SPC AC 160701

   Day 2 Convective Outlook CORR 2
   NWS Storm Prediction Center Norman OK
   0201 AM CDT Tue Mar 16 2021

   Valid 171200Z - 181200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM
   EAST-CENTRAL ARKANSAS AND SOUTHWESTERN TENNESSEE INTO NORTHERN AND
   EASTERN MISSISSIPPI AND MUCH OF ALABAMA...

   CORRECTED TO ADJUST LOCATION OF MRGL LABEL

   ...SUMMARY...
   A broad area of substantial severe weather potential -- including
   risk for large hail, damaging winds, and several strong tornadoes --
   is anticipated Wednesday from  the Arkansas/Louisiana vicinity
   eastward across the central Gulf Coast states/southern Appalachians.

   ...Synopsis...
   A compact/vigorous upper low initially over the Oklahoma area is
   forecast to move steadily eastward through the period, spreading
   strong flow aloft and a broad zone of enhanced ascent across the
   south-central and into the southeastern CONUS.  This low will reach
   the Ozarks overnight, flanked by ridging across the Rockies, and
   along the East Coast.

   At the surface, a 998 mb low is progged to advance eastward along a
   similar track, crossing northern Oklahoma/southern Kansas through
   the day, and then the Ozarks overnight.  A trailing cold front will
   shift from eastern portions of the southern Plains and across
   Arkansas/Louisiana through the afternoon, and then across the
   Tennessee Valley and central Gulf Coast states through the end of
   the period.  Meanwhile, a warm front extending eastward from the low
   across northern Arkansas/southern Missouri and then
   east-southeastward across the Tennessee Valley into Georgia will
   linger in place on its eastern fringe, but will lift slowly
   northward in advance of the progressing low.  These two fronts will
   outline a broad/moist warm sector, which will gradually destabilize
   through the day supporting a widespread/potentially significant
   severe weather event.

   ...Southern MO/AR/LA vicinity east to the TN valley/western GA...
   Scattered showers and thunderstorms are forecast to be ongoing ahead
   of the cold front from eastern Oklahoma/western Arkansas southward
   into east Texas, and east-southeastward along the warm front across
   the Tennessee Valley area to the southern Appalachians.

   As the synoptic system advances, convection over the central Gulf
   Coast region/Southeast should remain generally north of the warm
   front, while some decrease in pre-cold-frontal convection is also
   expected through the morning.  This should permit some heating of
   the moist (generally mid 60s dewpoints) warm-sector boundary layer,
   pushing mixed-layer CAPE values into the 1000 to 2000 J/kg range by
   early afternoon.

   New storm development is expected to occur from the southwestern
   Missouri vicinity southward across the Arklatex region by early
   afternoon.  Strong shear -- including veering of the wind field with
   height from southerly to southwesterly -- will support ready
   evolution of rotating updrafts, with some long-lived storms likely
   evolving with time.  Along with large hail potential, locally
   damaging winds will be possible, along with a steadily increasing
   tornado risk through the afternoon.  As storms move into central and
   eastern Arkansas, at least a few intense supercells are expected,
   within the broader area of storms.  Potential for a couple of
   significant tornadoes is apparent, with this risk spreading into
   southwestern Tennessee and northern Mississippi with either
   pre-cold-frontal storms moving eastward into the region, or with
   other cells developing in a zone of increasing low-level warm
   advection in the warm sector/near the warm front.  

   During the evening and into the overnight hours, substantial
   strengthening of the low-level southerlies across the central Gulf
   Coast region is expected.  While some diurnal decrease in
   instability is expected, this should be more than offset by the
   increasing low-level and deep-layer shear.  As such, risk for
   additional/significant tornadoes is anticipated to last through the
   overnight hours, focused particularly across much of Alabama.  Hail
   and relatively widespread damaging winds will also be possible
   across this same region.

   ..Goss.. 03/16/2021

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