Heads up in southern lower Michigan tonight.
The air is becoming increasingly unstable with possible severe storms developing over the next few hours. Storm Prediction Center says there's a 95% chance of issuing a Tornado Watch and the Severe Tornado Index around Grand Rapids/Kalamazoo/Lansing is a 9, which is quite high.
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Mesoscale Discussion 2039
NWS Storm Prediction Center Norman OK
0344 PM CDT Thu Aug 24 2023
Areas affected...Southern Lower MI...Northeast IN...Northwest OH
Concerning...Severe potential...Watch likely
Valid 242044Z - 242315Z
Probability of Watch Issuance...95 percent
SUMMARY...Potential for severe thunderstorms will increase
throughout the afternoon and into the evening across Lower MI and
adjacent portions of northeast IN and northwest OH. All severe
hazards are possible, including significant wind gusts and
tornadoes.
DISCUSSION...Visible satellite imagery has shown significant erosion
of the stratus across southwest Lower MI as the differential heating
zone becomes an effective warm front amid strong southwesterly
surface winds. Dewpoints are now in the upper 70s with temperatures
in the upper 80s/low 90s across southwest Lower MI. Temperatures are
still in the upper 70s/low 80s farther north and east, with lower
dewpoints there as well. Even with the more moist and warmer
conditions, some convective inhibition currently still remains
across southwest Lower MI, evidenced by the billow clouds on visible
imagery. Additional heating, coupled with low-level moisture
convergence over the region, may be able to overcome this convective
inhibition, promoting warm-sector thunderstorm development. There is
some uncertainty regarding this scenario, but any warm-sector storms
that do form would likely be supercellular and capable of all severe
hazards, including tornadoes.
Even if warm-sector development is not realized, additional forcing
for ascent attendant to subtle vorticity maximum should spread
across the area this evening. This forcing for ascent is just now
reaching southern WI and is responsible for the developing storms in
that region now. Expectation is that any storms ongoing ahead of
this vorticity max will intensify as they enter southern Lower MI,
with some in-situ development possible as well. Upscale growth
appears probable, with the resultant convective line then
progressing eastward/southeastward. Damaging gusts would be the main
severe threat, but hail and a tornado or two are possible as well.
It is feasible that a robust rear-inflow jet develops, resulting in
the potential for significant wind gusts and QLCS tornadoes.
..Mosier/Grams.. 08/24/2023
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