SPC Aug 13, 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
1132 AM CDT Thu Aug 13 2026

Valid 131630Z - 141200Z

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

...SUMMARY...
Isolated to scattered severe thunderstorms are possible today from
parts of the southern/central High Plains to the Midwest. Severe
wind gusts should be the main threat, but some hail may also occur.

...Midwest including parts of eastern Iowa and Illinois/Indiana...
Supported by an MCV, a long-lived MCS continues to move
east-southeastward into west-central/northwest Illinois late this
morning. Greater stability initially precedes the MCS across
northern Illinois, but the remnant cluster and additional
redevelopment will likely tend to favor a more southeastward
progression in closer proximity to the front/instability gradient
that extends across Illinois/Indiana, with additional/renewed
development and intensification possible into the afternoon and
evening. Damaging wind gusts will be the primary severe hazard,
although a brief tornado and marginally severe hail are also
possible into this evening. While not certain, additional severe
redevelopment may also occur tonight farther west/northeastward
across areas potentially including eastern Iowa and northern/central
Illinois as a low-level jet nocturnally increases.

...Southern/Central High Plains...
High-based thunderstorms are expected to initially develop over the
higher terrain of the central Rockies/Front Range this afternoon,
with post-frontal low-level upslope flow persisting across the
central High Plains. Storm motions into slightly richer moisture
will favor some aggregation of outflow within a hot boundary layer
featuring steep lapse rates. Isolated to widely scattered severe
wind gusts 60-75 mph are possible, along with occasional hail with a
few of the stronger cores.

...Great Basin...
Modestly enhanced southwesterly mid-level flow will persist today
across the Great Basin downstream of a weak mid-level trough over
California. Weak to locally moderate instability is forecast via
diurnal heating. Scattered to numerous thunderstorms are expected
and some of the stronger evaporatively cooled downdrafts will be
capable of 60-75 mph gusts.

...Northeast...
Seasonably cool mid-level temperatures are forecast today across
parts of the Northeast, with a mid-level trough expected to move
east-southeastward from Quebec into New England. While instability
is forecast to remain fairly limited, strong west-northwesterly flow
aloft may support a risk for isolated damaging winds (50-65 mph)
with thunderstorms that develop and spread southeastward through the
afternoon. Isolated hail may also occur with the stronger cells.

..Guyer/Chalmers.. 08/13/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV0djf

SPC Aug 13, 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
0738 AM CDT Thu Aug 13 2026

Valid 131300Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL IOWA
INTO EAST-CENTRAL ILLINOIS...

...SUMMARY...
Isolated to scattered severe thunderstorms are possible today from
parts of the southern/central High Plains to the mid Mississippi and
lower Ohio Valleys. Severe gusts capable of wind damage should be
the main threat, but occasional hail may also occur.

...Iowa into Illinois/Indiana...
Radar mosaic/IR imagery loops show a long-lived MCS over central IA
moving east towards the MS River this morning. Widely scattered
severe gusts 60-70 mph are possible with the more intense bowing
structures and short-lived mesovortices embedded within the line,
along with a brief tornado risk (for short-term details, reference
MCD #1966). This activity will continue into IL but limited
confidence regarding its evolution and subsequent severe risk cast
uncertainty whether it will reinvigorate or additional strong/severe
storms will develop on the leading edge of outflow. Regardless, a
moist airmass across the eastern Corn Belt will destabilize amid a
veil of high clouds. Forecast model guidance shows 35-45 effective
shear supporting organized storms. Isolated to scattered damaging
gusts will be the primary severe hazard, although a brief tornado
and marginally severe hail are also possible through the early
evening.

...Southern/Central High Plains...
High-based thunderstorms are forecast to initially develop over the
higher terrain of the central Rockies/Front Range this afternoon,
with post-frontal low-level upslope flow persisting across the
central High Plains. Storm motions into slightly richer moisture
will favor some aggregation of outflow within a hot boundary layer
featuring steep lapse rates. Isolated to widely scattered severe
gusts 60-75 mph are possible, along with occasional hail with a few
of the stronger cores that develop. It seems possible a
smaller-scale area within this broad region may focus a slightly
more concentrated severe-wind threat. However, given the modest
large-scale forcing mechanisms and marginal deep-layer shear for
storm organization, will defer higher severe-wind probabilities for
the time being.

...Great Basin...
Modestly enhanced southwesterly mid-level flow will persist today
across the Great Basin downstream of a weak mid-level trough over
CA. Weak to locally moderate instability is forecast via diurnal
heating. Scattered to numerous thunderstorms are expected and some
of the stronger evaporatively cooled downdrafts will be capable of
60-75 mph gusts.

...Northeast...
Seasonably cool mid-level temperatures are forecast today across
parts of the Northeast, with a mid-level trough expected to move
east-southeastward from Quebec into New England. While instability
is forecast to remain fairly limited, strong west-northwesterly flow
aloft may support a risk for isolated damaging winds (50-65 mph)
with thunderstorms that develop and spread southeastward through the
afternoon. Isolated hail may also occur with the stronger cells.

..Smith/Kerr.. 08/13/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV0MVl

SPC Aug 13, 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
1258 AM CDT Thu Aug 13 2026

Valid 131200Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
IOWA INTO ILLINOIS...

...SUMMARY...
Isolated to scattered severe thunderstorms appear possible today
from parts of the southern/central High Plains to the mid
Mississippi and lower Ohio Valleys. Damaging winds should be the
main threat, but occasional hail may also occur.

...Iowa into Illinois/Indiana...
An MCV has developed early this morning with an ongoing cluster of
thunderstorms across central NE. This activity is expected to spread
eastward through the morning, and should be in the vicinity of
western/central IA by the start of the period. There is still
uncertainty regarding how intense this cluster will be due to the
presence of fairly substantial MLCIN downstream into IA. Even so,
warm/moist advection associated with a low-level jet over the
southern/central Plains and the presence of a rather moist/unstable
airmass into IA suggest some potential for an organized cluster to
pose a risk for scattered severe/damaging winds as it moves eastward
through the morning. A brief embedded tornado may also occur if
convection can remain surface based.

Even greater uncertainty exists this afternoon regarding potential
convective evolution, with most guidance showing the cluster
weakening as it moves into IN. Regardless, the airmass downstream
and to the south of outflow associated with the morning cluster will
destabilize through the day, and any additional thunderstorms that
form could pose at least an isolated threat for damaging winds and
perhaps some hail given the strong buoyancy forecast.

...Southern/Central High Plains...
High-based thunderstorms are forecast to initially develop over the
higher terrain of the central Rockies/Front Range this afternoon,
with post-frontal low-level upslope flow persisting across the
central High Plains. As this activity spreads east-northeastward and
encounters greater instability, consolidating outflows should
support some increase for isolated severe gusts given steepened
low-level lapse rates. Occasional hail may also occur with the
stronger cores that develop. Consideration was given to including
greater severe wind probabilities across eastern CO into parts of
KS, but modest deep-layer shear casts some doubt on overall
thunderstorm organization/intensity. A somewhat separate area of
thunderstorms may also develop farther south across the southern
High Plains in a very hot and well-mixed boundary layer. This
activity should also pose a threat for isolated severe gusts through
the afternoon.

...Great Basin...
Modestly enhanced southwesterly mid-level flow will persist today
across the Great Basin downstream of a weak mid-level trough over
CA. Weak to locally moderate instability is forecast to develop
through the afternoon as filtered diurnal heating occurs. Scattered
to numerous thunderstorms are expected to form and spread
northeastward across this destabilizing airmass, with strong to
severe gusts possible. Based on latest guidance trends (00Z HREF),
have expanded the Marginal Risk for severe/damaging winds to include
more of the Great Basin.

...Northeast...
Seasonably cool mid-level temperatures are forecast today across
parts of the Northeast, with a mid-level trough expected to move
east-southeastward from Quebec into New England. While instability
is forecast to remain fairly limited, strong west-northwesterly flow
aloft may support a risk for isolated damaging winds with
thunderstorms that develop and spread southeastward through the
afternoon. Isolated hail may also occur with the stronger cells.

..Gleason/Moore.. 08/13/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV04zd

SPC Aug 13, 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
0758 PM CDT Wed Aug 12 2026

Valid 130100Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS INTO WESTERN IOWA...

...SUMMARY...
Multiple supercells with large hail potential across the
northern/central High Plains should evolve into a bowing cluster
tonight while spreading eastward across Nebraska and eventually into
Iowa by early Thursday morning. This cluster will be capable of
producing scattered severe/damaging winds.

...Northern/Central Plains into Iowa...
A mix of clusters and supercells is ongoing this evening from far
northeast CO into western NE. The environment downstream into
central/eastern NE remains favorable to maintain severe convection
along/near a surface front. Large hail will remain possible with any
sustained supercells given 35-45+ kt of deep-layer shear, and
eventual upscale growth into a bowing cluster appears probable
tonight with modestly enhanced east-southeasterly low-level flow
providing an influx of warm/moist air. If this occurs, then the
threat for severe/damaging winds would increase across
central/eastern NE and perhaps eventually western IA, with isolated
gusts of 75+ mph possible. Severe probabilities have been adjusted
based on latest observational and short-term guidance trends.
Reference Mesoscale Discussion 1961 for more details regarding the
near-term severe threat across northeast CO/western NE.

...Mid Mississippi Valley into the Lower Ohio Valley...
Ongoing thunderstorm clusters across parts of the mid MS and lower
OH Valleys have mostly diminished in intensity as they have become
generally displaced south of the stronger mid-level flow across the
Midwest/Great Lakes. Even with the gradual weakening trend observed,
a couple of stronger clusters persist. Isolated damaging winds will
remain possible for a couple more hours this evening as this
activity spreads slowly southward.

...Northeast...
Loosely organized cells may continue to pose an isolated hail/gusty
wind threat for the next hour or two across southern NY and vicinity
along/near a surface front. The loss of daytime heating and gradual
decrease in instability should result in eventual weakening of
ongoing convection.

...Lower Colorado River Valley...
High-based thunderstorms which developed this afternoon in a hot and
well-mixed boundary layer across interior southern CA and western AZ
may remain capable of producing occasional severe gusts for a couple
more hours this evening.

..Gleason.. 08/13/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TTzw5k