textproduct: State College

WHAT HAS CHANGED

* Slight decrease in temperatures throughout much of the week with an increase in cloud cover and precipitation chances.

KEY MESSAGES

1) Increasing heat and humidity this week will bring increased risk for heat-related illnesses, especially Thursday and Friday.

2) Shower and thunderstorm chances begin later today (Tuesday) and continue through the end of the work week.

DISCUSSION

KEY MESSAGE 1: Increasing heat and humidity this week will bring increased risk for heat-related illnesses, especially Thursday and Friday.

Increasing heat and humidity is almost certain throughout the rest of the week; however, the exact magnitude of heat will be the main uncertainty with respect to the forecast over the next couple of days. Main driver for the uncertainty will be cloud cover and occasional showers/storms throughout the week, with scattered coverage expected Wednesday and Thursday and more widespread coverage on Friday (see Key Message 2) likely allowing for a slight downtrend in temperatures. Forecast package this morning kept fairly close to previous forecast outside of potentially knocking down temperatures another degree or two as model guidance has trended slightly more aggressive on cloud cover. Dew points have stayed mainly stationary with this forecast package; however, not completely unreasonable to see a slight uptick in future forecast packages. If anything, looks like slightly lower HeatRisk on Thursday with slightly higher on Friday. The main driver for slightly increased risk on Friday mainly hones in on slightly warmer low temperatures Thursday night into Friday morning and are not representative of a substantial increase in temperatures or dew points. Current posture for mentions in HWO with no products appears to continue to be the way for this forecast cycle; however, probabilities in reaching Heat Advisory criteria have largely fallen over multiple cycles with the only location potentially hitting criteria across the Lower Susquehanna Valley Thursday and Friday.

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KEY MESSAGE 2: Shower and thunderstorm chances begin later today (Tuesday) and continue through the end of the work week.

Rain chances begin to increase across western Pennsylvania later today, with an extended stretch (four-to-five days) of rainfall across some portion of central Pennsylvania. Coverage of showers and thunderstorms remains the main question with respect to the forecast, as it usually is in this set-up, with scattered coverage in showers and thunderstorms expected Wednesday and Thursday. Increased moisture and better forcing (in the form of a strong upper-level low) is expected to be collocated across the region on Friday, thus higher confidence in more widespread precipitation chances Friday, especially during the afternoon and evening hours at this time. SPC has upgraded all of central Pennsylvania into Marginal Risks for severe thunderstorms on Wednesday and Thursday, likely given to the very unstable air across the region. Forcing is not the greatest and shear remains an uncertainty; however, some potential for damaging winds will be possible in strong-to- severe thunderstorms for the middle of the week. We'll also need to keep an eye on severe potential as we get closer to the latter half of the week with ample instability in place with shear being the biggest question mark at this time. In the "for what it's worth" category, machine-learning probabilities for severe weather do outline Friday for some severe potential across central Pennsylvania, likely given the enhanced forcing and instability in place across the region.

AVIATION /08Z TUESDAY THROUGH SATURDAY/

Anticyclonic flow around a departing high pressure system will bring drier air across the eastern half of the Commonwealth this morning. A moisture gradient will set up along the Alleghenies, with PWATs around 1.50" just westward where high pressure influence has been weaker.

The warm/moist air will continue creeping eastward as the high pressure loses influence over our area, with even a few showers (coverage <30%) possible across our western terminals (primarily KBFD/KJST/KAOO/KUNV) between after 18Z today. Flight restrictions are not expected with these showers, though briefly steady rain may occur given the moisture in place. Lightning may also be possible, though the tall/skinny low-CAPE (<500 J/kg) profile will favor rainfall efficiency over lightning production.

Ceilings will lower from west to east tonight, with IFR conditions favored at BFD/JST and MVFR at the rest of the airfields before dawn on Wednesday.

Outlook...

Wed-Thu...Restrictions possible in scattered -SHRA/-TSRA. Fri...Restrictions expected in a line of -TSRA. Sat...Mainly VFR.

CTP WATCHES/WARNINGS/ADVISORIES

None.