ACUS02 KWNS 180552
SWODY2
SPC AC 180550

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1250 AM CDT Fri Sep 18 2026

Valid 191200Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE CENTRAL PLAINS...

...SUMMARY...
Scattered severe wind and hail producing storms are likely across
portions of the central Plains, with more isolated severe storms
possible across the central High Plains, central Rockies, and the
Midwest to Southeast states tomorrow (Saturday).

...Synopsis...
Upper ridging over the central and eastern CONUS will begin to
de-amplify to a degree, allowing for multiple pronounced mid-level
impulses to traverse the central CONUS through the day tomorrow
(Saturday). The passage of these upper-level impulses will encourage
the southward shunting of a surface cold front across the central
Plains into the Midwest/OH Valley regions. Low-level convergence and
moisture advection along this front will encourage at least
scattered thunderstorm development during the day, from the High
Plains to the OH Valley. In addition to moisture-induced buoyancy,
the development of a low-level jet bisecting this front, especially
in the Plains states, will introduce vertical wind shear,
encouraging the development of a few severe storms as well.

...Central Plains to the southern High Plains...
As the surface cold front drifts southward through the day, surface
heating of the preceding airmass will boost surface temperatures
into at least the mid 80s F, amid 70 F dewpoints, yielding 2500-3500
J/kg MLCAPE, despite mid-level lapse rates only reaching 6.5-7 C/km.
Thunderstorms should develop across the cold front, from
southeastern IA to the southern High Plains by afternoon peak
heating. Low-level moisture and vertical wind shear will be most
favorable for severe storms over the central Plains. 30 kts of
effective bulk shear will encourage the development of multicells
and supercells along the front. The stronger storm cores may support
some severe hail production, while merging storms will have the
highest potential for producing severe wind gusts. At least isolated
severe gusts are also possible with high-based storms over a deeper
boundary layer across the southern High Plains, where some forecast
soundings show mixing up to 600 mb.

...Midwest to Southeast States...
Appreciably rich low-level moisture should encompass the periphery
of the upper ridge across the Midwest toward the Gulf Coast. Despite
mediocre lapse rates, flow, and forcing aloft, low to mid 70s F
surface dewpoints amid minimal MLCINH will encourage at least widely
scattered thunderstorm development through the afternoon. The 70s F
surface dewpoints will contribute to 1500+ J/kg of tall and thin
MLCAPE. A few water loaded downbursts may accompany some of the
stronger storms, where isolated damaging gusts will be a concern. 
 
...Central High Plains...
Upslope low-level flow and accompanying low-level moisture advection
will serve as the impetus for convective initiation across the
central High Plains on Saturday. 7.5+ C/km mid-level lapse rates
will overspread 60s F surface dewpoints, boosting MLCAPE to over
1500 J/kg. Furthermore, the upslope flow beneath mid-level
westerlies will yield over 30 kts of effective bulk shear, favoring
multicell and perhaps transient supercell development, accompanied
by a risk of at least isolated severe wind or hail.

...Portions of the central Rockies...
By Saturday afternoon, a low-amplitude mid-level trough will
overspread the central Rockies, accompanied by cooler mid-level
temperatures and westerly flow. The vertical wind field should be
unidirectional, but increasing flow aloft will yield over 30 kts of
effective speed shear. When also considering 7.5+ C/km mid-level
lapse rates, any storm that develops and becomes sustained may
become supercellular, with a few instances of severe wind or hail
possible.

..Squitieri.. 09/18/2026

$$
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