Synopsis: There is an Elevated Risk of severe weather across the extreme southwestern portions of the West Michigan Weather coverage area on Friday. North and east of a South Haven to Sturgis line a Minuscule Risk is in place and a Thunderstorm outlook is in place beyond the Minuscule Risk boundary.
Discussion: A pronounced mid/upper-level trough ejection and accompanying deepening low-pressure system will move northeast across the great plains and into the Great Lakes region late in the evening and into the overnight hours on Friday.
As is the norm for these early-season Michigan severe weather threats this will be a strongly sheared and low CAPE environmental setup that will lead to a somewhat conditional threat for strong to severe thunderstorms as this system moves through the region.
Thermodynamics will be modestly supportive of severe weather at best. Surface temperatures across much of southwestern lower Michigan will reach into the mid-upper 50's, and perhaps 60, as warm air/moist air advects into the region from the south ahead of the low-pressure system. Dew points are forecasted to be in the low to mid 50's with resulting dew-point depressions of about 5-10 degrees. Turning our attention to CAPE we have quite the spread when looking at the various models. The best guess right now is that southwestern lower Michigan will see MU/SB Cape values between 500 and 1000 J/kg.
Kinematics will be much more favorable, almost off the charts (when looking at the NAM 3km CAM), with forecasted 0-6km Bulk Shear between 60 and 100 knots across the frontal boundary as it approaches the Great Lakes region. Obviously, we will have to see if this persists into the threat time frame and what magnitude of threat is in place for those winds to mix down to the surface. Nevertheless, these kinematics are some of the more impressive values we have seen in a severe forecast for our region in quite some time.
The best chance for strong to severe weather (26%-40%) will be in the Elevated Risk region from about a South Haven, MI to Elkhart, IN line. Possible hazards will include frequent lightning and torrential rainfall leading to some flash flooding risk, scattered damaging wind gusts up to 60mph, and scattered small to large hail events up to quarter size in diameter. A brief/weak spinup tornado or two as a result of convergence from lake breezes can't be ruled out.
WMIWX will continue to monitor this threat and will provide updates as necessary in future outlooks.
Forecaster Information: Graphic: Owen / Jonah
Discussion: Jonah / Owen
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