SPC AC 051726

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1226 PM CDT Thu Apr 05 2018

   Valid 061200Z - 071200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF SOUTHEAST OK...NORTHEAST TX...SOUTHERN AR...NORTHERN LA...AND
   CENTRAL MS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EAST TX AND
   SOUTHEAST OK INTO WESTERN AL...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE SOUTHERN PLAINS AND LOWER MS VALLEY...

   ...SUMMARY...
   Threat for strong to severe storms capable of mainly large hail and
   damaging wind gusts, but possibly a few tornadoes is expected Friday
   afternoon and overnight over a portion of the Southern Plains and
   lower Mississippi Valley.

   ...Synopsis...
   Broadly cyclonic flow is expected to persist across the CONUS on
   Friday with a strong shortwave trough expected to pivot through the
   Upper Great Lakes and Northeast States and adjacent portion of
   Quebec. Farther south, a pair of more subtle shortwave troughs will
   likely move across northern portions of the Southern Plains. The
   first is anticipated very early in the period while the second will
   follow closely behind during the afternoon. 

   At the same time, a surface low will deepen across the southern High
   Plains while a strong cold front sweeps southward/southeastward. By
   00Z Saturday, this cold front is expected to extend from a low near
   the confluence of the MS and OH rivers southwestward into the TX Big
   Country and then back northwestward into northeast NM. Moisture
   advection is expected across the southern Plains and lower MS Valley
   throughout the day, with numerous thunderstorms, some severe,
   expected along and ahead of the front as it moves southeastward.

   ...Southern Plains into the Lower MS Valley... 
   Showers and thunderstorms will likely be ongoing north of the
   sharpening warm frontal zone initially extending from central OK
   southeastward through the Ark-La-Tex. This activity is expected to
   be elevated but mid-level lapse rates are steep enough to support
   isolated hail. General expectation is for this activity to persist
   largely in place Friday morning before eventually becoming more
   rooted at the surface and propagating southeastward along the warm
   front. The second shortwave trough mentioned in the synopsis will
   likely be the impetus for this additional strengthening and
   organizing of the initial convection. The convective line may
   initially be slow to organize but strengthening mid-level
   northwesterly flow as well as increasing low-level flow will act to
   enhance vertical shear, encouraging upscale growth into a well
   organized MCS. Anticipated well organized nature of this convective
   system is expected to support damaging wind gusts, some potentially
   significant, across the lower MS Valley. Embedded
   mesovorticies/tornadoes are also possible within this line,
   particularly across the northern end of the line where mesolow
   development is favored. However, confidence regarding the location
   of these mesoscale processes is currently low. 

   Warmer temperatures aloft will likely suppress convection across
   most of central and east TX until the cold front moves through
   during the evening and overnight. Steep mid-level lapse rates,
   favorable low-level moisture (i.e. dewpoints the mid-60s), and
   adequate vertical shear (around 50 kt from 0-6 km) will exist
   throughout the region, supporting the potential for severe hail.
   Some isolated very large hail is possible with the initial
   development, although confidence in occurrence is mitigated somewhat
   by the quick transition to a linear mode.

   ..Mosier.. 04/05/2018

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