. SPC introduced a MRGL severe weather outlook for a tstm wind threat across all of central PA with the exception of the Lower Susq Valley on Thursday. Rain chances continue into Thursday night and Friday morning, with precip gradually moving south and east and ending across the NW.

Another system originating as an area of convection in the foothills of the Rockies later today (Wednesday) will make its way into our region with perhaps a more widespread shield of stratiform rain with embedded/trailing convection Friday night into Saturday, similar to what we saw on Monday. However there is still a wide range in timing and location of these convective features moving across the country, so confidence is low to medium.

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

A deep trough settling into the Pacific Northwest and Intermountain West this weekend will likely result in a downstream upper ridge developing over the eastern US by early next week. Blended ensemble guidance driving the prototype probabilistic Heatrisk is showing a signal for a significant warmup for Central PA to end June and start July. CPC has placed a 20-40% risk of extreme heat over CPA from 6/30-7/4. There is still quite a bit of spread in ensembles regarding the placement of the upper level ridge, but there is the potential for high temperatures to exceed 90 degrees over a large portion of the area towards the end of the forecast period (Tue-Wed). With humidity also expected to be on the rise, we may see heat index values approach 100 degrees by mid to late week, especially in the lower Susq Valley. Depending on the exact positioning of the ridge, there may also be some potential for clusters of showers and thunderstorms moving in from the northwest, but in the absence of organized convection arriving from upstream, this may predominantly be a rain-free pattern for a few to several days starting Sunday. Highest chance for convection is mid to late week.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

VFR prevails for the next 24 hours with calm and dry conditions. Northwesterly flow prevails today but will be superseded tonight to southwesterly flow ahead of an approaching frontal passage Thursday.

Some showers and storms are possible towards the end of this 18Z TAF update as a disturbance moves in from the Great Lakes that will impinge upon NW PA in the late morning/early afternoon. However, confidence in including -SHRA/-TSRA mentions before 18Z at BFD isn't high enough to warrant mention in the TAF package at this time (<30%) due to some variability in model timing.

Outlook...

Thu...Restrictions possible in another round of showers and storms in the second half of the day.

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

Sun...Mainly VFR, dry conditions prevail.

Mon...Mainly VFR, dry conditions prevail.

CTP WATCHES/WARNINGS/ADVISORIES

None.