SPC AC 200117

   Day 1 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0817 PM CDT Wed Jun 19 2019

   Valid 200100Z - 201200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHERN TEXAS EASTWARD INTO THE ARKLATEX AND THE TENNESSEE/OHIO
   VALLEYS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHERN HIGH PLAINS...

   CORRECTED FOR WIND GRAPHIC IN NORTHERN PLAINS

   ...SUMMARY...
   Numerous severe thunderstorms are expected to this evening across
   north-central/northeast Texas east into the Arklatex. Very large
   hail and severe wind gusts are expected. Other isolated severe
   storms are expected from western Tennessee into the Ohio and
   Tennessee Valleys.

   ...Southern Plains/Arklatex...
   The latest water-vapor imagery shows a shortwave trough over western
   portions of the southern Plains. At the surface, a mesolow is
   located in north Texas with a cold front extending southwestward
   into west-central Texas. A moist airmass is located ahead of the
   front across the eastern half of Texas where surface dewpoints are
   in the lower to mid 70s F. This has contributed to the development
   of moderate to strong instability early this evening with the RAP
   and the Fort Worth sounding showing MLCAPE values across much of
   central and eastern Texas in the 3500 to 5000 J/kg range. A cluster
   of thunderstorms has developed on the northeastern edge of the
   strongest instability across the Arklatex. This MCS may continue to
   move eastward across the remainder of southern Arkansas and into
   northern Mississippi, western Tennessee and northwestern Alabama
   this evening into the overnight period. Moderate deep-layer shear
   along with enhanced low-level shear due to a low-level speed max in
   the Arklatex, will be favorable for supercells and a few tornadoes.
   Large hail and wind damage will also be possible with the stronger
   rotating storms and bow echoes within the cell cluster. A few storms
   could produce very large hail and wind gusts in excess of 70 knots.
   The wind-damage threat should persist as the MCS moves eastward into
   the northern Gulf Coast states later tonight.

   Further west, a cluster of thunderstorms has developed across
   north-central Texas, just ahead of the shortwave trough. This
   cluster will move eastward into northeast Texas this evening and
   should have an isolated tornado threat. Wind damage and isolated
   large hail will also be possible. Isolated large hail will also be
   possible this evening in northwest Oklahoma where a 15 percent hail
   probability contour has been added for ongoing storms.

   ...Ohio and Tennessee Valleys...
   The latest water-vapor imagery shows a shortwave trough over the mid
   Mississippi Valley with cyclonic mid-level flow over the Ohio and
   Tennessee Valleys. At the surface, a low is present over central
   Illinois with a cold front extending southward from the low into the
   mid Mississippi Valley. Ahead of the front, a moist airmass is in
   place with surface dewpoints mostly in the lower to mid 70s F. This
   is contributing to moderate instability with the RAP showing MLCAPE
   values in the 1000 to 1500 J/kg range. An MCS is located across
   west-central Kentucky extending southward into northern middle
   Tennessee. This MCS will continue to move eastward into the southern
   Appalachian foothills this evening. Wind damage will be likely along
   the leading edge with a couple tornadoes possible within embedded
   bow echoes. The threat should become more isolated later this
   evening as instability weakens across the region.

   ...Northern High Plains...
   The latest water-vapor imagery shows a shortwave trough over the
   northern Rockies with westerly divergent mid-level flow over the
   northern Plains. An axis of moderate instability is analyzed by the
   RAP from western South Dakota into eastern Montana where MLCAPE
   values are estimated to be in the 1000 to 1500 J/kg range. A broken
   line of thunderstorms is present on radar from northeast Montana
   extending southward into northern Wyoming. Some discrete storms are
   located further to the east across northeast Wyoming where the
   environment is more favorable for supercells. 0-6 km shear of 50 kt
   and steep mid-level lapse rates, evident on forecast soundings,
   should be sufficient for isolated large hail and a few damaging wind
   gusts this evening.

   ..Broyles.. 06/20/2019

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