Marine Weather and Tide Forecast for Withamsville, OH

NEAR TERM /THROUGH TONIGHT/
Deep surface low over the Great Lakes to tack into southern Canada today. An attendant cold front to push east into the Ohio Valley this evening evening prior to laying out east-west and stalling out near/just south of the Ohio River overnight.

Today's focus revolves around severe storm potential. ILN/s area is in the warm sector with an anticipated environment of temperatures around 80 with mid 60s dewpoints. This will yield moderate instability with SBCAPE values likely reaching 1500-2000 J/kg. While wind shear profiles aren't overly impressive, there still remains enough effective shear values of 30-35kts to support organized convection.

Thunderstorm cluster moving into southern Illinois to begin entering ILN/s area by midday. CAM solutions show intensification of this cluster as it interacts with the moderate instability that is expected to develop.

Wind flow is supportive of organized storms. Some initial discrete storms will likely develop into clusters. Strong to damaging winds will be the primary threat with the storms. With the potential for some supercells or even line embedded circulations - there will be an isolated tornado threat. Isolated large hail could also accompany supercell structures early this afternoon.

The favored timing for severe storms looks to start around noon with this initial cluster of storms that tracks east across the area.
There are indications that a second cluster tracks into the area during the late afternoon decreasing in intensity in the early to mid evening time frame. There is more uncertainty with this second cluster with - impacts expected to be further south - affecting southern portions of the FA thru early to mid evening.

Pressure gradient tightens and forecast soundings indicate favorable momentum transfer to support wind gusts of 30 to 35 mph outside of storms. Have increased sustained winds of 15 to 20 mph with gusts up to 35 mph. Also, have adjusted pops to account for current thinking for thunderstorm timing blending in the latest HRRR pops.

SHORT TERM /WEDNESDAY/
Cold front appears to stall near the Ohio River by Wednesday morning.
Most of the CAMs keep locations north of the river (especially up towards the I-70 corridor) dry on Wednesday being that they will be in a more stable air mass. However, locations near and south of the Ohio River will have increasing PoPs Wednesday afternoon given their proximity to the stalled boundary. Eventually, this boundary will begin to lift back northward as a warm front late in the day, further increasing shower/storm chances. Isolated strong storms are possible, but coverage should be pretty limited.

Surface winds will be much lighter on Wednesday. Expect highs to range in the middle 60s to middle 70s across the CWA

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
A robust short wave moving out of the Ozarks on Thursday will deamplify as it lifts up the Ohio Valley on Thursday night. At the surface, a warm front will lift across the region Wednesday night and there could be some showers and thunderstorms associated with that. Potential for showers and thunderstorms in the warm sector will increase with the combination of diurnal heating and the approach of upper support. Activity will wane somewhat as the short wave lifts away from the area later Thursday night. The short wave will take a surface low west and north of the region, but a trailing cold front will slide into the forecast area Thursday night.

The front will not make it all of the way through the area until Friday and possibly Friday night when a stronger push comes from a northern stream trough digging into the region. Showers and some thunderstorms will continue until this trough passes east of the area.

With the passage of this trough, the mid levels transition into a high amplitude, blocky pattern. A closed low will develop out of the base of the trough that moves through, but there is some potential that this low then retrogrades back into the region early next week.
With quite a wide range of solutions on where a closed low will occur, have stayed pretty close to the NBM for now keeping the region dry.

Temperatures will remain above normal through Friday and then drop below normal over the weekend. If the closed low stays east of the area, then temperatures will rebound early next week.

AVIATION /18Z TUESDAY THROUGH SUNDAY/
Thunderstorms have developed in the moderately unstable airmass ahead of an approaching cold front. Convective thunderstorm complex moving east impacting the TAF sites currently thru about 20-21Z across KCMH/KLCK. These storms causing a wind shift to the west with gusts of 40-50+kts. After the passage of this complex - expect a general lull in storm activity. Another complex over southern Illinois may affect the southern TAF sites late in the afternoon into early evening with cold front pushing south thru the area.

Have a PROB30 and tempo groups for additional showers and thunderstorms with the frontal passage early tonight. The cold front is expected to stall out near the Ohio River late tonight, which will likely result in MVFR CIGs at the southern TAF sites.

Southwest winds will gust up to 30 kts this afternoon and then shift to the northwest around 10 kts this evening with FROPA and then northeast to east at less than 10 kts overnight into Wednesday.

OUTLOOK...Additional thunderstorms are possible later Wednesday into Wednesday night. MVFR/IFR conditions likely Thursday into Thursday night along with a chance of thunderstorms. MVFR conditions possible Friday into early Saturday.

ILN WATCHES/WARNINGS/ADVISORIES
OH...None.
KY...None.
IN...None.