SPC AC 291959

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0259 PM CDT Fri Apr 29 2022

   Valid 292000Z - 301200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   AND EVENING OVER PORTIONS OF SOUTHEAST NEBRASKA AND NORTHEAST
   KANSAS...

   ...SUMMARY...
   A complex and significant severe weather episode is forecast this
   afternoon into tonight across the central Great Plains vicinity.

   ...Discussion...
   Only two minor changes were made to the previous convective outlook.

   1) Made slight adjustments by sharpening the severe probability
   gradient for parts of the dryline to reflect dryline position and
   developing high-based cumulus.
   2) Added low hail probabilities for parts of eastern CO.

   For short-term details regarding expected thunderstorm development
   and associated severe hazards, reference MCDs 580-582.

   ..Smith.. 04/29/2022

   .PREV DISCUSSION... /ISSUED 1119 AM CDT Fri Apr 29 2022/

   ...Southeast NE/Northeast KS...
   Morning water vapor imagery shows a negatively tilted upper trough
   over the central Rockies emerging into the High Plains.  An
   associated 60+ knot mid-level jet will move across KS this
   afternoon, aiding surface cyclogenesis and resulting in a favorable
   setup for severe storm development.  Backed low-level winds to the
   north/east of the surface low and warm front, along with persistent
   moisture convergence and mid-level capping through the early
   afternoon will result in a corridor of boundary layer moisture
   "pooling" roughly along the KS/NE border.  Forecast soundings in
   this corridor show very favorable parameters for tornadic
   supercells, but given the strong forcing that will overspread the
   area, it is uncertain how long supercells can be maintained before
   linear structures develop.  Regardless, significant tornadoes,
   destructive wind gusts, and very large hail are possible with the
   storms that move across southeast NE and far northeast KS this
   afternoon and evening.

   ...Eastern KS along the dryline...
   By late afternoon, the surface dryline is expected to extend from
   the surface low over north-central KS to near ICT.  Temperatures
   west of the dryline will warm to near 90F, while mid 60s dewpoints
   are maintained to the east.  While there is still uncertainty
   whether many storms form along this axis, most of the 12z CAM
   guidance now shows at least isolated supercell development over
   parts of this area.  Strengthening southerly low-level flow/shear by
   early evening would support the potential for strong tornadoes,
   along with very large hail and damaging winds from the most intense
   storms.  By mid-evening, the surface cold front will overtake the
   dryline, leading to widespread thunderstorms capable of large hail
   and damaging winds.  The MDT risk area has been expanded slightly
   southward to include parts of this area, and a 15% tornado risk area
   has been added.

   ...Central OK along the dryline...
   The uncertainty of convective initiation increases south of the
   KS/OK border, but most CAM guidance shows one or more isolated
   supercells forming along the dryline somewhere over OK by late
   afternoon/early evening.  Forecast soundings show an uncapped air
   mass along a somewhat convergent dryline, underscoring the potential
   for development.  Have maintained the SLGT/ENH risk areas across
   this region with a conditional risk of very large hail and tornadoes
   from any supercell that can form on the dryline today.

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