SPC AC 260525

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1225 AM CDT Fri Apr 26 2024

   Valid 261200Z - 271200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE LOWER TO MID MISSOURI VALLEY...AND CENTRAL PLAINS...

   ...SUMMARY...
   Severe thunderstorms will be likely today from parts of eastern
   Nebraska into western and central Iowa, southward into eastern
   Kansas and Northwest Missouri. All hazards will be possible,
   including tornadoes with some potentially strong, very large hail
   over two inches in diameter, and wind damage. A more isolated severe
   threat will extend south-southwestward into parts of the southern
   Plains, Ozarks and Ark-La-Tex from late afternoon into the evening.

   ...Significant Severe Weather Event Expected Today Across Parts of
   The Lower To Mid Missouri Valley and Central Plains...

   ...Lower to Mid Missouri Valley/Central Plains...
   A negatively tilted upper-level trough will move northeastward
   across the mid Missouri Valley today, as an associated 50 to 60 knot
   mid-level jet translates northeastward through the base of the
   system. At the surface, a low will deepen and move northeastward
   across Nebraska. A north-to-south corridor of maximized low-level
   moisture, with surface dewpoints in the mid 60s F, will be in place
   by midday across eastern Kansas and southeast Nebraska. Moderate
   instability will develop across most of the moist sector by
   afternoon, with thunderstorms first developing in east-central
   Nebraska around midday. These storms are expected to move eastward
   across eastern Nebraska during the afternoon, as convective coverage
   gradually expands south-southeastward into eastern Kansas. The
   environment will be favorable for severe storms, with several
   clusters moving eastward from Nebraska into Iowa, and from Kansas
   into Missouri during the late afternoon and early evening.

   Several factors appear to be supportive of a significant tornado
   event today across eastern part of the central Plains into the lower
   to mid Missouri Valley. The first is that a 60 to 70 knot mid-level
   jet, associated with a negatively tilted trough, will become coupled
   with a 50 to 60 knot low-level jet over a moist and unstable warm
   sector. A second factor is that a band of large-scale ascent will
   move over the warm sector this afternoon, as the capping inversion
   diminishes. Steep low to mid-level lapse rates are forecast to
   spread over the warm sector, which combined with moderate deep-layer
   shear, will be favorable supercells with strong updrafts at
   relatively low-levels within the storms. In addition, 0-3 km
   storm-relative helicity is forecast to increase into the 300 to 400
   m2/s2 range along the western edge of the low-level jet, which will
   be favorable for strong tornadoes. A few tornadic supercells are
   expected, with the greatest potential from near Omaha eastward to
   near Des Moines and southward to south of the Kansas City Metro.
   Along this corridor, the more dominant supercell storms will also
   have a potential to produce hailstones greater than 2 inches in
   diameter and wind damage. The severe threat is expected to shift
   eastward across Iowa and Missouri during the mid to late evening,
   with an isolated severe threat continuing after midnight.

   ...Southern Plains/Ozarks/Ark-La-Tex...
   Southwesterly mid-level flow will be in place today across the
   south-central U.S., with a broad moist warm sector located from the
   southern Plains eastward into the Ark-La-Tex and Ozarks. An MCS is
   expected to move across central and eastern Oklahoma during the
   morning, which will stabilize the airmass. However, instability is
   forecast to redevelop across Oklahoma by afternoon. Further south,
   strong instability is expected to develop across much of central and
   east Texas by afternoon, where MLCAPE should peak in the 2500 to
   3500 J/kg range. Although large-scale ascent will be weak across
   most of the southern Plains, the cap is expected to diminish and
   isolated thunderstorms appear likely to develop by late afternoon. A
   severe threat is expected to persist along and near the instability
   axis during the early to mid evening.

   RAP forecast soundings at 00Z/Saturday along and near the
   instability axis from southeast/south-central Oklahoma into
   north-central Texas have 0-6 km shear between 40 and 50 knots. Low
   to mid-level lapse rates will become steepest in areas that heat up
   the most. The environment will likely be favorable for isolated
   supercells with large hail. By late afternoon, forecast soundings
   also have 0-3 Km storm-relative helicity reaching 200 m2/s2
   suggesting that an isolated tornado threat will be possible. The
   tornado threat is expected to be the greatest across eastern
   Oklahoma, northeast Texas and western Arkansas, as the low-level jet
   ramps up in the early evening. Wind damage will also be possible
   with storms that develop.

   ..Broyles/Thornton.. 04/26/2024

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