SPC AC 021720

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1220 PM CDT Thu Aug 02 2018

   Valid 031200Z - 041200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ...

   ...SUMMARY...
   Isolated severe thunderstorms are possible across parts of the
   central and northern Plains in the upper Mississippi Valley. A few
   strong storms may also develop across the northern Middle Atlantic
   into parts of western New England.

   ...Central and Northern Plains/Upper Mississippi Valley...
   An upper-level trough will move eastward across the northwestern
   states on Friday as west to southwest mid-level flow remains over
   the central and northern Plains. An upper-level ridge will be in
   place across the upper Mississippi Valley. At the surface, a cold
   front will move eastward across the northern Plains with a pocket of
   maximized low-level moisture in place ahead of the front from
   eastern parts of the northern Plains into the upper Mississippi
   Valley. Surface dewpoints across this region should be in the mid
   60s to lower 70s F by afternoon. As surface temperatures warm during
   the day, convection is forecast to develop along the front in
   central and southern North Dakota and ahead of the front in central
   and eastern South Dakota. Due to warm air aloft and minimal
   large-scale ascent, convective coverage should remain isolated. The
   NAM forecast sounding at Aberdeen, SD during the late afternoon
   shows MLCAPE around 2000 J/kg and 0-6 km shear near 30 kt. This
   combined with steep low-level lapse rates would be enough for a
   marginal wind damage threat with any storm that can mature in spite
   of the warm air aloft. Hail will also be possible. Although the cap
   should strengthen during the evening, a gradual increase in
   low-level flow may be enough to keep a few marginally severe storms
   going into the early evening.

   ...Mid Atlantic/New England...
   An upper-level trough will move eastward across the Great Lakes and
   Ohio Valley on Friday as southwest mid-level flow remains over the
   Northeast. At the surface, a moist airmass will be in place along
   the eastern seaboard with surface dewpoints in the upper 60s and
   lower 70s F. As surface temperatures warm during the day and as
   large-scale ascent increases ahead of the approaching upper-level
   trough, scattered thunderstorms are expected to develop from the
   central Appalachians northeastward into New England. The best chance
   for a  marginal wind damage threat would be from the Mid-Atlantic
   into western New England where low-level flow is forecast to be
   maximized. Strong wind gusts would be most likely associated with
   peak heating late Friday afternoon.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   2%     - Marginal
   Wind:      5%     - Marginal
   Hail:      5%     - Marginal

   ..Broyles.. 08/02/2018

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