textproduct: Cleveland

WHAT HAS CHANGED

A complex of severe thunderstorms has developed across northwest Ohio and continues to push east. The primary hazard with these storms is strong to damaging wind gusts to observed reports of nearly 60 mph already recorded at Toledo Express Airport. As this line pushes east, it should gradually begin to weaken. In addition, there are some isolated storms ahead of the main line, although these have primarily remained sub-severe at this point. There is widespread, consistent lightning associated with all storms so please seek shelter and stay weather aware.

The heat headlines will be re-issued for Saturday this evening with a Heat Advisory for all Ohio counties. There will be no extension to Northwest Pennsylvania counties and those will be allowed to expire tonight.

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 /00Z Saturday THROUGH Wednesday/

The primary aviation concerns this evening and again on Saturday evening will be the expected convection. Currently, a line of convection extending from near Sandusky, OH southwest towards Findlay, OH is producing diminish visibilities to 1-2SM and strong winds with gusts up to 40 knots. KTOL has already been impacted with storms on the doorstep of KFDY. This line is expected to continue to move east but should gradually weaken as the area begins to stabilize. Opted to handle all convection in TEMPOs for each terminal with the general timing between now and 05Z. Behind this line of convection, some patchy fog is possible given the weak overnight flow but given low confidence opted to not include a mention in the TAF at this point.

For much of Saturday, widespread VFR conditions are anticipated with FEW/SCT high cloud decks building in during the afternoon hours. Near the end of this TAF period, another line of convection is expected to move across the area, likely reducing conditions to non-VFR again. Confidence in the timing and placement of this second round is low given model divergence, so opted to handle that with VCTS at this point.

Winds outside of the convection overnight will be light and variable. These will gradually increase from the west-southwest on Saturday afternoon to 8-12 knots with occasional gusts up to 15-20 knots. Winds may gain a bit more of a northern component for KCLE and KERI Saturday afternoon which would be associated with a weak lake breeze.

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...Heat Advisory until 8 PM EDT Saturday for OHZ003-006>014- 017>023-027>033-036>038-047-089. PA...None. MARINE...None.