SPC AC 140728

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0228 AM CDT Tue Aug 14 2018

   Valid 161200Z - 171200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE CENTRAL PLAINS AS WELL AS THE LOWER MISSISSIPPI...TENNESSEE
   AND OHIO VALLEYS...

   ...SUMMARY...
   A few strong to severe storms will be possible Thursday over a part
   of the central Plains, as well as from the lower Mississippi Valley
   into the Tennessee and Ohio Valleys.

   ...Synopsis...

   Deamplifying shortwave trough will move northeast through the Ohio
   Valley, while an upstream impulse embedded within northwest flow
   advances southeast through the Central Plains and middle MS Valley.
   A convectively reinforced front will advance slowly south through
   the central Plains, while a weaker front/trough accompanies the
   shortwave trough into the OH Valley, with trailing portion extending
   southwest into OK.

   ...Central Plains into the middle Mississippi Valley...

   A moist warm sector with dewpoints in the mid to upper 60s should
   reside in vicinity of front beneath modest (7 C/km) mid-level lapse
   rates, and the atmosphere will likely become moderately unstable as
   the surface layer warms during the day. Storms may be ongoing within
   zone of ascent along/north of the front across a part of NE, but
   with new development likely during the afternoon along the front and
   residual outflow boundaries as the surface layer destabilizes. A
   belt of modest northwesterly winds aloft accompanying the shortwave
   trough will support 35-45 kt effective bulk shear. A few organized
   storms including embedded supercell structures capable of isolated
   large hail and damaging wind are possible with some potential for
   upscale growth into a small MCS during the evening. Have introduced
   a marginal risk for this outlook, but a slight risk may be needed in
   later updates.

   ...Ohio, Tennessee and lower Mississippi Valley regions...

   A belt of stronger winds in the 850-700 mb layer is forecast to
   accompany the shortwave trough the OH Valley region during the day.
   Areas of showers and storms with widespread clouds will likely be in
   progress early Thursday within plume of subtropical moisture and
   weak cap. However, partial clearing and pockets of heating may
   occur, especially south of the warm conveyor belt, and additional
   storms may develop during the afternoon. While vertical shear will
   remain weak, the stronger flow in the 850-500 mb layer may increase
   the threat for locally strong to damaging wind gusts with
   redevelopment of multicells and line segments during the afternoon.
   Other storms may develop along trailing part of the boundary as far
   back as AR and OK. Uncertainty regarding evolution of the
   thermodynamic environment precludes more than a marginal risk this
   update, but area will continue to be monitored for a possible slight
   risk.

   ..Dial.. 08/14/2018

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z