SPC AC 220557

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1257 AM CDT Fri Apr 22 2022

   Valid 221200Z - 231200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN AND CENTRAL HIGH PLAINS...

   ...SUMMARY...
   Severe thunderstorms are expected to develop across parts of the
   Great Plains into Upper Midwest Friday from late this afternoon
   through tonight. Supercell thunderstorms capable of all severe
   hazards, including tornadoes and very large hail, are possible,
   particularly from the Texas Panhandle into north-central Nebraska.

   ...Southern and Central High Plains...
   A progressive upper-level trough will move quickly
   east-northeastward across the Desert Southwest today, as a 80 to 100
   knot mid-level jet rounds the base of the trough. The exit region of
   the mid-level jet will overspread the southern and central High
   Plains this afternoon, increasing large-scale ascent and
   strengthening deep-layer shear. This along with a moist and unstable
   airmass will make conditions favorable for severe storms.

   At the surface, a low will rapidly deepen across northeastern
   Colorado today as strong moisture advection occurs to the east of a
   High Plains dryline. Surface dewpoints will increase into the upper
   50s to lower 60s F by mid afternoon from the Texas Panhandle
   northward across western Kansas into west-central Nebraska. This
   will contribute to moderate destabilization as surface temperatures
   warm during the day, with MLCAPE reaching the 2000 to 2500 J/kg
   range. The capping inversion is forecast to weaken by late
   afternoon, which will allow for rapid convective development along a
   narrow corridor from the central Texas Panhandle north-northeastward
   across western Kansas into central Nebraska. Thunderstorms will
   quickly grow upscale early this evening, with multiple convective
   clusters persisting into the mid to late evening.

   In addition to the moderate instability, RAP forecast soundings
   along the instability axis early this evening have gradually veering
   winds with height in the low to mid-levels, with 0-6 km shear in the
   35 to 45 knot range. 0-6 km shear is forecast to steadily increase
   as the exit region of the mid-level jet overspreads the central
   Plains during the evening. This along with 700-500 mb lapse rates in
   the 7.5 to 8.5 C/km range will be very favorable for supercells with
   large hail. Hailstones of greater than 2 inches in diameter will be
   possible with the more intense supercell updrafts, from west Texas
   into southwest Kansas, where instability and lapse rates are
   forecast to be most favorable. As the low-level jet strengthens
   during the early to mid evening, 0-3 km storm relative helicity will
   become increasingly favorable for tornadoes as well. Wind damage is
   also expected with the stronger cells. The potential for wind damage
   and hail could persist into the late evening, as the mid-level
   system moves out into the central High Plains.

   ...Northern Plains/Mid Missouri Valley/Upper Midwest...
   An upper-level trough will quickly move eastward through the Desert
   Southwest today as a 80 to 100 knot mid-level jet moves through the
   base of the trough. Moderate instability and strong deep-layer shear
   will be in place by afternoon, making conditions favorable for
   organized severe storms. At the surface, a low will rapidly deepen
   across northeastern Colorado today, and move north-northeastward
   into western Nebraska. A warm front extending eastward from the low
   will advance northward across Nebraska this afternoon and into
   southern South Dakota this evening. As low-level convergence
   increases near and to the north of the surface low during the late
   afternoon, convection will likely initiate and move
   north-northeastward across northwestern Nebraska and southwestern
   South Dakota. Convective coverage is expected to rapidly increase
   across the northern Plains during the evening as the exit region of
   the mid-level jet moves into the area from the southwest. The
   current thinking is that a line of strong to severe storms will move
   eastward through western Nebraska and western South Dakota during
   the evening, with supercells developing ahead of the line further to
   the east.

   NAM Forecast soundings at Valentine, Nebraska near the peak of
   instability early this evening have a loaded gun profile with MLCAPE
   in the 2500 to 3000 J/kg range. This along with lapse rates
   approaching 8.0 C/km in the 700 to 500 mb layer will be favorable
   for supercells with large hail. In addition, hodographs are long and
   looped with 0-3 km storm relative helicities near 400 m2/s2. This
   will be favorable for tornadoes as well with the more dominant
   cells, especially as the low-level jet ramps up quickly during the
   early evening. Wind damage will also be possible. The threat should
   persist through the evening and into the early overnight period as
   storms move east-northeastward into the eastern Dakotas late in the
   period.

   Further east across the Upper Midwest, an isolated severe threat
   could develop during the evening along the warm front. However, weak
   instability should limit severe threat coverage. Hail and strong
   gusty winds will be the primary threats.

   ..Broyles/Jirak.. 04/22/2022

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