Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1224 AM CDT Sat Sep 12 2026

Valid 121200Z - 131200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL AND SOUTHERN PLAINS...OZARK PLATEAU...AND UPPER OHIO
VALLEY...

...SUMMARY...
Widely scattered severe storms capable of large hail up to two
inches and damaging wind gusts appear possible over portions of the
central and southern Plains into the Ozark Plateau on Saturday into
Saturday night. Isolated occurrences of damaging wind gusts may also
occur over portions of the upper Ohio Valley Saturday afternoon.

...Synopsis...

A belt of enhanced mid/upper-level flow will persist over the
north-central U.S., downstream from a vigorous upper low moving into
the Pacific Northwest. Meanwhile, a lower-latitude trough over the
lower OH and lower MS Valleys Saturday morning is forecast to weaken
while progressing through the OH and TN Valleys. At the surface, a
cold front will advance through the upper Great Lakes with the
trailing extension of the boundary pushing south through the lower
MO Valley and central Plains before linking with a surface low over
the southern High Plains.


...Central and Southern Plains into the Ozark Plateau...

Persistent capping across the pre-frontal warm sector and generally
weak forcing for ascent lead to considerable uncertainty in
thunderstorm evolution through the forecast period. A number of the
00Z models (both convection-allowing and parameterized) indicate
areas of thunderstorms ongoing at 12Z Saturday over the central
Plains within a zone of modest warm advection and moisture transport
associated with a weakening low-level jet. One possible scenario is
for the continued southeast movement of the early-day storms through
eastern KS and southwest MO into portions of OK and AR by afternoon,
where a hot and moderate to strongly unstable air mass (i.e., MLCAPE
up to 2000-3000 J/kg) is forecast to develop. The instability
combined with around 30 kt of deep-layer shear would support
organized cold pool development in that scenario with an associated
risk for damaging wind gusts and large hail.

Renewed storm development appears possible from late morning into
afternoon from north of the front in south-central and southeast NE
to along or ahead of the front in northeast KS. Up to 40 kt of
deep-layer shear will coincide with the northern extension of the
stronger instability mentioned above to support supercell storm
modes with an associated risk for large hail up to two inches and
damaging wind gusts.  

A separate thunderstorm regime may also evolve by mid to late
afternoon over the eastern OK and TX Panhandles into western OK in
the vicinity of the surface low and southward-sagging front.
Forecast soundings indicate a deep, well-mixed boundary layer, which
will be supportive of a few severe wind gusts and isolated large
hail.

Confidence in any of the above scenarios/regimes remains too low to
include Slight Risk wind and hail probabilities with this forecast.
A categorical upgrade is possible in subsequent Day 1 outlooks once
finer-scale details become more clear.


...Upper Ohio Valley...

A spatially narrow corridor of stronger heating and resultant
instability (MLCAPE up to 1500-2000 J/kg) is forecast to develop
during the afternoon between denser clouds and precipitation to the
west, and a backdoor front/stationary boundary to the east.
Thunderstorms are expected to increase in coverage and intensity
through the afternoon within the instability axis, aided by
increased forcing for ascent associated with the approaching
mid-level trough. While mid-level lapse rates are expected to remain
relatively weak, deep-layer shear increasing to 30-35 kt coupled
with steepening low-level lapse rates suggests the potential for
some storm organization with the primary hazard being damaging wind
gusts. Backed low-level winds in the vicinity of the surface front
will boost low-level shear slightly and a brief tornado cannot be
ruled out as mature storms approach the frontal zone from the west.

..Mead/Halbert.. 09/12/2026

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1209 AM CDT Sat Sep 12 2026

Valid 131200Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON
AND EVENING IN A CORRIDOR FROM WESTERN NEW ENGLAND THROUGH THE UPPER
OHIO VALLEY...

...SUMMARY...
Scattered strong storms accompanied by small to marginally severe
hail and potential for locally damaging wind gusts may impact parts
of the Northeast through upper Ohio Valley Sunday afternoon and
evening.

...Discussion...
Latest model output suggests that the initially notable mid-level
low inland of the Pacific Northwest coast by 12Z Sunday may be
slower to devolve into an open short wave trough.  However, it still
is forecast to remain progressive, slowly accelerating northeastward
across the northern U.S. Rockies, in advance of a short wave impulse
digging toward the northwestern Canadian Prairies.  Within the
downstream westerlies, models indicate that short wave ridging will
build across much of the northern U.S. Great Plains through Upper
Midwest, and adjacent portions of the southeastern Canadian Prairies
through northwestern Ontario, while downstream troughing digs across
Quebec and the lower Great Lakes region into Northeast.

It appears that the primary surface cyclone associated with eastern
troughing may migrate from northern Quebec into the Labrador Sea by
late Sunday night.  However, another surface low may begin to
form/consolidate near/northeast of coastal northern New England,
with a trailing cold advancing southeast of the lower Great Lakes
region into the northern Atlantic Seaboard through Allegheny Plateau
by the end of the period.  Westward through the Ohio and middle
Mississippi Valleys into the central Great Plains, it appears that
this front may stall south of the stronger westerlies, with a cool
surface high maintaining influence across much of the northern into
central Great Plains until it centers shifts east of the upper
Mississippi Valley late Sunday night.

...Parts of western New England into the Ohio Valley...
In the wake of a sheared mid-level perturbation shifting across and
east of the northern and middle Atlantic Seaboard during the day,
low-level convergence and destabilization ahead of the main cold
front advancing to the southeast of the lower Great Lakes region
remains unclear.  However, both HREF and REFS calibrated
thunderstorm guidance suggest at least widely scattered thunderstorm
development is probable by or shortly after peak heating Sunday,
from the lee of the lower Great Lakes through the upper Ohio Valley.
It is possible that this may coincide with sufficient strengthening
of westerly flow in the 700-500 mb layer to support modestly
organizing thunderstorm activity with potential to produce
marginally severe hail and localized damaging wind gusts, before
weakening Sunday evening.

...North central Great Plains/Middle Missouri Valley vicinity...
Latest model output continues to exhibit substantive spread
concerning convective potential across the region through this
period.  It now appears probable that at least a shallow relatively
cool/stable boundary layer will remain entrenched as far south and
west as Kansas into the northern high plains, beneath warming
elevated mixed-layer air advecting north-northeast of the higher
terrain.  Forcing for ascent downstream of the approaching mid-level
low/trough may support increasing thunderstorm development across
the Dakotas Sunday night.  However, based on forecast soundings,
this may be rooted within/above the elevated mixed-layer, with weak
CAPE limiting potential for severe hail.

..Kerr.. 09/12/2026

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0214 AM CDT Sat Sep 12 2026

Valid 141200Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE MONDAY INTO
 MONDAY NIGHT ACROSS PARTS OF THE CENTRAL GREAT PLAINS INTO UPPER
MIDWEST...

...SUMMARY...
Strong thunderstorm development, accompanied by at least some risk
for severe weather, appears possible across parts of the central
Great Plains into Upper Midwest late Monday through Monday night.

...Discussion...
Downstream of weak mid/upper troughing continuing to slowly dig
across the Pacific coast, models indicate that mid/upper ridging
(centered across the Southeast) may become increasingly prominent
across the southern Great Plains into the lower Great Lakes and
northern Mid Atlantic Seaboard through this period.  To the north of
this ridging, and in advance of a short wave impulse digging through
the Canadian Prairies, a notable remnant mid-level cyclonic
circulation is forecast to accelerate more rapidly east-northeast of
the northern U.S. Rockies, across the international border into
northwestern Ontario by late Monday night.  It appears that this
will be accompanied by modest surface cyclogenesis, and considerable
strengthening of south to southwesterly lower/mid-tropospheric wind
fields across much of the northern U.S. Great Plains through Upper
Midwest/Great Lakes region.

While an associated increase in vertical shear will contribute to an
environment conditionally supportive of organized severe weather
potential, destabilization within the warm sector remains much more
uncertain.  There does remain a general consensus among the various
model output that a northward retreating near-surface baroclinic
zone may provide the primary focus for stronger convective
development, generally near the southern fringe of the westerlies,
from parts of eastern Nebraska northeastward toward the Upper
Midwest.  However, even if the maintenance of a relatively cold,
stable boundary layer along this zone, as depicted in the latest NAM
forecast soundings, is too extreme, it remains unclear the extent to
which thermodynamic profiles will become conducive to the risk for
severe weather.

..Kerr.. 09/12/2026