SPC AC 031253

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0753 AM CDT Wed Jul 03 2024

   Valid 031300Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE CENTRAL/NORTHERN HIGH PLAINS...

   ...SUMMARY...
   A threat for all severe hazards is possible this afternoon into
   evening over portions of the central/northern High Plains.  Damaging
   to severe gusts may occur near a separate front, mainly from the
   Ozarks to Ohio.

   ...Synopsis...
   In mid/upper levels, broadly cyclonic flow will continue over much
   of the northern CONUS from the Pacific Northwest to the Upper Great
   Lakes, with numerous embedded vorticity maxima and shortwaves of
   varying amplitudes.  Of those, the most important for this outlook
   will be a shortwave trough now apparent in moisture-channel imagery
   over northern Rockies.  This feature should dig southeastward to
   southwestern ND, southeastern MT, northwestern WY and southeastern
   ID by 00Z.  By the end of the period (12Z), the trough should extend
   diagonal across SD, then to southeastern WY and northwestern CO. 
   Subtropical ridging will persist over the Gulf Coast States and
   portions of southern CA/AZ, with a height weakness in between, over
   northwestern MX and NM.

   At the surface, 11Z analysis showed a cold front across Lake
   Michigan, northwestern IL, central MO, and southeastern KS, becoming
   quasistationary across northwestern OK and the TX Panhandle to
   northeastern NM.  By 00Z, the front should move to Lake Huron,
   northwestern OH, southern IN, southern MO, while drifting southward
   again to  northeastern and west-central OK and the southern
   Panhandle/northern South Plains region of TX.  By 12Z, the front
   should extend over western parts of NY/PA, eastern/southern KY, and
   north-central AR, becoming a warm front over north-central/
   northwestern OK.  Cyclogenesis is forecast late this afternoon
   through this evening along a lee trough over east-central CO, with a
   cold front developing from the NE Sandhills into northeastern/
   central CO by 06Z.  By 12Z, the low should migrate to central NE,
   with warm front over southern IA, and cold front southwestward
   across western KS to northeastern NM.

   ...Central/northern High Plains and vicinity...
   Isolated to scattered thunderstorms are expected to develop this
   afternoon -- initially over higher terrain near the Palmer and
   Cheyenne Ridges and near lee trough, increasing in coverage while
   moving eastward to southeastward over the High Plains.  Large hail
   (some 2+ inches in diameter) and damaging wind (some gusts over 70
   mph) are expected over the north-central High Plains, and a couple
   tornadoes also are possible, mainly in and near western NE where
   some overlap of favorable moisture and low-level shear is expected.

   As the mid/upper trough approaches, expect a favorable strengthening
   of large-scale lift, winds aloft, deep shear, and mass response
   leading to northward moisture advection/transport, to the north of
   the southern frontal zone.  Optimal moisture return may be precluded
   by effects of ongoing clouds/precip to reinforce the baroclinic zone
   over the southern Plains; however, boundary-layer moisture should be
   sufficient to support development as heating of higher terrain
   preferentially erodes MLCINH.  Steep low/middle-level lapse rates
   will contribute to development of 1000-2500 J/kg MLCAPE in a
   corridor from eastern CO and northwestern KS to southwestern SD,
   decreasing from there westward toward the Bighorns and southward
   into less-unstable conditions of the Panhandles and northeastern NM.
   Veering of winds with height east of the lee trough will contribute
   to favorable vertical shear for supercells and organized/upscale-
   coalescing multicells, the latter being most commonly progged over
   parts of eastern CO and northwestern KS (where wind probabilities
   are relatively maximized).  Low-level hodographs should be
   relatively maximized in size over western NE, and rather elongated
   over a broader swath of the central High Plains, supporting large to
   significant hail production.

   ...Lower Ohio Valley region...
   Widely scattered to scattered, multicell thunderstorms are expected
   to develop this afternoon and focus mainly near the front and
   prefrontal outflow/differential-heating boundaries, from northern OK
   to the Lower Great Lakes.  The greatest concentration of convection
   is still expected over the area from the Ozarks to central OH from
   late afternoon into early evening.  Forecast soundings suggest that
   diurnal heating and rich boundary-layer moisture, represented by
   upper 60s to lower 70s surface dewpoints, will offset modest
   mid/upper-level lapse rates enough to support peak/preconvective
   MLCAPE in the 2500-3500 J/kg range over the Ozarks, to 1000-2000
   J/kg in OH.  Conversely, low-level and deep-layer shear will be
   fairly weak overall, and decreasing with southwestward extent. 
   Damaging to severe gusts will be the main concern.  A few short-
   lived convective clusters are possible, with locally maximized
   potential for severe gusts.

   ..Edwards/Kerr.. 07/03/2024

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