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Mesoscale Discussion 173
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   Mesoscale Discussion 0173
   NWS Storm Prediction Center Norman OK
   0229 PM CST Sun Feb 12 2017

   Areas affected...Portions of central/southern VA and northern NC

   Concerning...Severe potential...Watch unlikely 

   Valid 122029Z - 122300Z

   Probability of Watch Issuance...5 percent

   SUMMARY...A few instances of locally strong convection could affect
   the region through the afternoon and into the early evening hours,
   spreading across portions of the piedmont and coastal plain of VA
   and NC. Watch issuance is not anticipated.

   DISCUSSION...Temperatures have risen into the upper 70s to lower 80s
   south of a sharp boundary extending from parts of the Delmarva
   region to northern VA. Despite only marginal moisture return in the
   low levels (surface dewpoints generally in the upper 40s to the
   middle 50s) south of this boundary, low-level lapse rates have
   steepened sufficiently to support marginal amounts of buoyancy
   (MLCAPE around 200-400 J/kg) across portions of the piedmont and
   coastal plain. Meanwhile, relatively shallow convection -- some
   producing little or no lightning -- has developed over the central
   Appalachians in proximity to a weak northeast/southwest-oriented
   boundary. This activity is also being aided by large-scale ascent
   peripheral to a midlevel shortwave trough crossing the Great Lakes
   region. The convection could continue to increase in coverage and
   intensity while spreading eastward and east-southeastward across the
   area through the late afternoon and early evening hours.

   Despite large-scale westerly flow through a deep layer contributing
   to downslope warming/drying, some southerly component of the
   near-surface winds may maintain enough moisture influx for non-zero
   buoyancy. Meanwhile, the presence of 40-50 kt of effective shear
   could conditionally support occasionally organized convective
   clusters. Locally strong wind gusts and small hail could accompany
   the most intense convection (if it were to be sustained over the
   lower elevations), and an isolated severe thunderstorm cannot be
   ruled out. However, the paucity of buoyancy resulting from the
   limited moisture return should temper updraft strength and
   convective intensity.

   ..Cohen/Hart.. 02/12/2017


   LAT...LON   38067735 37657637 36577625 35907742 35827879 36068007
               36588012 37757858 38067735 

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