The Storm Prediction Center is getting a little more confident on how strong and where thunderstorms may be this afternoon and evening. Part of southern Michigan is warning about significant severe weather.
The latest severe weather forecast from the Storm Prediction Center (SPC), issued at 8:24 am this Monday morning, shows the highest chance of severe thunderstorms in a corridor across southwest and south-central Lower Michigan.
The orange shaded area south of a Muskegon to Detroit line is in what is termed an “enhanced risk” area for severe thunderstorms. The severe thunderstorm forecast can also be thought of as a five-level forecast. Enhanced risk is level three on that five-level scale.
The scenario we are expecting is a clump of thunderstorms developing this afternoon over southern Wisconsin. The storms are then expected to race southeast across southern Lower Michigan. This line of storms will probably only be one hundred miles long north to south. The line of storms could have spots that get what the Storm Prediction Center calls “destructive wind gusts.”
Here is the severe weather forecast broken out into specific types of severe weather.
The first forecast is for straight-line wind gusts. These severe wind gusts come in the first 10 minutes of a thunderstorm. The black-hatched path from Muskegon and the southwest Lake Michigan shoreline to near Ann Arbor and Detroit has the chance of 75 mph gusts or stronger. At 80 mph, wind gusts do significant damage to buildings, and can even break windows. It’s not a sure bet, but if thunderstorms get severe, they could produce brief, very severe gusts.
There is also a large enough risk of a few tornadoes to be concerned with, not just straight-line winds. The same area with the highest risk of severe wind gusts also has the highest tornado risk.
Large hail is a possibility, but not the main concern at the moment.
TIMING OF SEVERE THUNDERSTORMS
The thunderstorms should be entering the west side of Lower Michigan sometime between 4 pm and 7 pm We are not sure down to the hour just yet. We will know that in the early afternoon. It would then take about three hours for the storms to track across southern Lower Michigan.
Here are the cities in the highest risk of severe thunderstorms: Muskegon, Grand Haven, Holland, South Haven, Benton Harbor, Grand Rapids, Battle Creek, Kalamazoo, Lansing, Jackson, Coldwater, Adrian and Ann Arbor.
North of Grand Rapids to the Flint area still has the chance of a severe wind gust, but it should be more isolated and not as strong.
The storms may be weakening some as they move into the Detroit area, but this will also be watched by me.