textproduct: Cleveland

WHAT HAS CHANGED

Several rounds of showers and thunderstorms are expected to move across the region through Wednesday. Confidence is increasing in most of these rounds at least impacting the southwest half of the forecast area (Roughly along and southwest of a Bowling Green to Canton line) with the potential for severe thunderstorms and repeated rounds of heavy rain, which may lead to flash flooding. There is still some uncertainty on how much severe weather and flooding potential there will be in the northeast half of the area, as this will be dictated by the front location with each batch of storms that moves through the region.

KEY MESSAGES

1) Several rounds of showers and thunderstorms are expected to move across the region through Wednesday. Each round will have the potential to bring heavy rainfall, which could lead to localized flooding, and scattered severe thunderstorms with damaging wind gusts as the primary threat.

2) Dry weather is expected on Thursday and Friday, giving a break in the active pattern. Temperatures and humidity will taper off with high pressure entering the region.

3) Unsettled weather may return for the weekend with more scattered shower and storm chances across the Great Lakes region on Saturday and Sunday.

DISCUSSION

KEY MESSAGE 1... With one round of showers and storms exiting stage right into PA, all attention turns back to the west as a new complex has developed across northern Illinois into southwestern Lower Michigan. This area of shower and storm activity is being fueled by the warm air advection entering the region with the front lifting back north after the first round of activity. In addition, a potent low level jet with 30 to 35 kt of 925 mb flow will provide extra support for storm activity. The main question with this complex is: Where is it going? The activity south of Chicago is trying to follow the instability gradient and should allow for this activity to dive more southeast into Indiana and potentially southwest Ohio. This cluster should remain out of the forecast area. The more concerning portion of the complex are the storms over southwestern Lower Michigan. Storms are presently moving in a northeasterly direction. Meanwhile, storms closer to Grand Rapids are more tied to a boundary that arcs southeast into northern Ohio. Over the next couple of hours, expect these storms to congeal over southern Michigan. If they can organize a touch and form a cold pool, these storms do have the potential to move southeast and push toward the forecast area later this morning. If these storms just remain forced by the low level jet and end up staying tied to the surface boundary, then it is possible that this batch could miss much of the area to the north or at least move over/along Lake Erie. There is some elevated instability to work with ahead of this complex and precipitable water values around 1.75" depict that rain could have some efficiency. Storms should also quickly perk up with daytime heating as these will move through the region as the sun rises and activity could become concerning quickly after daybreak once the low level inversion mixes out.

This morning round of showers and thunderstorms will then dictate how the rest of the day will evolve. If the activity goes through most of the forecast area, then the front will be south of the area and new activity would not be favored during the daytime hours. If the morning activity stays north or just stays near Lake Erie, then most of the forecast area will remain south of the front in a conditionally unstable airmass with warm advection across the area. This would then allow for scattered shower and storm activity to develop over the area during the afternoon and evening hours. Storms would then have the potential for strong to damaging wind gusts and heavy rain that could bring localized flooding. These storms could persist into tonight.

For tonight, all attention returns back to Wisconsin and Illinois for the development of a new complex of showers and thunderstorms that will move southeast along the front. Again, the location of the front will be very important on where this complex will go - Either into our area or to the southwest. If there is already activity in our area this afternoon and evening, then this complex will stay southwest but there will already be activity overhead to contend with. If the area is dry, then there is a greater chance of this complex reaching the forecast area. The average solution suggests that at least the southwest half of the forecast area (Roughly along and southwest of a line from Bowling Green to Canton) should get some activity tonight.

For Tuesday, another southeastward diving MCS is expected to develop west of the forecast area during the morning hours. This complex should reach the area during the afternoon hours, favoring the southwest portion of the forecast area, roughly along and southwest of a Findlay to Millersburg line. Given that this complex will move through peak heating hours with maximum instability, there should be a severe wind threat that will materialize with this complex. Meanwhile, forecast soundings ahead of this complex show precipitable water values creeping back up to 1.80" showing that this complex will bring more heavy rain to the area. With this potentially being the third or fourth round of rain in 48 hours, the risk for flash flooding will increase.

For Tuesday night into Wednesday, the frontal boundary that has sustained these multiple rounds of storms should be south of the forecast area, allowing for any new development to favor areas to the southwest. There is some potential for the boundary to be close to our southwest counties and some scattered rain activity will be possible through Wednesday but the main severe and heavy rain threats should be out of the area. If the front does have trouble clearing the area with all of the uncertainty with the previous rounds of storms, then there could be more severe weather potential or heavy rain/flash flooding potential on Wednesday, which explains why some portions of northern Ohio remain in Day 3 SPC Severe and WPC Excessive Rainfall Marginal Risks.

KEY MESSAGE 2... High pressure is expected to build into the region on Thursday from the northwest. This will bring dry weather and less humidity into the region, giving some relief from the more muggy weather from earlier in the week. This system will maintain over the Great Lakes through Friday, allowing for temperatures to drop back into the 70s.

KEY MESSAGE 3... A subtle shortwave will move through the Great Lakes region this weekend and allow for the upper level pattern to return to northwest flow. Like earlier in the week, this northwest flow pattern will bring a few weak disturbances through the area on Saturday and Sunday, each with some scattered shower and storm chances. It is too early to tell if there will be any severe weather or flooding hazards at this time. If temperatures remain muted in the upper 70s, then convective activity may be reduced.

AVIATION /06Z Monday THROUGH Friday/

The first of many complexes of showers and thunderstorms that will impact the area in the coming days is now east of the area, so expect mainly dry and VFR conditions at all terminals through 10Z this morning other than a few lingering spotty showers. The next complex currently organizing over Lake Michigan should maintain strength and track across the region later this morning. Timing is a rough estimate and could end up being an hour faster if a cold pool develops and accelerates the system, but estimate it to reach KTOL and KFDY around 10Z, KMFD and KCLE around 12Z, KCAK and KYNG around 13Z, and KERI around 15Z. Brought all sites down to MVFR as a starting point in showers and thunderstorms, but IFR is possible in the briefly heavier rain and gusty winds. A lull is expected behind this complex for late morning through the afternoon with VFR conditions, but then additional showers and thunderstorms will start to develop this evening into tonight. Confidence on the location of the activity this evening and tonight is very low, but tried to show the western half of our area around KTOL, KFDY, and KMFD having better chances for thunder than sites farther east.

Light S to SW winds early this morning will increase by mid to late morning and become gusty through the afternoon. Expect SW winds of 10-15 knots by this afternoon, gusting to 20-25 knots at times. SW winds will decrease this evening.

Outlook...Periods of non-VFR conditions are expected through Thursday as several rounds of showers and thunderstorms move across the airspace. Some storms could be strong to severe during this timeframe.

MARINE

SW winds will increase to 15-20 knots later this morning through the afternoon behind a warm front. This will build wave heights to over 4 feet in the open waters of the central and eastern basins. At this point, expect the biggest waves and strongest winds to be in the open waters, so did not issue a Small Craft Advisory, but it will be very close. Boaters should nonetheless expect choppy conditions.

Winds will become light and variable tonight, and expect that to largely be the case through Wednesday as a frontal boundary oscillates just south of the lake. Stronger winds averaging a N direction will then begin late Wednesday and continue through Friday as the front finally pushes south and Canadian high pressure attempts to build across the Great Lakes.

Otherwise, multiple rounds of thunderstorms will impact the lake today through Wednesday. Any organized storms that cross the lake could produce locally strong winds over 50 knots and high waves.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.