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

SPC Aug 12, 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
1130 AM CDT Wed Aug 12 2026

Valid 121630Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM ILLINOIS TO
KENTUCKY AND FROM THE NORTHERN HIGH PLAINS TO THE MID MISSOURI
VALLEY...

...SUMMARY...
Scattered severe thunderstorms with occasional wind damage are
possible this afternoon/evening from Illinois/Indiana into Kentucky.
Initial supercells with very large hail will be possible this
afternoon/evening across the central/northern High Plains. The
storms are expected to evolve into a cluster or two overnight while
spreading eastward across Nebraska/South Dakota with the potential
for severe outflow gusts.

...OH Valley area through this evening...
An MCS is ongoing across northern IL with the primary cold pool
surge and bowing segment progressing from northeast IL into
northwest IN. Elevated convection is ongoing in the zone of warm
advection atop the cold pool in IN. This elevated convection will
pose a threat for isolated large hail into this afternoon, while a
feed of steeper midlevel lapse rates and low-level moisture from the
west will help maintain the IL/IN MCS into this afternoon with a
continued threat for occasional wind damage with gusts of 60-75 mph.
The eastern extent of the severe threat into OH is uncertain given
the ongoing/elevated convection and limited recovery time. Thus,
the eastward extent of any wind threat associated with the ongoing
IL/IN MCS is likewise uncertain. Additional thunderstorm
development is possible this afternoon along the trailing outflow
from central IL into southern IN and KY, where occasional wind
damage will be possible into this evening.

...Northern Plains this afternoon through tonight...
A subtle midlevel speed max over southwest WY will progress eastward
around the northwest periphery of the southern Plains ridge. Weak
ascent preceding this wave, in combination with surface heating in
cloud breaks and low-level upslope flow with boundary-layer
dewpoints in the 60s, will support scattered afternoon/evening
thunderstorm development from northeast CO into western SD.
Lingering steep midlevel lapse rates on the fringe of the monsoonal
moisture plume in WY and effective bulk shear near or above 40 kt
(with long hodographs aloft) will favor supercells initially with
the potential for very large hail (2-3 inches in diameter). There
will likely be some upscale growth into a cluster or two this
evening into tonight on the nose of a 30-40 kt low-level jet across
NE/SD, with a transition to severe outflow gusts of 65-80 mph as the
main threat. The storm cluster(s) will likely reach western IA
early Thursday morning.

...Lower MI into western NY/PA through late evening...
Subtle speed maxima will move east-southeastward from Lower MI to
NY/PA through this evening. Midlevel lapse rates of 6-7 C/km and
boundary-layer dewpoints in the mid 60s will support MLCAPE near or
above 1000 J/kg, in an environment with sufficient deep-layer
shear/hodograph length for storms with supercell structures.
Isolated large hail and wind damage will be the main threats, though
a more discrete mode would be less favorable for wind damage, and
storm coverage could remain somewhat isolated. Thus, will maintain
a MRGL risk, though there was some consideration for an upgrade to
SLGT across western NY and vicinity.

...South GA/north FL this afternoon...
Scattered thunderstorm development appears probable from south GA
into north FL this afternoon along a subtle confluence zone with
large buoyancy immediately southwest of a remnant MCV over southeast
GA. A few multicell clusters will be capable of producing isolated
strong outflow gusts/wind damage with downbursts.

..Thompson/Chalmers.. 08/12/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TTzmTm