Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1214 AM CDT Wed Aug 12 2026
Valid 121200Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE
NORTHERN/CENTRAL PLAINS TO THE LOWER OHIO VALLEY...
...SUMMARY...
Thunderstorms with severe gusts and hail will be possible this
afternoon and evening across parts of the central and northern High
Plains. Damaging gusts and isolated hail will also be possible
across parts of the Midwest and Ohio Valley.
...IA to OH Valley...
One or more MCSs migrating through enhanced northwesterly flow aloft
amid a very moist and unstable airmass is possible again today
across the Midwest toward TN. Most forecast guidance suggests an MCS
or thunderstorm clusters could be ongoing over IA at the start of
the period (12z), with warm advection storms arcing across parts of
IL/IN. The early day warm advection storms could develop southeast
across the OH Valley, while the IA MCS develop southeast across the
Mid-MS/Lower OH Valley through afternoon. The exact evolution of
convection that is not yet apparent is uncertain, and how outflow
may influence how this activity evolves through the afternoon.
Regardless, the overall environmental parameter space will be
favorable for a damaging wind and isolated hail risk through early
evening.
...Northern/Central Plains...
East/southeasterly low-level flow will maintain modest moisture
across the Dakotas, increasing with southward extent across NE into
northern KS. Near-60 F dewpoints will likely spread westward into
eastern CO/WY/MT. Modest moisture beneath steep midlevel lapse rates
and 30+ kt effective shear magnitudes will support scattered
thunderstorm development across the High Plains. Initial cells will
pose a large hail and damaging wind risk. It is unclear how
convection will evolve with eastward extent across the region as
outflow from prior convection may largely limit stronger
destabilization. A developing low-level jet during the nighttime
hours will be focused across the southern Plains toward KS/southern
NE. This could support some upscale growth potential, but confidence
is low.
...Lower MI into NY/PA/NJ...
A belt of stronger northwesterly flow aloft will extend from Lower
MI into NY/PA today. A seasonally moist/unstable airmass will be in
place. Vertically veering wind profiles will foster 35+ kt effective
shear magnitudes, while hodographs are fairly elongated. Midlevel
lapse rates will remain modest, with MLCAPE around 1000-1500 J/kg
expected. Isolated to widely scattered storms will pose a risk for
damaging gusts and small hail.
...TN Valley/Southeast...
Thunderstorms are expected to develop by midday within a very moist
and strongly unstable airmass. Deep-layer northwesterly flow will
remain weak, but steep low-level lapse rates and PW values near 2
inches could support isolated wet microbursts with stronger
multi-cell clusters.
..Leitman/Moore.. 08/12/2026
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