SPC AC 280718

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0218 AM CDT Tue Mar 28 2023

   Valid 301200Z - 311200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   CENTRAL AND EASTERN NEBRASKA...AND PARTS OF OKLAHOMA INTO NORTHERN
   TEXAS...

   ...SUMMARY...
   Isolated strong storms may produce hail across parts of
   central/eastern Nebraska Thursday evening. A more conditional threat
   for severe thunderstorms will exist late Thursday afternoon into
   early Friday morning across parts of Oklahoma and northern Texas.

   ...Synopsis...

   An upper trough extending from the northern Rockies to southern CA
   will shift east on Thursday, extending from the northern Plains to
   the southern Rockies by Friday morning. Strong deep-layer
   southwesterly flow will overspread much of the southern/central
   Plains toward the Mid-MO Valley and Upper MS Valley by late
   afternoon into the overnight hours. A surface lee cyclone is
   forecast to deepen as the upper trough and stronger height falls
   spread east over the Rockies. The resulting increase in southerly
   low-level flow will quickly transport moisture northward across
   TX/OK into eastern portions of the central Plains during the
   afternoon and continuing through the overnight hours. A conditional
   risk of severe storms will exist near/just east of a surface dryline
   across parts of OK/north TX. Meanwhile, elevated thunderstorms ahead
   of the surface low across parts of NE are expected during the
   evening and may pose a marginal hail threat.

   ...Central/Eastern NE...

   Strong warm advection through the first half of the period will
   transport 50s surface dewpoints northward across eastern NE ahead of
   the surface low tracking northeast across the central Plains.
   Steepening midlevel lapse rates will contribute to modest elevated
   instability amid strong vertical shear and increasing large-scale
   ascent. This may be sufficient to support a marginal hail threat
   with convection developing near 00z.

   ...OK/TX Vicinity...

   The severe risk across the southern Plains will likely remain
   conditional from late Thursday afternoon into early Friday morning.
   The main upper trough will remain too far west for strong ascent and
   height falls to overlap increasing boundary-layer moisture and
   favorable vertical shear until near the end of the forecast period.
   Capping will likely preclude convection through peak heating.
   However, forecast soundings indicate varied strength of the cap, and
   the 00z GFS/ECMWF/GEFS show a weak QPF signal near the dryline by
   21-00z. There are some indications that a weak lead shortwave
   impulse may eject from northern Mexico/southwest TX toward OK during
   the afternoon. It is uncertain if this will provide sufficient
   forcing along the dryline to establish convection. If a storm can
   develop, low to mid 60s F surface dewpoints and steep midlevel lapse
   rates will support 1000-1500 J/kg MLCAPE amid supercell wind
   profiles. If a storm can become sustained, all severe hazards would
   be possible. However, this scenario is highly conditional.

   Overnight, a southwesterly low-level jet will increase and stronger
   height falls/large-scale ascent will begin to impinge on the area.
   Elevated thunderstorms may develop, posing a hail threat, toward
   Friday morning.

   ..Leitman.. 03/28/2023

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