SPC AC 021259

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0659 AM CST Mon Jan 02 2023

   Valid 021300Z - 031200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
   OF EAST TEXAS...EASTERN OKLAHOMA...ARKANSAS...THE MO BOOTHEEL
   VICINITY...EXTREME WESTERN TENNESSEE... EXTREME NORTHWESTERN
   MISSISSIPPI...AND NORTHERN LOUISIANA....

   ...SUMMARY...
   All severe-thunderstorm hazards are possible today and tonight over
   eastern Oklahoma and the Arklatex region to southeastern Kansas, the
   Ozarks, and parts of the Mid-South.  Tornadoes (some strong) and
   damaging gusts will be the greatest threats.

   ...Synopsis...
   The mid mid/upper-level feature for this forecast will be a
   synoptic-scale cyclone, now covering much of the Four Corners region
   and eastern Great Basin.  The associated 500-mb low -- initially
   centered over southern UT -- will move erratically east-
   northeastward across CO and the central High Plains through the
   period, reaching central NE by 12Z tomorrow.  The trough to its
   south should shift over NM, west TX, and the southern High Plains,
   becoming less-amplified and more poorly defined overnight amidst a
   broad belt of prevailing cyclonic flow aloft.

   At the surface, 11Z analysis showed an elongated area of low
   pressure from near RTN to the northern TX Panhandle, with Pacific
   cold front from the central Panhandle across the Permian Basin to
   central Chihuahua.  A dryline preceded that front over the southern
   Caprock area of west TX, southward to northern Coahuila.  A
   double-structured warm front -- with the southern segment weakening
   and the northern strengthening -- was drawn across north TX to
   northern MS, and over northern OK and southern MO, respectively. 
   The warm front will consolidate close to the northern position
   through the remainder of the morning, then move northward to near
   I-70 in eastern KS/MO/IL/IN by 00Z.  By then, the low should move to
   central KS, with cold front southwestward across central OK and
   northwest/west-central TX to northern Coahuila, overtaking the
   dryline from north-south, and effectively becoming one boundary with
   characteristics of both.  By 12Z, the low should reach southeastern
   NE and occlude, with triple pint over western IL, and cold front
   across southern MO, southwestern AR, and east-central/south-central
   TX.

   ...Eastern OK/TX/KS to Ozarks/Mid-South...
   Multiple rounds of thunderstorms are forecast through the period in
   the form of supercells, clustered multicells and quasi-linear modes,
   offering all severe hazards.  A few strong tornadoes (capable of
   EF2+ damage) are possible, along with severe downdrafts.  Mainly in
   western to central parts of the outlook area, where relatively
   discrete modes and greater lapse rates will be possible, a
   large-hail threat will exist as well.

   Substantial height falls and increasing southwest flow aloft will
   spread over the central/southern Plains and lower/mid Mississippi
   Valley ahead of the mid/upper-level trough.  This will support a
   broad belt of low-level warm advection and moisture transport in the
   moist sector, as a modest EML spreads from the higher terrain of MX
   and NM across most of the southern Plains.  Lower/mid 60s F surface
   dewpoints already extend into southeastern parts of MO and OK, and
   should increase through the day over the outlook area. As that
   occurs, a 50-60-kt LLJ should cover much of eastern OK/TX and
   western AR/LA through the afternoon, shifting northeastward tonight
   across MO/AR toward the lower OH Valley and increasing to 60-70 kt,
   but remaining strong farther southwest over the Mid-South.  This
   process will enlarge low-level hodographs, leading to a broad area
   of 200-400 J/kg effective SRH (locally higher, with much of that SRH
   in the 0-1-km layer) collocated with favorable buoyancy.

   Over most of OK and north TX, EML-related capping/MLCINH should
   suppress convection until the afternoon, when increasing large-scale
   lift spreads over the area.  However, EML effects will weaken
   eastward, and thunderstorms should develop and deepen gradually as
   soon as midday in the warm-advection plume across east TX, northern
   LA, AR, and the adjoining lower Mississippi Valley.  Some severe/
   supercell potential may develop with any of this activity that can
   sustain access to surface-based parcels, particularly over east TX,
   LA and AR, where 1000-1500 J/kg MLCAPE should develop amidst slow,
   muted diurnal heating (through persistent cloud cover).

   Buoyancy should be stronger westward across east and north TX and
   eastern OK ahead of the front, where steeper deep-layer lapse rates
   and comparable boundary-layer moisture foster a plume of 1500-2000
   J/kg preconvective MLCAPE.  This will support one or more bands of
   convection -- initially with discrete supercells possible, evolving
   toward quasi-linear with time.  Thermodynamic conditions will get
   weaker with northward extent through and beyond the Ozarks, over
   eastern KS, MO and western IL.  However, where sustained convection
   can access surface-based effective-inflow parcels, the moisture,
   lift and low-level shear each will be in place to support at least a
   marginal all-hazards threat (but with eastward extent, trending away
   from hail toward wind/tornado).

   ..Edwards/Broyles.. 01/02/2023

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