851
ACUS01 KWNS 180558
SWODY1
SPC AC 180556

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Tue Aug 18 2026

Valid 181200Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS AND LOWER MISSOURI VALLEY...

...SUMMARY...
Thunderstorms with severe wind gusts and isolated large hail will be
possible this afternoon and evening from the central Plains into the
lower Missouri Valley. Isolated severe gusts and hail will also be
possible from the Northern High Plains eastward into the Midwest and
southern Great Lakes.

...Central and Northern Plains...
At mid-levels, a broad cyclonic flow pattern will be in place over
the northern U.S. A shortwave trough will move across the central
and northern Plains. At the surface, a cold front will advance
southward into Nebraska by afternoon. To the south of the front, an
outflow boundary from morning convection will move southward into
northern Kansas. A moist airmass will exist between the two
boundaries with surface dewpoints in the upper 60s to lower 70s F.
Within the moist air, moderate to strong instability will develop by
afternoon. The outflow boundary will be a focus for convective
initiation during the day, while additional storms are expected to
develop further west across the central High Plains in the late
afternoon. Increasing convective coverage during the early evening
should result in the development of a line segment.

RAP forecast soundings at 00Z from Salina to Kansas City have MLCAPE
in the 1500 to 2500 J/kg range with 0-6 km shear around 40 knots.
700-500 mb lapse rates are forecast to be in the 7 to 8 C/km range.
This environment will support supercells with isolated large hail.
The large hail threat will extend west-northwestward into southwest
Nebraska during the late afternoon where mid-level lapse rates will
be steeper and cells will likely remain discrete. The greatest
wind-damage potential is forecast from northern and eastern Kansas
into far western Missouri, where the development of an organized
bowing line segment will be possible in the early evening. Wind
gusts above 75 mph will be possible along the path of any intense
line segment. The severe threat may impact parts of lower Missouri
Valley and Ozarks by mid to late evening.

...Midwest/Great Lakes...
A mid-level shortwave trough will move across the north-central U.S.
today, as a cold front advances southeastward across the Midwest and
Great Lakes. To the south of the front, surface dewpoints in the 60s
F will contribute to moderate instability along an
west-northwest-to-east-northeast axis from the mid Mississippi
Valley into the southern Great Lakes. Isolated to scattered
thunderstorms appear likely to form along and south of the front in
the late afternoon and early evening. MLCAPE in the 1000 to 2000
J/kg range, 0-6 km shear around 40 knots and precipitable water in
the 1.7 to 1.9 inch range will be favorable for isolated severe
storms capable of severe wet downbursts.

...Northern High Plains...
Northwesterly mid-level flow will be in place today from the
Northern Rockies into the Northern High Plains. At the surface,
dewpoints along the moist axis from northeastern Wyoming into
central Montana will be around 50 F. As surface temperatures warm
during the day, MLCAPE is expected to increase to around 1000 J/kg
in parts of the northern High Plains. Thunderstorms are expected to
form in the higher terrain in the afternoon, moving
east-southeastward into the lower elevations. Due to the instability
and steep low to mid-level lapse rates, isolated severe wind gusts
will be possible with the stronger cells.

..Broyles/Jirak.. 08/18/2026

$$