SPC AC 010602

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0102 AM CDT Fri Jun 01 2018

   Valid 011200Z - 021200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
   AND EASTERN NEBRASKA...AND ACROSS CENTRAL AND WESTERN NORTH
   DAKOTA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHERN ALABAMA...GEORGIA...AND SOUTH CAROLINA...

   ...SUMMARY...
   Large hail, damaging winds, and a few tornadoes are expected from
   the northern Plains into the middle Missouri Valley from late
   afternoon through the evening. Areas of severe wind and hail are
   possible across parts of the Southeast, with isolated strong storms
   across west Texas.

   ...Synopsis...
   A shortwave trough will move from the Rockies into the northern
   Plains with a respective 50 to 80 kt mid to upper level speed max.
   Substantial cooling aloft/height falls will overspread the area,
   aiding large-scale ascent. At the surface, a trough will extend from
   the central Dakotas into west Texas by late afternoon, also
   coincident with a dryline from KS into TX, while a warm front lifts
   north across NE. A very warm and moist air mass with a plume of
   upper 60s F dewpoints will nose northward toward the NE/SD border by
   00Z Saturday leading to areas of very strong instability.

   To the east, a cool pocket aloft associated with a weak upper trough
   will move slowly across the southern Appalachians and Southeast,
   increasing the likelihood of a few severe storms during the day as
   conditions destabilize.

   ...ND into northern SD...
   A narrow plume of near 60 F dewpoints will extend into ND by
   afternoon as a surface low develops. Cold temperatures aloft and
   increasing large-scale lift will lead to scattered daytime storms.
   Backed low-level flow ahead of the surface trough will support
   supercells and perhaps a tornado or two. Large hail is also likely.
   Other isolated cells are expected farther west from northeast WY
   into western SD and southeast MT, where surface flow will be veered
   to westerly. Still, cold air aloft and steep lapse rates will favor
   hail.

   ...Southern SD across central and eastern NE and into northwest
   MO...
   Most of the day will be void of any thunderstorm activity, but
   conditions are expected to change rapidly from late afternoon
   through evening. Strong heating and a northward advection of
   moisture will lead to an extremely unstable air mass with MUCAPE
   forecast to be in excess of 4000 J/kg across NE into southern SD.
   Veering wind profiles will support initial supercell development
   near the surface trough, with very large hail and perhaps a tornado
   or two. With time, there is a strong likelihood of a severe MCS
   which may be capable of significant wind damage as it evolves out of
   merging supercells. Several CAMs support this possibility.

   ...Southern High Plains...
   It will be quite hot across west Texas with temperatures over 100 F
   west of a dryline. Although the area will be under an upper ridge,
   it will flatten slightly with the passage of the upper trough to the
   north. Very steep lapse rates surface and aloft and convergence near
   the surface trough should lead to at least isolated afternoon
   multicell storms capable of locally severe hail or wind.

   ...Northern AL, GA, western Carolinas...
   Convection ongoing as of this writing from AR into TN will likely
   play a role in focusing additional storms later today. Strong
   heating should precede the outflow, with strong instability
   developing. Forecast soundings indicate steep midlevel lapse rates
   due to the cool pocket aloft which will support vigorous updrafts.
   Wind shear will be weak but the likelihood of numerous storms
   focused along the west-east oriented boundary suggest areas of
   damaging winds are possible.

   ..Jewell/Gleason.. 06/01/2018

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