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Mesoscale Discussion 1827
NWS Storm Prediction Center Norman OK
0206 PM CDT Mon Aug 05 2024

Areas affected...portions of eastern South Dakota into southern
Minnesota and northern Iowa

Concerning...Severe potential...Watch likely 

Valid 051906Z - 052100Z

Probability of Watch Issuance...80 percent

SUMMARY...Scattered thunderstorms are expected to develop in the
vicinity of a triple point move east/southeast across the upper
Midwest. A mix of supercells and bowing segments may support a risk
for all hazards. Confidence on the exact timing of storm development
is low, but the severe risk will likely require a WW.

DISCUSSION...Early afternoon WV imagery showed a well-defined
shortwave trough embedded within expansive zonal/northwesterly flow
over the northern third of the CONUS. Ahead of the shortwave trough,
a weak wave cyclone along a quasi-stationary front has beco*e better
defined. Evident in visible imagery, subtle ascent from the
approaching trough and low-level convergence/WAA along the front and
ahead of the low is eroding early afternoon inhibition over parts of
eastern SD and western MN. A warming and very moist air mass (70s F
surface dewpoints) is supporting moderate to large buoyancy
(2000-3000 J/kg of MUCAPE). Seasonably robust vertical shear is also
in place ahead of the advancing trough with SPC mesoanalysis showing
deep-layer values on the order of 45-50 kt. The favorable overlap of
CAPE and shear will likely support organized storms with a mixed
mode of supercells and bowing line segments. 

Initial storm development may occur as early as mid afternoon
northwest of the surface low where low-level convergence is
strongest and inhibition has rapidly weakened. Should this occur
earlier in the day, as hinted by some CAM solutions, convection may
initially be elevated with lingering surface inhibition. However,
continued destabilization will likely support a transition to
near-surface based with additional storm development likely through
the remainder of the afternoon. Strong turning in the lowest few km
near the quasi-stationary front, in co*bination with the supercell
wind profiles, will likely support a risk for large hail. A couple
of tornadoes are also possible with any well-developed supercells
near the front. As storms evolve upscale along the boundary, a risk
for damaging winds also appears likely.Given the increase in severe
risk expected over the next few hours, a watch will likely be
needed.

..Lyons/Hart.. 08/05/2024

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DVN...ARX...MPX...DMX...FSD...ABR...

LAT...LON   43779151 43209131 42679139 42339248 42779683 43319759
            44279757 44989724 45129704 45089664 44709498 44179246
            43779151