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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SPC Sep 11, 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
0726 AM CDT Fri Sep 11 2026

Valid 111300Z - 121200Z

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

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

...Upper Midwest into the Central Plains...
Primary large-scale upper troughing will remain over central Canada
today, with an embedded mid-level shortwave trough forecast to eject
eastward over the northern Plains into the Upper Midwest through the
period. A modest surface response will occur across SD as the
shortwave trough ejects eastward, with most guidance suggesting a
sub-1000 mb low will develop into eastern SD by 12/00Z. A surface
cold front attendant to this low and the primary surface low over
central Canada will move east-southeastward across parts of the
Upper Midwest into the northern Plains, with a dryline extending
southward across the central Plains. A narrow corridor of 60s
surface dewpoints will be in place ahead of the cold front/dryline,
with diurnal heating aiding moderate destabilization along with
steepened mid-level lapse rates. Most guidance, including recent
NAM/RAP runs, show minimal MLCIN along/ahead of the front in far
northeast SD/western MN by 22-01Z. Convective development appears
likely in this time frame across this region, owing to sufficient
low-level convergence along the front coupled with forcing for
ascent associated with the mid-level shortwave trough.

Various NAM/RAP forecast soundings show strongly veering and
gradually strengthening winds with height through low/midlevels, 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. But, confidence in this scenario
occurring remains fairly low due to the mode transition expected.
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 MN into western WI by late this evening given the
narrow zone of destabilization forecast.

Convective initiation and overall thunderstorm coverage from
southeast SD/southwest MN into the central Plains are highly
uncertain and conditional this afternoon/evening, as the better
forcing for ascent with the shortwave trough will likely remain
across western/northern MN along and northeast of the surface low.
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. There is
some signal in model guidance for successful convective initiation
across southern NE into northern KS late this afternoon/evening
where hotter surface temperatures are forecast. The southern extent
of the Marginal Risk has been adjusted to account for this
possibility, and the Slight Risk has generally been confined to
where greater confidence exists in robust thunderstorm development
(far northeast SD into western/northern MN).

...Mid-South into the Tennessee Valley/Carolinas and Virginia...
Two weak mid-level perturbations are evident in water vapor
satellite imagery this morning across the Southeast: one over AR,
and the other along the central Gulf Coast. These features will
generally track east-northeastward through the day, and should aid
additional thunderstorm development this afternoon. A stalled
surface front extending from the ArkLaTex into the TN Valley and
northeastward to VA should also provide a focus for thunderstorms.
Current 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. But, modestly enhanced mid-level flow across parts of the
Mid-South and VA could promote loosely organized clusters with some
damaging wind threat as well.

..Gleason/Lyons.. 09/11/2026


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SPC Sep 11, 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
1226 AM CDT Fri Sep 11 2026

Valid 111200Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE UPPER
MISSISSIPPI VALLEY INTO THE MID MISSOURI VALLEY...

...SUMMARY...
Scattered severe thunderstorms capable of large hail, potentially in
excess of two inches, a few tornadoes, and damaging wind gusts are
expected over portions of the upper Mississippi Valley Friday
afternoon into night. Storm development is more uncertain with
southward extent into the central Plains, where a conditional risk
for mainly large hail and severe wind gusts exists late Friday
afternoon through evening. Isolated occurrences of damaging wind
gusts appear possible from the Mid-South into the Carolinas and
Virginia.

...Synopsis...

A low-amplitude short-wave trough moving onto the Pacific Northwest
coast late this evening will progress through the northern Rockies
before reaching the ND/SK/MB border region by Friday evening.
Meanwhile, a preceding, lower-latitude disturbance is forecast to
move through SD into MN on Friday with strengthening mid/upper-level
winds and modest height falls accompanying these perturbations over
the northern Plains into the upper MS Valley. Elsewhere, a vorticity
maximum/weak upper low will drift east from the Ozark Plateau into
the mid/lower MS Valley.

At the surface, an area of low pressure over western SD at 12Z
Friday is forecast to deepen slightly while developing into
northeast SD by afternoon, before subsequently weakening while
moving through central MN Friday night. The surface cyclone will
coincide with a cold front that will advance through the northern
Plains and the upper MS Valley. The trailing extension of the
boundary will move more slowly south into the mid MO Valley and
central High Plains. A dryline will precede the cold front with that
feature extending from eastern SD through central NE into western KS
by late afternoon. Elsewhere, a synoptic front modulated by
convective outflow is expected to stretch from the Mid-South into
the southern Mid-Atlantic on Friday afternoon.

...Upper Mississippi Valley into the mid Missouri Valley...

A low-level jet (LLJ) is forecast to strengthen through the day from
the mid MO Valley into the upper Midwest, enhancing the poleward
flux of an increasingly moist air mass ahead of the surface low and
attending frontal system. The moisture increase will occur beneath a
plume of steep mid-level lapse rates with MLCAPE increasing to
1500-2500+ J/kg by mid to late afternoon. Initial storm development
is expected at that time across portions of northern MN along or
ahead of the front, on the northern fringe of stronger capping.

Vertically veering wind profiles with 40-45 kt of deep-layer shear
will support supercells as the initial storm mode with the primary
hazard being large hail, some of which could exceed two inches. A
few tornadoes appear possible with any sustained supercells from
late afternoon into evening when the strengthening LLJ enhances
low-level shear with effective SRH increasing to 250-300 m2/s2.
Storms are expected to gradually grow upscale along the cold front
during the evening, at which point, the risk for damaging winds
should increase.

Severe weather potential becomes more conditional with southward
extent along the front and dryline in the mid MO Valley owing to
stronger capping and weaker height falls/forcing for ascent. The 00Z
models (convection-allowing and parameterized) indicate a relative
minimum in thunderstorm chances over eastern SD and southwest MN
with increasing probabilities from northeast NE into south-central
NE and north-central KS. Given surface-based storm initiation and
sustenance, CAPE-shear parameter space will favor supercells capable
of all hazards from eastern SD and southwest MN into northeast NE
and northwest IA, with generally a wind and hail threat farther
south along the NE-KS state line.

...Mid-South into the Carolinas and Virginia...

Areas of thunderstorms are expected to be ongoing at 12Z Friday from
the Ozark Plateau into the southern Mid-Atlantic. Stronger heating
on the southern fringe any lingering cloud cover will combine with
boundary-layer dewpoints in the low to mid 70s F to yield MLCAPE of
1500-3000 J/kg by afternoon. Aided by forcing for ascent associated
with the mid-level trough approaching the mid/lower MS Valley,
thunderstorms are expected to increase in coverage and intensity
through the afternoon along and ahead of the composite surface
boundary. Weak vertical shear will limit storm organization with
mainly pulse storms expected. Nonetheless, the presence steep
low-level lapse rates and abundant moisture will be supportive of
wet microbursts capable of locally damaging wind gusts.

..Mead/Halbert.. 09/11/2026


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SPC Sep 11, 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
0745 PM CDT Thu Sep 10 2026

Valid 110100Z - 111200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE SOUTHERN
TEXAS PANHANDLE INTO THE SOUTH PLAINS OF TEXAS...

...SUMMARY...
The threat for widely scattered large hail and a few severe wind
gusts is expected to continue through the remainder of the evening
into tonight over the southern Texas Panhandle into the South Plains
of Texas. Isolated damaging wind gusts appear possible over the
Mid-South and vicinity tonight.

...Texas Panhandle into the South Plains of Texas...

A cluster of strong to severe thunderstorms, including supercells,
is ongoing this evening between Amarillo and Lubbock amidst a
moderately unstable air mass with MLCAPE up to 1500 J/kg and
effective bulk shear of 40-50 kt, per the 00Z Amarillo sounding.
Hail in excess of two inches was reported earlier this evening near
Amarillo with a more recent wind gust of 65 mph near Plainview.
There is some signal in water vapor imagery for a weak disturbance
moving into the northern TX Panhandle, which may aid in sustaining
the ongoing storms through 03-05Z with a continued risk for large
hail and a few severe wind gusts.

...Mid-South...

Surface analysis indicates a convectively modified front from
west-central AR into middle TN, with a pocket of locally stronger
instability (i.e., MLCAPE up to 2000-2500 J/kg) near and to the
north of the boundary, per latest mesoanalysis. Forcing associated
with a subtle mid-level disturbance moving through south-central MO
is contributing to a gradual increase in storm coverage this evening
over far southeast MO into northeast AR. Time-lagged HRRR and RRFS
ensemble data suggest that a further increase in storm coverage is
possible late this evening into tonight over northern AR and
southeast MO into portions of northwest TN and western KY. Regional
VWPs indicate 0-6 km shear up to 30-35 kt, which may be sufficient
to support episodic storm organization with an associated risk for
isolated damaging wind gusts.

..Mead.. 09/11/2026


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