SPC AC 111953

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0253 PM CDT Thu May 11 2023

   Valid 112000Z - 121200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS KANSAS INTO
   SOUTHERN OKLAHOMA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHEAST
   LOUISIANA INTO SOUTHERN MISSISSIPPI...

   ...SUMMARY...
   Scattered severe thunderstorms remain possible into this evening
   across parts of the Great Plains centered on Kansas and Oklahoma.
   The greatest threat for a couple strong tornadic supercells should
   exist across central and southern Oklahoma between 5 to 9 PM CDT.
   Isolated severe storms including a couple of tornadoes and damaging
   winds are also expected across the Lower Mississippi Valley.

   ...Kansas into Oklahoma...
   The severe threat continues across much of KS where an arcing band
   of convection has developed from northwest to southern/southwestern
   KS. Reflectivity/velocity data from regional radars show some cells
   taking on supercellular characteristics with persistent
   mesocyclones, including at least one reported tornado. So while the
   overall kinematic environment appears somewhat marginal based on
   latest RAP mesoanalyses (effective SRH values 100 m2/s2 or less),
   the environment is conducive for organized convection, and should
   remain so through the evening as the nocturnal jet strengthens after
   00 UTC. 

   Further south, a residual cold pool across central to northern OK
   from early-morning convection has introduced considerable
   uncertainty into the severe weather potential. While an intense
   storm or two remains possible across north-central OK to southern
   KS, confidence in the tornado potential has diminished due to the
   detrimental influence of the cold pool on low-level thermodynamics
   and questions regarding adequate air mass recovery into the evening.
   The 10% tornado risk probabilities have been bifurcated to reflect
   where confidence in the tornado threat is highest. See MCD #764 for
   additional information on recent observed trends and forecast
   expectations for southern/central OK.

   ...Lower MS Valley...
   An organized, but outflow-dominant, MCS has developed over the past
   several hours and continues to propagate eastward into southern MS.
   Latest radar trends and surface observations/analyses suggest that
   this feature may begin to take on a more southeasterly track through
   the late afternoon/early evening along a diffuse buoyancy/theta-e
   gradient into southeast MS. Although the system appears to be
   outflow dominant, damaging winds remain probable given recent
   measured wind speeds above 50 mph.

   ..Moore/Leitman.. 05/11/2023

   .PREV DISCUSSION... /ISSUED 1141 AM CDT Thu May 11 2023/

   ...Southern/Central Great Plains...
   A cluster of storms continues to persist at late morning across
   south-central Oklahoma, and remain somewhat strong in proximity to
   the Red River, with other more recent/initial arcing bands of
   thunderstorm development in a separate regime across southeast
   Colorado. This is occurring near/ahead of the largely stacked
   cyclone centered near the Raton Mesa vicinity of northeast New
   Mexico/southeast Colorado. 12z upper-air analysis features of a zone
   of stronger mid/high-level winds across the south-central High
   Plains immediately preceding this cyclone, while winds aloft
   (especially high level) are otherwise relatively weak across the
   region. A moist boundary layer is noted across the south-central
   High Plains, with relatively high PW values and 12+ C 850mb
   dewpoints observed at both Dodge City and Amarillo per 12z RAOBs, a
   northwestward extension of the rich low-level moist axis that
   otherwise extends across the middle part of Texas.

   The surface cyclone is expected to deepen as it develops toward
   southwest Kansas today, with the dryline mixing into western
   Oklahoma and arcing south-southwest into the Edwards Plateau. A
   north/south-oriented inverted trough/quasi-stationary front will
   extend north to the western Dakotas.

   Multiple corridors of increasing severe potential are expected this
   afternoon. As focused ascent overspreads southeast Colorado into
   western Kansas, low-topped supercells will become increasingly
   probable midday to early afternoon within a marginally buoyant
   environment initially. A smaller area of supercell development may
   also form in the wake of this activity near the Colorado/Kansas
   border later in the afternoon and yield a persistent severe threat
   into early evening.

   Farther south, the aforementioned early day persistent cluster of
   storms across south-central Oklahoma casts some uncertainty,
   particularly in regards to its north, with potential ramifications
   for areas such as northern Oklahoma/far southern Kansas with the
   possibility of somewhat more isolated storms. A volatile supercell
   environment should still evolve to the west of this cluster and
   ahead of the dryline, especially across southwest into
   west-central/south-central Oklahoma. A pronounced gradient in MLCAPE
   is likely by late afternoon to early evening as the most robust
   boundary-layer heating post-dryline occurs in Texas, while a plume
   of richer moisture advects north ahead of it. This should support
   MLCAPE approaching 1500 J/kg near the OK/KS border to around 3500
   J/kg along the Red River. 

   While a mid-level jetlet over the southern High Plains will be in an
   overall weakening state, its favorably timed eastward translation
   across the dryline should support sustained supercells. Upper-level
   wind fields will weaken with height and the bulk of hodograph
   structure will consist of enlarged curvature from 0-3 km. This
   suggests supercells should tend towards an HP character with a
   slow-moving cluster type evolution. A moderate increase in low-level
   flow early this evening could support a strong tornado risk,
   especially across southern/central Oklahoma with the most intense
   supercells. A small MCS/embedded supercell cluster will probably
   persist into eastern Oklahoma before eventually weakening during the
   overnight.

   ...ArkLaMiss/Lower Mississippi Valley to Southeast...
   The environment that potentially produced a couple of tornadoes this
   morning across northern Louisiana is expected to generally persist
   eastward across the ArkLaMiss into the afternoon, with a continued
   potential for mostly brief tornadoes. There will also likely be some
   increase in damaging wind potential as storm mergers occur and the
   downstream boundary layer warms and destabilizes. Other more
   localized/episodic strong to severe storms capable of damaging winds
   are possible farther east into Alabama, southwest Georgia, and
   northern Florida, primarily before sunset.

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