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Valid For: 13/41/2000

Synopsis: There is an Elevated Risk of Severe Weather across a large portion of the West Michigan Weather coverage area which includes the following counties in Michigan: Oceana, Newaygo, Muskegon, Kent, Montcalm, Ottawa, Ionia, Allegan, and Barry. Multiple rounds of strong to severe thunderstorms are possible from late this morning through the evening hours. Damaging winds, large hail, and isolated flash flooding and tornadoes will be the main concern with this risk.

Discussion: Surface temperature forecasts for today have prompted the issuance of Heat Advisories across much of northwestern Indiana and southwest lower Michigan. Models, including the HRRR are indicating that surface temperatures will be in the extreme upper 80's and into the mid 90's across much of the region today.

These high temperatures, coupled with extreme moisture values, will lead to an extremely hot and humid environment, especially across southwest lower Michigan where heat indices could rise above 100 degrees. In terms of the moisture values; surface dew points today are expected to be in the mid 70's throughout the entire day.

Even in the wake of frontal and prefrontal convective activity, we will likely see very high dew points and surface temperatures fueled by warm air advection from the Gulf of Mexico being pushed by strong low-mid level flow northeast through the Chicago Metro Area and straight across Lake Michigan into the greater Grand Rapids area. This continuous stream of warm/moist air advection will allow for the recovery of surface heating, moisture, and dew points in a relatively rapid manner in the wake of any convection. This would allow for the sustainment of the severe weather threat well into the overnight hours, though I think that the lack of frontal activity after 11pm will obviously inhibit this potential after that time.

With that being said, strong instability is already moving into place across Illinois as it is pushed by the strong low-mid level flow closer to the greater Grand Rapids area, later today Surface Based CAPE values should be around 3000 J/kg across much of the area and similar levels will remain in place for much of the day and into the overnight hours, well after any convective threats. Bulk Shear values at 0-6km have increased substantially, especially across northern lower Michigan, however, these still remain rather modest here in the WMIWX Coverage Area with only isolated pockets of shear approaching 50 knots... 20-35 knots is much more common. 0-1km Shear is much more impressive with more widespread shear values of between 30 and 70 knots across central and northern lower Michigan. Lapse Rates remain severely isolated and will likely have no bearing on the threat today unless isolated/decoupled convection can mix into isolated areas of 6-9cm at the right time and place. SRH remains modest across much of the region though there are scattered pockets of values approaching 300 in some areas.

Convection today will likely be more impulse and cellular mode favored throughout much of the morning and will be generally scattered (there is some potential for these to be strong to severe though especially east of the US-131 corridor). By this afternoon, storms will likely develop overhead (especially within the blue-hatched area of greatest uncertainty) and take on a cellular mode favorable of downburst winds, large hail, and isolated brief/weak tornadoes before they consolidate into a more linear MCS/QLCS type system as they track southeast away from the US-131/I-96/I-196 corridor where they will pose more of a damaging wind and small-large hail threat.

'Training' of storms today will also be a concern, with multiple rounds of heavy rain and storms tracking over the same areas, localized flooding and isolated flash flooding will be possible.

Primary hazards associated with this threat look to be Damaging Wind Gusts to around 60 or 70mph, large hail to around 1" in diameter, and Flash Flooding, though a few isolated tornadoes cannot be ruled out.

WMIWX will continue to monitor this situation and will provide updates below as it is appropriate. Stay #WeatherAware today and have multiple ways to receive life-saving weather alerts.

Forecaster Information:

Outlook Diagram: Jonah

Outlook Synopsis/Discussion: Jonah

Posted: 08-03-2022 05:31am EDT

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