ACUS02 KWNS 140458
SWODY2
SPC AC 140456

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1156 PM CDT Sun Sep 13 2026

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY
AFTERNOON AND EVENING IN A CORRIDOR SOUTH/SOUTHWEST OF THE GREAT
LAKES THROUGH PORTIONS OF THE CENTRAL GREAT PLAINS...

...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...
Latest model output appears in better agreement concerning digging
mid-level troughing along the Pacific coast through this period,
downstream of a still notable mid-level high centered across the
northern mid-latitude eastern Pacific.  Coincident with this
upstream amplification, initially prominent mid-level ridging
centered over the Southeast is forecast to build northwestward
across much of the northern Great Plains through Great Lakes region.
As this occurs, a deamplifying short wave trough and associated
surface cyclone are forecast to continue an east-northeastward
migration across the remainder of northwestern Ontario through much
of northern Quebec by late Tuesday night.  

It appears that a cold front trailing the cyclone will gradually
overtake a preceding low-level baroclinic zone, reinforced by
considerable ongoing convection and initially slowly advancing
across and southeast of the southern Lower Michigan through southern
Iowa and northern Kansas vicinity at 12Z Tuesday.  A gradual
southward progression into the Ohio Valley and across the lower
Missouri Valley may proceed Tuesday into Tuesday night, beneath the
building mid-level ridge. 

...Southern Great Lakes through central Great Plains...
Particularly from portions of the southern Great Lakes region into
the lower Missouri Valley, it appears that the southward progression
of the convective outflow reinforced boundary will be initially slow
enough to allow for substantive destabilization in close proximity
to the modest southern fringe of the westerlies.  With surface dew
points increasing to near 70 F, steepening low-level lapse rates
with insolation may support the development of moderate mixed-layer
CAPE on the order of 2000 J/kg.  Although mid/upper heights may be
tending to slowly rise, it appears that mid-level inhibition may
remain weak enough to allow for the initiation of increasing,
scattered thunderstorm development through the mid to late
afternoon.  Warm profiles, in general (if not a developing warm
layer aloft), may tend to suppress large hail, but thermodynamic
profiles characterized by steep lapse rates of potential wet-bulb
temperature in lower/mid-levels could contribute to a few downbursts
and developing cold pools with a few strong gusts into Tuesday
evening.

..Kerr.. 09/14/2026

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