SPC AC 051944

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0244 PM CDT Sun Jul 05 2020

   Valid 052000Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   NORTHERN PLAINS...

   ...SUMMARY...
   Severe thunderstorms are expected through this evening across the
   Northern Plains, including northeast Wyoming to the Dakotas and
   northwest Minnesota.

   ...20z Update...

   The previous outlook remains on track, and no changes have been made
   with this update cycle.  Please see the previous discussion below
   for details.

   ..Leitman.. 07/05/2020

   .PREV DISCUSSION... /ISSUED 1153 AM CDT Sun Jul 05 2020/

   ...Northern Plains - southern MT/northeast WY to northwest MN...
   Scattered thunderstorms are expected to develop this afternoon along
   and near the front over the Dakotas, moving into a very moist and
   unstable warm sector, while widely scattered thunderstorms initially
   form on the higher terrain of southern Montana and northern Wyoming
   within a post-frontal environment. In both regimes, supercells and
   organized multicells will be possible, with large hail and severe
   wind gusts as the primary hazard.

   Strong destabilization is expected along an eastward-advancing
   front, with 2500-3500 J/kg MLCAPE plausible especially across
   northern South Dakota into eastern North Dakota/northwest Minnesota.
   Low- to middle-level flow will be modest, but convective
   organization should be aided by ventilating anvil-level winds, as
   200-500-mb layer flow strengthens with the approach of the mid/upper
   trough. Isolated large hail cannot be ruled out relatively early in
   the convective cycle, before activity congeals into clusters with a
   continued hail/wind potential into this evening.

   Farther west across the northern High Plains, moisture will be more
   limited behind the front, but still sufficient amidst steep
   low/middle-level lapse rates to support surface-based convection
   away from the mountains. Activity should move into a well-mixed and
   diurnally heated boundary layer supporting maintenance of hail/gusts
   to the surface. The northeasterly flow behind the front will
   elongate hodographs and augment the deep shear, beneath stronger
   mid/upper-level winds than experienced by frontal convection farther
   east. Forecast soundings show effective-shear magnitudes potentially
   reaching 50-60-kt. When combined with MLCAPE in the 1000-1500 J/kg
   range, supercells capable of large hail can be expected through
   early/mid evening. The storms may ultimately merge/cluster with one
   or more small MCSs continuing into/across South Dakota late tonight.

   ...Southern High Plains...
   On the western fringe of multiple MCVs from southeast Colorado into
   the Texas Panhandle (and related lingering cloud cover/some
   precipitation), widely scattered thunderstorms should redevelop late
   this afternoon across eastern New Mexico/southeast Colorado into
   west/northwest Texas. While some hail cannot be entirely ruled out,
   isolated severe-caliber wind gusts should be the primary hazard,
   particularly given the potential for some upscale growth/linear
   organization as they spread southeastward into the Texas South
   Plains/Texas Panhandle.

   ...New England...
   Widely scattered to scattered thunderstorms are expected this
   afternoon, particularly near a southeastward-advancing cold front
   and a preceding/southward-extending weak surface trough. Sufficient
   low-level moisture is present to support a narrow corridor of
   500-1000 J/kg MLCAPE. Although low-level shear will be weak, veering
   with height will contribute to 30-40-kt effective shear and
   quasi-straight low/middle-level hodographs. This suggests a blend of
   multicell and somewhat-organized supercell modes capable of isolated
   severe hail and locally damaging wind gusts. 

   ...Delmarva/Mid-Atlantic States...
   Widely scattered thunderstorms are expected to develop and intensify
   across the region today within a moist/unstable air mass, with
   upwards of 2000-3000 J/kg MLCAPE expected across the region. Some of
   the stronger storms this afternoon through early evening will be
   capable of localized wind damage.

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