SPC AC 041933

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0233 PM CDT Wed May 04 2022

   Valid 042000Z - 051200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM THE
   SOUTHEAST TEXAS PANHANDLE AND NORTHWEST TEXAS ACROSS MUCH OF
   OKLAHOMA...

   ...SUMMARY...
   Numerous severe thunderstorms are expected across parts of the
   southern Great Plains this afternoon through tonight. A few strong
   tornadoes and giant hail is most probable across the southeast Texas
   Panhandle into portions of southwest Oklahoma and north Texas. Wind
   damage as well as tornadoes are also possible across the remainder
   of central and eastern Oklahoma through tonight.

   ...Eastern TX Panhandle/South Plains into much of OK...
   The Moderate Risk has been expanded eastward across a large portion
   of OK, as the air mass continues to destabilize and remain free of
   storms. Visible imagery continues to show pockets of heating, and
   increasing CU fields near the Red River. Surface observations show
   an unbroken plume of 68-70 F dewpoints now into southern OK, with
   GPS water vapor sensors indicating a deepening moist boundary layer
   with values increasing to over 1.50" over northwest TX.

   Midday soundings reveal a capping inversion below 700 mb which is
   helping to maintain the pristine air mass and guard against early
   contamination. This inversion may also help to subdue the number of
   storms later today across OK and northern TX. Any supercell over the
   warm sector will have the potential to produce a strong tornado,
   aided by midlevel lapse rates near 8 C/km and dewpoints of 68 F or
   greater. Later this evening, storms moving out of the Panhandle may
   eventually merge into a severe MCS with significant wind damage
   potential. In addition, further supercell develop may occur tonight
   along the baroclinic zone extending eastward across OK.

   Farther west into the TX Panhandle and South Plains, rapid
   destabilization continues, beneath cooler air aloft. Supercells
   producing very large damaging hail are likely, with a threat of
   strong tornadoes as supercells interact with increasing low-level
   shear to the east.

   See mesoscale discussions 640, 642, 643 for more information.

   ..Jewell.. 05/04/2022

   .PREV DISCUSSION... /ISSUED 1122 AM CDT Wed May 04 2022/

   ...Southern Great Plains...
   Complicated forecast today/tonight as a broad/destabilizing warm
   sector enlarges as a warm front advances northward today. 
   Considerable forecast uncertainty remains evident for a multitude of
   possible scenarios, some of which differ both spatially in terms of
   severe hazard and intensity.  Nonetheless, with the lack of morning
   convection across northwest TX into the TX Panhandle, thinking is
   this area will remain void of convection through the midday/early
   afternoon.  Consequently, it seems a categorical Moderate Risk is
   warranted for dryline/triple point storms. 

   Visible-satellite imagery late this morning shows a cirrus canopy
   across much of the outlook area.  A warm front is rapidly moving
   northward across north TX with upper 60s F dewpoints reaching the
   Red River as of 16z.  A destabilizing boundary layer beneath a
   capping inversion, which seems likely to hold through the early
   afternoon, will become quite unstable by peak heating with 3000-4000
   J/kg MLCAPE forecast over northwest TX by 4pm.  The RAP/HRRR seems
   to have the best handle on morning storm activity compared to the
   ARW and associated CAM models.  In general, model guidance indicates
   storms will develop over the TX Panhandle during the mid-late
   afternoon with more widely spaced thunderstorms farther south along
   the dryline.  Very steep 700-500 mb lapse rates, enlarged low-level
   hodographs via easterly component to low-level flow, and long
   hodographs all suggest discrete supercells will be the preferred
   mode over the TX Panhandle into northwest TX late this afternoon. 
   Very large to giant hail (potentially 3+ inches in diameter) and a
   few strong tornadoes are possible during the late afternoon into the
   early evening as this activity moves into parts of western OK/far
   western north TX.  Less certain but a plausible scenario involves
   free warm sector development farther east across parts of OK and
   perhaps north TX.  A potentially significant tornado risk could
   develop if discrete supercells were to develop within an
   increasingly moist/strongly sheared environment during the late
   afternoon/early evening.  

   By early to mid evening, the strengthening of a southerly LLJ and
   coalescing of storms/outflow will probably lead to the development
   of a severe MCS moving east across parts of OK.  Severe gusts,
   possibly greater than 65 kt, and tornadoes will become the primary
   severe hazards with time.  As this activity approaches the western
   part of the Ozarks, a lessening in the severe risk is anticipated
   late overnight.

   ...Southeast VA and the Carolinas...
   Not much change from the previous forecast in the overall
   thunderstorm scenario for VA/Carolinas.  A low-amplitude shortwave
   trough over the Lower Great Lakes will move east into southern New
   England this evening. To the south of this wave, a cold front will
   push southeast across the Lower Mid-Atlantic into the Carolinas.
   Convergence along the cold front and coastal sea breezes should
   support scattered thunderstorms this afternoon. While deep-layer
   shear will be modest, it should be adequate for multicells capable
   of isolated severe hail and damaging winds. Convection should
   largely shift offshore and/or weaken after dusk.

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