SPC AC 100628

   Day 2 Convective Outlook RESENT 1
   NWS Storm Prediction Center Norman OK
   1228 AM CST Fri Dec 10 2021

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO
   AND TENNESSEE VALLEYS...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may occur Saturday from
   parts of the Ohio/Tennessee Valleys into the Southeast and
   Mid-Atlantic. Damaging wind gusts should be the main threat.

   ...Ohio and Tennessee Valleys/Southeast...
   An upper-level trough will move quickly eastward across the Great
   Lakes region and mid Mississippi Valley on Saturday. At the surface,
   a cold front will advance east-southeastward through the Ohio and
   Tennessee Valleys. A squall line is forecast to be ongoing ahead of
   the front at the start of the period with this squall line moving
   eastward across the Ohio and Tennessee Valleys into the Appalachians
   by late afternoon. NAM forecast soundings ahead of the front around
   16Z from southwest Ohio to middle Tennessee have MLCAPE from 500 to
   750 J/kg. Surface winds are veered to the south-southwest and very
   strong speed shear is present in the low to mid-levels. 0-6 km shear
   is forecast to be in the 85 to 95 knot range along the front. This
   should support a severe threat, with wind damage and an isolated
   tornado threat possible along the stronger parts of the squall line.
   The weak instability and time of day does add conditionally to the
   severe potential. But parameters suggest that the shear should be
   strong enough to overcome the weakness in instability. At this time,
   will add a slight risk mainly for wind-damage potential from
   southern Ohio south-southwestward into middle Tennessee.

   Further southwest into parts of the Southeast, a cold front will
   advance southeastward through the lower Mississippi Valley during
   the day. Surface dewpoints in the mid 60s F ahead of the front
   should yield MLCAPE around 500 J/kg. This combined with 0-6 km shear
   in the 50 to 60 kt range should support an isolated wind-damage
   threat. Large-scale ascent will be weak suggesting that low-level
   convergence will be the main driver for convective development. For
   this reason, any severe threat associated with the squall-line
   should remain marginal.

   ...Mid-Atlantic...
   An upper-level trough will move quickly northeastward across the
   lower Great Lakes region on Saturday. At the surface, a cold front
   will move eastward across the central Appalachians during the
   afternoon, with a squall line located ahead of the front. Surface
   dewpoints ahead of the front in the Mid-Atlantic are forecast to be
   in the upper 50s and lower 60s F with instability remaining weak
   (MUCAPE of 200 to 400 J/kg). The stronger part of the upper-level
   system will move northeastward into southern Quebec and this should
   result in a weakening squall line during the early to mid evening.
   An isolated wind-damage threat and potential for brief spinups may
   still be possible if parts of the squall line remain organized.
   However, any severe threat should be conditional and will probably
   be isolated. Will keep the threat level at marginal at this time.

   ..Broyles.. 12/10/2021

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z