SPC AC 151927

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0127 PM CST Wed Feb 15 2023

   Valid 152000Z - 161200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   ARKANSAS INTO WESTERN TENNESSEE AND NORTHERN MISSISSIPPI...

   ...SUMMARY...
   Severe thunderstorms with large hail are possible over parts of
   north Texas and southern Oklahoma this afternoon and evening.  A
   threat for tornadoes, severe-thunderstorm winds and isolated hail
   will also develop overnight over the lower Mississippi
   Valley/Mid-South region.

   Little change was made to the previous outlook.

   Low-level moisture continues to increase across the southern Plains,
   although total precipitable water values remain quite low with the
   northern portion of the 50+ F dewpoints plume. Eventually, strong
   heating and continued moisture advection will lead to an uncapped
   air mass with scattered storms developing over western north TX into
   southern OK. Large hail will be the main concern, mainly after 00Z.

   Overnight, a tornado threat is expected to develop over eastern AR,
   northern MS, and western TN, beneath a strong low-level jet and with
   access to an instability plume extending southwest through the
   ArkLaTex. Effective SRH near 300 m2/s2 and MLCAPE over 1500 J/kg may
   support a strong tornado or two.

   ..Jewell.. 02/15/2023

   .PREV DISCUSSION... /ISSUED 1032 AM CST Wed Feb 15 2023/

   ...Synopsis...

   A closed upper low and attendant shortwave trough located over the
   Four Corners this morning will continue to shift east toward the
   southern Rockies and adjacent central/southern Plains through
   tonight. A lead shortwave impulse was noted in 15z water vapor
   imagery as of 15z ejecting over the southern Rockies in NM into the
   southern High Plains. Increasing ascent and a strengthening
   low-level jet associated with this feature will drive convective
   initiation by late afternoon/early evening across northern
   TX/southern OK.  

   At the surface, strengthening cyclogenesis is expected to ensue over
   the next few hours across the southern High Plains. As this occurs,
   increasing southerly low-level flow will continue to transport Gulf
   moisture northward across the eastern half of TX into southeast OK,
   and eastward across the Lower MS Valley. A sharpening
   dryline/Pacific front oriented north to south from south-central OK
   into central TX, and a warm front lifting north of the Red River
   will focus initial thunderstorm development in the 21-00z time
   frame. 

   ...Southern OK/Northern TX...

   Most guidance, including CAMs, initially develops supercells near
   the I-35 corridor in south-central OK/north TX in the 21-00z time
   frame. Modified forecast soundings for expected afternoon dewpoints
   near 60 F and temperatures in the mid/upper 70s indicate strong
   MUCAPE around 1500-2500 J/kg. Much of this instability is focused in
   the mid and upper levels of the sounding profile. Rapidly increasing
   and vertically veering winds with height are producing enlarged
   low-level hodographs, becoming elongated above 3 km. This
   thermodynamic and kinematic profile will favor initial supercell
   development. Furthermore, many significant hail sounding analogs are
   noted and hail in excess of 2 inches in diameter appears possible
   early in thunderstorm evolution. Deeper low-level moisture and a
   more established warm sector will remain somewhat east of this area.
   As a result, initial thunderstorms may have a higher LCL with some
   low-level dryness above the surface to around 1-1.5 km. This could
   enhance downdraft strength and also result in isolated to widely
   scattered damaging gusts as well.

   As a low-level jet increases after 00z, SRH values are forecast to
   increase from around 150 m2/s2 to over 250 m2/s2 and low-level
   moistening will increase with eastward extent. At this point, any
   semi-discrete convection will likely become more linear.
   Nevertheless, strong low-level shear and favorable 0-3 km hodographs
   will support rotation within embedded cells and mesovortices. 

   ...Arklatex/East TX, to TN Valley/Mid-South...

   The severe threat will shift east across the Arklatex vicinity
   toward the Mid-South this evening into the overnight hours. Damaging
   gusts, isolated large hail, and tornadoes (a couple EF-2+ in
   strength) are expected.

   A more conditional severe threat will exist this afternoon/early
   evening across east TX into southern/central LA. Large-scale ascent
   will remain weaker across this area, and the surface front will
   remain well east of this area until late in the period. However, a
   quality warm sector will reside across this area with mid to upper
   60s surface dewpoints expected. Low-level confluence and some
   influence on the margins of strong low/midlevel flow could support
   the development of a supercell or two. If this occurs, all severe
   hazards will be possible. However, this scenario remains uncertain
   and too conditional and will maintain a categorical Slight risk.  

   Between 03-06z a southwesterly low-level jet will increase to 50-60
   kt and overspread AR into northern MS and western TN, and eventually
   into KY and vicinity by 12z Thursday. Multiple bands/clusters of
   thunderstorms will be possible in low-level confluence within the
   northward developing low-level moisture plume. Embedded supercells
   will offer all severe hazards. The most favorable overlap of rich
   boundary-layer moisture and favorable low-level hodographs and SRH
   will exist across eastern AR into northwest MS/western TN vicinity
   after 00z. The tornado threat will be greatest across this area,
   with environmental parameter supporting the potential for a couple
   of significant tornadoes (EF-2+ intensity) in addition to damaging
   gusts. 

   With northward extent, instability will become less toward western
   KY and vicinity later tonight. Nevertheless, strong shear and
   sufficient instability will support damaging wind potential into
   early Thursday morning.

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