872
ACUS11 KWNS 090140
SWOMCD
SPC MCD 090139
WIZ000-MNZ000-SDZ000-090345-

Mesoscale Discussion 1905
NWS Storm Prediction Center Norman OK
0839 PM CDT Fri Aug 08 2025

Areas affected...Eastern South Dakota into central Minnesota and
northwest Wisconsin

Concerning...Severe potential...Watch likely

Valid 090139Z - 090345Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorm development is anticipated across eastern
South Dakota into southwest Minnesota in the coming hours. These
storms will quickly intensify and pose a threat for large hail and
severe gusts downstream into central Minnesota and eventually
northwest Wisconsin later tonight. Watch issuance is expected.

DISCUSSION...Recent GOES IR imagery shows the early stages of
deepening updrafts along a cold front to the north/northwest of the
Sioux Falls, SD area and south of Alexandria, MN. Based on 00z
soundings from ABR and OAX, this portion of the front appears to
have sufficiently weak MLCIN to allow for convective development,
which has been anticipated by afternoon/early-evening CAM guidance
during the 02-04 UTC period. As such, confidence is somewhat high
that this is the beginning of tonight`s more appreciable severe
threat across the upper MS Valley. Regional 00z soundings also
sampled steep-mid-level lapse rates supporting extreme MLCAPE values
on the order of 4000-4500 J/kg. While deep-layer shear within the
open warm sector is somewhat weak (around 15-20 per the MPX
sounding), northerly post-frontal winds are elongating hodographs
within the frontal zone and should promote organized convection
shortly after sustained/deep initiation. While a few initial
supercells are possible (with an attendant threat for large hail),
upscale growth is expected through the late evening hours across
central/northeast MN and northwest WI with an increasing risk for
severe winds and perhaps brief line-embedded tornadoes - within the
warm sector where 0-1 km SRH is on the order of around 100-150
m2/s2. Watch issuance is expected to address this potential.

..Moore/Guyer.. 08/09/2025

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

ATTN...WFO...DLH...MPX...FGF...FSD...ABR...

LAT...LON   43869705 44319706 47079521 47499494 47799439 47929371
            47929306 47869233 47619162 47459127 47169104 46779089
            46289098 46019102 45699132 45439147 45089192 43669537
            43539585 43519631 43589672 43869705

MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN