Day 3 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0159 AM CDT Wed Sep 09 2026

Valid 111200Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MID-MISSOURI VALLEY INTO THE UPPER MIDWEST...

CORRECTED FOR GENERAL THUNDERSTORM LINES

...SUMMARY...
Severe thunderstorms are possible across portions of the Upper
Midwest late Friday afternoon into Friday night.

...Upper Midwest into Nebraska...

An upper shortwave trough will move across the northern Plains and
Upper Midwest on Friday. This will result in enhanced westerly flow
and cooling aloft across the region, mainly after 00z. A surface
cold front is forecast to develop southeast across the Dakotas
through the afternoon, and continue east/southeast across the Upper
Midwest and portions of the central Plains through the nighttime
hours. Southerly low-level flow will transport 60s dewpoints
northward across the MO Valley into MN ahead of the front. Northward
advection of low-level moisture beneath cooling aloft/steepening
midlevel lapse rates will lead to at least a narrow corridor of
moderate destabilization during the late afternoon into evening from
central/eastern NE into MN. Stronger large-scale ascent and vertical
shear will be focused across MN. With southward extent, instability
may be greater, but shear and large-scale ascent will be weaker.
Additionally, warmer midlevel temperatures may persist further
south, resulting in capping and a more conditional severe risk.
Large hail and damaging gusts appear to be the predominant hazard
with storms from late Friday afternoon into the nighttime hours.

..Leitman.. 09/09/2026

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0227 AM CDT Wed Sep 09 2026

Valid 121200Z - 171200Z

...DISCUSSION...
...Day 4/Sat - Central Plains...

A cold front will stall across the central Plains on Saturday.
Low-level east/southeasterly flow will maintain rich boundary layer
moisture across KS and into eastern CO. Early day convection may be
ongoing in the vicinity of the stalled boundary within the low-level
warm advection regime. It is uncertain if airmass recovery and
renewed thunderstorm development will occur within the unstable warm
sector given nebulous large-scale ascent and modest vertical shear.
While low severe potential may eventually evolve, probability
appears less than 15 percent at this time.

...Days 5-6/Sun-Mon -- Central Plains to the Great Lakes...

An upper trough is forecast to move from the northern Rockies to the
Great Lakes through early Day 7/Tuesday. This will bring enhanced
southwesterly flow to portions of the northern/central Plains into
the Great Lakes, particularly on Monday. With the approach of the
trough, lee low development is forecast across the northern/central
High Plains on Sunday. Increasing southerly low-level flow will
transport moisture northward to NE/SD ahead of a
southeastward-advancing cold front. This could support some severe
risk across parts of the northern/central Plains and Mid-MO Valley
vicinity on Sunday. However, large spread exists among forecast
guidance with regards to the surface low placement, northward extent
of moisture return, and frontal position. As a result, corridors of
greater severe potential are uncertain on Sunday.

As the upper trough continues to lift east/northeast through the
Great Lakes on Monday, severe potential could develop eastward into
parts of the Mid/Upper MS Valley and upper Great Lakes vicinity.
Stronger deep-layer flow may become displaced to the north of better
instability, and similarly large model spread continues into this
time frame. Depending on trends, severe probabilities could
eventually be needed for Sunday and/or Monday.

...Days 7-8/Tue-Wed...

Lower amplitude, quasi-zonal flow is expected to develop by the end
of the forecast period as the early-week uppers shortwave trough
lifts into eastern Canada and the sub-tropical high begins to
rebuild over the southern U.S. This should largely limit severe
potential, though abundant moisture will reside from the southern
Plains into the Southeast and Mid-Atlantic and daily sporadic strong
storms could still occur.