SPC AC 281630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Tue Mar 28 2017

   Valid 281630Z - 291200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN
   NORTH TX AND SOUTHWEST OK...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL OK
   TO THE EDWARDS PLATEAU OF SOUTHWEST TX...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   SOUTHERN PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   SOUTHERN PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS VA AND
   NC...

   ...SUMMARY...
   Numerous severe storms are expected across the southern Great Plains
   including parts of Texas and Oklahoma, especially late this
   afternoon and evening. Very large hail, damaging winds, and
   tornadoes are likely.

   ...Southern Plains...
   A combination of 12Z upper-air analysis and water vapor satellite
   imagery features an east/southeastward-digging shortwave trough over
   southeast AZ/southwest NM at late morning, with a preceding belt of
   40-50 kt mid-level southwesterly winds overspreading eastern NM and
   west TX. These south-southwesterly mid-level winds will continue to
   advect a stout elevated mixed layer east-northeastward today atop an
   increasingly moist sector ahead of a dryline and upstream Pacific
   front. Regional 12Z soundings and upper-air analysis featured 7.7+
   C/km 700-500mb lapse rates across all of west TX, while around 14
   g/kg mean mixing ratios were noted at Del Rio and Corpus Christi TX,
   with 850 mb dewpoints of 12C+ as far north as Midland/Dallas-Fort
   Worth.

   Initially, increasing elevated storms may pose a severe hail risk
   early this afternoon across the TX panhandle/northwest TX. Reference
   Mesoscale Discussion 350 for additional short-term details.

   To the east of the dryline, low clouds remain prevalent at late
   morning, although a relatively narrow upper dry slot continues to
   steady approach west Texas and low clouds are steadily eroding
   across the Permian Basin vicinity. As additional moistening/heating
   occurs, moderate to strong destabilization with minimal inhibition
   is expected particularly near the surface low/warm
   front/dryline-related triple point across the TX south Plains/low
   rolling plains, southward to near/east of the dryline as it extends
   into the Permian Basin vicinity. Here, aforementioned moisture/lapse
   rates should yield MLCAPE in excess of 2500 J/kg. 

   Current thinking is that at least isolated surface-based severe
   storms will develop near the triple point vicinity by around
   mid/late afternoon, with additional development possible near the
   dry line. Although current (late morning) cloud cover casts some
   uncertainty, a somewhat displaced corridor of warm-conveyor-related
   storms are expected by late afternoon/early evening farther east
   across additional parts of western north TX into southwest OK.
   Initially discrete supercell mode should favor large hail and
   localized severe wind gusts. Although the upper flow pattern will
   become increasingly meridional with time (with general tendency of
   backing mid-level winds), and a more linear/mixed mode should evolve
   during the evening, enlarged low-level hodographs will support the
   potential for tornadoes through at least early/mid-evening. Linear
   bands should accelerate northeast into southern/central Oklahoma
   during the evening, with attendant risks for damaging winds, hail,
   and a couple tornadoes.

   Farther south across west-central/southwest TX including the Edwards
   Plateau, initially isolated late afternoon/early evening storms near
   the dryline should become widespread in coverage during mid/late
   evening as the Pacific front merges and overtakes the dryline. This
   should result in a predominant risk to large hail transitioning
   quickly to strong to severe wind gusts. An extensive squall line
   will likely evolve east overnight with at least an isolated severe
   risk spreading eastward into central TX including the Hill
   Country/Interstate 35 corridor late tonight.

   ...VA/NC...
   A dampening shortwave impulse over WV will shift off the VA/NC coast
   by mid-evening. Ongoing showers and isolated storms will subdue
   destabilization early in the diurnal heating cycle. However, by late
   afternoon, widely scattered storms should develop ahead of the
   impulse. Increased veering of the wind profile with height should
   foster mainly discrete cells, some of which should weakly rotate.
   Isolated severe hail and damaging winds will be possible.

   ..Guyer/Jewell.. 03/28/2017

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