SPC AC 071730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Mon Aug 07 2023

   Valid 081200Z - 091200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHEAST
   COLORADO...SOUTHWEST NEBRASKA...AND FAR NORTHWEST KANSAS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
   MISSISSIPPI EASTWARD INTO SOUTHERN GEORGIA...

   ...SUMMARY...
   Scattered severe thunderstorms are possible across portions of the
   central High Plains Tuesday afternoon into Tuesday night.  Large to
   very large hail along with a risk for a tornado and widely scattered
   severe gusts will be the potential hazards.

   ...Synopsis...
   Water-vapor imagery midday Monday shows a potent mid-level shortwave
   trough over the Pacific Northwest.  This feature is forecast to be
   over the northern Intermountain region Tuesday morning and move
   east-southeast through the central Rockies during the period. 
   Farther east, a mid-level trough over the Lower Great Lakes
   southward into the Mid-Atlantic states will pivot eastward and be
   located to the east of the New England coast by late Tuesday night. 
   At the surface, low pressure near Lake Ontario will shift northeast
   along the St. Lawrence Valley.  A cold front attendant to the low
   will develop eastward across southern New England through the day
   and offshore the northeast Atlantic coast during the
   evening/overnight. The southern extent of the front will stall over
   South Carolina.  Southerly low-level flow will maintain a very moist
   airmass from the central Plains into the Southeast.

   ...Central Plains...
   Large-scale ascent associated with the aforementioned disturbance
   will overspread the central High Plains by mid-late afternoon. 
   Low-level upslope flow will maintain a moist airmass from northwest
   KS towards the Cheyenne Ridge and feature dewpoints ranging through
   the 50s and into the 60s over northwest KS/southwest NE.  Steep
   700-500 mb lapse rates near 8 C/km atop the moist boundary-layer
   will support MLCAPE around 2000-3000 J/kg.  Elongated hodographs
   will favor supercells with the stronger updrafts through the early
   evening.  The relatively moist conditions centered over northeast CO
   could yield a focus risk for a tornado during the early evening, in
   addition to the threat for large to very large hail (diameters 2 to
   3 inches).  A 30-kt southerly LLJ is forecast to develop during the
   evening/overnight with the terminus located within an 850-mb moist
   axis.  Considered higher severe-wind probabilities adjoining to the
   east of the 30-percent severe hail probabilities but uncertainty
   remained high regarding the convective morphology/orientation of
   storms as the activity moves into north-central KS/southern NE. 

   ...Southeast...
   Residual outflow from convection in the Day 1 period will likely
   reside from northern MS into central AL/GA.  This will result in
   differential heating ahead of convection expected to be ongoing
   across eastern OK/AR Tuesday morning in response to a vorticity
   maximum migrating through northwesterly flow aloft.  As this
   convectively enhanced vorticity max and related MCV shifts east by
   early afternoon, thunderstorm are expected to increase rapidly
   intensify from central MS east into AL during the early-mid
   afternoon.  An organized cluster/MCS is forecast to spread east
   across central/southern AL/GA during the afternoon and reach
   southern GA by early evening.  Very high PW (2+ inches) and around
   4000 J/kg MLCAPE forecast downstream of the evolving thunderstorm
   complex will likely result in isolated severe gusts and at least
   widely scattered wind damage.

   ...Southern New England...
   Storms will likely be ongoing Tuesday morning in a warm advection
   band ahead of the surface cold front. Backed low-level winds and
   proximity to the surface low will result in 0-1 km SRH around
   than 250 s2/m2.  Weak lapse rates will limit updraft intensity, but
   very moist low-levels coupled with the low-level shear will support
   an environment conditionally favorable for storm rotation.  The
   severe threat will probably diminish by midday as the warm
   advection-related storms shift northeast and move into the adjacent
   Atlantic waters.

   ..Smith.. 08/07/2023

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