ACUS02 KWNS 110501
SWODY2
SPC AC 110500

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1200 AM CDT Fri Sep 11 2026

Valid 121200Z - 131200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE SATURDAY
AFTERNOON AND EVENING ACROSS PARTS SOUTHEASTERN
NEBRASKA...SOUTHWESTERN IOWA...NORTHEASTERN KANSAS AND MUCH OF
NORTHWESTERN INTO CENTRAL MISSOURI...

...SUMMARY...
Isolated severe storms, and perhaps at least a small organizing
cluster of storms, appear possible across parts of the lower
Missouri Valley late Saturday afternoon into Saturday night.

...Discussion...
Downstream of a blocking mid-level high, which will likely be
maintained to the southeast of the Aleutians through this period,
models indicate that another vigorous digging short wave trough will
contribute to lower/mid-tropospheric cyclogenesis offshore of the
Pacific Northwest, before slowly pivoting inland Saturday through
Saturday night.  Farther east, it appears that attempts at building
ridging across the northern Rockies into adjacent Great Plains will
be suppressed by a digging short wave trough across the central
Canadian/U.S. border vicinity, within the southwestern periphery of
larger-scale troughing east of the Canadian Prairies through the
Canadian Maritimes.

By 12Z Saturday, perhaps the strongest short wave perturbation
within the eastern Canadian troughing is forecast to be in the
process of digging near the southwestern shores of Hudson Bay.  As
this feature turns eastward during the day, renewed cyclogenesis is
forecast to the southeast of the primary surface cyclone, across
northern Quebec.  A cold front trailing to the southwest may advance
across much of the upper Great Lakes, Upper Midwest and northern
Great Plains by late Saturday night, preceded by a weaker cool
surge, perhaps reinforced by convective outflow, across the lower
Missouri Valley and central Great Plains.

It does appear that southern mid- to subtropical latitude ridging
will remain prominent across much of the central/southern Great
Plains through Southeast into early Sunday.  Within and near the
northern periphery of this feature, a weak perturbation initially
migrating east of the  mid/lower Mississippi Valley is forecast to
become increasingly sheared across the Appalachians through Northeast.

...Parts of central Great Plains/lower Missouri Valley...
Stronger warm sector low-level wind fields and forcing for ascent
are generally forecast to remain in closer proximity to the primary
and secondary surface cyclones, to the Canadian side of the
international border through this period.  However, in the wake of
the shearing perturbation to the east of the Mississippi Valley,
models continue to suggest that forcing for ascent aided by
lower/mid-tropospheric warm, beneath a difluent regime near/just
south of the mid-level westerlies, may provide a focus for strong
thunderstorm development Saturday through Saturday night.  

By early Saturday, it appears that this may set up across the lower
Missouri Valley vicinity, where a zone of stronger differential
surface heating may evolve by late Saturday afternoon.  Seasonably
high boundary-layer moisture near the interface of the stronger
heating, beneath a plume of elevated mixed-layer air, may support a
corridor of large mixed-layer CAPE on the order of 2000-3000+ J/kg. 
Coinciding with at least modest deep-layer shear, aided by
pronounced veering of winds with height in lower to mid-levels, this
regime may become conducive to the development of isolated to widely
scattered supercells.  It is possible that stronger activity
persisting into Saturday evening could grow upscale into an
organizing southeastward propagating cluster, near the nose of a
modestly strengthening southwesterly nocturnal boundary-layer jet.  


Due to substantive continuing spread within and among the various
model output, including the latest available convection-allowing
guidance, severe probabilities have been maintained at 5 percent. 
However, this could still change in later outlooks for this period.

..Kerr.. 09/11/2026

$$
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