textproduct: Cleveland

WHAT HAS CHANGED

The risk for severe thunderstorms have decreased for tonight, while increases for Sunday. There is a marginal risk for severe thunderstorms on Sunday across most of the area.

KEY MESSAGES

1) Showers and thunderstorms are expected at times through Sunday night. Heavy rain may cause localized flooding tonight through Sunday evening. Stronger storms Sunday afternoon may produce damaging winds though an isolated tornado cannot be ruled out.

2) Rain-free conditions with high pressure are likely Monday afternoon through Tuesday night before showers and thunderstorms return Wednesday.

DISCUSSION

KEY MESSAGE 1... A stationary front located well to our south in the lower Ohio Valley will lift north across the area tonight in response to low pressure moving eastward across the Great Lakes region. Several periods of showers and thunderstorms are expected areawide through at least Sunday evening, when the cold front sweeps southeastward across the area.

A complex of thunderstorms currently located in central Illinois will gradually shift eastward through the day, with most model guidance initially presenting this as light isolated to scattered rain showers spreading eastward through the day Saturday, well ahead of the warm front aloft. At some point late this evening into tonight, should be convective redevelopment as the 850mb theta-e gradient shifts eastward, and the LLJ strengthens behind it. Convection is likely to focus along our southwest counties tonight. Any convection that develops tonight would pose a flash flooding risk due to PWAT values in the 2-2.5" (near a climatological max), which would support efficient, heavy rainfall. There is significant uncertainty with placement and coverage of convection tonight, aided by run- to- run variability. Compared to the 12Z guidance, most of the latest 00Z models have backed off on LLJ strength, and QPF amounts by quite a bit tonight. This trend (and general model guidance volatility) precludes the issuance of a flood watch for the time being, though we will continue to monitor latest forecast trends to see if one may be needed. If one were needed, it is mostly needed for our southwest counties (e.g. Hancock to Knox Counties), where the flooding risk is greatest.

While heavy rain and flooding risk are the primary weather hazards, strong wind gusts and a weak tornado cannot be ruled out this evening into tonight, particularly for our southwest counties (E.g. Hancock to Knox Counties).

Additional convection is expected throughout the day Sunday before the cold front sweeps through Sunday evening, though the evolution is even more uncertain. In general though, expect several rounds of showers and thunderstorms affecting the entire forecast area. High PWAT exceeding 2" will provide a favorable environment for heavy rain, leading to localized flooding. MUCAPE > 1500 J/kg and deep layer shear around 30 knots would support severe weather (primary hazards are damaging winds and perhaps a weak tornado), though this is a secondary hazard to the heavy rain and flooding threat.

Isolated to scattered rain showers may linger Sunday night into Monday morning across Northeast Ohio and Northwest Pennsylvania.

KEY MESSAGE 2... High pressure will bring rain-free conditions to the region Monday afternoon through Tuesday night. A weak low pressure system will move across the Great Lakes region, bringing scattered showers and thunderstorm to the region on Wednesday.

AVIATION /12Z Saturday THROUGH Wednesday/

Any remaining patchy fog will dissipate within the first hour or two of the TAF period and VFR is expected through this afternoon and possibly into this evening. Isolated light showers can't be ruled out across the area between roughly 12Z and 18Z today, but confidence in placement/coverage is too low to include in the TAFs at this point. Even if it does rain, significant impacts to flight conditions are not anticipated. Confidence in the evening and overnight convection is still pretty low at this point so have broad showers with PROB30 groups for thunderstorms. Rain will likely linger through early Sunday morning, especially at southern terminals. Will need to make amendments and updates as confidence increases throughout the day. Either way, any evening and overnight showers/storms could produce non-VFR conditions in moderate to heavy rain and lower ceilings. Winds will be light and variable today with winds becoming more southwesterly and increasing to 5 to 10 knots after 06Z Sunday.

Outlook...Non-VFR possible with periodic showers and thunderstorms through Sunday night. Additional non-VFR possible in showers and thunderstorms Wednesday.

MARINE

East/southeast winds 10 knots or less are expected through early this afternoon before east winds increase to 10 to 15 knots this evening through tonight. Winds will shift to the southwest on Sunday with flow becoming northwesterly Sunday night through Monday. May need to consider Small Craft Advisories/Beach Hazards Statements if onshore winds trend higher, but as of now winds/waves should remain below criteria. Winds will be out of the southwest on Tuesday and Wednesday with offshore winds possibly reaching 15 to 20 knots in the western basin as a cold front approaches Lake Erie.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Dense Fog Advisory until 9 AM EDT this morning for OHZ036>038- 047. PA...None. MARINE...None.