SPC Sep 12, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Sat Sep 12 2026

Valid 121300Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL/SOUTHERN PLAINS...

...SUMMARY...
Isolated to scattered severe thunderstorms capable of producing
large to very large hail and severe/damaging winds may occur across
parts of the central/southern Plains into the Ozarks this afternoon
and evening.

...Central/Southern Plains into the Ozarks...
Mainly elevated thunderstorms have persisted overnight into the
early morning across southern NE into eastern KS/western MO, aided
by a modest low-level jet. This activity will probably tend to
weaken through the remainder of the morning, but some recent
guidance suggests additional thunderstorms developing along its
outflow across southern KS/northern OK over the next few hours. If
this development occurs, it would potentially complicate
destabilization and severe potential later today. Recent surface
observations also show a fairly strong cold front draped from
eastern CO into KS and northwest MO. This boundary will likely serve
as a focus for robust thunderstorm development this
afternoon/evening as well. With a rather moist low-level airmass
forecast to be present along/south of the front, current
expectations are for a narrow zone of moderate to strong instability
(MLCAPE 2000-3500 J/kg) to develop this afternoon from the eastern
OK/TX Panhandles into southern KS/northern OK. Weak low-level winds
will veer to west-northwesterly and strengthen some with height
through mid/upper levels, supporting around 30-40 kt of deep-layer
shear and updraft organization. While large-scale ascent will remain
fairly weak/nebulous across the southern/central Plains, most
guidance shows at least isolated robust thunderstorm development
along the front by 21-23Z as convective temperatures are reached.

While there is still uncertainty regarding convective evolution and
persistence of ongoing thunderstorms this morning, some signal
exists in most recent short-term guidance that isolated to scattered
convection will form along much of the length of the front later
today in a rather favorable environment to support severe
thunderstorms. Any sustained supercells would pose a threat for
large to very large hail, with steep mid-level lapse rates and ample
instability in the hail-growth zone supporting potential for 2+ inch
diameter hail on an isolated basis. Somewhat higher-based convection
also appears probable from the eastern OK/TX Panhandles into parts
of southwest/south-central KS and northern OK, where a very
well-mixed boundary layer with steep low/mid-level lapse rates
should promote an environment that supports scattered severe
downdraft winds. Some gusts could exceed 75 mph. The potential for
clustering this afternoon and evening remains unclear, but some
chance for at least isolated severe/damaging winds may persist into
much of OK and the Ozarks, dependent on upstream convective
evolution in KS/western MO.

...Upper Ohio Valley...
A narrow corridor of filtered diurnal heating and related moderate
instability should develop across parts of the upper OH Valley this
afternoon between denser clouds and precipitation occurring across
OH, and a stationary boundary to the east. Thunderstorms will
gradually increase in coverage and intensity through the afternoon,
aided by forcing for ascent associated with an approaching weak
mid-level shortwave trough. While mid-level lapse rates will remain
poor, sufficient deep-layer shear coupled with modest steepening of
low-level lapse rates suggest some risk for occasional damaging
winds with any loosely organized clusters/line segments that can
form.

..Gleason/Lyons.. 09/12/2026


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SPC Sep 12, 2026 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


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


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SPC Sep 12, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0728 PM CDT Fri Sep 11 2026

Valid 120100Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER FAR EASTERN
SOUTH DAKOTA INTO PORTIONS OF MINNESOTA...

...SUMMARY...
Widely scattered severe thunderstorms capable of producing large
hail up to two inches, damaging winds, and a couple of tornadoes
will continue through the remainder of the evening into tonight from
far eastern South Dakota into portions of Minnesota. Isolated
occurrences of severe wind gusts and large hail remain possible over
parts of the central Plains tonight.

...Upper Mississippi Valley into the central Plains...

A broken band of thunderstorms has recently developed from far
eastern SD into north-central MN within a relatively narrow
instability axis preceding a surface cold front and dryline. The
presence of steep mid-level lapse rates (per 00Z ABR sounding) atop
boundary-layer dewpoints in the mid to upper 60s F is resulting in
MLCAPE up to 1500-2000 J/kg. As mentioned above, the corridor of
stronger instability and minimal capping is rather narrow
longitudinally, which suggests the severe weather threat may remain
somewhat limited spatially into tonight.

The KFSD VWP is likely indicative of the ambient kinematic
environment, which features 35-40 kt of deep-layer shear and
relatively strong low-level shear, supportive of a supercell storm
mode with the primary hazard being large hail up to two inches.
Tornado potential will be conditional on the maintenance of
semi-discrete supercells residing within the narrow axis of minimal
convective inhibition. Damaging wind potential may tend to increase
by late evening as thunderstorms evolve into line segments.

Additional storms appear possible late this evening into tonight
ahead of a southeastward-moving cold front over portions of eastern
and central NE. Similar to locations to the north, a relatively
narrow zone of minimal convective inhibition and moderate
instability exists ahead of the front, which leads to uncertainty in
the areal coverage and duration of the threat. Severe wind gusts
will be the primary hazard with any surface-based storms that can
become established, though isolated occurrences of large hail are
also possible.

..Mead.. 09/12/2026


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SPC Sep 11, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1127 AM CDT Fri Sep 11 2026

Valid 111630Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
MIDWEST...

...SUMMARY...
Scattered severe thunderstorms capable of producing large hail,
(some 2+ inches), damaging winds, and a couple of tornadoes are
expected late this afternoon and tonight across parts of the Upper
Midwest. Thunderstorm development is more uncertain farther south
into the central Plains, where a risk for large hail and severe
gusts may exist late this afternoon into the evening.

...Upper Midwest/central Plains...
An eastward-progressive belt of quasi-zonal westerlies exists over
the northern half of the CONUS, to the south of upper troughing over
the Canadian Prairies/central Canada, and the east of the amplifying
upper trough off the coastal Pacific Northwest. Weak frontal wave
development will occur from eastern South Dakota into Minnesota as a
cold front spreads eastward, with the front eventually overtaking a
pre-frontal trough/dryline across the central Plains.

A narrow corridor of 60s F surface dewpoints are in place ahead of
the cold front/dryline, with diurnal heating aiding moderate
destabilization along with steepened mid-level lapse rates. Minimal
MLCIN is expected along/ahead of the front in far northeast South
Dakota/western Minnesota into/just after peaking heating. Convective
development appears likely in this time frame across this region,
especially across Minnesota, owing to sufficient low-level
convergence along the front coupled with forcing for ascent
associated with the mid-level shortwave trough.

Strongly veering and gradually strengthening winds with height
through low/mid-levels, and 35-45 kt of deep-layer shear will easily
support organized convection. Initial supercells should pose a
threat for large hail (isolated 2+ inches possible), but convective
mode will probably trend towards clustering fairly quickly given the
presence of the cold front and strengthening low-level jet this
evening. Any supercells that can remain at least semi-discrete into
the early evening may also have a tornado threat with greater
low-level shear forecast in this time frame. Scattered
severe/damaging winds should occur with any clusters or bowing line
segments that can develop and spread eastward through the evening.
However, the wind threat will likely wane with eastward extent
across Minnesota into western Wisconsin by late this evening given
the narrow zone of destabilization forecast.

Farther southwest, convective initiation and overall thunderstorm
coverage from southeast South Dakota/southwest Minnesota
southwestward into Nebraska and northern Kansas are more uncertain
and probably more limited/conditional late this afternoon and
evening, as the better forcing for ascent with the shortwave trough
will remain regionally focused to the north. Still, a favorable
thermodynamic environment and sufficient (25-35 kt) deep-layer shear
would conditionally support severe hail/wind with any thunderstorms
that can develop and be sustained.

...Mid-South/Tennessee Valley/Carolinas and Virginia...
Multiple convectively augmented mid-level perturbations remain
evident at midday in satellite/radar imagery, including over the
Ozarks as well as the middle Gulf Coast in vicinity of southern
Alabama. A stalled surface front extending from the ArkLaTex
east-northeastward into the Tennessee Valley and Virginia will
provide a focus for thunderstorms. Generally speaking, expectations
are for generally disorganized/pulse-type convection to pose a
threat for occasional damaging winds as diurnal heating destabilizes
the boundary layer and steepens low-level lapse rates. However, a
modest enhancement to mid-level flow across parts of the Mid-South
(25 kt mid-levels per Little Rock AR WSR-88D VWP), as well as
Virginia, could promote a couple of loosely organized clusters with
a bit more of a focused damaging wind threat.

..Guyer/Weinman.. 09/11/2026


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