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Mesoscale Discussion 679
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   Mesoscale Discussion 0679
   NWS Storm Prediction Center Norman OK
   1156 PM CDT Fri May 22 2020

   Areas affected...North Texas...Southeast Oklahoma...Western Arkansas

   Concerning...Severe Thunderstorm Watch 205...206...

   Valid 230456Z - 230700Z

   The severe weather threat for Severe Thunderstorm Watch 205, 206

   SUMMARY...A severe threat will continue across Weather Watches 205
   and 206. Wind damage and large hail will be the primary threats.
   Although a brief tornado can not be ruled out in eastern Oklahoma or
   western Arkansas.

   DISCUSSION...Two convective clusters are ongoing from the Red River
   Valley into the Ozarks. The first convective cluster is located in
   eastern Oklahoma and western Arkansas along the northern edge of a
   very moist airmass. Surface dewpoints are generally in the upper 60s
   and lower 70s F. This is contributing to moderate instability
   estimated by the RAP in the 2000 to 3000 J/kg range. In addition,
   the Fort Smith WSR-88D VWP shows directional shear in the lowest 2
   km AGL with westerly flow in the mid-levels at about 40 kt. The
   moderate deep-layer shear will be favorable for a severe threat for
   a couple more hours. Discrete cells may have supercell
   characteristics with a potential for isolated large hail and
   possibly a brief tornado. Wind damage may also occur along the
   leading edge of line segments.

   Further southwest, a second cluster of strong to severe
   thunderstorms is ongoing along the Red River in north Texas and far
   southern Oklahoma. These storms are located along the northern edge
   of a pocket of strong instability with the RAP estimating MLCAPE of
   3500 to 4000 J/kg. The Fort Worth WSR-88D VWP shows 0-6 km shear
   near 40 kt with some directional shear in the lowest 1 km AGL. In
   addition, forecast soundings have very steep lapse rates in north
   Texas approaching 8.0 C/km, suggesting supercells will continue to
   produce isolated large hail. A wind damage threat will also exist on
   the southern and eastern edge of the more intense line segments.
   These threats may continue for a couple more hours. With the storms
   sagging slowly southward, it remains unclear if the storms will
   affect the Dallas/Fort Worth vicinities, with the need for a watch
   extension in time and area.

   ..Broyles.. 05/23/2020

   ...Please see for graphic product...


   LAT...LON   32539753 32539910 32989914 32989898 33429900 33410003
               34290007 34139990 34129968 34069948 34459942 34449931
               34369918 34619913 34679902 34649890 34639884 34869881
               34839807 34709811 34719767 34899768 34869696 34989694
               34929685 34879667 34939663 34929659 34929652 35299643
               35309595 35149599 35239566 35349534 35269520 35409511
               35459504 35529511 35649512 35619448 35779447 35739281
               35569281 35529285 35489285 35459242 35399246 35359205
               35049212 35029206 34689209 34639198 34529198 34529216
               34069220 34079233 34169250 34179303 34239310 34299322
               34359338 34349424 34199423 34219446 33609449 33739480
               33979517 33909523 33879540 33909556 33919568 33899583
               33789585 33399584 33359628 32999630 32979755 32539753 

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