SPC AC 270727

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0227 AM CDT Mon Jun 27 2022

   Valid 291200Z - 301200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY
   AFTERNOON INTO WEDNESDAY  NIGHT ACROSS MUCH OF SOUTH DAKOTA AND
   SOUTHERN/EASTERN NORTH DAKOTA INTO MUCH OF CENTRAL/NORTHERN
   MINNESOTA AND THE ADJACENT WESTERN LAKE SUPERIOR AREA...

   ...SUMMARY...
   Strong thunderstorms may impact a corridor across the northern Great
   Plains into portions of the Upper Midwest late Wednesday afternoon
   into Wednesday night, posing at least some risk for severe wind and
   hail.

   ...Synopsis...
   Models suggest that blocking may begin to become more prominent once
   again during this period across the northeastern Pacific and
   adjacent northwestern North America vicinity, with a mid/upper high
   slowly beginning to form across Alaska/Yukon.  Downstream of this
   regime, a deep mid-level low emerging from the Canadian Arctic
   latitudes is forecast to continue to slowly dig to the west of
   Hudson Bay.  The increasingly deformed remnants of another low,
   emerging from persistent mid-level troughing offshore of the Pacific
   coast, appear likely to merge into the broader-scale cyclonic flow
   to the south of the more prominent digging low.  Models indicate
   that this will be accompanied by cyclogenesis across the southern
   Canadian Prairies into northwestern Ontario Wednesday through
   Wednesday night, along with strengthening southwesterly to westerly
   lower/mid tropospheric wind fields across the northern Great Plains
   into Upper Midwest and central Canadian/U.S. border vicinity. 
   Coincidentally, a plume of very warm and capping elevated
   mixed-layer air is forecast to nose northeast of the Rockies, toward
   the Upper Midwest/Great Lakes region.

   Meanwhile, in lower latitudes, lower/mid-tropospheric ridging will
   prevail across much of the central and southern tier of the U.S. 
   While a return flow of monsoonal moisture will continue around the
   western through northern periphery of the ridging, across and
   north-northeast of the Southwest and southern Rockies vicinity,
   seasonably high boundary-layer moisture content will remain largely
   confined to the Southeast and northwest Gulf Coast states.

   ...Northern Great Plains into Upper Great Lakes region...
   Within the deepening surface troughing, boundary-layer moistening
   may largely be confined to that associated with gradual continued
   evapotranspiration/return of evapotranspiration driven moistening
   from the Corn Belt.  Models do suggest that surface dew points could
   increase above 60F, with perhaps localized pockets of mid 60s F. 
   However, beneath the plume of warm elevated mixed-layer air, this
   may only yield generally modest mixed-layer CAPE on the order of
   1000-1500+ J/kg across most areas.

   The lack of more substantive low-level moistening, coupled with the
   strong inhibition, continues to contribute to uncertain severe
   weather potential for this period.  However, models suggest that at
   least widely scattered thunderstorm development is possible during
   the late afternoon and evening, which could include isolated
   supercells capable of producing severe hail and locally strong
   surface gusts.  And, though there is sizable spread, there is at
   least some signal within the various model output that large-scale
   forcing for ascent could become supportive of an upscale growing
   cluster of thunderstorms Wednesday night.  It appears that this
   could occur anywhere from entirely north of the Minnesota
   international border to south of the international border.  However,
   if this occurs, the strong wind fields, coupled with the dry
   well-mixed sub-cloud air, could contribute to strong outflow capable
   of producing severe wind gusts.

   ..Kerr.. 06/27/2022

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