Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1232 AM CDT Fri Aug 15 2025
Valid 151200Z - 161200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...
...SUMMARY...
Scattered severe storms are likely over parts of the northern Plains
and Upper Mississippi Valley.
...Northern Plains/Upper MS Valley...
Broad anticyclonic flow is forecast to continue across the
central/southern Plains during the day1 period. Stronger 500mb flow
will extend around the periphery of this feature, extending from the
northern Rockies-northern Plains-upper Great Lakes. While a few
disturbances will eject across the northern Rockies toward the upper
MS Valley, latest model guidance suggests heights will actually rise
much of the period. One such feature currently extends from eastern
WY into northeast CO. Scattered thunderstorms are noted immediately
downstream from the Black Hills into western NE. This disturbance
should advance into central SD by the start of the period, then into
MN by early afternoon. While a few strong storms may be ongoing at
the start of the period, renewed development is expected during the
afternoon across the upper MS Valley. LLJ is forecast to increase a
bit into southwest MN ahead of the short wave, and this should
encourage robust convection along a front that will be draped from
southwest MN-northern WI. Strong buoyancy will be noted south of the
front across much of this region and MLCAPE could exceed 3000 J/kg
from MN/IA into SD/NE. While the short wave should encourage
organized convection, boundary-layer heating will prove instrumental
in thunderstorm development. Forecast soundings suggest CINH weakens
considerably by 19-21z and convection should expand in areal
coverage as convective temperatures are breached. Wind/hail are the
primary risks, though a brief tornado can not be ruled out with any
supercell structures.
Farther west, convective temperatures will be breached across
eastern WY by 22z. Scattered storms will once again develop over the
higher terrain/Plains then spread downstream into western
SD/northwestern NE during the evening. Some consideration was given
to a SLGT risk for this activity but the short-wave trough that
should affect this region will eject across northern AZ into
southwest WY around 16/00z. Timing of this feature suggests stronger
support will not affect this region until well after sunset.
..Darrow/Lyons.. 08/15/2025
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