SPC AC 180555

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1255 AM CDT Thu Apr 18 2024

   Valid 181200Z - 191200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PART OF
   THE OZARKS...MID MISSISSIPPI VALLEY...AND LOWER OHIO VALLEY...

   ...SUMMARY...
   A line of strong to severe storms will impact the Ozarks, mid
   Mississippi Valley and lower Ohio Valley this afternoon and evening,
   with wind damage, isolated large hail and a few tornadoes. Scattered
   to widely-scattered storms with a large hail and wind-damage threat
   will also be likely in parts of the Ark-La-Tex and southern Plains.

   ...Ozarks/Mid Mississippi Valley/Lower Ohio Valley...
   An upper-level trough, and an associated mid-level jet, will move
   through the north-central U.S. today. At the surface, a low will
   move through Missouri as a cold front advances east-southeastward
   into the Ozarks. Ahead of the front, the moist sector will be in
   place by late morning across much of southern and central Missouri
   extending eastward into the Mid Mississippi Valley. Surface heating
   and enhanced low-level convergence ahead of the front will lead to a
   gradual intensification of convection during the morning in western
   Missouri. Scattered storms will eventually organize into a line,
   moving eastward from the Ozarks into the mid Mississippi Valley
   during the mid to late afternoon.

   Ahead of the front, a moderately unstable airmass will be in place
   by midday, with MLCAPE reaching the 1500 to 2500 J/kg range over
   much of the moist sector. Forecast soundings near the instability
   axis this afternoon suggest that 0-6 km shear will generally be in
   the 35 to 40 knot range. This should be sufficient for supercell
   development early in the event when cells are more likely to be
   discrete. Large hail will be possible with supercells. Convective
   development will be driven by low-level convergence, and this should
   result in linear development as convective coverage increases in the
   early to mid afternoon. Wind damage will become likely as a nearly
   continuous line of storms develops. Although low-level shear is not
   forecast to be that strong, a few QLCS tornadoes will be possible
   with rotating cells embedded within the line. The severe threat will
   likely continue into the evening, as the line cross the Mississippi
   River and moves through the lower Ohio Valley.

   ...Ark-La-Tex/Southern Plains...
   A shortwave trough will move through the Ark-La-Tex today, as a cold
   front advances southeastward across the southern Plains. Ahead of
   the front, surface dewpoints in the upper 60s and lower 70s F will
   contribute to moderate to strong instability across much of the
   moist sector by afternoon. Surface heating and increasing low-level
   convergence ahead of the front will lead to the development of
   isolated to scattered thunderstorms. Several clusters of storms are
   expected to move across the warm sector during the late afternoon
   and early evening.

   RAP forecast soundings by mid afternoon from the Texas Hill Country
   into north-central Texas have MLCAPE reaching the 2500 to 3500 J/kg
   range. 0-6km shear is forecast to be in the 35 to 40 knot range with
   700-500 mb lapse rates near 8.0 C/km. This environment will likely
   support supercells with isolated large hail. Hailstones greater than
   2 inches in diameter will be possible with the more intense and
   dominant supercells. A wind-damage threat is also expected to
   develop. Storm coverage in many areas will remain isolated due to a
   weak capping inversion that is evident above 850 mb on many forecast
   soundings.

   ..Broyles/Lyons.. 04/18/2024

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