textproduct: Cleveland

WHAT HAS CHANGED

Wildfire smoke is expected to affect the region Wednesday night into Thursday. There is uncertainty but it could linger into Friday and Saturday. The probability for showers and thunderstorms has increased (now 60-80%) Saturday but decreased Sunday (now 10-20%).

KEY MESSAGES

1) Peak heat indices of 95 to 105 degrees are expected today resulting in Major HeatRisk (level 3 of 4) areawide.

2) Wildfire smoke to affect the region tonight and Thursday.

3) Periodic showers and thunderstorms are expected Friday through early next week.

DISCUSSION

KEY MESSAGE 1... Mid/upper-level high continues to affect the region with hot and humid conditions today. Highs in the low to mid 90s are expected areawide with heat indices ranging from the mid 90s in the lakeshore areas of Northeast Ohio and Northwest Pennsylvania to as high as 104 in parts of Northwest Ohio. Major Heatrisk (level 3 of 4) will affect the entire forecast area today. This means that heat-related illnesses could impact much of the population without effective cooling or hydration. The Heat Advisory is unchanged and remains in effect from 12 PM through 8 PM today.

KEY MESSAGE 2... Smoke from wildfires in northern Minnesota and Ontario is projected to impact the region starting Wednesday evening, and will spread south across the area late Wednesday night into Thursday. Expect reduced air quality and hazy conditions. Smoke could linger through at late as Saturday, though there is a high degree of uncertainty due to limited model data beyond Thursday.

KEY MESSAGE 3... The mid/upper ridge will start to become suppressed farther southwest into the Ohio and Tennessee Valleys Wednesday night and Thursday in response to a mid/upper trough deepening over eastern Canada, setting up broad northwest flow aloft over our region this weekend into early next week.

A shortwave will move southeast across the area on Saturday. This will promote the development of storms late Friday afternoon, spreading eastward through Friday night. The best forcing for ascent will be on Saturday as the shortwave gets closer, with a more likely period of showers and thunderstorms Saturday afternoon through Saturday night. Modest mid-level flow and instability would support a severe weather threat. However, there is some uncertainty with timing and strength of this system. Even so, model guidance are starting to pinpoint Saturday as the day to watch.

After a mostly dry period on Sunday, another shortwave is set to bring more periodic showers and thunderstorms Monday into Tuesday.

AVIATION /12Z Wednesday THROUGH Sunday/

VFR conditions are seen across the region with scattered high clouds. The main impact during this TAF period and the following days are the potential for wildfire smoke across the region. Current models have the smoke moving in late tonight and persisting through the day on Thursday. Onset of reduced visibility should be after 00Z this evening, though there may be some scattered reduction in visibility earlier in the day. Northern sites will see impacts first as the smoke moves north to south.

Winds to start this morning will be light, around 5 knots, then increase to around 10 knots out of the west over the next few hours and persist through the day. Winds will become light and variable after 00Z tonight.

Outlook...Non-VFR visibility possible tonight through Thursday due to wildfire smoke. Non-VFR likely Friday night through Saturday night in showers and thunderstorms.

MARINE

Wind and waves across Lake Erie this morning will continue to diminish to less than 10 knots and less than 2 feet as high pressure builds into the region throughout the day. A weak cold front will move north to south across the lake late tonight and winds will shift to be out of the north at 5-10 knots and waves around a foot or less. Through late Friday night, winds will generally be around 5 knots and variable. A warm front will move north through the region Saturday morning and winds will shift to be out of the south at around 10 knots. Unsettled weather is expected throughout the weekend as a low pressure system moves through. Winds will veer around to the north behind the low and cold front on Sunday and increase to 10-15 knots with waves building along the shoreline as well.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Heat Advisory from noon today to 8 PM EDT this evening for OHZ003-006>011-017>023-027>033-036>038-047. PA...None. MARINE...None.