506
ACUS11 KWNS 180651
SWOMCD
SPC MCD 180650
MNZ000-IAZ000-NEZ000-SDZ000-180815-

Mesoscale Discussion 1982
NWS Storm Prediction Center Norman OK
0150 AM CDT Mon Aug 18 2025

Areas affected...Southeast SD...eastern NE...western IA...southwest
MN

Concerning...Severe Thunderstorm Watch 598...

Valid 180650Z - 180815Z

The severe weather threat for Severe Thunderstorm Watch 598
continues.

SUMMARY...Isolated damaging wind and hail are possible overnight.

DISCUSSION...An outflow-dominant storm cluster is moving across
southeast SD and northeast NE early this morning. While instability
is favorable, with MUCAPE near/above 2000 J/kg, midlevel flow and
deep-layer shear (as observed from area VWPs) are generally weak,
which may continue to limit organization of this cluster through the
overnight hours. The strongest outflow is currently moving eastward
across southeast SD, and this area may have the greatest relative
threat for damaging wind as it moves toward far southwest
MN/northwest IA. The strongest embedded updrafts may also be capable
of producing isolated hail.

Farther south, convection is trailing the gust front across
northeast NE, with other elevated convection noted in advance of the
storm cluster into east-central/southeast NE. The weak deep-layer
shear should generally limit storm organization in this area as
well, though at least a brief uptick could occur as the larger-scale
outflow encounters the preceding convection. A localized threat for
damaging wind and perhaps some marginal hail could accompany these
storms as they eventually move from eastern NE into parts of western
IA.

..Dean.. 08/18/2025

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

ATTN...WFO...MPX...DMX...FSD...OAX...GID...LBF...

LAT...LON   42219823 43119717 43929772 44369785 44519649 44389514
            42839483 41219545 40809601 40689712 40789775 41379812
            41629851 41839885 42219823

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN