SPC AC 300654

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1254 AM CST Thu Dec 30 2021

   Valid 311200Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTH TEXAS
   INTO THE TENNESSEE VALLEY....

   ...SUMMARY...
   Severe weather is possible from north Texas to the Tennessee Valley
   New Years Eve into the early morning hours on Saturday. Storms will
   be capable of all severe-weather hazards including large hail,
   damaging winds, and a few tornadoes.

   ...Synopsis...
   A mid-level shortwave trough will be located near the Baja Peninsula
   Friday morning and move northeast through the day to the Central
   Plains by 12Z Saturday. This will result in a strengthening surface
   low in the southern High Plains during the day Friday, which will
   move along the surface front to somewhere near the Ozarks by
   Saturday morning. 

    ...Red River vicinity...
   Low-level flow will strengthen through the day in response to the
   deepening surface low near the TX/OK Panhandles through the day
   Friday. This will bring low to potentially mid 60s dewpoints
   northward to at least the Red River and possibly overspreading much
   of southeast Oklahoma. This low-level moisture will contribute to
   weak to potentially moderate instability in the Red River region
   Friday afternoon/evening. As height falls overspread the southern
   High Plains Friday evening and isentropic ascent increases due to
   the strengthening low-level jet, some thunderstorms may develop
   across northeast Texas into southeast Oklahoma Friday evening. There
   is still considerable uncertainty whether storms can form in this
   area with the ECMWF the most aggressive developing storms. Moderate
   buoyancy and strong tropospheric flow would support supercell storm
   mode. All severe hazards possible with any storms which can develop
   in this region.

   Farther west, there is better agreement among guidance for
   thunderstorms to develop ahead of the mid-level shortwave trough on
   the western extent of the low-level moisture field somewhere from
   east of Lubbock to east of Midland, Texas. Limited instability
   should temper the severe-weather threat initially, but the threat
   will likely increase as it continues east toward greater low-level
   moisture. This thunderstorm activity may evolve into elevated storms
   into Oklahoma and potentially surface-based convection across
   northern Texas through the overnight hours Saturday night. 

   ...Mid Mississippi Valley into the Tennessee Valley...
   All 00Z guidance has trended slower with the mid-level shortwave
   trough on Friday night which has pushed back the expected timing of
   convection in the Mid-Mississippi Valley into the Tennessee Valley.
   The GFS now has convection forming between 04Z and 06Z across
   Arkansas with the NAM after 06Z. However, despite these timing
   differences, widespread thunderstorms are anticipated along this
   front between 06Z from eastern Oklahoma into the Ohio Valley.

   Thunderstorms will likely remain near the front as drier air aloft
   moves in from the south, limiting instability. All model guidance
   shows this dry air aloft across much of the Gulf of Mexico this
   morning which was observed by the 00Z KBRO and KCRP RAOBs.
   Therefore, the zones of decreased low-level moisture and instability
   depicted in the model guidance are likely true. The primary impact
   this drier air will have is keeping most of the warm sector capped
   away from the surface front, while the impacts to storm activity
   near the front are less clear. Have trimmed the marginal and slight
   risk from the prior Day 3 outlook on the southern and eastern edge
   where capping is likely. 

   Otherwise, storm intensity along the front remains questionable due
   to only modest instability. The shear will be very favorable along
   this zone and would support all severe-weather threats including a
   few tornadoes, but most forecast soundings show weak lapse rates and
   MLCAPE around 250 to 500 J/kg. However, better moisture aloft is
   expected to spread northward from the Gulf late in the period. This
   would increase low-level instability and possibly lead to a greater
   severe-weather threat, especially if this moisture plume arrives 3
   to 6 hours earlier.

   ..Bentley.. 12/30/2021

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