SPC AC 110754

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0154 AM CST Fri Dec 11 2020

   Valid 131200Z - 141200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk for severe thunderstorms appears negligible across the
   U.S., Sunday through Sunday night.

   ...Discussion...
   A vigorous short wave trough digging out of the Arctic latitudes may
   be accompanied by a more substantive cold intrusion into portions of
   the northern Great Plains and Upper Midwest.  Otherwise, a belt of
   westerlies emanating from the mid-latitude Pacific appears likely to
   maintain considerable influence across much of the U.S. through this
   period.  

   One significant embedded short wave trough, likely digging to the
   lee of the southern Rockies by 12Z Sunday, may support renewed
   surface wave development along a frontal zone, initially stalling
   across the lower Mississippi Valley into southern Great Plains. 
   With the latest ECMWF (11/00Z) a bit slower than prior runs (and
   other model output) with the eastward progression of this feature
   through 12Z Monday, there is meaningful spread among the guidance
   that contributes to uncertain convective potential across parts of
   the northwestern Gulf coast vicinity into the Southeast.

   This mostly appears to impact the placement of the 10 percent
   probability of thunderstorm line for Sunday through Sunday night, as
   the rather modest amplitude of the surface wave forecast by most
   guidance is not particularly suggestive of appreciable severe
   weather potential.  Furthermore, it appears that stronger mid/upper
   forcing for ascent will remain well inland of coastal areas, as
   boundary-layer moistening over the northwestern Gulf of Mexico
   becomes more supportive of appreciable destabilization.  However,
   given the strengthening lower/mid tropospheric wind fields forecast
   across coastal areas, if storms can form within the destabilizing
   offshore waters, it might not be out of the question that some could
   advect into coastal areas and pose some risk for severe weather.  

   Due to the conditional, in addition to apparent marginal, nature of
   this potential, severe weather probabilities are currently being
   maintained at less than 5 percent, but trends will continue to be
   monitored.

   ..Kerr.. 12/11/2020

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