SPC AC 061932

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0232 PM CDT Tue Jun 06 2023

   Valid 062000Z - 071200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE NORTHEAST...NORTHERN CALIFORNIA TO NORTHERN UTAH/SOUTHERN
   IDAHO...NEW MEXICO/TEXAS TRANS-PECOS...SOUTH FLORIDA...AND THE SOUTH
   CAROLINA VICINITY...

   ...SUMMARY...
   Isolated severe thunderstorms with threats of damaging winds and
   large hail will be possible through this evening across several
   portions of the country: the South Carolina vicinity, the Northeast,
   northern California to northern Utah/southern Idaho, New
   Mexico/Texas Trans-Pecos, and south Florida.

   ...20Z Update...
   Overall forecast outlined in the previous outlook remains valid.
   Thunderstorms remain possible across a large portion of the CONUS,
   with stronger storms anticipated in a few areas, including portions
   of the Northeast, northern CA into the Great Basin, and southern
   High Plains. Each of these areas are addressed in the previous
   discussion. Additional details for the Northeast can be found in
   recently issued MCD #941, and for portions of northern California,
   north and central Nevada, and western Utah in MCD #942. In all,
   generally modest buoyancy and the lack of stronger flow aloft is
   expected to preclude a more widespread severe-thunderstorm threat.

   ..Mosier.. 06/06/2023

   .PREV DISCUSSION... /ISSUED 1123 AM CDT Tue Jun 06 2023/

   ...SC Vicinity...
   A plume of moderate buoyancy with MLCAPE of 1000-2000 J/kg centered
   on north GA will shift east into SC later this afternoon. Isolated
   to scattered thunderstorms will develop along and just ahead of a
   weak surface trough shifting slowly south across NC to upstate SC.
   The region will lie within the gradient of weak to moderate
   mid-level northwesterlies, well to the southwest of a deep upper low
   over the Canadian Maritimes. While low-level flow will remain weak
   and veered to the west-southwest, 15-25 kt effective bulk shear
   should support some multicell clustering and a threat for isolated
   damaging winds and severe hail.

   ...Northeast...
   A secondary mid-level impulse embedded within the larger-scale
   trough on the backside of the deep upper low over the Canadian
   Maritimes should aid in isolated to scattered higher-based
   convection. MLCAPE will remain weak owing to surface dew points only
   in the mid 40s to around 50 F. But moderate speed shear through the
   cloud-bearing layer should foster small to marginally severe hail
   growth in the deeper cores. This combined with an inverted-v
   thermodynamic profile will support a threat for locally damaging
   winds. Refer to the SPC Fire Weather Outlook for additional
   information.

   ...Northern CA to northern UT/southern ID...
   An upper low will wobble over the San Joaquin Valley through
   tonight. A belt of modest buoyancy with MLCAPE of 600-1200 J/kg
   should develop at peak heating within a largely west/east-oriented
   arc across northern CA to northern UT/southern ID. Scattered
   thunderstorms are expected within this buoyancy plume by late
   afternoon. While moderate mid-level flow will generally be displaced
   to the south, 20-30 kt southeasterlies around 500 mb will support
   some multicell clustering and a primary threat of isolated severe
   wind gusts. Small to marginally severe hail will also be possible in
   deeper updrafts.

   ...NM and the TX Trans-Pecos...
   Downstream of the CA upper low, scattered thunderstorms will develop
   within a modest buoyancy plume characterized by MLCAPE of 700-1400
   J/kg. The bulk of stronger mid-level flow should remain displaced
   west of the buoyancy/higher PW plume in AZ, as a low-amplitude
   mid-level ridge tries to hold over central NM. As such, convection
   will likely struggle to initially organize with sporadic severe
   gusts and small hail being the main threats. Somewhat greater
   effective shear should occur from the TX Trans-Pecos to the Raton
   Mesa during the early evening, where isolated marginally severe
   storms may occur.

   ...South FL...
   Morning convection along the southeast FL coast has yielded outflow
   that has pushed inland over the Everglades. Later afternoon
   convection will probably be focused along this boundary into
   southwest FL. While a 50-kt speed max at 500 mb was sampled in the
   12Z Miami sounding, guidance is consistent with weakening mid-level
   winds through the afternoon. It still should remain sufficient for a
   transient cell or two with mid-level rotation, and supportive of a
   brief threat for severe wind/hail.

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