SPC AC 260054

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0754 PM CDT Thu Jun 25 2020

   Valid 260100Z - 261200Z

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

   ...SUMMARY...
   Scattered severe thunderstorms with isolated large hail and damaging
   wind gusts will be possible across the northern Plains this evening.
   Isolated severe thunderstorms are also possible in the southern and
   central High Plains and westward across Wyoming. Marginally severe
   thunderstorms may also occur in the central Gulf Coast States and
   Mid-Atlantic for a couple more hours.

   ...Great Plains/Intermountain West...
   The latest water-vapor imagery shows a shortwave trough over the
   northern High Plains extending southwestward into southern parts of
   the northern Rockies. West-southwesterly mid-level flow is evident
   in the northern Plains where widely scattered thunderstorms are
   ongoing. At the surface, a cold front is advancing southeastward
   across central North Dakota and northwest South Dakota. Ahead of the
   front, a moist airmass is present with surface dewpoints mostly in
   the 60s F. This is contributing to a pocket of strong instability in
   the central and northern Plains with the RAP estimating MLCAPE in
   the 2000 to 3500 J/kg range.

   Two clusters of strong to severe thunderstorms are ongoing. The
   first is located along the northeastern side of this pocket of
   strong instability in far southeastern South Dakota. This convection
   will likely persist for another hour or two, moving eastward into
   southwestern Minnesota. Hail and isolated damaging wind gusts will
   be possible. In the wake of the first cluster of storms, new
   thunderstorms may also develop across eastern South Dakota later
   this evening. This new convection may also have a severe threat. The
   second cluster of strong to severe thunderstorms is ongoing near the
   front in northwestern Nebraska. This cluster is likely to continue
   for much of the evening, moving eastward across central and northern
   Nebraska. This is where the RAP is analyzing the strongest
   instability suggesting large hail and wind damage will be likely
   with the more intense supercell cores...see MCD 1005.

   Further to the southwest into parts of Wyoming and northern Utah,
   weak instability is analyzed by the RAP. Thunderstorms that persist
   this evening along this corridor of instability may have potential
   for marginally severe wind gusts and hail. This is due to moderate
   deep-layer shear and steep mid-level lapse rates, which are evident
   on forecast soundings. This will also be true for thunderstorms that
   form along an instability corridor in the southern and central High
   Plains.

   ...Central Gulf Coast States...
   The latest radar imagery shows two short line segments across
   western Alabama. These storms are located along the western edge of
   a corridor of moderate instability, oriented from south-to-north
   across Alabama. Although deep-layer shear is relatively weak,
   low-level lapse rates are steep. For this reason, marginally severe
   wind gusts will be possible along the leading edge of the line
   segments for a couple more hours...see MCD 1004.

   ...Mid-Atlantic...
   The latest radar imagery shows widely scattered strong to severe
   thunderstorms located from central and eastern Virginia into
   Maryland. The storms are located along an axis of moderate
   instability with the RAP showing MLCAPE in the 1000 to 1500 J/kg
   range. In addition, regional WSR-88D VWPs in the Mid-Atlantic show
   veering of the winds with height in the lowest 2 Km above ground
   level with speed shear in the mid-levels. This should be enough for
   marginally severe storms with hail and isolated damaging wind gusts.
   The threat should persist for another or two, diminishing with the
   loss of surface heating.

   ..Broyles.. 06/26/2020

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