004
ACUS02 KWNS 181732
SWODY2
SPC AC 181730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Tue Aug 18 2026

Valid 191200Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEDNESDAY INTO
WEDNESDAY NIGHT ACROSS MUCH OF SOUTHERN MISSOURI...PARTS OF SOUTHERN
ILLINOIS...WESTERN KENTUCKY AND TENNESSEE AND NORTHERN ARKANSAS...

...SUMMARY...
One or two organized clusters of thunderstorms with potential to
produce swaths of damaging surface gusts appear possible across
parts of the Ozark Plateau into Mid South, and perhaps central and
southeastern Arizona, Wednesday through Wednesday night.

...Discussion...
An initially notable cyclone to the southwest of Hudson Bay is
forecast to weaken, with its broadening mid-level circulation
redeveloping across and east of southern Hudson/James Bays through
this period.  To the south of this feature, broad cyclonic mid-level
flow will overspread much of the Upper Midwest/Great Lakes and Ohio
Valley through Northeast, downstream of initially building mid-level
ridging across the Pacific Northwest through northern Rockies, to
the north of a prominent mid-level high slowly shifting
northeastward toward the Four Corners region.

Beneath a plume of elevated mixed-layer now advecting along the
southern fringe of the westerlies, across the central Great Plains,
toward the Mid South, a lower-level baroclinic zone, likely
reinforced by convective outflow, may be in the process of advancing
southward across the Mid South/Ozark Plateau and south central Great
Plains (Kansas/Oklahoma border vicinity) at the outset of the
period.  In the wake of one possible MCV initially migrating
east-southeastward into the Mid South, and ahead of a possible
trailing MCV, and trailing digging short wave impulse, it appears
that the southward progression of the front may slow or stall across
the Ozark Plateau/Mid South, while continuing more steadily, but
slowly, across Oklahoma and the Texas Panhandle.  There is
substantive spread evident in the model output concerning these
developments, however.

...Ozark Plateau/Mid South...
Potential convective evolution Wednesday through Wednesday night
remains uncertain.  However, it appears that a notable belt of
convectively augmented mid-level flow, including 30-50+ kt around
700 mb, will gradually nose from the lower Missouri through lower
Ohio Valley during the day.  Depending on how the near-surface
boundary becomes oriented as this occurs, aided by a corridor of
seasonably high moisture content along it, there appears potential
for destabilization and shear to become conducive to organized
severe thunderstorm development.  This may include supercells and/or
one or two evolving clusters accompanied by developing swaths of
strong to severe wind gusts through the period.

...Southern Rockies into Great Plains...
In the wake of the primary front, it appears that the boundary-layer
will remain sufficiently moist to support modest instability in the
presence of relatively weak mid-level inhibition across the middle
into lower  Missouri Valley.  Aided by forcing for ascent associated
with one lead digging short wave impulse, and a trailing one digging
into/across the international border, at least widely scattered
strong to severe storm development appears possible through the
period, in the presence of favorable strong deep-layer shear.

A drier, but more strongly heated and deeply mixed boundary-layer by
late Wednesday afternoon, near and to the lee of the Front Range
through Sangre de Cristo Mountains, may also become conducive to
widely scattered to scattered strong storms with potential to
produce severe wind and hail, aided by a weak short wave impulse
migrating around the Four Corners ridge.

...Arizona...
With the evolution/progression of the mid-level ridge, potential
steering flow for convective development is forecast to take on a
prominent easterly component with weak to modest strength by late
Wednesday afternoon across much of the Mogollon Rim through lower
deserts.  Coupled with a preceding Gulf moisture surge, forecast
soundings indicate profiles supportive of at least weak to moderate
CAPE, even as the boundary-layer becomes hot and deeply mixed with
40-50F+ surface temperature/dew point spreads by peak afternoon
heating.

Initially more modest late afternoon instability in the lower
deserts around Phoenix may gradually destabilize with boundary-layer
moistening after sunset, eventually supporting the propagation of
convection into/across the Greater Phoenix area by late evening.
Details of the potential convective evolution remain uncertain, but
at least some model output suggest the evolution of a substantive
convective cluster is possible, which could become accompanied by
more widespread strong to severe gusts.

..Kerr.. 08/18/2026

$$