SPC AC 260534

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1234 AM CDT Thu Mar 26 2026

   Valid 261200Z - 271200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE MID-MISSISSIPPI VALLEY AND OHIO VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms are expected late this afternoon and
   evening across parts of the Mid-Mississippi and Ohio Valleys. Very
   large hail, a few tornadoes, and severe wind gusts will be possible.

   ...Mid-Mississippi Valley and Ohio Valley...

   Early-morning water-vapor imagery depicts a weak short-wave trough
   topping the dominant southwestern anticyclone over southern WY.
   Latest lightning data supports this with isolated thunderstorms
   currently noted from southern WY into the NE Panhandle. 00z model
   guidance suggests this feature will advance into the Mid-MO Valley
   by 18z, then progress into the Mid-MS Valley by 27/00z. As this
   short wave advances east, surface ridging will build south across
   the Plains and force a pronounced cold front across much of IA by
   early afternoon with the sharp boundary settling south across
   northern IL as a weak surface wave tracks toward southern Lower MI.

   Deep westerly flow should allow surface temperatures to warm quickly
   into the lower-mid 80s south of the front over IL/western IN. Even
   so, convective temperatures may struggle to be breached until late
   afternoon. Current thinking is upper 50s to near 60 F dew points
   should return to this region prior to frontal passage, thus modest
   MLCAPE is expected to develop. Forecast soundings suggest weak
   capping may hold across the warm sector so it's not entirely clear
   how much activity will develop well ahead of the front. However,
   strong frontal forcing will easily encourage thunderstorm
   development and convection will evolve within a strongly sheared
   environment. Profiles favor organized rotating updrafts and
   supercells are expected, especially early in the convective cycle.
   Given the strength of the front there is an expectation for storm
   mergers and line segments to evolve. Very large hail is possible,
   especially with early supercell development. As a frontal MCS
   evolves, damaging winds are expected to be more common with the LLJ
   strengthening into the evening hours across the OH Valley. Some
   tornado threat also exists with storms that are not undercut by the
   surging cold front, both with supercells and within the extensive
   frontal squall line. This activity will spread toward the Ohio River
   where gradual weakening is expected during the late-night hours.

   ..Darrow/Chalmers.. 03/26/2026

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