SPC AC 212000

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0300 PM CDT Wed Jun 21 2023

   Valid 212000Z - 221200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   EASTERN COLORADO...SOUTHEAST WYOMING...AND THE NEBRASKA
   PANHANDLE...AND FROM THE EASTERN TEXAS PANHANDLE AND WESTERN
   OKLAHOMA INTO CENTRAL TEXAS...

   ...SUMMARY...
   Intense severe thunderstorms are expected late this afternoon into
   this evening over parts of the central and southern Plains, where
   severe gusts, very large hail, and a few tornadoes are possible.

   ...20Z Update...
   The Marginal and Slight Risks have been trimmed over parts of OK, in
   the wake of an earlier storm cluster that has since weakened.
   Otherwise, the previous forecast reasoning remains valid. 

   ...Eastern CO/Southeast WY
   Intense supercell development is underway across northeast CO into
   the NE Panhandle, with additional supercells expected later this
   afternoon into this evening farther west toward the CO Front Range
   and southeast WY. Very large hail, severe gusts, and a few tornadoes
   will be possible in this area. See MCD 1188, WW 349, and WW 350 for
   more information regarding the threats in this area. 

   ...Extreme southwest KS into the TX/OK Panhandles and northwest
   TX...
   A separate zone of intense supercell development is expected late
   this afternoon from extreme southwest KS into the TX/OK Panhandles,
   within a region of very rich low-level moisture, steep midlevel
   lapse rates, and strong to extreme buoyancy. Very large hail, severe
   wind gusts, and a couple of tornadoes will be possible with initial
   supercells. Some upscale growth is possible this evening, which may
   result in a larger swath of destructive wind gusts as storms move
   southeastward, though the areal extent of MCS development remains
   somewhat uncertain, as a westward-moving outflow may result in a
   narrowing of the instability axis with time. See MCD 1189 and WW 351
   for more information regarding the short-term threat in this area.

   ..Dean.. 06/21/2023

   .PREV DISCUSSION... /ISSUED 1123 AM CDT Wed Jun 21 2023/

   ...TX/OK...
   Morning water vapor imagery shows a large upper trough over the
   western states, with moderately strong southwesterly mid-level winds
   across much of the central and southern High Plains.  At the
   surface, an extremely moist and potentially unstable air mass
   (dewpoints in the mid 70s) is present from the eastern TX Panhandle
   eastward into western OK, and extending southeastward into central
   TX.  Full heating will lead to afternoon MLCAPE values of 5000-6000
   J/kg and minimal cap.  Large scale forcing is weak, but circulations
   along the surface dryline will lead to rapidly thunderstorm
   development from extreme southwest KS into the eastern TX Panhandle.
   These storms are likely to be supercells capable of very large hail
   and a few tornadoes.

   These storms are likely to slowly congeal into one or more bowing
   complexes by mid evening, tracking southeastward into northwest and
   central TX.  Several morning CAM solutions suggest the potential for
   a corridor of significant wind damage if this scenario unfolds.

   ...Eastern CO/Southeast WY...
   An extremely moist and unstable low-level air mass is streaming into
   the central High Plains, with dewpoints in the 70s being transported
   westward into the higher elevations of the eastern CO/southeast WY
   plains.  Strong daytime heating and steep mid-level lapse rates will
   yield afternoon MLCAPE values over  3000 J/kg.  All morning CAM
   solutions agree on the development of scattered thunderstorms by
   mid-afternoon along the front range and foothills, as well as the
   DCVZ along the Palmer Ridge.  A combination of backed low-level
   winds and 30+ knots of southwesterly flow aloft will promote
   supercell structures capable of very large hail and a few tornadoes.
    The threat of severe storms may persist much of the evening,
   building southward along the Front Range into southeast CO.

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