Mesoscale Discussion 1396
NWS Storm Prediction Center Norman OK
0518 PM CDT Mon Jun 24 2024
Areas affected...parts of southeastern Minnesota...southwestern
Wisconsin and northeastern Iowa
Concerning...Severe potential...Watch possible
Valid 242218Z - 250015Z
Probability of Watch Issuance...40 percent
SUMMARY...Sustained vigorous thunderstorm development remains
uncertain, but seems more likely after sunset than before. Trends
are being closely monitored, with rapid thunderstorm intensification
possible, including potential for supercells posing a risk for large
hail in excess of 2 inches in diameter, locally damaging downbursts
and a risk for tornadoes.
DISCUSSION...As a weak mid-level perturbation progresses through
broader-scale anticyclonic flow across the Upper Midwest/Great Lakes
region, modest low-level warm advection has become focused
east-southeast of a surface low over northeastern South Dakota,
across southern Minnesota and adjacent portions of northeastern
Iowa/southwestern Wisconsin. This forcing for ascent appears likely
to be contributing to the recent thunderstorm initiation near/north
of the Interstate 90 corridor of southern Minnesota. The
boundary-layer is characterized by seasonably high moisture content
and large CAPE beneath steep mid-level lapse rates, but a plume of
very warm/dry elevated mixed-layer air is in the process of
overspreading much of the region, and some further warming
near/below the 700 mb level may still occur into early evening.
While it still appears probable that inhibition associated with the
warm, dry air aloft will tend to suppress this convection, this is
not entirely certain, and the environment is conditionally
supportive of intense organized convection give the extreme
potential instability. Higher-based ongoing convective development,
rooted in warm advection closer to the northeastern periphery of the
elevated mixed-layer air, east-southeast of Brainerd, is also being
monitored. As this spreads into northwestern Wisconsin this
evening, it might undergo considerable further intensification in
the presence of increasing lift and instability near the nose of a
strengthening southwesterly low-level jet (30-50 kt around 850 mb).
..Kerr/Gleason.. 06/24/2024
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GRB...MKX...DLH...ARX...MPX...DMX...
LAT...LON 44719324 45239319 46009364 46479382 46569224 45879048
44248951 43559016 43029111 43229272 43819399 44719324