SPC AC 291230

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0730 AM CDT Sun Jun 29 2025

   Valid 291300Z - 301200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
   MIDWEST TO THE CENTRAL HIGH PLAINS...

   ...SUMMARY...
   Isolated to scattered strong to severe thunderstorms are possible
   from the upper Great Lakes into the central High Plains. Wind is the
   primary risk, though hail is expected across portions of the High
   Plains.

   ...Upper Great Lakes to the Central High Plains...
   Belt of stronger westerlies will remain confined to the
   U.S.-Canadian border states as a mid- to upper-level trough shifts
   east from the MT/ND vicinity into the Upper Midwest late.  A surface
   front is analyzed this morning from the Upper Midwest, where it is
   ill defined and modulated by convective outflow, southwestward into
   northern KS and arcing west-northwest into the central High Plains. 
   Some eastward movement is forecast during the day across the Upper
   Midwest whereas the frontal segment over the central Great Plains
   will become stationary this afternoon.  This boundary and associated
   composite outflow will serve as the primary focus for renewed
   shower/thunderstorm activity this afternoon into tonight.  

   A decaying MCS over western IA/southeast NE this morning will
   further weaken and an ongoing corridor of weak thunderstorms extends
   southeast from the MCS through the lower MO Valley.  Removed from
   cloud debris, strong heating of a seasonably moist boundary layer
   will result in strong destabilization from WI southwestward into KS,
   where 2000-3500 J/kg MLCAPE is forecast by mid afternoon.  The
   aforementioned displacement of this region from stronger mid and
   high-level flow will limit potential for greater storm organization.
   However, isolated to scattered thunderstorms will likely evolve into
   several small-scale bands and clusters from the western Great Lakes
   into the lower MO Valley posing mainly a wind risk with the stronger
   storms.  Stronger heating farther west over central KS westward into
   parts of the central High Plains will result in steep low to
   mid-level tropospheric lapse rates.  Evaporative cooling of stronger
   water-laden downdrafts will yield a threat for severe gusts across
   the central Great Plains into the lower MO Valley.  Hail may
   accompany the stronger cores, but this risk will be limited by a
   deep melting layer and a multicellular storm mode.  A couple of
   clusters may persist through the evening and into the overnight as
   this activity shifts southward, perhaps into southeast KS and
   northern OK late. 

   Another corridor where strong/severe convection is expected is
   across the High Plains from eastern WY into northeast CO. Northwest
   flow is forecast to strengthen across the northern High Plains along
   the back side of the trough.  Isolated supercells are expected to
   develop along the synoptic front that will be draped across this
   region.  Forecast soundings do not exhibit strong buoyancy, but
   modest shear and moist profiles favor organized updrafts that should
   spread southeast toward the NE Panhandle. Large hail and wind are
   expected.

   ...Mid Atlantic states...
   A moist and moderately unstable airmass will favor isolated to
   scattered thunderstorms developing during the afternoon across the
   region.  High PW and steepened surface to 850-mb lapse rates amidst
   weak shear will result in relatively disorganized individual storms
   and smaller clusters.  Localized strong to severe gusts (50-60 mph)
   may result and yield pockets of wind damage with the stronger cores.

   ..Smith/Broyles.. 06/29/2025

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