185
ACUS02 KWNS 210600
SWODY2
SPC AC 210558

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Thu Aug 21 2025

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE CENTRAL/NORTHERN HIGH PLAINS INTO THE UPPER MIDWEST...

...SUMMARY...
Strong to locally severe thunderstorms are possible Friday from
parts of the central and northern High Plains into the Upper
Midwest.

...Northern/central High Plains into the Upper Midwest...
A mid/upper-level cyclone and attendant surface low is forecast to
move eastward across parts of MB and northwest ON Friday. An
outflow-influenced surface boundary may drift southeastward across
the central Plains into the Upper Midwest during the day, while a
strong trailing cold front begins to move across the Dakotas and
northern MN.

The greatest relative confidence in diurnal storm development is
within the post-frontal regime across parts of eastern WY/CO. Steep
midlevel lapse rates, moderate buoyancy, and relatively elongated
hodographs will support potential for strong to potential severe
storm development, initially near the higher terrain. Isolated hail
and locally gusty winds could accompany the strongest cells. While
uncertain, there is some potential for storm clustering during the
evening, which could result in some severe potential spreading into
parts of western NE and perhaps northwest KS Friday night.

Farther east, confidence is low regarding the details of convective
evolution from central/eastern NE/SD into the Upper Midwest. In
general, a zone of moderate buoyancy, with MLCAPE of 1000-2000 J/kg
(locally higher), is expected to develop by afternoon near/north of
the leading surface boundary, and ahead of the trailing cold front.
Gradually strengthening midlevel flow is forecast to provide
modestly favorable effective shear (25-35 kt).

There may be some potential for early-day convection to intensify as
it moves through a destabilizing environment during the afternoon.
Otherwise, isolated to widely scattered storm development will be
possible during the afternoon/evening within the zone of favorable
moisture/instability, with a threat of locally damaging gusts and
isolated hail.

...Arizona...
Similar to D1/Thursday, scattered storm development will be possible
Friday afternoon across higher terrain areas of AZ, with easterly
flow potentially steering storms (or at least their remnant
outflows) into the lower deserts with time. Isolated damaging wind
cannot be ruled out with this activity, given the presence of a hot
and well-mixed environment, though it remains uncertain if more
substantial storm clustering and outflow consolidation will evolve
during the evening.

..Dean.. 08/21/2025

$$