526 
ACUS03 KWNS 131926
SWODY3
SPC AC 131925

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0225 PM CDT Sun Sep 13 2026

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
PLAINS TO THE GREAT LAKES...

...SUMMARY...
Scattered strong thunderstorms may impact a corridor south to
southwest of the Great Lakes through the lower Missouri Valley
Tuesday afternoon and evening, accompanied by at least some risk for
locally damaging wind gusts.

...Discussion...
A mid-level trough will move into Ontario on Tuesday with the
mid-level ridge building in its wake across the Midwest and into the
Upper Midwest. Beneath this ridge, a cold front will move slowly
southeastward from southern Iowa and northern Kansas at the
beginning of the period, to northern Oklahoma to central Missouri by
the end of the period. Dewpoints will increase into the low to mid
70s south of the front with weak to moderate instability
anticipated. Forcing will be somewhat nebulous given the rising
heights aloft and weak convergence along the slow-moving, decaying
front. 

Nonetheless, moderate to potentially strong instability and an
uncapped airmass should support some thunderstorms capable of severe
wind gusts. Some lingering 30 to 40 knot mid-level flow is forecast
to remain across portions of the warm sector Friday afternoon
(particularly across northern Illinois/Indiana) which may aid in
storm organization, but warm air aloft and a lack of clear supercell
mode should limit the overall hail threat.

..Bentley.. 09/13/2026

$$


File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS03/20260913T1926.txt



420 
ACUS03 KWNS 130705
SWODY3
SPC AC 130704

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0204 AM CDT Sun Sep 13 2026

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY
AFTERNOON INTO EVENING IN A CORRIDOR SOUTH/SOUTHWEST OF THE GREAT
LAKES THROUGH THE LOWER MISSOURI VALLEY...

...SUMMARY...
Scattered strong thunderstorms may impact a corridor south to
southwest of the Great Lakes through the lower Missouri Valley
Tuesday afternoon and evening, accompanied by at least some risk for
locally damaging wind gusts.

...Discussion...
A deamplifying mid-level short wave trough and associated surface
cyclone are forecast to continue an east-northeastward migration
through this period, generally across the remainder of northwestern
Ontario through much of northern Quebec by late Tuesday night.  In
the wake of the cyclone, an initial low-level baroclinic zone across
the lower Great Lakes region through the lower Missouri Valley and
central Great Plains may make some southward progression, before
stalling and perhaps retreating northward beneath the building
northwestern periphery of prominent ridging still centered across
the Southeast.  There is variance among the guidance concerning this
latter development, and the evolution of digging upstream mid-level
troughing across the northern Intermountain Region and Pacific
Coast.

...Southern Great Lakes through central Great Plains...
Mainly where mid-level heights remain suppressed, prior to the onset
of the mid-level height rises, coincident with daytime
boundary-layer destabilization along and southeast of the slow
moving frontal zone, a corridor of increasing, scattered
thunderstorm development appears possible through mid to late
Tuesday afternoon.  Steepening low-level lapse rates may support the
evolution of moderate mixed-layer CAPE on the order of 1000-2000+
J/kg, near the modest southern fringe of the mid-level westerlies,
which may still include speeds of 30+ kts in the 700-500 mb layer. 
A warm layer in mid/upper levels may tend to suppress large hail,
but thermodynamic profiles characterized by steep lapse rates of
potential wet-bulb temperatures in lower/mid-levels could contribute
to a few downbursts and developing cold pools with a few strong
gusts into Tuesday evening.

..Kerr.. 09/13/2026

$$


File: /home/ldm/var/data/BY_SOURCE/KWNS/ACUS03/20260913T0705.txt