SPC Sep 16, 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
1253 AM CDT Wed Sep 16 2026

Valid 161200Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER NORTHERN
UTAH AND EASTERN PARTS OF THE OHIO VALLEY...

...SUMMARY...
A couple of strong to severe thunderstorms appear possible across
northern Utah and eastern parts of the Ohio Valley today.

...Synopsis...
A mid-level anticyclone will prevail over the southern Plains to the
TN Valley as a stationary upper trough morphs into a cut-off upper
low along the West Coast today. Multiple mid-level impulses will
pivot around the anticyclone and overspread the Midwest to OH
Valley, supporting occasional rounds of showers and thunderstorms.
Given rich low-level moisture along the northern periphery of the
mid-level anticyclone, a couple of strong to severe storms may
occur. A few strong to severe storms may also occur over portions of
northern UT as a pronounced mid-level impulse rotates around the
developing West Coast upper low, resulting in overlapping cooler
temperatures and stronger flow aloft.

...Northern UT...
As the aforementioned impulse pivots around the evolving upper low,
a 50+ kt 500 mb jet streak and corresponding 7 C/km mid-level lapse
rates will overspread northern UT during the day. Surface heating
will be limited given widespread cloud cover. Nonetheless, forecast
soundings suggest that surface temperatures near 70 F may yield
MLCAPE as high as 1500 J/kg given steep tropospheric lapse rates.
Furthermore, stronger winds aloft that gradually veer with height
will yield around 50 kts of effective bulk shear and elongated
hodographs with some low-level curvature. Multicells and perhaps
embedded supercells should be the primary storm mode, capable of
isolated instances of severe wind and/or hail.

...Midwest into the OH Valley...
Multiple rounds of showers and thunderstorms will be ongoing at the
start of the period (12Z Wednesday) and will continue through the
period (to 12Z Thursday). Some intensification of storms may occur
over OH and immediate surrounding areas with one weak impulse by
afternoon peak heating. Assuming some appreciable insolation can
occur, surface temperatures may rise through the 80s F, amid 70s F
dewpoints, contributing to 1500-2500 J/kg MLCAPE. Given meager
vertical wind shear, mainly pulse cellular and multicellular storms
are expected. The stronger storm cores may produce wet downbursts,
accompanied by an isolated damaging gust threat.

Another mid-level impulse will traverse the Midwest overnight, with
several CAM guidance members supporting nocturnal convective
initiation over IA in the 03-12Z period. At the moment, the
evolution of this convection is uncertain, so no severe
probabilities have been added. However, should more established
convection develop overnight, an instance of marginally severe hail
cannot be completely ruled out.

..Squitieri/Supinie.. 09/16/2026


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SPC Sep 16, 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
0759 PM CDT Tue Sep 15 2026

Valid 160100Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
WESTERN TEXAS AND NORTHWESTERN OKLAHOMA TO THE SOUTHERN GREAT
LAKES...

...SUMMARY...
A couple of severe thunderstorms, accompanied by a severe wind and
hail threat, remain possible this evening across the southern High
Plains to the southern Great Lakes.

...Synopsis...
A broad upper ridge remains in place across the central and eastern
CONUS, with a low-amplitude trough currently located over the
Pacific Northwest. Ahead of the upper trough, a 500 mb jet streak,
accompanying a mid-level impulse, is currently overspreading the
Upper MS Valley. As a result, weak surface troughing and northward
low-level moisture advection are supporting a band scattered
thunderstorms along the west-northwestern periphery of the upper
ridge. Stronger flow aloft glancing the upper ridge periphery, amid
moderate buoyancy, will support a few strong to severe thunderstorms
for a few more hours, from the southern High Plains to the Lower
Great Lakes.

...Southern High Plains...
Pulse cellular and multicellular clusters, with a history of severe
gusts, continue to traverse a mixed boundary layer, characterized by
low to mid 90s F surface temperatures. Despite the persistent warm
temperatures, nocturnal cooling should eventually reduce severe gust
potential. In the meantime, 1500+ J/kg DCAPE will promote adequate
evaporative cooling potential with the stronger storm cores to
support a short-duration severe gust threat.

...Northwestern OK to the southern Great Lakes...
Scattered to widespread thunderstorms remain in progress along the
west-northwest periphery of the upper ridge. Given the 500 mb jet
streak over the Upper MS Valley, 30-40 kts of effective bulk shear
is overspreading the upper ridge periphery, especially over northern
MO, where the strongest storms are currently located. 1000-2000 J/kg
MLCAPE overlapping the aforementioned shear will continue to promote
multicellular clusters and a couple of supercells, accompanied by a
severe wind and hail threat for at least a few more hours.

..Squitieri.. 09/16/2026


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SPC Sep 15, 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
1117 AM CDT Tue Sep 15 2026

Valid 151630Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING ACROSS PARTS OF THE CENTRAL PLAINS AND MIDWEST....

...SUMMARY...
Strong to locally severe thunderstorms may occur from the
south-central Plains into parts of the Midwest this afternoon and
evening, with at least isolated damaging wind gusts possible.

...Central Plains into Midwest...
Moderately fast zonal flow remains across the northern US today,
with the primary surface boundary extending from the TX Panhandle
east-northeastward into parts of KS/MO/IL. This boundary will be
enhanced by daytime differential heating, and will provide the focus
for scattered thunderstorms along its length. Most of this activity
will be relatively disorganized, but in an environment of moderate
CAPE and steep low-level lapse rates favorable for occasional
strong/severe downdrafts.

One area of greater concern extends across northern MO into
west-central IL. Morning CAM solutions suggest higher confidence in
storm coverage in this area, and forecast soundings show sufficient
deep-layer shear for organized multicell or occasional supercell
structures. However, much of this activity may occur on the north
side of the baroclinic zone with slightly weaker support for intense
downburst winds. Warm temperatures aloft should limit hail concern.
Therefore, have opted to maintain the MRGL risk category and
re-evaluate at the 20z update.

..Hart/Chalmers.. 09/15/2026


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SPC Sep 15, 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
0728 AM CDT Tue Sep 15 2026

Valid 151300Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN/CENTRAL PLAINS INTO THE MIDWEST...

...SUMMARY...
Strong to locally severe thunderstorms may occur from the
south-central Plains into parts of the Midwest this afternoon and
evening, with at least isolated damaging wind gusts possible.

...Southern/Central Plains into the Midwest/Great Lakes...
The primary mid/upper-level trough over central/eastern Canada will
remain displaced well north of the surface warm sector today, with
upper ridging remaining anchored over the Southeast. A surface cold
front will make generally slow south-southeastward progress over the
central Plains and mid MS Valley/Midwest through this evening,
before eventually stalling late in the period. A seasonably moist
airmass characterized by surface dewpoints in the 60s to low 70s
will be in place ahead of the front from the southern High Plains
northeastward to the southern Great Lakes vicinity. While lapse
rates aloft will remain modest, daytime heating will support the
development of moderate instability by mid afternoon along much of
the length of the front (perhaps locally stronger across parts of
eastern KS into MO/IL).

Enhanced mid-level flow will tend to remain north of the cold front,
but some veering and gradual strengthening of the wind field with
height through mid levels should support sufficient deep-layer shear
for modest updraft organization, especially from parts of the
central Plains into the Midwest. Current expectations are for
thunderstorms to gradually develop by 20-23Z along/near much of the
length of the front as convective temperatures are reached. Loosely
organized clusters capable of producing mainly damaging winds should
be the primary concern as this convection spreads generally
east-northeastward through the evening, especially where low-level
lapse rates can become steepened. This appears more likely across
parts of the southern/central Plains where stronger heating is
forecast. Some chance for marginal supercell structures may exist
from parts of eastern KS into MO this afternoon, with isolated hail
possible. Considered greater wind probabilities and a Slight Risk
across this region, but potential for an organized cluster remains
too uncertain for an upgrade with this update.

...Southwest/Four Corners...
A rather moist low-level airmass (surface dewpoints generally in the
50s) will remain across parts of the Four Corners region today.
Modestly enhanced west-southwesterly mid-level flow will persist
from UT into western CO ahead of a mid/upper-level trough over the
Pacific Northwest. While occasional strong thunderstorms appear
possible, modest heating and overall weak destabilization are
currently expected to limit the magnitude of the severe threat.
Small hail and gusty winds could accompany the strongest cores, but
confidence in organized severe thunderstorms remains too low to
include any hail/wind probabilities at this time.

..Gleason/Mead.. 09/15/2026


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