textproduct: Cleveland

WHAT HAS CHANGED

Minor adjustment to rain/storm timing and amounts through early Thursday. Increasing confidence in gusty non-thunderstorm winds late Wednesday night into Thursday across much of the area.

KEY MESSAGES

1) Scattered showers and storms move through from west to east this evening and tonight. Storms will be on a weakening trend, but may still pack isolated stronger wind gusts along I-75 where a Marginal Risk for severe weather is in place this evening.

2) Another round of showers and storms moves through from west to east late Wednesday and Wednesday night. Uncertainty remains regarding the magnitude and placement of the severe risk with this activity, but all severe hazards and localized flash flooding are possible. Storms have the greatest probability of being severe across the western half of the area, where a Slight Risk for severe weather is in place.

3) Synoptic (non-thunderstorm) winds will be gusty out of the south Wednesday night and out of the west on Thursday. Gusts have potential to reach 40 to 50 MPH at times and a Wind Advisory may be needed for portions of the area.

4) Cooler than average with mainly isolated or minor rain chances are expected to end the week and start the weekend. A system may move through Sunday or Monday.

DISCUSSION

KEY MESSAGE #1: Water vapor, satellite, and radar imagery all depict a seasonally impressive shortwave trough and associated surface low and cold front pushing into the southwestern Great Lakes this afternoon. This package will move east and affect the local area late today into tonight.

The main focus will be shower and thunder potential along and ahead of the cold front. This activity is taking shape from Northwest Ohio into Michigan/Indiana this afternoon and will sweep east tonight. Both the front itself and a pre-frontal trough may act as triggers for showers/thunder. Overall, expect a batch or two of showers/thunder to move east across the area with activity slowly weakening as we lose daytime heating and with a drier/more stable airmass to the east. Some showers likely will make it east across the area given the forcing with the shortwave trough. The SPC maintains a Marginal Risk (level 1 of 5) for severe weather in the form of isolated damaging winds across the I-75 corridor for late this afternoon and evening. The environment will feature marginal deep-layer shear, deep low-level inverted-v profiles, but modest/skinny/shallow instability profiles. This overall environment can support isolated damaging downburst winds, but as convection weakens through the evening and as the low-levels stabilize with sunset this modest risk should diminish fairly quickly.

It will be another cooler/pleasant night, especially late tonight behind the showers, with lows mainly falling into the 50s with closer to 60 along the lake. The first half or so of the day Wednesday will be dry and pleasant with a fair amount of sun. Highs will mainly top out in the 70s to perhaps near 80.

KEY MESSAGE #2: A potent shortwave will dive into the Upper Midwest tonight, quickly amplifying and taking on a negative tilt while swinging into the Great Lakes Wednesday night. This evolution will force a strong surface low through the Great Lakes Wednesday night into early Thursday. The low will lift a warm front back across the area late Wednesday, followed quickly by a cold front late Wednesday night/early Thursday. Thunderstorms with a risk for severe weather and heavy rain will be a concern, mainly along and just ahead of the cold front Wednesday evening and night, though the forecast is tricky with sources for uncertainty.

Guidance is hinting at two potential rounds of convection...a first, lower-confidence round late Wednesday afternoon/early evening as the warm front lifts across the area, and then a second and more widespread round from the west later Wednesday evening/night along and ahead of the cold front.

In terms of any activity with the warm front late Wednesday afternoon or evening, several models attempt to show some rain and possibly a few storms moving east-northeast across the area after about 3 PM and the forecast has a corresponding increase in POPs. However, a limiting factor for severe weather with this first round will be a fairly cool, dry, and stable airmass in place ahead of the warm front and overall slow moisture return until later in the evening. This environment may ultimately make it hard to destabilize enough for a severe weather threat with the warm front. Both low-level and deep- layer shear will be quite strong, so if we do see a sustained storm or two with the warm front as the 12z HRRR depicts the activity may be supercellular with at least some potential for any severe hazard...however, it's worth noting most guidance is less aggressive than the 12z HRRR in this window, so unless we trend towards quicker destabilization than currently expected the main severe threat will be with the overnight cold front. If there is an earlier severe storm with the warm front, it would be favored towards the Marion/Mt Vernon areas in our southwest.

In terms of the main convective potential with the cold front, the environment to our west is expected to be very conducive to severe weather with all hazards Wednesday afternoon and evening. Severe convection is expected to develop to our west and spread east, and there's high confidence that most of the area will at least see some rain and thunder as the cold front and that convection progress through overnight. What's of lower confidence is severe weather potential across the local area with this second round. What we know is that wind shear will be very impressive Wednesday night as a 60-70kt low-level jet sweeps across the area...not common for the middle of June, and this makes it such that we will not need much instability to see severe weather if we see organized, surface-based convection. However, most guidance suggests deeper instability will struggle to advect into our area Wednesday night, with hi-res models showing mixed depictions of the exact timing, track, and evolution of more organized convection across our area. Any severe threat with the cold front likely arrives in the Toledo area after 7-8 PM and continues east-southeast through 2-3 AM.

The general consensus is that the severe weather risk will peak to our west on Wednesday with a gradual weakening trend across our area due to a combination of less conducive diurnal timing and a generally drier and more stable environment to the east. However, the amount of forcing and shear are concerning still locally...guidance generally suggests convection will be transitioning from a supercellular to more linear mode Wednesday night while pushing into our area. Given the amount of wind shear, any surface-based supercells that make it into our area could bring all severe hazards (wind, tornadoes, possibly hail), with more linear storm models favoring wind damage and still some QLCS tornado potential. The general impression is that the environment should remain conducive enough for a severe threat into at least Northwest Ohio with the cold front Wednesday night, but it becomes increasingly murkier and less favorable overall for severe weather to the east. Given the amount of wind shear this setup certainly has some upside or ceiling, as indicated by the SIG1 hatching on the Day 2 SPC outlook across Northwest Ohio for wind and tornadoes. However as discussed confidence is on the lower side given questions about timing and instability locally, particularly farther east. Feel the SPC Day 2 Slight Risk (level 2 of 5) for the western half of our area tapering to a Marginal Risk (level 1 of 5) to the east captures the general flavor of this forecast/messaging well.

Deep-layer flow will become fairly parallel to the sagging cold front Wednesday night as high PWATs (1.70-1.90") advect in on a strong low-level jet. This offers potential for some training convection with a local flash flooding risk Wednesday night. Many hi-res models have swaths of 3-5" of rain somewhere across the broader region with Wednesday night's convection, but do not agree on a more defined corridor of where this may occur yet.

KEY MESSAGE #3: This notably strong system for mid-June will bring impressive synoptic wind gusts for meteorological summer to the area Wednesday night and Thursday. There are two windows for stronger gusts...one will be beneath the strong, 60-70kt southerly low- level jet ahead of the cold front Wednesday night. These winds will not mix down very efficiently, but there may be some sporadic stronger gusts as the weakening convection moves across the area ahead of the cold front. The lakeshore from near Cleveland points northeast may also experience a window of stronger 45-55 MPH type gusts due to localized downslope enhancement. The next window will be during the day Thursday behind the cold front, as winds aloft remain strong and as mixing heights quickly deepen with daytime heating behind the cold front. The general impression is much of the area can see 40-50 MPH wind gusts out of the west-southwest on Thursday.

We are a forecast cycle or two too early for Wind Advisories, but we may need advisories along the eastern lakeshore for Wednesday night and a more widespread headline for the day Thursday. We normally do not see widespread/synoptic winds that are this gusty when trees are fully leafed out, which could cause more to come down than would typically occur with these types of winds during the winter months.

KEY MESSAGE #4:

The rest of the 7-day forecast will be relatively quieter after Thursday. A nice cooldown is expected to end the week and start the weekend, with highs in the 70s and lows in the 50s. A system looks to move east across the general region Sunday or Monday, bringing the next more organized rain potential.

AVIATION /06Z Wednesday THROUGH Sunday/

Scattered showers and thunderstorms continue to drift east out of the area this morning with KYNG the only terminal still impacted. There is a potential for some patchy fog to develop in areas where it rained this past evening, although confidence is very low at this point of where this may occur. Have included BR at CAK which already has reduced visibilities, but will continue to monitor any expansion from there. Any fog that does develop will quickly dissipate near sunrise and rebound to VFR as southwest winds begin to increase from the southwest at 10-12 knots.

As a strong cold front approaches from the east Wednesday evening, winds will quickly increase ahead of the boundary to be more southerly at 12-15 knots, initially gusting up to 30 knots before 00Z across western terminals. These winds accompanied by widespread showers and storms will spread east through the end of the TAF period. Gusts up to 40 knots are possible at all terminals with the potential for stronger gusts within thunderstorms. In addition, very heavy rain will likely reduce visibilities to non-VFR at terminals after 00Z but given some timing uncertainty, opted to cap those visibilities at 4SM for most spots. Some of the thunderstorms across the area may become severe, with the highest confidence across western terminals. Will continue to monitor trends in the forecast to hone in more specifically. In addition to these diminished aviation conditions, an extremely strong LLJ of 60-70 knots will push over the area resulting in very strong LLWS. Opted to handle the strong winds with the gusts, but given the anomalous nature of a jet like this in summer, wanted to note it here.

Outlook...Periodic showers and thunderstorms with non-VFR will continue through Friday.

MARINE

The main weather concerns with this marine forecast update is the potential for rough conditions to develop on Lake Erie late tomorrow afternoon through Thursday. There will be a strong low pressure system deepening to around 988 mb and moving through the eastern Great Lakes region. Before then, winds are expected to be southwesterly to southerly for the rest of this afternoon 10 to 20 knots and waves 1 to 3 feet. Winds will increase from the south 20 to 30 knots Wednesday evening and overnight. There is some potential for winds to reach up to Gales of 35 knots for a few hours as the strong surface low tracks just north of Lake Erie Wednesday night. Winds will become southwesterly to westerly 20 to 30 knots Thursday. Higher waves of 4 to 9 feet are expected Wednesday evening through Thursday. Higher end Small Craft Advisories are very likely needed. Gales may be possible and will be watching future trends in model guidance. There will also be the potential for water levels to drop to near or just below the critical low water mark for safe marine navigation on the western basin of Lake Erie Wednesday night into Thursday. Westerly winds of 10 to 20 knots will continue over the lake Friday and Saturday with waves of 1 to 4 feet.

CLE WATCHES/WARNINGS/ADVISORIES

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