SPC AC 191257

   Day 1 Convective Outlook RESENT 1
   NWS Storm Prediction Center Norman OK
   0657 AM CST Wed Jan 19 2022

   Valid 191300Z - 201200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EAST TEXAS TO
   SOUTHERN ARKANSAS AND WESTERN MISSISSIPPI...

   ...SUMMARY...
   Damaging thunderstorm winds, isolated large hail, and a tornado or
   two may occur from afternoon and evening thunderstorms, mainly from
   east Texas to southern Arkansas and western Mississippi.

   ...Synopsis...
   In mid/upper levels, a series of shortwaves will contribute to the
   sharpening of a positively tilted mean trough from eastern Canada
   across the central Plains and southwestern CONUS to northwestern MX,
   by 12Z tomorrow.  A downstream perturbation -- apparent in moisture-
   channel imagery near the TX/NM line -- will eject east-northeastward
   into confluent flow aloft and deamplify through the period.  By 00Z,
   the feature should be located from the Ozarks to north-central TX. 
   By 12Z, it should extend from WV southwestward toward MEM.

   Surface analysis at 11Z showed a substantial cyclone centered over
   ON northeast of Lake Huron -- ahead of a northern-stream, mid/upper-
   level shortwave trough.  A cold front was drawn across southeastern
   Lower MI, western IN, southern IL, southeastern MO, and northwestern
   AR, to a weak frontal-wave low over east-central OK that is related
   to the approaching southern-stream perturbation.  The cold front
   extended from there across northwest TX, the TX South Plains, and
   east-central/north-central NM.  By 00Z, the cold front should extend
   across eastern NY, southwestern PA, eastern KY, mid TN, northern
   parts of MS/LA, and southeast/south-central TX.  By 12Z, the front
   should reach the Delmarva Peninsula, western NC, northern GA,
   southern parts of MS/LA, and the northwestern Gulf. 

   ...East TX to lower Mississippi Valley region...
   Scattered thunderstorms should form this afternoon into tonight
   along/ahead of the surface cold front, between the Mid-South region
   and southeast TX.  Damaging to marginally severe gusts and isolated
   large hail are possible, especially over LA/TX portions of the
   outlook areas, along with a tornado or two. 

   Lift should occur both with the front and a prefrontal, warm-sector
   convergence zone in a warm-advection plume.  Diurnal heating of an
   increasingly moist wedge of partially modified return-flow air
   (surface dew points of upper 50s to mid 60s F) will weaken MLCINH to
   negligible amounts by around 21Z.  This will help to offset modest
   but adequate mid/upper-level lapse rates and yield MLCAPE ranging
   from around 500-800 J/kg over east-central/southeastern AR to 800-
   1200 J/kg in east TX and northwestern LA.  Initial discrete to
   partly linear afternoon development is expected, amidst mean-wind
   and deep-shear vectors oriented about 30 deg rightward of convective
   lift axes.  Forecast soundings reasonably depict around 100 kt
   anvil-level winds and similar magnitudes of cloud-layer shear, with
   35-45-kt effective-shear magnitudes, supporting both organized
   multicells and at least some supercell potential.  After the initial
   mixed-mode phase, activity should become more linear, with embedded
   supercells and LEWPs/mesocirculations possible.

   With time this evening and tonight, the front will impinge on the
   warm sector and prefrontal ascent zone, faster than the inland
   advance of favorable boundary-layer theta-e.  This ultimately will
   narrow the surface-based warm sector from north to south across the
   lower Mississippi Valley region late this evening and tonight.  In
   addition, the lack of substantial upper support (with the
   perturbation's weakening and pulling away to the north) will
   contribute to declining overnight severe potential as well.

   ..Edwards/Broyles.. 01/19/2022

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