Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1247 AM CDT Thu Sep 17 2026

Valid 171200Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE INTERMOUNTAIN WEST AND IN THE CENTRAL HIGH PLAINS...

...SUMMARY...
Thunderstorms with isolated severe wind gusts and hail will be
possible in parts of the Intermountain West late this afternoon and
early this evening. A few strong gusts may also occur in parts of
the central High Plains.

...Intermountain West...
An upper-level low will move inland into the Intermountain West
today, as southwest flow remains at mid-levels over much of the
region. At the surface, a trough will deepen from southern Idaho
into western Utah. To the east of the trough, dewpoints in the 50s
F, will contribute to weak instability by afternoon. As surface
temperatures warm, thunderstorms will develop in the higher terrain.
RAP forecast soundings to the east of the trough at 00Z have 0-6 km
shear in the 30 to 40 knot range. In addition, low to mid-level
lapse rates are forecast to be in the 6.5 to 7.5 C/km range. This
environment will likely support an isolated threat for severe gusts
and hail. The threat should be concentrated during the late
afternoon and early evening, as cell coverage maximizes near the
instability axis.

...Central High Plains...
An upper-level ridge will move eastward today across the
north-central U.S, as a shortwave trough embedded in the ridge moves
through the central High Plains. At the surface, a warm front is
forecast to move slowly northward across southern and western
Nebraska this afternoon. An axis of moisture, with surface dewpoints
in the 60s and 70s F, will be oriented north of the front from the
mid Missouri Valley west-northwestward into the central High Plains.
During the late afternoon, scattered thunderstorms are expected to
develop near the shortwave trough, with storms moving gradually
northeastward across the central High Plains. Forecast soundings
near the area of greatest expected convective coverage have moderate
deep-layer shear suggesting an isolated severe threat will be
possible. However, lapse rates are forecast to be poor, which should
keep any severe threat marginal. If storms near the front can remain
nearly surface-based, then an isolated wind-damage threat could
develop, mainly during the early to mid evening, as low-level flow
increases.

..Broyles/Thornton.. 09/17/2026

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1230 AM CDT Thu Sep 17 2026

Valid 181200Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY INTO
FRIDAY NIGHT ACROSS PARTS OF THE NORTHERN INTERMOUNTAIN WEST...THE
CENTRAL GREAT PLAINS INTO SOUTHERN PORTIONS OF THE MIDDLE MISSOURI
VALLEY...AND PIEDMONT OF CAROLINAS INTO GEORGIA...

...SUMMARY...
Areas of scattered strong thunderstorm development posing at least
some risk for severe hail or wind appear possible across parts of
the northern Intermountain West into the central Great Plains and
southern middle Missouri Valley, and portions of the Carolina into
Georgia Piedmont Friday afternoon and evening.

...Discussion...
Latest model output continues to indicate that larger-scale
mid-level troughing, with a vigorous lead embedded short wave
impulse, will dig across the northern Atlantic Seaboard accompanied
by significant surface cyclogenesis near and east of the Canadian
Maritimes through this period. In the wake of the cyclone, it
appears that a cold front will continue advancing offshore and
through the southern Mid Atlantic Seaboard, before becoming
quasi-stationary beneath the northern periphery of persistent
mid-level ridging, across the lower Ohio through lower and middle
Missouri Valleys.

Upstream of the mid-level ridge, a mid-level trough and embedded low
are forecast to slowly progress across the Intermountain West
through Rockies vicinity, preceded by a couple of more subtle
perturbations migrating around the northwestern through northern
periphery of the ridge.

...Piedmont of Carolinas into Georgia...
Low-level lapse rates may become rather steep by Friday afternoon,
within pre-frontal surface troughing to the lee of the southern
Appalachians, where a relatively moist and mixed boundary-layer
might become characterized by CAPE on the order of 1000-2000 J/kg. 
Perhaps aided by forcing for ascent associated with a convectively
augmented perturbation, storms may increase off the higher terrain
and pose a risk for localized downbursts.  It appears possible that
activity could eventually consolidate into a southward/southwestward
propagating cluster, with the cold pool strengthening sufficiently
to maintain a risk for potentially damaging wind gusts into Friday
evening, despite the weakness of the ambient deep-layer mean flow.

...Northern Intermountain West and adjacent Rockies...
Beneath the leading edge of the cold core of the mid-level low, cool
thermodynamic profiles, with at least modestly steep mid-level lapse
rates, may contribute to scattered strong storms capable of
producing severe hail Friday afternoon, in the presence of strong
deep-layer shear and difluent mid/upper flow.

...Great Plains into middle Missouri Valley...
Convective potential remains uncertain, with the timing of the short
wave perturbations impacting the region unclear.  

The latest model output, including convection-allowing and related
guidance, suggest that forcing for ascent with a secondary impulse
may not begin to emerge from the Raton Mesa vicinity until Friday
evening.  However, the remnants of a very warm and deeply
mixed-boundary layer within the lee surface troughing may still be
conducive to a few strong downbursts near convection overspreading
southeastern Colorado through at least portions of western Kansas
before weakening later Friday night.

Closer to a weak frontal wave/warm frontal zone across parts of
eastern Nebraska into western Iowa and northwestern Missouri, a
corridor of moderate to large CAPE will contribute to an environment
conditionally supportive of organized strong thunderstorm
development.  However, forcing for ascent to support boundary-layer
based thunderstorms remains unclear through late Friday afternoon. 
By mid to late evening, if not earlier, warm advection along a
nocturnally strengthening boundary-layer jet, beneath an
increasingly divergent upper regime, may support an evolving
supercell structure and small upscale growing cluster.  This may
still occur mostly above a stable and/or stabilizing boundary-layer,
but the environment might still be conducive to the development of a
few strong surface gusts.  Relatively warm thermodynamic profiles
seem likely to minimize the risk for severe hail.

..Kerr.. 09/17/2026

Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1248 AM CDT Thu Sep 17 2026

Valid 171200Z - 181200Z

...Synopsis...
Expanding high pressure over the Southeast and central U.S will
contribute to widespread above normal temperatures and dry
conditions today. Meanwhile, an upper-level low will remain centered
over northern California/southern Oregon, sustaining strong
southwesterly flow over the Great Basin. 

...Southern Plains...
Strong surface heating and deep vertical mixing will contribute to
15-25% RH values and sustained southerly winds of 10-15 mph this
afternoon. These meteorological conditions will overlap an
exceptionally dry and receptive fuelscape in southwestern Oklahoma
and along the Red River Valley, supporting the introduction of
Elevated highlights.

...Great Basin...
South-southwesterly sustained surface winds of around 15 mph are
expected to evolve under an expanding 50 kt mid-level jet this
afternoon. A dry and well mixed boundary layer will promote RH
values of around 15% across central/northern NV and southern ID.
Consecutive days of dry and windy conditions have led to
increasingly more receptive fuels across the region, maintaining an
Elevated fire weather risk. 

...Central Idaho and Northeastern Oregon...
Isolated to scattered showers and thunderstorms are expected across
northern California, Oregon, and the Northern Rockies as the
upper-level low begins to pivot northeastward out of northern CA.
The primary driver of limited rainfall will be fast
north-northeastward storm motions of 30-40 mph, particularly on the
nose of the mid-level jet across the central ID mountains; however,
marginal fuels, and subsequent showers/thunderstorms on Day 2/Friday
and Day 3/Saturday as the low transitions into the Northern Rockies
should reduce holdover ignition concerns.

..Elizalde-Garcia.. 09/17/2026

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