Mesoscale Discussion 1679
NWS Storm Prediction Center Norman OK
0617 PM CDT Mon Jul 20 2026
Areas affected...eastern U.P. of Michigan and northern lower
Michigan
Concerning...Severe potential...Watch likely
Valid 202317Z - 210115Z
Probability of Watch Issuance...80 percent
SUMMARY...Severe weather potential is expected to increase across
the discussion area this evening with the primary hazards being
damaging winds and large hail. A watch will likely be required prior
to 01Z.
DISCUSSION...Within the exit region of an upper-level jet streak
advancing into WI, large-scale forcing for ascent will overspread
the region from the west this evening. In response, a southwesterly
low-level jet will strengthen from southern WI into lower MI, which
in turn will enhance the flux of an increasingly moist and unstable
air mass into the region from the west. That destabilization process
will allow ongoing storms, including supercells, to spread southeast
across Lake Michigan into northern lower MI later this evening.
Inspection of forecast soundings suggests that storms may be
slightly elevated atop a shallow, near-surface inversion, which may
tend to mitigate a more robust tornado threat, despite strengthening
low-level shear. Nonetheless, the presence of seasonably strong
deep-layer shear will support the continuation of organized storm
modes, including supercells and bowing structures, with the primary
hazards being large hail and damaging wind gusts.
..Mead.. 07/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...APX...GRR...MQT...
LAT...LON 44568687 45558617 46368511 46208385 45618344 45108332
44558440 44048628 44168674 44568687
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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