Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Wed Aug 06 2025
Valid 062000Z - 071200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE
CENTRAL/NORTHERN PLAINS TO THE UPPER MISSISSIPPI VALLEY AND
MINNESOTA...
...SUMMARY...
Isolated strong to severe thunderstorms are possible across parts of
the northern/central Plains to the Mid-Mississippi Valley, and over
part of northern Minnesota this afternoon and tonight.
...20z Update...
The prior forecast remains largely on track with minimal changes.
Current observations show stout capping in place over much of the
central Plains. However, robust surface heating of a seasonably
moist air mass (surface dewpoints upper 60s to low 70s F) is ongoing
across parts of South Dakota and northern Nebraska. With continued
heating this afternoon, gradual destabilization is expected to
continue. Initial high-based convection should develop late this
afternoon across eastern WY and western SD, and will gradually move
eastward into moderate to large buoyancy. With 40 kt of mid-level
flow also in place, there exists the potential for isolated
supercells with hail and damaging gusts as the primary threats. The
main uncertainty for higher severe probabilities today remains the
nebulous forcing for ascent which should continue to favor
sparse/isolated storm coverage into early evening.
...Eastern Plains and Missouri Valley to Midwest...
Afternoon model guidance continues to show an increase in convection
tonight associated with low-level warm air advection from the
expected 30-40 kt low-level jet. The highest confidence in scattered
storms is from the eastern half of SD/NE into parts of IA and
southern MN late tonight. With steep mid-level lapse rates above a
predominately stable boundary layer, hail and isolated damaging gust
are possible. The MRGL risk was adjusted over southern NE to better
match recent model guidance for higher storm coverage.
Otherwise, the outlook remains unchanged. See the prior discussion
for the previous discussion.
..Lyons.. 08/06/2025
.PREV DISCUSSION... /ISSUED 1129 AM CDT Wed Aug 06 2025/
...Northern/Central Plains into the Mid MS Valley...
Water-vapor imagery late this morning shows a quasi-zonal flow
regime from the northern Intermountain region east into the central
Great Plains. A disturbance along the ND/Canadian border will
continue east into the western ON vicinity late tonight. Weak
mid-level height rises are forecast over the northern Great Plains
downstream of a trough moving east into the northwestern CONUS from
the eastern Pacific. A belt of stronger mid-level flow (i.e. around
40 kt at 500 mb) will extend across the region, and diurnal heating
of the moist airmass in place will foster moderate to strong
buoyancy.
Forecast soundings show a vigorous combination of shear/buoyancy but
nebulous forcing mechanisms suggest storm coverage later
today/tonight will likely remain isolated/sparse. Little in the way
of large-scale forcing for ascent will contribute to suppressing
convective development through at least mid afternoon. Considerable
uncertainty in storm development is apparent in convection-allowing
models and some of these models show isolated storms perhaps
favoring the greater Black Hills area. Will maintain a Marginal
risk (level 1 of 5) despite favorable environmental conditions for
supercells. Later tonight in association with low-level warm-air
advection, a cluster or two of storms may evolve from the eastern
half of SD/NE into the lower MO Valley/mid MS Valley. An isolated
hail/wind threat could accompany this activity.
...Northern MN...
A few storms may develop along the southern periphery of the
Canadian Prairies shortwave upper trough and surface low. Lapse
rates will be weaker across this area and the favorable
thermodynamic environment will be narrow. Any stronger storms will
likely remain close to the international border, but could produce
locally strong gusts or marginal hail.
Read more CHECK UPDATE ZOOM GRAPHIC
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