SPC AC 071259

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0759 AM CDT Sun Jun 07 2020

   Valid 071300Z - 081200Z

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

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

   ...SUMMARY...
   Severe thunderstorms capable of tornadoes, large to very large hail,
   and severe wind gusts are likely across parts of the Dakotas into
   northern Minnesota. A tornado risk will also exist across portions
   of the Gulf Coast region in association with the landfall of
   Tropical Storm Cristobal.

   ...Northern Plains...
   Preceding the northern Rockies/Great Basin-centered upper trough, a
   belt of strong southwesterly mid/high-level winds will overspread
   the north-central High Plains and Dakotas to northern Minnesota
   through tonight. Southerly low-level winds will contribute to
   moisture streaming northward through the eastern Dakotas during the
   day. Strong heating and the increasingly rich low-level moisture
   will yield a moderate to very unstable air mass, particularly across
   central/northeast South Dakota into eastern North Dakota and
   northwest Minnesota. In this corridor, upwards of 3000-4000 J/kg
   MLCAPE is expected in association with surface dewpoints in the
   middle/upper 60s to around 70 F. 

   The most intense surface-based development is expected by mid/late
   afternoon near/northeast of a weak surface wave and near/just east
   of a southward-extending trough across central South Dakota, and
   north-northeastward across eastern North Dakota/far northwest
   Minnesota toward the warm frontal vicinity. Given the degree of
   instability and long hodographs with robust 50+ kt effective shear,
   intense supercells capable of very large hail are initially expected
   within this corridor. Other storms developing near/behind the front
   across the Black Hills vicinity and northeast Wyoming/southeast
   Montana toward west-central North Dakota will also pose a severe
   risk as they quickly spread northeastward late this afternoon and
   evening.

   Large hail aside, several tornadoes are possible, including the
   possibility for a strong tornado or two. Such a strong tornado
   threat would be heightened pending a maintenance of some
   semi-discrete supercells through the early evening (roughly 00Z-03Z
   time frame). This is when low-level jet aided shear/SRH is expected
   to appreciably strengthen across north-central/northeast South
   Dakota into eastern North Dakota/northwest Minnesota. A mixed
   convective mode should otherwise evolve during the evening with
   increasingly prevalent northeastward-spreading clusters/bowing
   segments, with damaging wind potential also increasing.

   ...Utah/northern Colorado/Wyoming...
   The left exit region of a powerful cyclonically curved upper jet
   will overspread the eastern Great Basin/central Rockies today. Steep
   low-level lapse rates and strong mid-level flow will support strong
   to severe thunderstorm development by peak heating near/ahead of an
   eastward-moving cold front. The potential will exist for
   thunderstorm-related severe-caliber wind gusts this afternoon/early
   evening, particularly across northeast Utah/northwest Colorado into
   Wyoming. That said, the severe risk is not expected to be quite as
   intense or widespread as yesterday.

   ...Gulf Coast from Louisiana to northern Florida...
   Refer to the National Hurricane Center for the latest details
   regarding tropical cyclone Cristobal. As Cristobal approaches the
   southeast Louisiana this afternoon, low/mid-level winds are forecast
   to gradually intensify particularly across southeast Louisiana and
   southern Mississippi/Alabama and western Florida Panhandle. Diurnal
   destabilization will contribute to a risk for shallow rotating
   storms and a couple of tornadoes are possible across region.

   Farther to the east, across the northern Florida Peninsula,
   low-level winds/shear are expected to be weaker, but potentially
   sufficient for a few organized/rotating storms through the
   afternoon. A tornado and/or thunderstorm-related wind damage could
   occur.

   ..Guyer/Leitman.. 06/07/2020

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