Synopsis: There is an Elevated Risk (26%-40%) of Severe Weather across a large portion of the West Michigan Weather coverage area on Friday. The Elevated Risk extends south and west from a Grand Haven to Portland to Jackson line. North and East of Grand Rapids or an I-96 to US-127 line a Minuscule Risk is in place for the remainder of the Greater Grand Rapids and Ann Arbor areas and a Thunderstorms Risk is in place beyond that.
Discussion: A well-defined significant mid/upper-level trough ejection is forecasted to track northeast from the Rocky Mountains towards Ontario with an accompanying deepening low-pressure system causing the potential for widespread severe impacts across much of the southwestern Great Lakes region.
Here in western Michigan, there is a smaller chance of some scattered severe weather impacts across our coverage area, especially in extreme southwestern lower Michigan where there will be a slightly increased chance for surface-based storms to develop.
Thermodynamics will be modestly supportive of severe weather. Surface temperatures across much of southwestern lower Michigan will reach into the upper 50's and low-mid 60's, as warm/moist air advects into the region from the south ahead of the low-pressure system. Dew points are forecasted to be in the mid to upper 50's with resulting very low dew-point depressions of around 5 degrees. The biggest limiting factor is the lack of surface-based instability with SBCAPE values only forecasted to be between 300 and 1,200 J/kg at best.
Kinematics, even pre-frontal kinematics, still remain highly favorable for severe weather. It appears we will have to contend with 0-1km bulk shear values of more than 40 knots throughout much of the day today (which will likely lead to many marine and land-based non-convective wind products) and values between 50 and 80 knots just ahead of and during the severe weather threat time frame from about 9pm to 3am eastern time.
Possible hazards will include frequent lightning and torrential rainfall leading to some flash flooding risk, scattered damaging wind gusts up to 60mph with extremely isolated higher gusts (possibly to considerable levels) of up to 80mph, scattered small to large hail events up to quarter size in diameter, and an isolated brief/weak spinup tornado or two as a result of convergence from lake breezes and/or increasingly supportive tornadic environments are possible.
There is potential for expansion and perhaps even upgrades for this risk later this afternoon and evening if the overall threat appears to be increasing just ahead of event time. Currently, confidence remains somewhat low so we are opting to hold off on the introduction of higher-risk categories within our coverage area at this time. WMIWX will continue to monitor this threat and will provide updates as necessary in future outlooks.
Forecaster Information:
Graphic: Owen
Discussion: Jonah
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