SPC AC 071640

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1140 AM CDT Mon Aug 07 2023

   Valid 071630Z - 081200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS FAR
   EASTERN KY/NORTHEAST TN/NORTHWEST NC...WESTERN AND NORTHERN
   VA...SOUTHERN AND EASTERN WV...CENTRAL MD...AND SOUTH-CENTRAL PA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
   AND SOUTHERN HIGH PLAINS...

   ...SUMMARY...
   A severe weather outbreak is expected across parts of the eastern
   U.S. today with widespread and locally destructive damaging winds
   and tornadoes as the greatest threats, especially across the
   southern/central Appalachians and Mid-Atlantic States.

   ...Southeast to the Upper Ohio Valley to the Mid-Atlantic States...
   Owing to a very moist/unstable air mass and very strong winds aloft
   for August, a widespread severe-weather risk is already unfolding at
   late morning/midday across a broad region, initially west of the
   Appalachians spine. Refer to ongoing Watches and Mesoscale
   Discussions for the latest regional details.

   A shortwave trough over the Lower Ohio Valley will continue to
   advance toward the northern Appalachians by evening. A pair of
   500-mb speed maxima from 55-65 kts are expected to be centered by
   late afternoon across eastern KY/TN and southern WV into western
   VA/NC, and separately over the Mid-South. Peak flow within an
   expansive 700-mb jet should be centered between the 500-mb maxima
   across the TN Valley. A plume of large potential buoyancy supported
   by high PW and steep mid-level lapse rates, and centered over the
   Mid-South/TN Valley will expand east-northeast towards the
   central/southern Appalachians with an expansive swath of MLCAPE from
   2000-3500 J/kg expected by peak heating.

   Ongoing storms across eastern portions of TN/KY and WV/southern OH
   will progress into an increasingly favorable thermodynamic and
   kinematic environment downstream, yielding many supercells capable
   of producing large hail, damaging winds, and tornadoes. Upscale
   growth into several linear clusters with embedded supercells is
   anticipated this afternoon as convective coverage becomes widespread
   from PA/MD south-southwest across the southern Appalachian states.
   Forecast soundings suggest the greatest tornado threat will probably
   exist across eastern KY/TN northeast across southern/eastern WV,
   western VA, central MD and into southeast PA. Given the supercell
   wind profiles, significant severe wind gusts will also be possible
   on a localized basis.

   Across the Southeast, aided by a separate mid-level speed max,
   linear clusters of storms will continue to develop and spread
   generally eastward across parts of the TN Valley toward the southern
   Appalachians and Carolinas, with damaging winds as the most common
   hazard.

   ...Central High Plains...
   No changes warranted for this region. A 50-60 kt mid-level speed max
   should become centered near the NE/CO/KS border vicinity by late
   afternoon with approach of a low-amplitude shortwave impulse
   currently over southeast ID. This will overlap a confined
   north/south-oriented corridor of moderate buoyancy with MLCAPE of
   1500-2500 J/kg along a lee trough across the similar tri-state area.
   Initial high-based thunderstorm development is anticipated off the
   higher terrain of CO/WY and will intensify as it impinges on the
   larger buoyancy during the early evening. A few supercells with very
   large hail will be possible along with a meso-beta scale corridor
   favorable for a tornadic supercell or two. Clustering of supercells
   may yield a short-duration uptick in severe wind gust potential
   across parts of western KS before convection spreads away from the
   relatively narrow instability plume and encounters increasing MLCIN
   after sunset.

   ...Southern High Plains...
   A wind-driven Slight Risk has been introduced for portions of
   eastern New Mexico into the Texas South Plains for later this
   afternoon and evening. Strong westerlies, particularly by August
   standards, and a hot/well-mixed boundary layer should support at
   least some severe storms capable of severe-caliber wind gusts.

   ..Guyer/Wendt.. 08/07/2023

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