SPC Aug 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
0748 PM CDT Tue Aug 11 2026

Valid 120100Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE DAKOTAS AND NORTHERN NEBRASKA...AND FROM NORTHERN ILLINOIS TO
WESTERN NORTH CAROLINA...

...SUMMARY...
Severe storms posing a risk for large hail and damaging winds are
possible into tonight from the Dakotas into the Midwest.

...IL to western NC...

A bowing line of storms from central KY into northeast TN/western VA
will continue to develop southeast the next few hours. A damaging
wind risk will continue with this activity in the short term.
However, convection should begin to wane with southeast extent into
the Appalachians as instability wanes and loss of daytime heating
results in a cooling boundary layer. Convection across KY and
perhaps portions of eastern TN may remain stronger into the evening
given the large reservoir of instability ahead of storms, but
overall expected is for a gradual weakening trend. Reference MCD
1939 for more short term details.

Overnight, most CAMs guidance suggests convection will redevelop
within a warm advection regime across parts of northern IL into IN
and the Ohio Valley. The 00z DVN and ILX RAOBs depict an impressive
thermodynamic and kinematic environment. Midlevel lapse rates near 8
C/km amid 40 kt effective shear and MUCAPE near 5000 J/kg with weak
inhibition suggests any storms developing within this environment
could be severe. Convection may develop along the instability
gradient and large hail is possible. If sufficient clustering
occurs, damaging wind also could be possible. As a result, the
Slight (level 2 of 5) risk as been expanded back to the northwest
across northern IL.

...Dakotas into IA...

Supercells across the western Dakotas and far northern NE will
continue to pose a risk for very large hail and damaging gusts the
next few hours. See MCD 1938 for short term information on severe
risk.

It is uncertain how convection will evolve longer-term during the
overnight hours. Some guidance suggests clustering will occur and an
MCS could develop, moving east/southeast across SD/northern NE and
perhaps as far east as IA. Ample west/northwesterly flow aloft is in
place, along with a very moist airmass with strong to extreme
instability. If sufficient clustering can occur, MCS
development/maintenance seems plausible. have expanded the Slight
(level 2 of 5) risk eastward across SD/NE into western IA border
vicinity for this possibility.

..Leitman.. 08/12/2026


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SPC Aug 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
1111 AM CDT Tue Aug 11 2026

Valid 111630Z - 121200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO EARLY TONIGHT FROM EASTERN ILLINOIS ACROSS PARTS OF THE OHIO
VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN PLAINS...AND FROM EASTERN ILLINOIS TO VIRGINIA AND NORTH
CAROLINA...

...SUMMARY...
Severe thunderstorms with damaging wind gusts will occur today from
the northern Indiana into parts of the Ohio Valley and central
Appalachians. Areas of severe wind gusts and hail will also be
possible over parts of the northern Plains.

...IL/IN/OH...
A fast moving and intense bowing MCS is affecting the Chicago metro
area this morning with significant severe wind gusts. This activity
will race east-southeastward across northern IN and eventually
western OH. Increasingly widespread thunderstorms and associated
outflow ahead of this complex lends uncertainty to the evolution of
the bow, and the corridor of greatest damaging wind potential.
Refer to MDs #1921 and #1922 for further details.

...OH/WV/KY/VA...
Another linear MCS is affecting southeast OH, and will spread across
WV and into VA later today. The air mass ahead of this complex is
not as unstable, and considerable uncertainty exists regarding this
system's longevity. Nevertheless, sufficient flow aloft and
mesoscale organization will maintain a risk of damaging wind gusts.
Refer to MD #1923 for further details.

...ND/SD/NE...
Moderately strong westerly flow aloft is present today across the
Dakotas, with a moist and unstable air mass in place over the Black
Hills region. This will likely lead to widely scattered
thunderstorm development by early evening. Supercells capable of
large hail and damaging winds are expected. It is unclear how far
southeast these storms will maintain intensity, but model guidance
suggests at least into central SD before weakening overnight.

..Hart/Weinman.. 08/11/2026


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SPC Aug 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 Tue Aug 11 2026

Valid 111300Z - 121200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHERN
ILLINOIS INTO THE OHIO VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN PLAINS...AND FROM EASTERN IOWA TO VIRGINIA AND NORTH
CAROLINA...

...SUMMARY...
Severe thunderstorms with damaging wind gusts will be possible today
from the eastern Iowa/northern Illinois vicinity into parts of the
Ohio Valley and central Appalachians. Areas of severe wind gusts
and hail will also be possible over parts of the northern Plains.

...IA to the Mid-Atlantic and Southeast...
An uncertain and inherently complex forecast is apparent this
morning from IA east-southeastward into the central Appalachians.
An impulse embedded within west-northwest flow and an overnight MCV
moving into IA from NE appear to be aiding in MCS development this
morning over eastern IA, with this thunderstorm complex moving into
northern IL through the late morning.

While the exact evolution of a potential severe MCS moving across
the Midwest is uncertain, a possible scenario is the thunderstorm
activity over IA either merges with additional storms developing
ahead of it or it continues to intensify into the main severe-wind
producing MCS. Another severe cluster is located over eastern IN
within the eastern envelope of the EML. Considered higher wind
probabilities to be delineated this outlook update, but it remains
unclear regarding sequential details that would lead to a
high-confidence mesoscale corridor of severe wind and associated
wind damage. Nonetheless, environmental parameters (e.g., very rich
moisture, steep 700-500 mb lapse rates, adequate deep-layer shear)
will strongly favor the development of mature/severe linear
clusters/bows with the more intense storms that eventually evolve
today. This activity will likely move along a large CAPE gradient
that will likely be reinforced by early morning convection.
Scattered severe gusts (60-85 mph) will be likely in the favored
mesoscale corridors with swaths of concentrated wind damage. A
lower but appreciable severe risk may extend into VA and NC with a
lower severe threat with south extent into SC/GA.

...Northern Plains...
East/southeasterly flow along the surface trough is forecast to
maintain 60s F dewpoints across the western Dakotas and parts of NE
this afternoon. Steep midlevel lapse rates atop the relatively
moist boundary layer, and strong heating will support a corridor of
moderate to strong instability across the western Dakotas.
Scattered storms are expected by early evening amid supercell wind
profiles. Elongated hodographs favorable for splitting cells with
an accompanying risk for large to very large hail are forecast.
Isolated severe gusts also could occur. Given the lack of a
stronger low-level jet during the nighttime hours, it appears
unlikely that upscale growth will occur, and convection is expected
to wane with eastward extent overnight.

...Mojave Desert of CA...
Early morning radar imagery shows an MCV moving slowly northwest
over the lower CO River Valley and this feature is likely associated
with a weak disturbance moving northwest into southern CA. The
airmass across the desert will undergo strong heating in wake of
early day cloud debris. Another likely convectively augmented
mid-level impulse will move across southern AZ towards southern CA
today. Widely scattered thunderstorms are forecast to develop this
afternoon amid a seasonably moist airmass and an inverted-V
thermodynamic profile is depicted in forecast soundings. Isolated
severe gusts are possible with the more intense downdrafts.

..Smith/Kerr.. 08/11/2026


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SPC Aug 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
1200 AM CDT Tue Aug 11 2026

Valid 111200Z - 121200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
ILLINOIS INTO THE OHIO VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN PLAINS...AND FROM IOWA TO VIRGINIA...

...SUMMARY...
Severe thunderstorms with damaging wind gusts will be possible today
from the eastern Iowa/northern Illinois vicinity into parts of the
Ohio Valley and central Appalachians. Areas of severe wind gusts and
hail will also be possible over parts of the northern Plains.

...IA to the Mid-Atlantic...

A complex forecast scenario is expected today from IA into the Ohio
Valley and adjacent Appalachia. More than one MCS may be ongoing at
the beginning of the period. The first across IA/southern MN, and
one further southeast across parts of the Midwest (exact location is
uncertain, but most likely IN/OH). Possible early day convection
across IN/OH will spread east/southeast across the Ohio Valley
during the morning posing risk for strong gusts. This activity is
likely to emerge across Appalachia, and eventually VA and the
broader Mid-Atlantic during the afternoon/evening. How much
destabilization will occur across VA and the Mid-Atlantic remains
uncertain given prior convection the previous day and potential
convective debris across the region. Some damaging wind potential
could materialize if sufficient destabilization occurs during the
afternoon.

The anticipated MCS over IA/southern MN early in the forecast period
is then expected to continue east/southeast across the Midwest,
fueled by a very moist and strongly unstable boundary layer.
Midlevel flow is forecast to be quite strong (by August standards),
with forecast guidance suggesting 700 mb greater than 60 kt
spreading across the Midwest through evening. While the exact
evolution of a potential severe MCS moving across the Midwest is
uncertain, it is possible the morning activity over IA will develop
southeast along outflow across the Ohio Valley. Given the strong
kinematic field and ample instability, if a well organized MCS is
maintained from IA southeast into the OH Valley, a swath of damaging
gusts (some 75+ mph) will be possible.

...Northern Plains...

East/southeasterly flow along the surface trough is forecast to
maintain 60s F dewpoints across the western Dakotas and parts of NE
this afternoon. Steep midlevel lapse rates atop the relatively moist
boundary layer, and strong heating will support a corridor of
moderate to strong instability across the western Dakotas. Scattered
storms are expected by early evening amid supercell wind profiles.
Elongated hodographs favorable for splitting cells with an
accompanying risk for large to very large hail are forecast.
Isolated severe gusts also could occur. Given a lack of stronger
low-level jet during the nighttime hours, it appears unlikely that
upscale growth will occur, and convection is expected to wane with
eastward extent overnight.

..Leitman/Moore.. 08/11/2026


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