Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1125 AM CDT Mon May 18 2026
Valid 181630Z - 191200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING OVER PARTS OF EASTERN KANSAS...SOUTHEAST
NEBRASKA...NORTHWEST MISSOURI...AND SOUTHWEST IOWA....
...SUMMARY...
Numerous severe thunderstorms are expected this afternoon and
evening across the south-central Plains and mid Missouri Valley.
Supercells capable of producing very large to giant hail and
multiple strong to intense tornadoes are most likely from central
Kansas and southeast Nebraska into Iowa and northwest Missouri.
...Central Plains...
Morning water vapor loop shows a potent shortwave trough rotating
across the central Rockies into western KS. The primary surface
boundary extends from western IA into central KS, with a pronounced
outflow boundary associated with overnight convection extending from
southeast KS into southern MO. The outflow boundary will lift
northward today, allowing a very moist and extremely unstable air
mass to spread into eastern KS/northwest MO/extreme southeast
NE/southwest IA. This is the area most concerning for intense
supercells later today.
Initial storms are expected to develop by early afternoon near the
triple point of the retreating outflow boundary and cold front.
These storms will track northeastward through the afternoon and
early evening in a strongly sheared environment favorable for
tornadoes, very large hail, and damaging winds. It remains unclear
how stormscale interactions will impact discrete supercell mode, but
strong tornadoes are a concern in this region.
Farther southwest, thunderstorms will develop in vicinity of the
cold front across south-central KS by late afternoon. Recent CAM
solutions suggest these storms may be affected by the linear frontal
forcing, and may be slightly anafrontal. This would lessen the
tornado risk, but very large hail and damaging winds would remain a
concern. No changes have been made to the Moderate Risk area due to
conflicting model signals.
...Western OK/Northwest TX...
Full sunshine will lead to hot temperatures along the dryline over
western OK into northwest TX. At least isolated thunderstorms are
expected to form in this area, with a risk of large hail and
damaging winds. Weak large scale forcing may limit storm duration
and intensity.
...OH Valley/Great Lakes...
A line of thunderstorms along the IL/IN border is tracking
northeastward into a warm/moist air mass. Relatively strong
low-level wind fields and steep low-level lapse rates suggest a
continued risk of scattered wind damage with the strongest storms as
they track across parts of IN/Lower MI/Northwest OH.
..Hart/Halbert.. 05/18/2026
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