727
ACUS01 KWNS 171612
SWODY1
SPC AC 171610

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1110 AM CDT Thu Sep 17 2026

Valid 171630Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING OVER PARTS OF IDAHO/UTAH...AND A SMALL PART OF THE
CENTRAL HIGH PLAINS....

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

...ID/UT...
Morning water vapor imagery shows an upper low over northern CA,
with a band of strong flow aloft with associated embedded shortwave
troughs extending across NV into UT/ID. Strong heating across this
area will aid in the development of scattered thunderstorms from
southern ID into northern UT by mid-afternoon. Sufficient vertical
shear is present for rotating updrafts capable of large hail and
gusty/damaging winds. While coverage of storms will likely be
limited, one or two severe cells are expected later today - mainly
over the eastern Snake River Plain.

...CO/KS/NE...
The remnants of a weak tropical low are tracking northeastward
across the four-corners region this morning. Ample moisture and
weak ascent associated with this feature will lead to considerable
clouds and scattered thunderstorms today over the mountains of CO
and southern WY. This activity will spread eastward into eastern CO
and western NE/KS with high-based convection posing a risk of
locally damaging wind gusts. The extent of this severe threat will
be modulated by daytime heating, which is uncertain at this time due
to lingering cloud cover.

..Hart/Chalmers.. 09/17/2026

$$

206
ACUS02 KWNS 170533
SWODY2
SPC AC 170530

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

$$

466
ACUS03 KWNS 170740
SWODY3
SPC AC 170739

Day 3 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0239 AM CDT Thu Sep 17 2026

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SATURDAY INTO
SATURDAY EVENING ACROSS PARTS OF THE MIDDLE MISSISSIPPI VALLEY
THROUGH CENTRAL AND SOUTHERN GREAT PLAINS AND NEAR THE FRONT RANGE
OF THE ROCKIES...

CORRECTED FOR TYPOS

...SUMMARY...
Isolated to widely scattered strong storms posing some risk for
severe wind and hail are possible across parts of the middle
Mississippi Valley into central and southern Great Plains, and east
of the Front Range, Saturday afternoon and evening.

...Discussion...
The stronger westerlies will remain confined to the northern
mid-latitudes, with mid-level troughing forecast to dig across
Hudson Bay, Ontario and Quebec, downstream of broad ridging
overspreading the Canadian Prairies, and in the wake of a
significant cyclone migrating away from the Canadian Maritimes. In
response to these developments, it appears that cool surface ridging
will be maintained to the east of the southern Appalachians, while
the associated high center shifts off the northern Atlantic
Seaboard. Another modest high is forecast to begin shifting across
the central Canadian/U.S. border through much of the northern Great
Plains, Upper Midwest and adjacent upper Great Lakes by late
Saturday night.

This will be preceded by a notable cold front advancing slowly
southward into/across the Ohio and lower Missouri Valleys and
central Great Plains, beneath a weaker belt of westerlies across the
southern mid-latitudes. Within this regime, broad mid-level
troughing is forecast to continue a slow eastward progression across
the Rockies through central Great Plains, downstream of weak
troughing slowly approaching the California coast.

Mid-level ridging downstream of the lead trough will become
increasingly suppressed across the southeastern Great Plains through
lower to middle Mississippi Valley vicinity. A perturbation along
it southeastern periphery may continue slowly west-southwestward
across Florida and the northeastern Gulf Basin.

...Front Range vicinity into middle Mississippi Valley...
Generally warm thermodynamic profiles and modest to weak vertical
shear to the east of the Rockies will continue to limit the severe
weather potential, but isolated to widely scattered strong
thunderstorm development posing at least some risk for severe wind
and/or hail appears possible in a few evolving regimes Saturday into
Saturday night.

Convection with potential to produce strong surface gusts may be
supported by the evolution of a very warm and deeply mixed boundary
layer by late afternoon, within weak pre-frontal surface troughing
across parts of eastern New Mexico, the Texas South Plains and
Panhandle, and northwestern Oklahoma into southeastern Kansas.

Seasonably high moisture content and lift along the low-level
baroclinic zone across the lower Missouri/middle Mississippi Valleys
may support an upscale growing cluster or clusters of storms, which
could organize sufficiently to support a period or two of strong
surface gusts.

Although the mid-level cold core may tend to remain to the northwest
of the region through the period, cooling aloft across and southeast
of the Front Range, coupled with moistening southeasterly
near-surface flow, may still contribute to favorable thermodynamic
profiles for a few storms capable of producing severe hail and wind,
in the presence of modest shear late Saturday afternoon and evening.

..Kerr.. 09/17/2026

$$

603
ACUS48 KWNS 170850
SWOD48
SPC AC 170848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Thu Sep 17 2026

Valid 201200Z - 251200Z

...DISCUSSION...
The latest ECENS and GEFS appear similar in their depiction of the
evolving mid/upper flow late this weekend through the middle of next
week. A weak mid-level trough and embedded low emerging from the
Intermountain West may weaken further while slowly progressing
across the central Great Plains through Ohio Valley, to the south of
a transient building mid-level high near the central Canadian/U.S.
border into the upper Great Lakes/northwestern Ontario vicinity.
Toward the middle to latter part of next week, remnant mid-level
troughing may tend to dig into and across the Mid Atlantic, as
mid-level ridging builds again across the Great Plains/Mississippi
Valley, downstream of a weak mid-level perturbation progressing into
the Southwest, and amplifying troughing within the stronger
westerlies offshore of the Pacific coast.

In association with this evolving regime, generally weak deep-layer
mean wind fields and increasingly limited potential for stronger
destabilization are likely to minimize the risk for severe weather.

..Kerr.. 09/17/2026