Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 210317
SWOMCD
SPC MCD 210317
MIZ000-210515-
Mesoscale Discussion 1686
NWS Storm Prediction Center Norman OK
1017 PM CDT Mon Jul 20 2026
Areas affected...northern lower Michigan
Concerning...Severe Thunderstorm Watch 505...
Valid 210317Z - 210515Z
The severe weather threat for Severe Thunderstorm Watch 505
continues.
SUMMARY...Through 05Z, the greatest damaging wind potential will
extend from Grand Traverse Bay toward Saginaw Bay.
DISCUSSION...As of 0310Z, radar imagery indicated a bowing storm
complex with an associated bookend vortex moving over Grand Traverse
Bay. Volumetric base velocity data from KAPX suggest some indication
of a rear-inflow jet with 50+ kt inbound speeds as low as about 3
kft above ground. RAP-based proximity soundings suggest that the
storms are slightly elevated and rooted within a moist layer
centered around 850 mb. The stable near-surface layer is expected to
limit the potential for a more concentrated damaging wind event.
However, the seasonably strong vertical shear and influx of stronger
instability from the west will remain supportive of strong
up/downdrafts capable sporadic occurrences of 60-65 kt wind gusts.
Extrapolation of the current system motion takes it just to the
northwest of Saginaw Bay by 05z.
..Mead.. 07/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...APX...GRR...
LAT...LON 43888448 44338553 44768611 45238597 45398546 44898431
44368380 44008379 43858405 43888448
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN