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
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