355
ACUS01 KWNS 101921
SWODY1
SPC AC 101920

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0220 PM CDT Mon Aug 10 2026

Valid 102000Z - 111200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
CENTRAL AND EASTERN SOUTH DAKOTA INTO FAR SOUTHWESTERN MINNESOTA AND
NORTHWESTERN IOWA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE CENTRAL HIGH PLAINS TO THE MID ATLANTIC...AND PARTS OF SOUTHERN
ARIZONA...

...SUMMARY...
Damaging gusts will continue with a cluster of storms progressing
across the Mid Atlantic area this afternoon. Several other severe
wind/hail producing storms remain possible across the Ohio Valley. A
severe wind swath, with a few 75+ mph gusts is possible across
portions of the northern Plains into the Midwest tonight. A few
severe gusts may also occur this evening over central and southern
Arizona.

...20Z Update...
The main change made to this outlook was to upgrade portions of SD
into MN and IA to a Category 3/Enhanced risk, driven by 30
percent/CIG1 probabilities. Confidence is increasing that robust
supercell/multicellular development this evening will result in the
upscale growth of a cold-pool-driven MCS tonight. The best time for
the wind swath will be in the 03-09Z period. 8.5-9 C/km mid-level
lapse rates, and 40-50 kts of effective bulk shear (aligned normal
to forecast MCS orientation) will favor a swath of severe gusts from
at least central SD into northern IA tonight. There is some chance
that the wind swath may continue to the IA/IL/WI border by 12Z
Tuesday morning, hence the joining of the two Slight risk areas
along the MS River. Given such steep mid-level lapse rates, at least
a few 75+ mph gusts are possible, even if storms remain more
supercellular or multicellular. A few instances of 2+ inch diameter
hail may also occur with initial storms, and a tornado could develop
either with initial supercells, or line-embedded mesovortices should
a bow echo form. Severe wind/hail probabilities and CIG1 areas were
also expanded farther west across the central High Plains for the
possibility of a 2+ inch diameter hail instance or a 75+ mph gust
(given the aforementioned lapse rates/shear).

Additionally, 30 percent severe wind probabilities were expanded to
the East Coast ahead of an ongoing cold-pool-driven MCS, where
numerous wind damage reports continue to be received. Finally,
several other minor adjustments were made to the ongoing severe and
thunder probabilities to account for the latest observations and
guidance consensus.

..Squitieri.. 08/10/2026

.PREV DISCUSSION... /ISSUED 1100 AM CDT Mon Aug 10 2026/

...PA/NY/NJ...
Multiple clusters and lines of thunderstorms are ongoing this
morning from western PA.  So far, this activity has produced limited
severe wind gusts due to weak low-level lapse rates.  However,
continued heating over central/eastern PA will eventually allow the
storms to be more efficient wind-producers with locally damaging
gusts expected.  See MD #1894 for further details.

...OH/WV...
A secondary cluster of storms over central OH is tracking
southeastward in a moderately sheared environment.  Rapid heating is
occurring to the southwest of this cluster, which should result in
intensification by mid afternoon.  Storms will likely spread into
northern WV with a risk of damaging wind gusts and perhaps hail.

...SD/MN/IA...
A large reservoir of unstable air will reside across much of SD
today, with MLCAPE values over 3000 J/kg, steep lapse rates, and
dewpoints in the upper 60s.  A capping inversion should preclude
sustained convection until after 00z when strengthening southerly
low-level flow and warm advection will aid initiation.  Supercells
capable of large hail and damaging winds are expected, with eventual
upscale organization into a bowing MCS possible through the
evening/night.

...CO/KS...
Most model guidance shows the likelihood of scattered high-based
thunderstorm development late this afternoon over northeast CO,
spreading into northwest KS and southwest NE this evening.  Cloud
cover is somewhat limiting heating, but sufficient CAPE and winds
aloft may promote a period of damaging wind potential later today.

...AZ...
Another round of evening thunderstorms is expected to initiate off
the higher terrain of east-central AZ and spread westward toward the
TUS/PHX metro areas.  Parameters remain conditionally favorable for
damaging winds in any sustained/organized clusters of storms that
may develop.

$$