SPC AC 251246

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0746 AM CDT Thu Jun 25 2020

   Valid 251300Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHERN GREAT
   PLAINS...

   ...SUMMARY...
   Scattered severe thunderstorms with hail and wind will be possible
   across the northern Great Plains, mainly between 2 to 11 PM CDT.
   Isolated severe thunderstorms are also possible south into the
   central/southern High Plains and west across Wyoming and northern
   Utah, and also across parts of the Mid-Atlantic and Southeast
   states.

   ...Northern Great Plains...
   A shortwave trough over western MT will move east into the Dakotas
   by late evening. A pair of leading MCVs ahead of this trough (one
   over northwest SD and the other over far northeast MT) should be the
   primary foci for early to mid-afternoon thunderstorm development
   along an eastward-moving cold front from eastern ND to central SD
   and northwest NE. While deep-layer winds will largely remain
   moderate, some enhancement to mid-level westerlies attendant to the
   MCVs should support at least 25-35 kt effective shear. This will
   favor organized clusters and a few supercells. Any discrete cells
   will be capable of significant severe hail along the northeast
   periphery of a pervasive EML plume emanating from the Southwest.
   Otherwise, widely scattered clusters of severe hail and wind should
   be the primary hazards before convection wanes after dusk.

   ...WY into southwest SD and the NE Panhandle...
   A mid-level vort max near the NV/ID/UT border should slowly progress
   into western WY by evening. This feature will aid in scattered
   thunderstorms initially across the western and central portions of
   WY. With some strengthening of low-level north/northeasterlies
   enhancing upslope flow in the wake of frontal passage, convection
   could become widespread across the eastern portion of WY in the
   early evening. The buoyancy/shear/lapse rate combination will
   probably yield a broad multicell cluster/MCS with strong to
   marginally severe wind gusts and marginally severe hail as the most
   likely hazards. This may spread into parts of southwest SD and the
   NE Panhandle prior to weakening overnight.

   ...Southern/central High Plains...
   Isolated to scattered high-based thunderstorms are expected along
   the lee trough by late afternoon/early evening. Modest deep-layer
   shear within a very deeply mixed boundary layer could support
   isolated severe wind gusts.

   ...Mid-Atlantic States to the Carolinas...
   An MCV with predominately stratiform convection will shift east
   across central/eastern SC this morning. Enhanced low-level
   southwesterlies as sampled by the 12Z Charleston, SC sounding could
   support a short-term damaging wind/brief tornado threat near the
   coast if convection can diurnally intensify before the MCV shifts
   offshore.

   Otherwise, a shortwave trough centered on the OH Valley will move
   east-southeast into VA by evening. A lee surface trough ahead of
   this feature should encourage generally isolated thunderstorms from
   northern VA to the western Carolinas. Poor mid-level lapse rates
   will probably support only modest MLCAPE ahead of the trough, around
   750-1500 J/kg. Although low-level winds will be weak as well, robust
   speed shear should exist above 700 mb, elongating the upper portion
   of the hodograph. This could yield a few splitting cells capable of
   isolated marginally severe hail, in addition to locally strong gusts
   and resultant tree damage.

   ...Southeast...
   A belt of 30-40 kt 700-mb flow should remain prevalent in an arc
   from the northwest Gulf across southern GA through this afternoon. 
   Where boundary-layer heating should be more pronounced, appearing
   likely over the northeast Gulf Coast region, a few multicell
   clusters embedded within this flow regime may develop and be capable
   of producing locally damaging winds.

   Farther south over central and southwest FL, large buoyancy with
   MLCAPE of 3000-3500 J/kg is expected this afternoon. While
   deep-layer shear will be quite weak, isolated to scattered storms
   will likely develop along the sea breezes. These pulse storms will
   offer a risk of locally severe wind/hail.

   ..Grams/Kerr.. 06/25/2020

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