RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Sat Sep 12 2026
Valid 122000Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTH-CENTRAL 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 south-central Plains into the Ozarks this afternoon and
evening.
...20Z Update...
The SLGT Risk in the central/southern Plains was expanded
southwestward across parts of western OK. Here, visible satellite
imagery shows increasingly agitated boundary-layer cumulus and
isolated convective initiation along the western portion of a
remnant outflow boundary. Temperatures in the 102-104F range
along/south of the wind shift will support scattered severe wind
gusts with any clusters that evolve. Additionally, the 15-percent
hail probabilities were expanded westward into parts of southwest KS
and northwest OK. Given steep midlevel lapse rates accompanying an
EML (sampled by the 18Z DDC sounding), initial semi-discrete
supercells should pose a risk of scattered severe hail before
clustering occurs. Elsewhere, the previous forecast remains on track
and minimal changes were needed.
..Weinman.. 09/12/2026
.PREV DISCUSSION... /ISSUED 1135 AM CDT Sat Sep 12 2026/
...Central/Southern Plains to the Ozarks...
Scattered mainly elevated thunderstorms continue at midday across
the region, including the strongest/occasionally-severe storms
across southeast Nebraska into northeast Kansas that are occurring
near/just behind a southeastward-moving cold front. Some severe hail
will remain possible as these storms continue southeastward on the
edge of the primary instability reservoir.
This front, augmented by early day outflows, will otherwise serve as
a focus for more 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
Oklahoma/Texas Panhandles across southern Kansas and northern
Oklahoma. 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.
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
is expected from the eastern Oklahoma/Texas Panhandles into
southwest/south-central Kansas and northern Oklahoma, where a very
well-mixed boundary layer with steep low/mid-level lapse rates
will promote an environment that supports severe-caliber downdraft
winds. Some gusts could exceed 75 mph. A degree of storm clustering
could occur into this evening.
...Upper Ohio Valley...
A regional pocket of relatively cloud-free skies at midday will
contribute to filtered diurnal heating and moderate instability
across the region. Thunderstorms will further 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 develop.
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0212 PM CDT Sat Sep 12 2026
Valid 141200Z - 151200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
EASTERN NEBRASKA INTO WESTERN IOWA...
...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...
A mid-level trough will move across the northern Plains on Monday
with a strengthening 60-70 knot mid-level jet streak. The surface
pattern will feature a surface low across the Canadian Prairies and
a secondary weaker surface low across the central Plains. A moist
airmass will advect northward to the east of the surface trough with
mid to upper 60s dewpoints advecting into Nebraska and Iowa.
Thunderstorms will likely be ongoing at the beginning of the period
across eastern South Dakota and Minnesota amid moderate isentropic
ascent. The primary forecast concern for Monday will be northward
progression of the surface boundary across eastern Nebraska and
Iowa. Guidance varies with the northward recovery in the wake of
morning activity, but forecast soundings in regions where this
recovery does occur show a conditional supercell environment with
the threat for all severe weather hazards.
Given the influence of morning convection, the exact location of the
greatest threat will likely shift in the coming days. However, given
that most guidance showed a convective signal aligned with a
conditionally favorable supercell environment in the vicinity of
eastern Nebraska and western Iowa, added a small Slight Risk across
this region to account for this threat.
An elevated hail threat may persist into Monday evening farther
northeast given a strong low-level jet and moderate elevated
instability. Some surface based storm threat could continue into the
overnight hours along the boundary, but most guidance shows storms
north of the boundary during the overnight period.
Storms will likely form within the well-mixed environment across
eastern Colorado and western Kansas Monday afternoon. Weak shear
should limit storm organization, but strong heating and steep lapse
rates may support isolated severe wind gusts.
..Bentley.. 09/12/2026
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