SPC AC 111954

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0254 PM CDT Sat Jun 11 2022

   Valid 112000Z - 121200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
   QUAD-STATE AREA OF SOUTHEASTERN NEBRASKA/SOUTHWESTERN
   IOWA/NORTHEASTERN KANSAS/NORTHWESTERN MISSOURI...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEASTERN
   MONTANA EAST-SOUTHEASTWARD INTO CENTRAL SOUTH DAKOTA...

   ...SUMMARY...
   A few clusters of strong to severe thunderstorms are expected to
   develop from the northern Rockies into the middle and lower Missouri
   Valley this afternoon and tonight. Damaging winds and hail will be
   most likely. An isolated tornado is possible over the middle
   Missouri Valley and vicinity.

   ...Discussion...
   Few substantive changes are being implemented to the outlook in this
   update, as prior reasoning continues to adequately reflect
   expectations regarding convective evolution/severe risk this
   afternoon and tonight.

   The primary adjustment to the areal risk depiction is being made
   over the eastern Missouri vicinity, where an eastward expansion in
   both SLGT and MRGL risk areas is being included.  Continued
   heating/destabilization is forecast across this area, which may
   support southeastward-moving storms emanating from Iowa to affect
   areas as far east as the Mississippi Valley this evening.

   Otherwise, the existing outlook remains aligned with current
   thinking.

   ..Goss.. 06/11/2022

   .PREV DISCUSSION... /ISSUED 1125 AM CDT Sat Jun 11 2022/

   ...IA/NE/MO/KS...
   Have upgraded portions of the Slight Risk area to Enhanced (Level 3
   of 5) Risk with this outlook based on increasing confidence in a
   corridor of severe hail (possibly significant) and wind developing
   late this afternoon/early evening and moving south tonight.

   Daytime heating of a very moist (upper 60s/lower 70s surface dew
   points) air mass will contribute to strong instability across the
   region by afternoon with MLCAPE values at or above 3000 J/kg from
   southeast NE south across eastern KS/western MO. Combined with
   strong mid/upper-level northwest flow on the periphery of an
   expansive southwest U.S. upper high, a very favorable environment
   for supercells should be in place by late afternoon. Expect
   initiation by late afternoon or early evening across eastern
   NE/western IA in the vicinity of a southward-moving surface
   boundary, with storms moving generally south tonight. Forecast
   soundings support a risk for very large hail during the first few
   hours after initiation, with damaging winds becoming increasingly
   likely as storms develop into a cluster/bowing mode with time.  Some
   tornado risk will exist given forecast curved low-level hodograph
   structure, especially across the Enhanced Risk area. 

   ...MT/SD...
   Strong westerly flow aloft will reside across the northern Plains as
   a weak cold front moves slowly south across MT. Pockets of daytime
   heating will result in afternoon temperatures in the 80s from
   southern MT into SD, with dewpoints averaging in the upper 40s and
   50s. 12z guidance is in agreement that scattered thunderstorms will
   form over the mountains of western MT and develop/move eastward
   along the front during the afternoon/evening. Forecast soundings
   suggest only marginal CAPE will develop, but given the strong winds
   aloft and considerable vertical shear, a few supercell storms are
   expected capable of large hail and damaging wind gusts. These storms
   may be rather isolated, but may persist through much of the evening
   and track quickly eastward into western/central SD.

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