textproduct: State College

WHAT HAS CHANGED

* Targeted Moderate Risk Excessive Rainfall Outlook (level 3/4) for east-central Pennsylvania through tonight * Flood Watch issued this afternoon through Monday for east- central Pennsylvania

KEY MESSAGES

1) Breakdown of heat wave pattern gives rise to severe storms and torrential downpours today and tonight; flood risk lingering in the east on Monday.

DISCUSSION

KEY MESSAGE 1: Breakdown of heat wave pattern gives rise to severe storms and torrential downpours today and tonight; flood risk lingering in the east on Monday.

40 severe thunderstorm warnings issued in the past 2 days. The days following a transition from an extreme heat pattern are often marked by severe/active weather, and that trend continues through at least Monday. As the heat dome shifts to the west and troughing develops over the Great Lakes/Ohio Valley/Northeast, the upcoming week will feature relatively cooler (more seasonal) temperatures with a bullish signal for almost daily rain chances particularly early and late in the week.

Another active wx day ahead with dual severe T-storm and flash flood risks. We anticipate another diurnal uptick in convective development within a very warm, moist and increasingly unstable environment indicative of steep low-mid level lapse rates. Pockets of stronger deep layer shear 30+ kt may exist in the upper OH Valley and eastern PA, but the general expectation is for pulse to multicell storms to once again merge/form into line segments with some cold pool organization to promote damaging wind potential from mid afternoon into the evening. Terrain boundaries will also play an important role in initiating/organizing convection given lack of other strong forcing. SPC placed the highest damaging wind probs near/southeast of I81/78 where max temps should reach 90F.

Focus will evolve from severe to flash flood/hydro ops by later this evening and continue into Monday as a robust +RA signal continues to manifest over east-central PA. Atmos conditions will be quite favorable for heavy rainfall and flash flooding potential with 2+ inch pwats correlating to intense rain rates >2 in/hr. Still some question on degree of repeating/back- building storms along q-stnry/wavy frontal zone. Latest HREF/REFS mean QPF guidance is signaling 1-3" in the 24hr period ending 00Z Tue with PMM/LPMM max values exceeding 5 inches. WPC coordinated a targeted and relatively small moderate excessive rainfall outlook (level 3/4) within a broader level 2/4 or SLGT risk area. We issued a relatively large/broad flood watch along with WFO PHI as there remains some spatial uncertainty to exactly where the greatest rainfall will occur. The setup (multiple rounds of slow moving/torrential downpours) favors locally significant flash flooding particularly in terrain areas and highly urbanized corridors. One limiting factor is obviously the drought conditions and corresponding elevated FFG values that may offset the overall risk to some extent.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Showers and thunderstorms will develop during the afternoon and are once again likely to impact all TAF sites through the evening. PROB30s have been included to highlight this potential, though the timing will need to be adjusted as confidence increases. Storms will be capable of producing strong wind gusts, intense rainfall rates, and frequent lightning. Any storms that move directly over an airfield will likely lead to brief periods of IFR conditions.

Much of the heavier showers and thunderstorms come to an end from west to east between 00z and 06 Mon, though lighter showers may linger past 06Z. Fog and low clouds appear likely behind these showers and widespread IFR conditions will be likely into Monday morning as easterly upslope flow provides ample moisture.

Outlook...

Mon-Tue...Restrictions possible in A.M. fog and P.M. T-storms. Wed-Fri...Restrictions possible in showers/storms, most widespread on Friday.

CLIMATE

Rare Heat at Harrisburg: 3 consecutive days with maxT >= 100F from July 2-4, 2026. The last time this streak occurred was July 1999 (2x) and is only the 6th time on record going back to 1888.

CTP WATCHES/WARNINGS/ADVISORIES

Flood Watch through Monday evening for PAZ019-026>028-036-045- 046-049>053-056>059-063>066.