649
ACUS03 KWNS 060731
SWODY3
SPC AC 060730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Wed Aug 06 2025

Valid 081200Z - 091200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PART OF
THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...

...SUMMARY...
Thunderstorms with large hail and severe wind gusts are likely on
Friday across parts of the northern Plains and upper Mississippi
Valley. Hailstones greater than 2 inches in diameter will be
possible.

...Central and Northern Plains/Upper Mississippi Valley...
A mid-level trough will progress eastward into the northern High
Plains on Friday, as an associated speed max moves over the northern
Plains. At the surface, a low will deepen across the central Plains,
as a cold front advances eastward the north-central states. Ahead of
the front, a moist and unstable airmass will be in place from the
central Dakotas eastward to the upper Mississippi Valley. A
pronounced axis of strong instability is forecast by afternoon from
northeastern South Dakota into far eastern North Dakota.
Surface-based thunderstorms are expected to develop along an
instability gradient located just ahead of the front during the mid
to late afternoon. A cluster of strong to severe thunderstorms will
move eastward across the eastern Dakotas into Minnesota from late
afternoon into the evening.

At 21Z on Friday, forecast soundings near the axis of instability
have an impressive thermodynamic environment. To the west of Fargo,
North Dakota, MLCAPE is forecast to peak in the 4500 to 6000 J/kg
range, with 700-500 mb lapse rates in the 8 to 9 C/km range. In
addition, 0-6 km shear is forecast to be in the 35 to 40 knot range,
suggesting supercells with large hail will be likely. Hailstones
greater than 2 inches in diameter will be possible with the stronger
cores. In addition, 0-3 km storm-relative helicity is forecast reach
the 200 to 275 m2/s2 range by late afternoon, suggesting that a
tornado threat could develop. The potential for severe gusts is
expected to increase in the early evening, as a cluster or broken
line of strong to severe storms moves eastward across the region.

Further south into southeastern South Dakota and northeastern
Nebraska, cell coverage is forecast to be more isolated due to a
capping inversion that is evident on forecast soundings. In spite of
the cap, low-level convergence is forecast to become strong just
ahead of the front. This should be enough for convective initiation
during the evening. The environment along this part of the front
will likely support large hail and severe wind gusts, but the threat
should be more isolated with southward extent.

..Broyles.. 08/06/2025

$$