SPC AC 081254

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0654 AM CST Fri Dec 08 2023

   Valid 081300Z - 091200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   THE ARKLATEX REGION TO THE OZARKS...

   ...SUMMARY...
   Isolated large hail is possible this evening and tonight from parts
   of the Arklatex region to the Ozarks.

   ...Synopsis...
   An eastward-moving, amplifying, mid/upper-level trough is expected
   to shift into the central CONUS during the period, spreading an
   extensive field of height falls and strengthening flow aloft across
   much of the Plains States and Mississippi Valley.  Within the
   associated cyclonic flow, two main shortwave troughs will exert the
   most influence on large-scale lift and low-level mass response:
   1.  A northern-stream perturbation, apparent in moisture-channel
   imagery over the northern High Plains, forecast to move eastward and
   evolve to a closed 500-mb cyclone over MN by 12Z tomorrow.
   2.  An elongated, initially negatively tilted trough from the
   southern ID/northern NV region southeastward toward the Four
   Corners.  The southeastern part will break eastward/northeastward
   across the south-central Rockies today, reaching the MKC area around
   06Z, then accelerating northeastward into confluent flow fringing
   the northern-stream shortwave trough.  Meanwhile, the remainder
   should dig southeastward, consolidate and amplify, reaching northern
   NM and southern CO by 12Z.

   At the surface, 11Z analysis showed a low over extreme northwestern
   MN, with occluded/cold front arching across south-central IA and
   south-central KS to a weak low over northwestern OK, then over
   portions of the central/southern TX Panhandle and northeastern NM. 
   By 00Z, the main low should eject to northwestern ON, while the
   southern one ripples northeastward along the trailing cold front to
   southeastern KS.  The front should extend from there southwestward
   across south-central OK to northwest TX and east-central/
   southeastern NM.  By 12Z, the southern low should continue moving
   northeastward along the front to the MKE vicinity, with front
   trailing over east-central IL, southeastern MO, to near a line from
   LIT-TXK-ACT-FST.  An early-stage dryline was drawn from west-central
   OK south-southwestward to near BPG, then southward into northern
   Coahuila.  The dryline should shift eastward and become better-
   defined through the day, and by 00Z, extend from a frontal
   intersection over northeastern OK across north-central TX to the DRT
   area.  Overnight, the front will overtake a then-quasistationary
   dryline from north-south across OK.

   ....Ozarks to Arklatex...
   Widely scattered to scattered thunderstorms are possible tonight
   from western MO southward into parts of eastern OK/western AR,
   becoming more isolated toward the Arklatex region.  A few cells may
   organize enough to produce severe hail, particularly where more
   discrete convection is at least temporarily possible from the Ozarks
   southward.  Strong gusts also may penetrate to the surface from more
   linear, frontal convection over MO, but boundary-layer instability
   in that regime currently appears too limited to warrant an organized
   severe threat.

   Thunderstorms may develop over western parts of the outlook area
   (eastern OK and perhaps northeast TX) between 00-03Z, then move
   eastward to northeastward into portions of AR and the Arklatex
   region, offering occasional hail near severe limits.  In general,
   deep shear will increase with time area wide, while still being
   stronger with northward extent.  Meanwhile, moisture and buoyancy
   should increase southward.  The environment over southern parts of
   the outlook area -- around the Red River and Arklatex east of the
   front and dryline -- will become increasingly moist throughout the
   period, with 60s F surface dewpoints becoming common into parts of
   eastern OK and western AR.  This will support technically surface-
   based effective-inflow parcels in forecast soundings overnight. 
   However, a nocturnally cooled (temperatures also in the 60s),
   somewhat diabatically stabilized near-surface layer should be
   present.

   Frontal convection may be messy in mode, and lift sufficient to
   force surface-based storms in the warm sector appears nebulous at
   best.  As such, a seemingly favorable parameter space (e.g., MLCAPE
   around 1000-1500 J/kg collocated with 300-400 J/kg effective SRH
   under the LLJ, and 250-300 J/kg of 1/2-km SRH), may not be fully
   realized.  For now, the tornado potential (dependent on sustained,
   surface-based storm) is not zero, but still looks too conditional
   and low-end to introduce an unconditional area for that hazard.  The
   bulk of convection should be at least slightly elevated, with
   similar MUCAPE values and around 40-45 kt effective-shear
   magnitudes.

   ..Edwards/Gleason.. 12/08/2023

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z