Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1226 AM CDT Fri Sep 11 2026

Valid 111200Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE UPPER
MISSISSIPPI VALLEY INTO THE MID MISSOURI VALLEY...

...SUMMARY...
Scattered severe thunderstorms capable of large hail, potentially in
excess of two inches, a few tornadoes, and damaging wind gusts are
expected over portions of the upper Mississippi Valley Friday
afternoon into night. Storm development is more uncertain with
southward extent into the central Plains, where a conditional risk
for mainly large hail and severe wind gusts exists late Friday
afternoon through evening. Isolated occurrences of damaging wind
gusts appear possible from the Mid-South into the Carolinas and
Virginia.

...Synopsis...

A low-amplitude short-wave trough moving onto the Pacific Northwest
coast late this evening will progress through the northern Rockies
before reaching the ND/SK/MB border region by Friday evening.
Meanwhile, a preceding, lower-latitude disturbance is forecast to
move through SD into MN on Friday with strengthening mid/upper-level
winds and modest height falls accompanying these perturbations over
the northern Plains into the upper MS Valley. Elsewhere, a vorticity
maximum/weak upper low will drift east from the Ozark Plateau into
the mid/lower MS Valley. 

At the surface, an area of low pressure over western SD at 12Z
Friday is forecast to deepen slightly while developing into
northeast SD by afternoon, before subsequently weakening while
moving through central MN Friday night. The surface cyclone will
coincide with a cold front that will advance through the northern
Plains and the upper MS Valley. The trailing extension of the
boundary will move more slowly south into the mid MO Valley and
central High Plains. A dryline will precede the cold front with that
feature extending from eastern SD through central NE into western KS
by late afternoon. Elsewhere, a synoptic front modulated by
convective outflow is expected to stretch from the Mid-South into
the southern Mid-Atlantic on Friday afternoon.  


...Upper Mississippi Valley into the mid Missouri Valley...

A low-level jet (LLJ) is forecast to strengthen through the day from
the mid MO Valley into the upper Midwest, enhancing the poleward
flux of an increasingly moist air mass ahead of the surface low and
attending frontal system. The moisture increase will occur beneath a
plume of steep mid-level lapse rates with MLCAPE increasing to
1500-2500+ J/kg by mid to late afternoon. Initial storm development
is expected at that time across portions of northern MN along or
ahead of the front, on the northern fringe of stronger capping. 

Vertically veering wind profiles with 40-45 kt of deep-layer shear
will support supercells as the initial storm mode with the primary
hazard being large hail, some of which could exceed two inches. A
few tornadoes appear possible with any sustained supercells from
late afternoon into evening when the strengthening LLJ enhances
low-level shear with effective SRH increasing to 250-300 m2/s2.
Storms are expected to gradually grow upscale along the cold front
during the evening, at which point, the risk for damaging winds
should increase.  

Severe weather potential becomes more conditional with southward
extent along the front and dryline in the mid MO Valley owing to
stronger capping and weaker height falls/forcing for ascent. The 00Z
models (convection-allowing and parameterized) indicate a relative
minimum in thunderstorm chances over eastern SD and southwest MN
with increasing probabilities from northeast NE into south-central
NE and north-central KS. Given surface-based storm initiation and
sustenance, CAPE-shear parameter space will favor supercells capable
of all hazards from eastern SD and southwest MN into northeast NE
and northwest IA, with generally a wind and hail threat farther
south along the NE-KS state line.


...Mid-South into the Carolinas and Virginia...

Areas of thunderstorms are expected to be ongoing at 12Z Friday from
the Ozark Plateau into the southern Mid-Atlantic. Stronger heating
on the southern fringe any lingering cloud cover will combine with
boundary-layer dewpoints in the low to mid 70s F to yield MLCAPE of
1500-3000 J/kg by afternoon. Aided by forcing for ascent associated
with the mid-level trough approaching the mid/lower MS Valley,
thunderstorms are expected to increase in coverage and intensity
through the afternoon along and ahead of the composite surface
boundary. Weak vertical shear will limit storm organization with
mainly pulse storms expected. Nonetheless, the presence steep
low-level lapse rates and abundant moisture will be supportive of
wet microbursts capable of locally damaging wind gusts.

..Mead/Halbert.. 09/11/2026

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

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0203 AM CDT Fri Sep 11 2026

Valid 111200Z - 121200Z

...CRITICAL FIRE WEATHER AREA FOR WESTERN NEBRASKA INTO SOUTHWESTERN
SOUTH DAKOTA...

...Synopsis...
A mid-level shortwave trough embedded within westerly flow over the
northern Rockies will aid in the development of a surface cyclone
across the Northern Great Plains, bringing dry and windy conditions
to portions of eastern Wyoming, Nebraska, and South Dakota today.
Critical fire-weather conditions are forecast across portions of
southeastern Wyoming and western Nebraska into southwestern South
Dakota as the surface low and subsequent cold front progress towards
the east.

...Eastern Wyoming into western Nebraska and southwestern South
Dakota...
From late morning into early afternoon, the surface low over western
and central South Dakota is forecast to deepen and progress
eastward. Prefrontal strong westerly downslope winds of 20-25 MPH
are forecast with relative humidity of 15-20%, and postfrontal winds
of roughly the same magnitude will be out of the north-northwest by
mid-to-late afternoon. The dry and windy conditions will overlap
with fuels that are critically receptive to wildfire ignition and
spread, warranting the introduction of Critical highlights. Fuel
receptiveness drops off fairly rapidly with eastward extent, so
highlights were confined to where the meteorological and fuel
conditions best overlap. 

Further west into eastern Wyoming, winds will remain around 20 MPH
but relative humidity should remain above 25%. Fuel receptiveness
extends well into eastern Wyoming, so if forecast updates come in
windier and dryer, there could be an extension of the Critical
highlights westward.

..Halbert.. 09/11/2026

...Please see www.spc.noaa.gov/fire for graphic product...