textproduct: Cleveland

WHAT HAS CHANGED

Severe thunderstorm potential continues this afternoon and evening, with additional chances over the weekend. Heat risk continues through Saturday. Heat headlines will need to be re- issued for Saturday.

KEY MESSAGES

1) Dangerous heat and humidity will continue today followed by temperatures not as hot this weekend.

2) Daily chances for showers and thunderstorms will return later today with better opportunities for rainfall this weekend into next week.

DISCUSSION

KEY MESSAGE 1... Heat and humidity last into the holiday weekend. We will need to issue a new Heat Advisory for the July 4th holiday though confidence in sites reaching the criteria is slightly lower compared to previous days. However, given the increased vulnerability with the prolonged nature of this heat wave and expected number of large outdoor gatherings, felt that a Heat Advisory will be justified despite maximum heat index values largely in the upper 90s. Drink plenty of water and avoid caffeine and alcohol. Be sure to take regular breaks in air- conditioned locations! For people without effective cooling, especially heat-sensitive groups, this level of heat can be deadly. High temperatures will return to more seasonable values in the mid to upper 80s Sunday onward.

KEY MESSAGE 2... The upper level ridge will begin to breakdown as more zonal flow takes over the weather pattern to begin the holiday weekend. Shower and thunderstorm chances will be on the increase this afternoon/evening. Hi-res guidance continues to hint at isolated to scattered thunderstorms developing later today. Weak forcing will likely lead to thunderstorms primarily initiating off of lingering outflow boundaries. A Slight Risk (Level 2 of 5) remains in effect across the entire forecast area today given the robust thermodynamic environment with MLCAPE values in excess of 2500 J/kg and DCAPE of 1000+ J/kg. Primary hazard will be damaging wind gusts in a few strong to severe clusters of thunderstorms.

Showers and thunderstorms will be possible again on Saturday, particularly in the afternoon and evening. There may be a bit more upper level support as a shortwave moves overhead that will trigger showers and storms in the afternoon. More robust forcing comes Sunday and Monday as an upper trough digs across the eastern Great Lakes which will likely increase coverage of showers and thunderstorms to end the weekend and begin next week.

Given the very moist airmass in place with PWATs of 1.5 to 2 inches any thunderstorm that does develop will be capable of producing locally heavy rainfall. There is a Marginal Risk (Level 1 of 4) for Excessive rainfall both Saturday and Sunday.

AVIATION /18Z Friday THROUGH Wednesday/

VFR conditions are seen across the region currently with scattered clouds around 4-5kft and will continue for the next several hours. There is low confidence in thunderstorms forming this afternoon and early evening and impacting terminals. If this does occur, it would be along a boundary from south of KERI southwest through KFDY. Though, with low confidence in impacts to terminals, opted to leave off of this TAF issuance. There is more confidence is late evening thunderstorms impacting KTOL, KFDY, and KCLE around 23-05Z. Confidence is lower the further south and east of KCLE, so continued the PROB30 wording for those TAF sites. Another round of thunderstorms are possible early Saturday morning, though confidence is still low in impacting TAF sites. VFR is expected for much of the end of the TAF period with more thunderstorms possible Saturday afternoon and evening.

Winds through the TAF period will generally be out of the west- southwest at 7-12 knots and occasionally gusting up to 15-20 knots. Within thunderstorms, can expect stronger gusts up to 40 knots.

Outlook...Non-VFR possible in occasional showers and thunderstorms Saturday afternoon and evening. Non-VFR possible Sunday evening into Monday morning with showers and thunderstorms as a cold front moves through the region.

MARINE

Winds will be out of the southwest this afternoon at 5-15 knots with waves generally 2 feet or less. Conditions should continue through Saturday evening. There will be thunderstorms chances through this weekend which could briefly increase winds and waves within and around storms. Weak low pressure and a cold front will pass over Lake Erie late Sunday night and shift winds to be out of the east to northeast at 5-15 knots by Monday morning. Waves could be choppy in the near shore with the onshore flow, but should stay below 2 feet. High pressure begins to build over the region late Monday and winds and waves will begin to subside into Tuesday.

CLIMATE

Dangerous heat and humidity is expected again today. Record warm high temperatures may be challenged. Here are those records for each of our climate stations:

Date Toledo Mansfield Cleveland Akron Youngstown Erie 07-03 100(1911) 93(2020) 98(1949) 97(1911) 98(1898) 93(1934) 07-04 100(2012) 96(2012) 98(1990) 99(1911) 99(1897) 99(1990)

CLE WATCHES/WARNINGS/ADVISORIES

OH...Extreme Heat Warning until 8 PM EDT this evening for OHZ003- 006>014-017>023-027>033-036>038-047-089. PA...Heat Advisory until 8 PM EDT this evening for PAZ001>003. MARINE...None.