SPC AC 270500

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1100 PM CST Fri Nov 26 2021

   Valid 281200Z - 291200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk of thunderstorms appears negligible across most of the U.S.
   Sunday through Sunday night.  However, some lightning may accompany
   stronger lake-effect snow showers and bands expected to develop near
   and southeast of Lake Erie during the late afternoon and evening.

   ...Discussion...
   Models indicate that amplification within the main belt of
   westerlies emanating from the mid-latitude Pacific will translate
   from ridging, inland of the Pacific coast into the Great Plains,
   into downstream troughing, east of the Mississippi Valley into
   western Atlantic.  Within this regime, the most prominent short wave
   trough is forecast to dig sharply southeast of the upper Great
   lakes, through the northern/mid Atlantic Seaboard vicinity by late
   Sunday night.  As it does, associated forcing for ascent appears
   likely to contribute to renewed surface cyclogenesis offshore,
   accompanied by a reinforcing cold intrusion across much of the East.

   At the same time, the remnants of a cut-off low appear likely to
   continue to weaken while becoming absorbed within a confluent regime
   across the Gulf Coast states, through the base of the large-scale
   mid-level troughing, across and offshore of the south Atlantic coast
   by Sunday evening.  While this may be accompanied by mid/upper-level
   moisture return and weak high-based convection across the Gulf coast
   vicinity and Florida Peninsula, generally dry and stable
   near-surface conditions appear likely to persist across this region,
   as an initial low/mid-level moisture return to Texas on Saturday
   becomes suppressed southward across the northwestern into central
   Gulf of Mexico.

   ...Lake Erie vicinity...
   A corridor of strong mid-level cooling (including temps of -20 to
   -30 C in the 700-500 mb layer) due to lift and cold advection is
   forecast to nose southeastward, across and southeast of the Lake
   Erie vicinity late Sunday afternoon and evening.  This will
   contribute to steepening low-level lapse rates and weak CAPE,
   particularly near the relatively warm lake waters.  The latest NAM
   forecast soundings, supported by the Rapid Refresh, suggest that
   thermodynamic profiles might become conducive to convection capable
   of producing lightning, primarily after 28/21Z into the 29/03-04Z
   time frame.

   ..Kerr.. 11/27/2021

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