Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Sat Aug 09 2025
Valid 092000Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE FRONT
RANGE TO THE CENTRAL PLAINS AND WESTERN GREAT LAKES....
...SUMMARY...
Scattered strong/severe storms are possible through tonight from
eastern Colorado, across the Central Plains and into the western
Great Lakes. Isolated damaging wind gusts are possible in southeast
Arizona.
...20z Update Western Great Lakes...
A large convective complex remains ongoing as of this afternoon from
portions of eastern WI, into eastern IA and northern MO. Diurnal
heating ahead of the remnant storms and outflow should promote some
redevelopment/organization this afternoon and evening. Behind the
system, widespread cloud cover and precipitation has largely
overturned the air mass. This suggests little if any redevelopment
and severe risk is expected. The Slight Risk for damaging gusts will
be maintained ahead of the ongoing storms, with severe probabilities
removed where air mass recovery is unlikely in the wake of the
complex. See MCD#1914 for short-term guidance.
..Central Plains to Midwest...
On the southwestern flank of the ongoing convective complex over the
Upper Midwest, gradual air mass recovery is ongoing ahead of a
slow-moving cold front, likely continuing into this evening.
Afternoon model guidance shows an increase in low-level warm air
advection from a 35-50 kt low-level jet is likely along the front
and prior outflow intersection across southeast NE and northwest KS.
The increase in ascent should foster widespread thunderstorms after
dark across the central Missouri Valley. Very large, but likely
elevated, CAPE along the boundary (3500+ J/kg) should support one or
more clusters with damaging winds and some hail potential tonight.
Minor changes were made to the Slight Risk area to better align with
current frontal position and guidance.
...Front Range...
Confidence continues to increase that upslope flow and the passage
of a mid-level trough should support scattered thunderstorms,
including supercells, in several rounds through tonight. Storms
should continue developing this afternoon off the higher terrain
over eastern CO/WY. Moderate buoyancy, steep lapse rates and 40+ kt
of deep-layer shear suggests hail (some potentially 2+ inch) will be
likely along with the potential for damaging gusts and a tornado or
two. Minimal changes were made to this outlook area for the latest
guidance, see MCD#1913 for short-term info.
..Lyons.. 08/09/2025
.PREV DISCUSSION... /ISSUED 1122 AM CDT Sat Aug 09 2025/
...IA/WI Vicinity...
An intense small-scale MCS affected parts of eastern NE and western
IA overnight and this morning. The remnants of this system are
moving across eastern IA and have weakened below severe limits.
This activity will likely persist eastward across WI and into parts
of Upper MI through the day, but a sagging cold front ahead of the
storms coupled with some cloud cover limit the confidence it can
re-intensify to severe levels. Nevertheless will maintain a SLGT
risk for the areas ahead of this activity.
...NE/MO/IA tonight...
Substantial airmass stabilization has occurred across this area in
the wake of the overnight storms. It appears likely that relatively
strong heating and return of a very moist air mass will result in
strong CAPE values by early evening. A strengthening low-level jet
will enhance lift along the retreating outflow boundary, likely
resulting in rapid thunderstorm development after 00z over northeast
KS. These storms will build east-northeastward into southern
IA/northern MO through the evening/night with a risk of upscale
organization and damaging winds/hail.
...CO/NE/KS...
Southeasterly low-level winds will help maintain a very
moist/unstable air mass over eastern CO this afternoon, with
dewpoints in the 60s and MLCAPE values of 2500+ J/kg. Present
indications are that thunderstorms will form off the Palmer Ridge by
mid-afternoon and spread eastward toward western KS this evening.
Forecast soundings show an environment favorable for supercell
structures. Very large hail, damaging winds, and a tornado or two
are possible. This activity may persist into the night, spreading
eastward across central KS.
After dark, persistent southeasterly low-level winds into the
foothills of central/southern CO will interact with an approaching
shortwave trough to pose the risk of continued re-development of
strong/severe storms, with very large hail possible.
...Southeast AZ...
Considerable low/mid level moisture are present today over parts of
southeast AZ and southwest NM, with dewpoints in the low 60s. Full
sunshine will result in scattered afternoon thunderstorms over the
higher terrain that will propagate westward during the evening.
Locally damaging wind gusts are possible.
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