SPC AC 260834

   Day 3 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0234 AM CST Sun Feb 26 2017

   Valid 281200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER THE OZARK
   PLATEAU INTO SOUTHEASTERN MISSOURI...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   TEXAS NORTHEASTWARD INTO THE MIDDLE MISSISSIPPI VALLEY AND OHIO
   VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   CORRECTED FOR THE MENTION OF POSSIBLE SEVERE IN THE OHIO VALLEY IN
   THE SUMMARY SECTION

   ...SUMMARY...
   Severe thunderstorms will be possible on Tuesday and Tuesday night
   from eastern portions of Oklahoma and Texas eastward into parts of
   the lower and middle Mississippi Valley and Ohio Valley.

   ...Synopsis...
   A large-scale mid-level trough over the western U.S. will move into
   the central states on Tuesday as a belt of strong southwesterly
   500-mb flow intensifies further during the period as a 100-kt speed
   max moves to the lower MO Valley by early Wednesday morning.  In the
   low levels, a broad warm sector will become established from the
   central Gulf Coast states northward into the OH Valley and bounded
   on the north with an advancing warm front.  The west edge of the
   low-level moisture will likely be located over the eastern portions
   of TX/OK as an elongated area of low pressure extends from the
   middle MS Valley/Great Lakes southwestward into OK/KS and developing
   eastward into the Ozarks during the overnight.  

   ...eastern OK/northeast TX northeastward into the MS Valley and
   lower OH Valley...
   Complicated forecast scenario with significant uncertainty is
   evident in both the coverage and intensity of severe thunderstorms
   across a large warm/moist sector.  Steep 700-500 mb lapse rates (7-8
   degrees C per km) atop lower to middle 60s dewpoints over AR and
   dewpoints near 60 degrees F in the OH Valley will contribute to weak
   to moderate buoyancy.  Strong shear profiles (60-70 kt effective
   shear) will result in a supercell-wind profile.  A wide array of
   possibilities are plausible at this time, including a risk for
   warm-air-advection storms developing during the late
   afternoon/evening over portions of AR and the MS Valley and yielding
   a tornado and hail risk.  Complicating this scenario includes a
   cirrus canopy implied by model data as well as the degree of
   heating.

   A cold front is forecast to move into the western portions of the
   broad outlook area during the evening and overnight and push
   east-southeastward.  Thunderstorms are likely to develop along the
   front and severe is possible with this activity as well.  Damaging
   winds and hail will be the predominate risks early on with this
   activity before upscale growth into one or more larger convective
   lines and bowing segments yields a continued wind risk and perhaps a
   lingering tornado threat.

   ..Smith.. 02/26/2017

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