ACUS02 KWNS 180601
SWODY2
SPC AC 180600
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1200 AM CST Wed Feb 18 2026
Valid 191200Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MUCH OF CENTRAL
AND SOUTHERN ILLINOIS AND INDIANA...PARTS OF WESTERN AND NORTHERN
KENTUCKY AND SOUTHWESTERN OHIO...
...SUMMARY...
Severe thunderstorms, with potential to produce a few tornadoes and
damaging wind gusts, are possible across parts of the middle
Mississippi into lower Ohio Valleys Thursday afternoon into early
evening.
...Discussion...
There remains notable spread evident in the latest model output
concerning a number of synoptic and sub-synoptic developments within
the evolving pattern across North America through this period. In
general, though, guidance continues to indicate that larger-scale
mid-level troughing will slowly begin to shift inland of the Pacific
coast Thursday through Thursday night, while being maintained
downstream across the Rockies, Great Plains and Mississippi Valley,
and slowly developing toward the lower Great Lakes and Appalachians
vicinity. As this occurs, the center of a mid-level subtropical
ridge is likely to shift from the southern Gulf Basin into the Bahamas/Caribbean, with its northern periphery maintaining an
influence across parts of the Southeast.
A couple of initially lower amplitude short wave perturbations,
within a seasonably strong belt of flow emerging from the Southwest,
may be in the process of progressing into and across the central
Great Plains toward the middle Mississippi and lower Ohio Valleys at
the outset of the period. The lead perturbation, probably
accompanied by a 500 mb speed maximum of 90-100+ kts, is forecast to
continue into and across the lower Ohio Valley during the day, as
the trailing one pivots northeastward and perhaps intensifies across
the middle Mississippi Valley toward southern Great Lakes region
later Thursday through Thursday night.
Associated with these developments, a sub-1000 mb surface cyclone is
forecast to migrate across and northeast of the lower Missouri
Valley during the day, perhaps slowly deepening, before continuing
toward the upper Great Lakes accompanied by more substantive
deepening Thursday night.
...Middle Mississippi/Lower Ohio Valley...
It appears that warming aloft, associated with subsidence to the
south of the trailing mid/upper jet, will tend to eventually
overspread the better (but still relatively modest) low-level
moisture return to the evolving warm sector across the lower Ohio
Valley. However, to still differing degrees, the latest runs of the
various model output indicate a window of opportunity for strong to
severe thunderstorm development, perhaps beginning by early
afternoon, aided by daytime heating and subtle mid-level
cooling/forcing for ascent accompanying the lead jet streak.
The consensus of latest guidance, supported by the High Resolution
Ensemble and related machine learning output, suggests that this may
initiate across portions of Illinois, near or to the north and east
of the Greater St. Louis area, with strongest activity tending to
develop eastward and perhaps peak while spreading across east
central and portions of southeastern Illinois through portions of
central and southern Indiana by early Thursday evening.
Forecast soundings across this corridor remain generally
characterized by at least modest convective instability, and CAPE on
the order of 500-750+ J/kg, in the presence of strong deep-layer
shear. Sizable clockwise-curved low-level hodographs, beneath
40-50+ kt south to southwest flow in the 850-700 mb layer, may
promote supercells capable of producing severe hail and a few
tornadoes, and activity may eventually grow upscale enough to
support increasing potential for damaging wind gusts before
convection wanes late Thursday evening.
..Kerr.. 02/18/2026
$$
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