SPC AC 050600

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Fri Jun 05 2020

   Valid 061200Z - 071200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER CENTRAL
   AND WESTERN SOUTH DAKOTA AND PORTIONS OF ADJACENT STATES...

   ...SUMMARY...
   Severe thunderstorms capable of producing damaging hail and wind,
   along with a tornado threat will be possible over parts of the
   northern Plains Saturday afternoon and evening. Isolated strong to
   severe storms may also occur over parts of Utah and Colorado, and
   across northern New England.

   ...Synopsis...
   A large-scale upper trough will develop over the western states,
   with cold midlevel temperatures to -30 C into OR/CA by Sunday
   morning. Preceding the main trough, a leading shortwave trough will
   eject northeast across the Four Corners area during the day on
   Saturday and into the northern Plains by evening. To the east, an
   upper trough will also progress across the northeastern states, with
   strong cooling aloft and -20 C at 500 mb from northern NY into ME.
   Meanwhile, an upper ridge will hold over the central/southern
   Plains.

   At the surface, low pressure will deepen appreciably during the day
   from eastern MT into the central High Plains, with southeast winds
   bringing a plume of robust low-level moisture northwestward into SD.
   Warm/moist advection will increase further overnight over the
   northern Plains with the development of a 60 kt low-level jet.

   To the east, a surface low will move east across ME during the day,
   with a cold front extending southwest and surging toward the coastal
   Mid Atlantic by late afternoon. Lift with the upper trough and 60s F
   dewpoints preceding the front will likely support isolated daytime
   storms there.

   ...Eastern UT...western CO...southern WY...
   Thunderstorms may be ongoing early in the day, as large-scale ascent
   increases with the negative-tilt shortwave trough. The combination
   of cooling aloft and very strong shear will likely support at least
   isolated severe storms capable of damaging wind and hail. The NAM
   model appears too unstable when compared to several other models.
   Uncertainty regarding early day storm coverage and subsequent
   destabilization precludes a Slight Risk at this time.

   ...Northern NY into ME...
   Storms are expected to form early in the day along the cold front
   which will sweep across northern New England. Winds will veer in the
   low levels with time, resulting in mainly long, straight hodographs.
   Due to the linear forcing mechanism, a mixture of cells and line
   segments is possible. Cold temperatures aloft will favor hail, and a
   supercell is possible if modest effective SRH values can be
   maintained ahead of the front.

   ...Northern Plains...
   Showers and storms will develop by midday and surge northeast across
   CO and WY, and into NE and SD. A plume of strong instability is
   forecast to develop from NE into SD ahead of the cold front, and
   south of the warm front. A mixture of bows and supercells will be
   possible, intensifying as they reach the stronger instability.
   Forecast soundings support supercells, though high-based in the
   well-mixed air over CO/NE. Given these profiles, outflow will likely
   be substantial, with damaging winds expected as bows move northeast
   toward the warm front. North of the warm front, it will remain
   capped, but may still favor large hail. Given the possibility of
   numerous storms, predictability as far as timing and location is
   low.

   ..Jewell.. 06/05/2020

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