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Mesoscale Discussion 141
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   Mesoscale Discussion 0141
   NWS Storm Prediction Center Norman OK
   1031 PM CST Mon Feb 06 2017

   Areas affected...Portions of AR...western TN...extreme southern MO

   Concerning...Severe potential...Watch possible 

   Valid 070431Z - 070700Z

   Probability of Watch Issuance...60 percent

   SUMMARY...The area is being monitored for an increase in the
   severe-thunderstorm potential late this evening into the overnight
   hours. Specifics of convective evolution are uncertain, and some
   risk for all severe hazards could conditionally exist. Watch
   issuance will be possible.

   DISCUSSION...Surface observations indicate a dryline sharpening from
   its intersection with a quasi-zonally oriented warm front, near
   Chanute KS, extending south-southwestward through parts of eastern
   OK and south-central OK into north-central TX. The latest infrared
   satellite loop suggests mid/high clouds, accompanying the leading
   edge of stronger height falls attendant to a series of weakly phased
   midlevel perturbations, overtaking the dryline. As this ascent
   continues to overspread the western extent of partially modified
   Gulf moisture (surface dewpoints in the lower 60s) across far
   eastern OK and western AR, radar echoes are becoming apparent across
   the deeper moisture east of the dryline. An increase in the
   number/intensity of convective elements could occur during the next
   several hours.

   While notable capping near the base of a prominent elevated mixed
   layer (EML) sampled by the Springfield MO and Little Rock AR 00Z
   soundings casts doubt on the coverage/sustainability of convection,
   steep midlevel lapse rates related to this EML may conditionally
   offer robust upward, convective-scale accelerations. Furthermore,
   the presence of 40-50 kt of effective shear would conditionally
   support organized convective structures including supercells. Given
   the combination of nocturnal cooling, and the relatively early
   stages of boundary-layer moistening, convective inflow may tend to
   be elevated with primarily a large-hail risk. However, if sufficient
   moistening were to occur -- owing to poleward moisture transport
   within the warm sector -- near-surface-based convection could ensue,
   especially across parts of central AR. Backed surface winds,
   associated with low pressure presently analyzed near Wichita KS,
   will support sufficient low-level hodograph length/curvature for
   non-zero tornado potential, and locally damaging wind gusts may also

   Ultimately, uncertainty in the exact convective evolution/severe
   risk tonight is notable. This is especially the case for incipient
   stages of this activity. During the overnight hours, stronger mass
   fluxes directed toward the Mid South and lower OH Valley may tend to
   focus greater convective coverage/clusters toward the MS River.
   Low-level theta-e/buoyancy in these areas, however, should be
   comparatively lower.

   ..Cohen/Hart.. 02/07/2017


   LAT...LON   35289417 36179326 36769113 36728973 35818926 35039008
               34479120 34159288 34149386 34539430 35289417 

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