SPC AC 081723

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1123 AM CST Wed Feb 08 2023

   Valid 091200Z - 101200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE SOUTHEAST AND THE GREAT LAKES/OHIO VALLEY...

   ...SUMMARY...
   Isolated severe thunderstorms are possible on Thursday across the
   Southeast including parts of Alabama, north Florida and Georgia, as
   well as the Midwest including Indiana, Ohio, and southern Michigan.

   ...Synopsis...
   A mid-level shortwave trough and attendant jet streak will move
   across the Great Lakes/Ohio Valley region on Thursday. Meanwhile,
   the larger-scale positively tilted trough will amplify across the
   central CONUS and into the Southern Plains. A ~1000mb surface low is
   expected to be located in the vicinity of central Illinois at 12Z
   Thursday. This surface low is expected to maintain its intensity
   around 1000 mb as it moves northeast into southern Ontario by
   Thursday evening. A cold front will trail this surface low and could
   be the focus for severe convective wind gusts across portions of the
   Great Lakes/Ohio Valley during the day Thursday. Farther south along
   the cold front, limited forcing should keep thunderstorm activity
   minimal in eastern Tennessee/Kentucky. However, more robust
   convection is expected across portions of the Southeast where
   low-level Gulf moisture should provide ample instability for a few
   strong to severe storms amid broad, weak ascent. 

   ...Ohio Valley/Great Lakes...
   An unseasonably moist low-level airmass will be present ahead of the
   cold front Thursday morning with a HREF ensemble mean dewpoint in
   the mid 50s across eastern Indiana. This will result in low-level
   buoyancy along and ahead of the cold front Thursday morning. In
   fact, convection will likely remain quite shallow with forecast
   soundings showing an equilibrium below 3km. However, strong forcing
   from frontal convergence and dCVA across the region should lead to a
   fast moving broken line of convection during the day. Lightning is
   unlikely with this activity due to its shallow nature, but
   convection along the cold front could bring strong to potentially
   severe winds to the surface given the 70-75 knot 1km flow across the
   region. Extensive cloud cover and minimal boundary layer heating
   should keep mixing depth shallow. However, if even brief clearing
   can occur ahead of the front with some boundary layer heating, a
   greater threat for severe wind gusts will likely occur. If this were
   to occur, it would be most likely across portions of north-central
   and northeast Ohio where some CAM guidance suggests some clearing
   could occur during peak heating. 

   ...Gulf Coast from far southeast Mississippi to southwest
   Georgia/Florida Panhandle...
   Remnant Gulf moisture with low to mid 60s dewpoints will remain
   ahead of the cold front across southeast Mississippi on Thursday
   morning. This best moisture will only extend around ~75 miles inland
   and therefore the marginal severe weather threat will be confined to
   areas in closer proximity to the coast. The cold front will move
   slowly east across this region during the day before stalling by
   Thursday afternoon across the central Florida Panhandle. Weak height
   falls across the region and convergence along the front should be
   sufficient for storm development during the day. A few strong to
   severe storms are possible, including the potential for supercell
   structures given 35-40 knots of effective shear. However, weak
   instability (400-700 J/kg MLCAPE) and weak lapse rates (~ 6 C/km)
   will foster a thermodynamic environment which is less than favorable
   for a more widespread threat. The primary threats will be damaging
   winds from any supercell structures or bowing segments which
   develop. In addition, a tornado or two is possible given the
   significant directional shear in the lowest 1km, but the relatively
   weak flow in this layer (less than 25 knots) and the aforementioned
   limited thermodynamic environment should mitigate the overall
   tornadic threat.

   ..Bentley.. 02/08/2023

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