Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Sat Aug 09 2025
Valid 091200Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN
NE INTO IA/WI...NORTHERN MO/IL AND SOUTHERN UPPER MI...AND ALSO
ACROSS EASTERN CO...
...SUMMARY...
Multiple damaging wind swaths are possible later today into tonight,
centered on parts of Wisconsin, Iowa, and northwest Illinois.
Multiple rounds of large hail are possible across eastern Colorado
starting in the late afternoon.
...Upper Great Lakes into the lower MO Valley...
Prior to the start of the forecast period, extensive convection is
expected to develop across MN early this morning, in association
with a seasonably strong mid/upper-level trough. A separate
organized storm cluster may develop across the central Plains and
approach parts of the MO Valley by 12Z this morning. Evolution of
the morning convection is uncertain, but there will be some
possibility for intensification as storms move eastward into a
potentially destabilizing airmass. Should this occur, a swath of
damaging wind will be possible across parts of WI and northwest IL
later today. Also, depending on the southern extent of convection
this morning, any organized cluster emerging from the central Plains
could continue through the day across parts of IA, with a threat of
damaging wind and hail.
In the wake of early-day convection, an outflow-reinforced surface
boundary may become quasi-stationary somewhere from the central
Plains into parts of the Midwest, though uncertainty remains
regarding the position of this boundary by late afternoon. Renewed
storm development will be possible near the boundary, within a
strongly unstable environment. While some weakening of deep-layer
flow may occur, effective shear will remain sufficient for organized
convection. Initial supercell development is possible near the
boundary, with a threat of isolated hail and possibly a tornado.
Upscale growth into one or more clusters will be possible during the
evening, in association with a nocturnally strengthening low-level
jet. This could support another round of damaging-wind potential.
...Central/southern High Plains...
A cold front may become quasi-stationary by this afternoon across
the south-central High Plains. A favorable post-frontal regime for
severe storms is expected to develop across eastern CO. Steep
midlevel lapse rates, moderate instability, and favorable deep-layer
shear will support scattered supercells capable of large to very
large hail, localized severe gusts, and possibly a tornado, mainly
this afternoon into the evening.
Farther south, high-based convection may again develop across parts
of eastern NM into the TX/OK Panhandles, which could pose a threat
of localized severe gusts.
..Dean/Moore.. 08/09/2025
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