SPC AC 260600

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Fri May 26 2017

   Valid 271200Z - 281200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN AND CENTRAL PLAINS EAST-NORTHEASTWARD INTO THE MID
   MISSISSIPPI VALLEY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
   ENHANCED RISK AREA ACROSS PARTS OF THE SOUTHERN AND CENTRAL PLAINS
   EAST-NORTHEASTWARD INTO THE MID MISSISSIPPI VALLEY...CENTRAL
   APPALACHIAN MOUNTAINS AND MID-ATLANTIC...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
   SLIGHT RISK AREA FROM PARTS OF THE OUTSIDE OF THE ENHANCED RISK AREA
   ACROSS PARTS OF THE SOUTHERN AND CENTRAL PLAINS EAST-NORTHEASTWARD
   INTO THE MID MISSISSIPPI VALLEY...CENTRAL APPALACHIAN MOUNTAINS AND
   MID-ATLANTIC...

   ...SUMMARY...
   Widespread severe thunderstorms with wind damage, large hail and a
   few tornadoes are expected Saturday and Saturday night from parts of
   the southern and central Plains east-northeastward into the mid
   Mississippi Valley and Mid-Atlantic.

   ...Southern and Central Plains/Mid Mississippi Valley...
   An upper-level trough is forecast to move east-southeastward across
   the northern Plains and central Rockies on Saturday as
   west-southwesterly flow remains located across the southern and
   central Plains east-northeastward into the mid Mississippi Valley.
   At the surface, a cold front is forecast to advance southeastward
   across the central Plains and southern High Plains. A very moist and
   unstable airmass should be in place Saturday from eastern parts of
   the southern Plains northeastward into the mid Mississippi Valley.
   Surface dewpoints are forecast to be in the lower to mid 70s F
   across much of this corridor contributing to moderate to strong
   instability by afternoon. Deterministic and high-res solutions
   suggest that a complex of thunderstorms will first develop across
   the central Plains around midday with this complex growing in size
   and moving east-southeastward into the mid Mississippi Valley during
   the afternoon. The development of a linear MCS will be possible by
   early evening across the enhanced risk area.

   GFS forecast soundings on Saturday along the northern edge of the
   strongest instability from southeast Kansas into southern Missouri
   show a capping inversion in place for much of the day. This cap is
   forecast to weaken by late afternoon. Forecast soundings also show
   an impressive thermodynamic environment with MLCAPE values around
   4000 J/kg across much of northeast Texas, eastern Oklahoma and
   southern Missouri. In addition, 40 to 50 kt of 0-6 km shear is
   forecast along this corridor suggesting thunderstorms will have no
   problem organizing. The main question is what mode will be favored.
   Some high-res solutions show two bowing line segments moving
   east-southeastward across the enhanced risk area. This would be more
   favorable for a wind-damage threat. If the storms can form into
   clusters instead of lines, then supercells with large hail and
   isolated wind damage will be favored. Hailstones of greater than 2
   inches in diameter will be possible with supercells mainly from
   southwest Missouri into northeast Texas. A tornado threat should
   occur across parts of the region especially as low-level flow
   strengthens across the region. The severe threat should be more
   isolated with southwestward extent across parts of northeast and
   central Texas.

   ...Ohio and Tennessee Valleys/Mid-Atlantic...
   An upper-level ridge is forecast to move eastward across the Ohio
   and Tennessee Valleys on Saturday as a warm front advances
   northeastward into the southern Great Lakes and upper Ohio Valley. 
   Thunderstorms are forecast to develop along the warm front with this
   convection moving east-southeastward across the region during the
   afternoon. Forecast soundings at 21Z on Saturday along and to the
   south of the warm front in eastern Kentucky, southern Ohio and West
   Virginia show moderate instability with MLCAPE values of 1000 to
   2000 J/kg, 0-6 km shear values around 30 kts and steep low-level
   lapse rates. This environment should support a wind-damage threat
   with multicell line segments that can become organized. Hail will
   also be possible with the stronger updrafts.

   ..Broyles.. 05/26/2017

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