textproduct: Cleveland

WHAT HAS CHANGED

No major changes to the forecast with elevated heat risk and severe weather the main impacts today and Thursday.

KEY MESSAGES

1) Elevated heat risk conditions continue today for Ohio as heat indices will be in the upper 90s to low 100s.

2) There will be severe weather potential across Northeastern Ohio and Northwestern Pennsylvania this morning through overnight tonight.

DISCUSSION

KEY MESSAGE 1... Well above normal temperatures will continue today along with increased dew points keeping heat indices in the upper 90s to low 100s. The upper level ridge continues to be in place across the southern CONUS allowing for persistent west to southwesterly flow across the region to continue today into the overnight. This will push highs today a touch warmer into the low 90s with dew points climbing into the low to mid 70s again. Heat indices as a result will rise up into the upper 90s to low 100s. Portions of Western Ohio will be warmer than to the east as there should be limited precipitation and cloud cover for much of the day. For Cleveland eastward, precipitation is expected this morning and again in the evening, but there should be a long enough break in between to allow for temperatures to climb quickly. For the Northwestern Pennsylvania areas, they will be far enough east to were temperatures shouldn't climb up into the 90s, therefore heat indices will be below advisory criteria. With that being said, it still will feel hot with heat indices in the mid 90s, and precautions should be taken as needed. Overnight lows Wednesday into Thursday will still be elevated as well into the low to mid 70s offering little relief. Heat risk will stay elevated at a level 3 out of 4 for the entire CWA due to this.

Thursday will start to bring some relief to the region as a cold front approaches from the north and more widespread precipitation is expected at some point during the day. Western and Central Ohio will still have elevated heat indices and heat risk though, as precipitation will not have reached before peak heating. There is some uncertainty in this as morning convection may be moving across the area that would limit the high temperatures for the day. If the convection does not pan out, then thinking is that an area from roughly Wayne/Holmes northwest to Lucas will need an extension in the advisory. The remainder of the eastern portions of the CWA should have enough precipitation and cloud cover to keep temperatures and heat indices down in the upper 80s and low to mid 90s respectively.

Temperatures will begin to regulate Friday into the weekend to more seasonal as Canadian high pressure builds south into the region. Highs will be in the upper 70s to mid 80s with overnight lows in the upper 50s to mid 60s through the weekend.

KEY MESSAGE 2... More rounds of showers and thunderstorms are expected this morning through the overnight hours. For this morning, there is a shortwave trough located over Southern Ontario that will push southeastward into New York through the mid-morning. This will help support scattered showers and thunderstorms this morning across Northeastern Ohio and Northwestern Pennsylvania. There will be some instability in place along with around 40 knots of bulk shear that, if storms organize, could support damaging wind gusts. Will monitor upstream in Southern Ontario and Eastern Michigan for storm formation, but currently storms across Western Michigan have started to weaken and the environment may not be suitable for thunderstorm development.

There will be a break in the showers and precipitation once the shortwave moves eastward and the next shortwave enters the region later this afternoon/evening. This will allow for instability to build back to around 2000 J/kg and lapse rates of 7-7.5 C/km across Eastern Ohio and Northwestern Pennsylvania. Bulk shear will also in the neighborhood of 30-40 knots in that same region. Thunderstorm development is possible ahead of the shortwave with a more linear mode expected with the shortwave later in the evening. The western extent of this feature is still uncertain and could reach as far west as Cleveland. The highest confidence in thunderstorms currently for this evening is across far Northeastern Ohio and in Northwestern Pennsylvania. This is shown in SPC's Day 1 Severe Weather Outlook as there is a slight risk (level 3 of 5) from a line from Toledo southeast to Canton and eastward with higher probabilities for severe winds in Northeastern Ohio and Northwestern Pennsylvania. Damaging winds will be the main threat with todays storms, though large hail will also be a factor with the increased lapse rates and instability. A quick spin up tornado is also possible though 0-1 km bulk shear is minimal, so the threat is on the low end. Thunderstorms should exit to the southeast around midnight. Given the warm, moist environment over the region, PWAT values will be around 1.5-2.00" across the region. The will bring the threat for heavy rain with any thunderstorms and could cause isolated flooding issues if there are persistent rainfall over and area.

Additional thunderstorms are possible early Thursday morning as well though there is still a lot of uncertainty in where and the severity of these as it will be dependent on the storms from Wednesday evening. A cold front will approach from the north throughout the day on Thursday that will bring more widespread precipitation to the region. The severe weather threat will be more focused on Central Ohio with the better instability and lapse rates, though can't rule out any storms to become severe across the region ahead of the front. The front will be slow to move to the south and should exit by late Thursday night.

Lingering showers and thunderstorms are possible Friday as another shortwave moves through the region, though the severe threat should be lower than previous days. High pressure builds into the region from the north and should persist through the weekend with dry weather expected.

AVIATION /12Z Wednesday THROUGH Sunday/

Several rounds of convection are likely this morning across NE OH and NW PA as clusters of thunderstorms over Lake Erie come ashore. Strong to severe winds are possible with these storms, as well as frequent lightning and hail. Storms are expected to move out of the area by late morning, but a second round of scattered convection will develop this afternoon and evening across in roughly the same locations. At this time, uncertainty exists as to the exact timing and location of these storms.

The rest of the region will stay VFR with scattered to broken high and mid level clouds. South and southwest 5 to 10 knots are expected, with a few gusts to 20 knots during the afternoon hours.

Outlook...A cold front will slowly move across the area from the northeast towards the southwest on Thursday. Scattered showers and storms will bring non-VFR conditions Wednesday night through Thursday night. High pressure and fair weather will return Friday into the weekend.

MARINE

Severe storms have made their way across eastern Lake Erie and into the coastal waters this morning, with several rounds of storms likely across the lake today and tonight as a cold front eventually drops south. Wind gusts up to 40 knots are possible in the strongest storms. Outside of thunderstorms, southwest winds with 1-3 foot waves are expected.

A gradual wind shift to the north will occur by Thursday night behind the cold front, with winds diminishing Friday. Northeast flow over the weekend could result in some choppy conditions with waves of 1-3 feet.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Heat Advisory until 8 PM EDT this evening for OHZ003-006>011- 017>021-027>031-036-037-047. Heat Advisory from 11 AM this morning to 8 PM EDT this evening for OHZ012>014-022-023-032-033-038-089. PA...None. MARINE...None.