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

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0320 AM CDT Sun Sep 13 2026

Valid 161200Z - 211200Z

...DISCUSSION...
Latest medium-range model output indicates that the initially
prominent Southeastern mid-level ridge will slowly retrograde
west-southwestward and become increasingly suppressed across the
lower latitudes late this coming work week into next weekend. 
However, it appears that the evolving westerlies across the U.S.
will remain modest to weak, with little potential for appreciable
surface cyclogenesis.  While guidance suggests some continuing
potential for widely scattered strong thunderstorm development near
a lingering frontal zone across the Ohio into lower Missouri Valley
on Wednesday, it appears that this will diminish thereafter, with
generally negligible risk for organized severe thunderstorm
potential into and through next weekend.

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0159 AM CDT Sun Sep 13 2026

Valid 131200Z - 141200Z

...Synopsis...
A strong upper-level low with a 65-70 kt jet streak is expected to
progress eastward across the Pacific Northwest today, resulting in
widespread dry and windy conditions across portions of the Great
Basin into the Snake River Valley and far southwestern Montana. 

...Great Basin into portions of Idaho and Montana...
Dry and windy conditions owing to deep boundary layer mixing beneath
the strong upper low and associated jet streak will result in
widespread 15-20 MPH winds across much of the Great Basin during the
afternoon. From southern Nevada into far western Utah, relative
humidity could reach as low as 10-15% with southwesterly winds,
while the post-frontal airmass across northern Nevada will possess
westerly winds with 15-20% relative humidity. With ERCs approaching
the 80th annual percentiles, at least Elevated fire-weather
conditions are expected, and locally Critical conditions are
possible where terrain induced wind gusts are favored. Further north
into the Snake River Valley and portions of southwest Montana,
southwest winds of 20 MPH (with locally higher gusts) are
anticipated to overlap with relative humidity of around 15%. While
there appears to be a potential corridor for Critical fire-weather
concerns, they overlap with more modest fuels and a lower density
fuelscape.

..Halbert.. 09/13/2026

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