Mesoscale Discussion 1677 NWS Storm Prediction Center Norman OK 0515 PM CDT Mon Jul 20 2026 Areas affected...western U.P. of Michigan Concerning...Tornado Watch 501... Valid 202215Z - 210015Z The severe weather threat for Tornado Watch 501 continues. SUMMARY...The threat for a few tornadoes appears to be increasing across the discussion area. DISCUSSION...Over the past hour, several discrete supercells have developed over the western U.P. of MI within a moist and moderate environment with MLCAPE as high as 2500-3000 J/kg, per latest objective analysis. The KMQT VWP currently resides within the eastern fringe of stronger instability, where locally backed near-surface winds are resulting in relatively strong low-level and deep-layer shear with 0-1 km SRH of over 200 m2/s2 and 0-6 km shear of 50 kt, respectively. Current radar observations indicate the supercells maturing near the eastern edge of greater instability (around the longitude of Marquette) and within the zone of enhanced vertical shear. Non-hydrostatic pressure perturbations existing with the ongoing supercells will sustain the storms farther east into the central U.P.; however, the tornado threat may be muted by the higher convective inhibition with eastward extent, at least in the short term. As of 2205Z, the best tornado potential appears to exist with the supercells near the MI-WI state line, northwest of Iron Mountain, and over far northeast Dickinson and southeast Marquette Counties. In addition to the tornado threat, the potential will exist for large hail with the strongest supercells. ..Mead.. 07/20/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MQT...GRB... LAT...LON 46108986 46498971 46738899 46718797 46608687 46208660 45658678 45528777 45488871 45638936 45818975 46108986 MOST PROBABLE PEAK TORNADO INTENSITY...120-145 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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