ACUS01 KWNS 092000
SWODY1
SPC AC 091959

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Aug 09 2026

Valid 092000Z - 101200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE MIDWEST INTO THE OHIO VALLEY...

...SUMMARY...
Scattered damaging winds are possible today into this evening from
southern Wisconsin eastward across parts of northern Illinois,
southern Lower Michigan, northwest Ohio, and northern Indiana. 
Damaging wind and hail may also occur across portions of the Dakotas
tonight.

...20Z Update...
The main changes made to the outlook were to remove the Slight Risk
and more broadly expand Marginal Risk severe probabilities across
the central/northern Plains. CAM guidance has shown appreciable
uncertainty regarding storm coverage in this region, and trends in
model output continue to show sparse coverage. Nonetheless,
widespread 2000+ J/kg MLCAPE amid 50+ kts of effective bulk shear
may support a couple of severe multicells or supercells should any
storms manage to become sustained this afternoon or evening. The
Slight Risk along/south of the Great Lakes was expanded slightly
eastward into northern OH to account for some boundary layer
destabilization ahead of an approaching MCS, where a few damaging
gusts are possible.

Otherwise, the previous forecast remains on track, with only minor
changes made to the severe/thunder probabilities to account for the
latest observations and guidance consensus.

..Squitieri.. 08/09/2026

.PREV DISCUSSION... /ISSUED 1056 AM CDT Sun Aug 09 2026/

...Midwest...
A persistent cluster of thunderstorms over southern WI appears
likely to continue southeastward through much of the day into parts
of IL/MI/IN and eventually OH.  This activity will track near a
NW-SE oriented baroclinic zone, with dewpoints in the lower 70s to
the south.  Eventually, low-level lapse rates will become
sufficiently steep to support damaging wind gusts along the leading
edge of the storms.  Later tonight, strengthening southwesterly
low-level winds will enhance warm advection and lift over parts of
IL/IN, potentially leading to another round of strong/severe storms
capable of damaging winds and hail after 06z.  

...Dakotas...
12z model guidance continues to decrease the confidence in overnight
severe storms, with some CAM solutions showing no thunderstorms. 
Therefore have made the SLGT area smaller and focused where there is
highest confidence in isolated storms.  Forecast soundings continue
to indicate steep mid-level lapse rates and strong deep shear,
providing a conditional risk of supercells if convection can be
sustained.

...AZ...
Thunderstorms are once again predicted to form along the Rim and
track westward toward the PHX metro area this evening.  The strength
of the steering flow, instability, and mid-level moisture all appear
favorable for a severe risk.  However, mesoscale details of the
evolution of the storms over high terrain will dictate the eventual
risk.

$$


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