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    Hurricane-force wind gusts, Derecho may plow through West Michigan

    A line of serious severe thunderstorms may make it into Lower Michigan on Thursday morning. As a result, the Storm Prediction Center is indicating higher-end severe weather is possible for part of southwest Lower Michigan, with even the potential of a derecho.

    A complex of severe thunderstorms is expected to form early this evening over the far northwest part of Wisconsin. The storms are expected to move southeast and evolve into a line of damaging wind generating storms. By a few hours either side of sunrise, the severe storms may be still intact and moving into southwest Lower Michigan.

    This line of storms could be deemed a derecho if it crosses several states. Here is NOAA’s definition of a derecho: “A derecho (pronounced “deh-REY-cho”) is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to the strength of tornadoes, the damage typically is directed in one direction along a relatively straight swath.”

    Let’s start with the general outline of the expected severe weather area.

    You can get a great feel for the severe weather scenario. The red shaded area of moderate risk of severe weather is in Wisconsin. The next level down on chances of severe weather is called an enhanced risk, and the southwest quarter of Lower Michigan is in that risk category. Surrounding the enhanced risk is the yellow shaded slight risk of severe weather.


    Overall severe weather forecast for 8 a.m. Wednesday to 8 a.m. Thursday. (Forecast by Storm Prediction Center)

    This could be a severe weather event with all three forms of severe weather- damaging winds, tornadoes and large hail. Just below is the risk of straight-line damaging winds. Again you can clearly get the idea of a big storm complex starting in northern Wisconsin and moving southeast.


    Chance of severe wind gusts from this afternoon to 8 a.m. Thursday. Black hatched area, including southwest Lower, has 10 percent chance of 75 mph wind or stronger. (Forecast from Storm Prediction Center)

    The black-hatched area in the wind forecast above is a 10 percent chance of 75 mph wind gusts or stronger. That highest wind gust chance extends into the western fringe of Lower Michigan, including all of the Lake Michigan shoreline cities from Ludington southward. The high wind gust potential area also includes the Grand Rapids area, Battle Creek and Kalamazoo. It’s also worth noting the most recent forecast issued at 8:00 a.m. this morning shifted the significant wind gust potential into Lower Michigan. The previous forecast keep the 75 mph+ potential in Wisconsin. So there is a trend toward shifting the most severe weather east.

    Of course we all think about tornadoes when watching for severe weather. The forecast below shows the main threat of tornadoes is in Wisconsin this evening. We could have isolated “book-end” tornadoes if a bow-echo line of storms forms. The book-end tornadoes occur at each end of the line of storms.


    Chance of a tornado within 25 miles of a given point.

    Large hail, over two inches in diameter, is also possible when the storms initially develop over northern Wisconsin. The thunderstorm potential to produce large hail should go down a few hours after formation.


    Chance of large hail this afternoon and overnight to 8 a.m. Thursday. Black hatched area is 10 percent chance of two inch or larger hail. (Forecast from Storm Prediction Center)

    Finally let’s look at what one of the severe weather models shows as a radar forecast. This will give you a feel for the timing of storm arrival in Michigan, if you are even in the path.

    radar forecast

    Radar forecast from the 8 a.m. Wednesday run of the North American Model.

    The severe storms are projected to arrive in western Lower between 2 a.m. and 4 a.m., and then move into southern Lower Michigan from 4 a.m. to 7 a.m. Thursday.

    I do want to note that this newest run continues the trend of shifting the line of storms more into Michigan. Last evening’s run of this same model had the line of storms plowing straight south through the Milwaukee area.

    MLive and I will keep you updated. The confidence will grow on eventual placement and timing of storms once we see where the storms initially form early this evening.

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