textproduct: State College

WHAT HAS CHANGED

Little changes for this update.

KEY MESSAGES

1) Rain returns to the forecast today with with afternoon and evening showers and scattered thunderstorms, concentrated across the NW half of PA. Steady, light to moderate rain Friday night into Saturday. Lingering risk for a pop up shower in the Laurels Sunday.

2) Increasing heat risk builds through the middle and latter part of next week.

DISCUSSION

KEY MESSAGE 1:Rain returns to the forecast today with with afternoon and evening showers and scattered thunderstorms, concentrated across the NW half of PA. Steady, light to moderate rain Friday night into Saturday. Lingering risk for a pop up shower in the Laurels Sunday.

Showers and scattered thunderstorms return to the forecast today with a few light showers ongoing moving across the Northern Tier counties of our CWA late this morning.

Rain chances will increase to the south and east across the rest of central PA during the afternoon and evening hours as an upper trough and a few Deg C of cooling in the 700-500 mb layer moves across the region.

Most places in Central PA south and east of I-80/I-99 will be dry through at least 2-3 PM, and the lower Susq valley will likely be dry through sunset (low levels are quite dry there with min sfc RH in the low 30s pct). 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 expanded their MRGL severe weather outlook primarily for a tstm wind threat (5 pct) across all of central PA today, with the exception of the majority of Adams, York and Lancaster counties.

They maintained the same areawide coverage of the 2 pct tornado risk with slight SEWRD expansion of the 5 pct hail and wind risk.

Rain chances continue into tonight and very early Friday morning, ahead of a slow moving cfront. Precip will gradually move south and east across the CWA, while ending across the NW.

Patchy fog is possible in the valleys of the north late tonight into early Fri AM if there is some clearing after the rain moves out.

Another system 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 great deal of model-to-model and run-to-run spread in timing and location of these convective features moving across the country, so confidence is low to medium.

---------------------------------------------------------------

KEY MESSAGE 2: Increasing heat risk builds through the middle and latter part of next week.

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. There is still 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-Thu). 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 later in the week.

AVIATION /15Z THURSDAY THROUGH MONDAY/

Southerly flow will bring in some higher dewpoint air today, but the airmass not very humid to start. Thus looking at mainly VFR conditions today, with the highest chance of a shower or thunderstorm occurring across the northwest mountains (BFD).

Showers and storms less likely across the far southeast sites (MDT, LNS) prior to 06Z Friday.

The area overall is more likely to see more in the way of widespread showers (or a steady light to moderate rain) late Friday night into Saturday morning, as a weak low tracks eastward across far southern PA or just south of PA.

Outlook...

Friday night-Sat...Restrictions possible in additional showers and storms.

Sun...Mainly VFR with restrictions unlikely in any afternoon -SHRA.

Mon...Mainly VFR, dry conditions prevail.

CTP WATCHES/WARNINGS/ADVISORIES

None.