SPC AC 050559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Mon Jun 05 2023

   Valid 051200Z - 061200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE CENTRAL APPALACHIANS...DEEP SOUTH TEXAS...AND WESTERN MONTANA...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may occur today across
   portions of the central Appalachians, deep south Texas, and western
   Montana. Both occasional damaging winds and hail appear possible.

   ...Synopsis...
   A mid-level trough will meander along the Northeast coastline as a
   second upper trough impinges on the Southwest today. Adequate
   low-level moisture will continue to overspread much of the western
   and central U.S. into the Southeast amid weak tropospheric flow,
   encouraging the development of at least scattered pulse
   thunderstorms from late morning into the evening hours. Given
   adequate buoyancy associated with these storms, a sparse severe gust
   or instance of large hail may occur. However, embedded within the
   broad area encompassing thunderstorm potential are a few regions
   where organized rounds of strong to isolated severe thunderstorms
   are possible.

   ...Central Appalachians...
   A mid-level impulse, embedded in the broader northwesterly flow on
   the backside of the aforementioned mid-level trough, will graze the
   central Appalachians during the afternoon. By this time, adequate
   boundary-layer heating will support 70+ F surface temperatures amid
   low 60s F dewpoints and 6.5-7.5 low to mid-level lapse rates,
   contributing to 2000-3000 J/kg MLCAPE. Modest speed shear above 700
   mb will encourage somewhat elongated hodographs, which may promote a
   few organized multicellular clusters and longer-lived single cells
   capable of producing some large hail and a couple of strong to
   potentially severe gusts.

   ...Deep South Texas...
   An MCV is expected to drift slowly southward across central into
   southern TX through the forecast period, with an increase in
   thunderstorm development and intensity expected by late morning into
   the afternoon in tandem with surface heating. While lapse rates are
   not forecast to become particularly steep, 6-7 C/km tropospheric
   lapse rates atop mid 80s/low 70s F surface temperatures/dewpoints
   will contribute to 2500-3500 J/kg SBCAPE. Furthermore, some
   veering/strengthening of winds with height to the right of the MCV
   trajectory will contribute to elongated and curved hodographs.
   Multicellular clusters and transient supercells are possible. Large
   hail and damaging gusts are the main threats, though a brief tornado
   cannot be ruled out.

   ...Western Montana...
   A mid-level impulse will graze western MT this afternoon as the
   boundary layer destabilizes. While low-level moisture will be
   modest, 7-8 C/km low to mid-level lapse rates will contribute to
   tall, thin MLCAPE over 1500 J/kg. While tropospheric flow will be
   predominantly unidirectional, adequate speed shear will promote
   elongated hodographs, supporting some longer-lived, organized
   multicells capable of an isolated severe gust/hail threat.

   ..Squitieri/Goss.. 06/05/2023

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