SPC AC 070550

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1250 AM CDT Sun Jun 07 2020

   Valid 071200Z - 081200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
   CENTRAL AND EASTERN DAKOTAS INTO NORTHWEST MINNESOTA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR SOUTHEAST
   LOUISIANA...SOUTHERN MISSISSIPPI...AND FAR SOUTHWEST ALABAMA...

   ...SUMMARY...
   Severe thunderstorms capable of tornadoes, large to very large hail,
   and severe gusts are possible across parts of the Dakotas and
   Minnesota.  A risk for tornadoes may also develop across the central
   Gulf Coast region in association with the landfall of Tropical Storm
   Cristobal.

   ...Synopsis...
   A potent large-scale mid-level trough over the western states will
   slowly pivot east with a broad belt of strong flow extending from
   the base of the trough northeastward into the Upper Midwest.  An
   elongated area of surface low pressure will remain across the
   central High Plains northeastward into the eastern Dakotas.  A warm
   frontal zone will be draped across MN from north-northwest to
   south-southeast by early evening.  Farther south, tropical cyclone
   Cristobal will make landfall over the central Gulf Coast and move
   inland into the lower MS Valley.  

   ...Upper Midwest...
   A strong belt of southwesterly 500mb flow will remain overhead as a
   lead shortwave trough moves northward into central Saskatchewan
   during the day.  A weaker disturbance is forecast to move northeast
   from the central High Plains into the central Dakotas by mid-late
   afternoon.  Southerly low-level flow will contribute to moisture
   streaming northward through the eastern Dakotas during the day. 
   Strong heating in wake of earlier cloud debris will combine with the
   increasingly rich low-level moisture to yield a moderate to very
   unstable airmass across the Dakotas and into MN.  Lowest 100mb mean
   mixing ratios near 16 g/kg were sampled by the Saturday evening
   raobs over northeast KS/eastern NE.  This moisture will advect
   northward and contribute to dewpoints rising into the upper 60s to
   lower 70s across the Red River Valley.  Near the warm frontal zone,
   backed low-level flow coupled with enlarging hodographs during the
   afternoon into the early evening will support supercells with strong
   low-level rotation developing in the warm sector.  Several tornadoes
   are possible, including the possibility for a strong tornado or two.
   Farther southwest into south-central SD westward to the Black Hills,
   strong heating within a more deeply mixed boundary layer will likely
   also contribute to the erosion of a capping inversion by late
   afternoon/early evening.  Supercells capable of large to very large
   hail and severe gusts are possible.  The upscale growth of storms
   into clusters and bowing segments is expected to eventually evolve
   as the LLJ intensifies during the evening.  

   ...UT/CO/WY/MT...
   The left exit region of a powerful cyclonically curved upper jet is
   forecast to overspread the eastern Great Basin/central Rockies
   during the day.  Steep low-level lapse rates and strong mid-level
   flow will support strong to severe thunderstorms developing during
   peak heating.  Isolated severe gusts are the primary concern.  A
   portion of the this region from northeast UT into northwest CO and
   into central WY may need to be considered for higher severe-wind
   probabilities in later outlooks.  

   ...Central Gulf Coast...
   Please refer to the National Hurricane Center regarding
   timing/forecast path information for tropical cyclone Cristobal.  As
   TC Cristobal approaches the coast today, wind fields are forecast to
   intensify.  Diurnal destabilization will contribute to a conditional
   risk for shallow rotating storms and a couple of tornadoes are
   possible.  The tornado threat will likely spread further inland
   during the evening into the overnight and into southern/central MS
   by early Monday morning.

   ..Smith/Nauslar.. 06/07/2020

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