SPC AC 271748

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1248 PM CDT Sat Jun 27 2020

   Valid 281200Z - 291200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   NORTHERN HIGH PLAINS...NORTHWEST IA INTO SOUTHERN MN...AND FROM
   SOUTHERN IN INTO THE CAROLINAS...

   ...SUMMARY...
   Severe thunderstorms capable of large hail and strong gusts are
   expected across portions of the northern High Plains Sunday
   afternoon into Sunday night. Additional severe storms capable of
   strong gusts, hail, and possibly a tornado or two also are expected
   on Sunday over parts of Iowa and southern Minnesota, as well as the
   lower Ohio Valley into the Carolinas. Isolated strong storms, mainly
   producing occasionally strong gusts and hail are expected across
   portions of the Mid-Atlantic into New England through late Sunday
   afternoon.

   ...Northern High Plains...

   An upper low will pivot south/southeast across the northern
   Rockies/Intermountain West on Sunday. Several shortwave impulses
   will eject northeast across WY/MT into the western Dakotas. At the
   surface, low pressure will persist over the area with a stalled
   front extending along the western border of the Dakotas during the
   morning. This front will drift eastward some through the period but
   the overall surface pattern will not change much. Strong heating
   during the afternoon and surface dewpoints in the 60s will result in
   2500+ MLCAPE along/east of the boundary. Instability will be less to
   the west of the boundary, but upper 50s to low 60s dewpoints are
   still expected on the back side of the low across northeast WY and
   eastern MT. Steepening midlevel lapse rates will aid in further
   destabilization west of the surface boundary with 500-2000 J/kg
   MLCAPE forecast. As forcing for ascent increases during the
   afternoon/evening storms are expected to develop across the higher
   terrain of northern WY into southern MT. High-based, possibly
   elevated supercells are possible, posing a threat for large hail. As
   a low level jet increases during the evening, some guidance suggests
   one or two bowing segments may develop. If these storms can become
   surface-based, an accompanying threat for damaging winds could
   spread northeast across parts of eastern MT into western ND during
   the evening/overnight.

   ...IA/MN vicinity...

   A Slight risk has been introduced across northwest IA into southern
   MN. Most guidance shows an embedded shortwave impulse or possible
   MCV migrating across the area on Sunday. This appears plausible
   given expected convection over the central Plains in the Day 1
   period. A weak warm front will also be draped across the region from
   near the Sioux Falls area southeastward toward the Quad Cities IA
   vicinity. Strong heating and upper 60s F surface dewpoints will
   result in strong destabilization and any storms that develop will
   have the potential for damaging wind gusts and hail. Additionally,
   given the warm front draped across the area, a few tornadoes are
   also possible due to enhanced SRH and mean mixing ratios near 16
   g/kg.  Some guidance suggests capping could limit coverage of
   storms, but most guidance does develop at least isolated storms.
   Given the thermodynamic and kinematic parameter space supportive of
   severe supercells/bowing segments, an upgrade to Slight appears
   warranted.

   ...Lower Ohio Valley to the Carolinas...

   Convection will likely be ongoing Sunday morning across the lower
   Ohio Valley. Some of this convection could be severe, mainly capable
   of produce locally damaging gusts and perhaps a tornado given strong
   low level shear and a very moist (although weakly unstable)
   environment. As heating occurs through the afternoon and a belt of
   30-40 kt midlevel flow associated with a midlevel trough overspreads
   the region, additional strong to severe thunderstorms are expected
   across portions of eastern KY/TN into NC/SC. Steep low level lapse
   rates and moderate instability coupled with high PW values will
   mainly support microburst winds, though a few instances of hail are
   possible. 

   ...Northeast...

   A midlevel trough will pivot across the region Sunday
   morning/afternoon. 25-35 kt effective shear and MLCAPE as high as
   1000-1500 J/kg will support semi-organized clusters of storms. Steep
   low level lapse rates will aid in occasionally strong wind gusts
   through the afternoon.

   ..Leitman.. 06/27/2020

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z