Mesoscale Discussion 1817
   NWS Storm Prediction Center Norman OK
   0100 PM CST Fri Nov 27 2020

   Areas affected...Parts of southern Louisiana and southern
   Mississippi

   Concerning...Severe potential...Watch unlikely 

   Valid 271900Z - 272130Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated strong storms may continue to develop eastward
   along the Interstate 10 corridor of southern Louisiana through 4-6
   PM CST, posing a risk for locally damaging winds gusts and perhaps
   some potential for a brief tornado.  The need for a severe weather
   watch still appears unlikely, but trends will be monitored.

   DISCUSSION...A broad area of rain and embedded convection is in the
   process of spreading into/across and east of the lower Mississippi
   Valley vicinity, associated with a focused divergent upper flow
   field between coupled speed maximum within a strong high-level jet. 
   30-50 kt westerly flow appears to extend down through the 700-500 mb
   layer, and it appears that a speed maximum within this layer may be
   contributing to the sustained storm exhibiting supercell structure,
   currently along the Interstate 10 corridor east of Lake Charles.

   This storm also appears focused along a mid-level thermal gradient
   (roughly around 700 mb), which appears to delineate the northern
   periphery of more strongly capping elevated mixed-layer air.  In
   lower levels this appears to coincide with a zone of stronger
   differential surface heating, with inflow of seasonably moist air
   from the south, characterized by modest CAPE (500-1000 J/kg),
   supportive of the maintenance of this cell or renewed storm
   development through early evening.  By 28/00Z, the latest Rapid
   Refresh suggests that the mid-level speed maximum may be nosing into
   far southern Mississippi.

   Although low-level wind fields are weak, there may be sufficient
   shear to contribute to some risk for a brief tornado in the presence
   of moist boundary-layer air with dew points around 70F, near/north
   of the Interstate 10 corridor.  However, strong surface gusts may be
   the primary hazard with occasionally strengthening low-level
   mesocyclones, with downdrafts enhanced by heavy precipitation
   loading and latent cooling due to melting of small hail.

   ..Kerr/Hart.. 11/27/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...JAN...LIX...LCH...

   LAT...LON   30909135 31308951 30238923 30079319 30609348 30719282
               30909135