SPC AC 061959

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0259 PM CDT Sat May 06 2023

   Valid 062000Z - 071200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHERN TEXAS INTO EXTREME SOUTH-CENTRAL OKLAHOMA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   IOWA...ILLINOIS...AND NORTHERN MISSOURI...

   ...SUMMARY...
   Intense severe thunderstorm development remains likely during the
   late afternoon and evening across a portion of the southern Great
   Plains. Very large hail and destructive wind events are possible
   across the Big Country and North-Central Texas into southern
   Oklahoma. Severe thunderstorms capable or producing a few tornadoes,
   very large hail, and damaging gusts remain a concern across parts of
   the Mid-Mississippi Valley States this evening into tonight.

   ...20Z Update...
   One of the primary changes made to the Day 1 Outlook was to remove
   the Category 1/Marginal Risk from LA. Multiple training MCSs have
   overturned the airmass in this region, reducing buoyancy and the
   associated severe threat. The only other change to the Day 1 Outlook
   was to adjust the severe probabilities over IA into northwestern MO
   to align with a baroclinic zone, where a focus for initial discrete
   supercells exists before storms potentially grow upscale into an MCS
   later this evening. 

   Otherwise, the remainder of the Outlook remains on track, with
   severe hail and wind likely with outflow dominant storms across the
   southern Plains. An instance or two of large hail may still
   accompany a small convective cluster across central IL (see
   Mesoscale Discussion 0688 for more details). Likewise, a couple of
   severe wind gusts remain possible with storms overspreading a
   relatively dry boundary layer over parts of NE into SD.

   ..Squitieri.. 05/06/2023

   .PREV DISCUSSION... /ISSUED 1105 AM CDT Sat May 06 2023/

   ...TX/OK...
   A broad/flat upper trough is present today over the western states,
   with a ridge axis across the MS Valley.  A diffuse surface dryline
   is analyzed over west TX, and will mix eastward through the
   afternoon and provide the focus for intense thunderstorm development
   later today.

   Full sunshine will lead to dry-adiabatic lapse rates throughout most
   of the low/mid troposphere today near the dryline.  High-based
   storms are expected to develop by mid-afternoon from near Wichita
   Falls southward to west of San Angelo, where high CAPE values and
   sufficient flow will support supercells storms capable of very large
   hail and damaging winds.  These storms will persist through much of
   the evening and spread eastward.  Richer low-level moisture profiles
   and strengthening low-level winds during the evening will maintain
   the wind/hail risk while also increasing the potential for a tornado
   or two, although early outflow dominance may complicate storm modes.


   ...IA/MO/IL...
   a small cluster of strong-severe storms is ongoing this morning over
   northeast MO.  The air mass ahead of this activity is relatively
   cloudy and only marginally unstable, leading to considerable
   uncertainty regarding the longevity of the severe risk.  A few 12z
   CAM solutions do show convective maintenance through much of the
   afternoon, so will maintain the SLGT risk into central IL for this
   scenario.

   Farther north and west, southeasterly low-level winds will continue
   to transport an increasingly moist airmass into parts of northern MO
   and southern IA.  Partial afternoon heating is expected to lead to
   moderate CAPE and the development of isolated thunderstorms.  The
   storms that form will track eastward through the late afternoon and
   evening across southern IA/northern MO and eventually into western
   IL.  Confidence is low regarding the location and timing of
   development, so have opted to make few changes to the ongoing SLGT
   risk.  However, there is relatively high conditional potential for
   supercell storm structures capable of large hail and isolated
   tornadoes for those storms that can develop.

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z