SPC AC 311730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Fri Jul 31 2020

   Valid 011200Z - 021200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MID OHIO
   VALLEY EAST TO THE MID ATLANTIC REGION...

   ...SUMMARY...
   Strong thunderstorms may impact parts of the Ohio and Tennessee
   Valleys and east to the Mid Atlantic region Saturday afternoon and
   evening, accompanied by at least some risk for damaging wind gusts
   and a couple of tornadoes. A few storms capable of producing gusty
   winds will also occur over the High Plains/southern Rockies region.

   ...Synopsis...
   A highly amplified flow field aloft is progged across the U.S. Day
   2/Saturday, with a trough remaining centered along the Mississippi
   River Valley, flanked by ridges over the western and southeastern
   portions of the country.  

   At the surface, a weak low is forecast to shift east-northeastward
   across the Ohio Valley, with a weak/trailing cool front crossing the
   Tennessee Valley region and a warm front extending eastward to the
   Mid Atlantic area.  Elsewhere, high pressure will largely prevail,
   though Hurricane Isaias will approach southern/eastern Florida
   through the period.

   ...OH/TN Valleys to the Mid Atlantic region..
   Showers and thunderstorms will be ongoing at the start of the period
   -- mainly north and west of the surface low -- from the Mid
   Mississippi Valley across the Ohio Valley region.  As the low shifts
   east-northeastward, limited heating of the moist warm sector -- but
   weak lapse rates aloft -- will result in generally modest
   destabilization, with average CAPE across the area reaching into the
   1000 to 1500 J/kg range.

   Widely scattered storms are forecast to develop by afternoon -- both
   along the cool front, and from the surface low east across the
   central Appalachians toward the Chesapeake Bay.  With moderate flow
   through the lower troposphere, veering with height to southwesterly
   at 30 to 40 kt at mid levels, shear will support organized/rotating
   storms.  Along with potential for hail and damaging winds with
   stronger storms, a tornado or two could also occur -- mainly from
   the low eastward, along the warm front.

   Though severe potential should peak by late afternoon, some risk
   will likely linger into the evening as the low drifts slowly
   east-northeastward.

   ...High Plains/Southern Rockies...
   Enhanced/northerly mid level flow around the periphery of the
   western ridge will yield a broad region of 30-40 kt effective shear
   from the northern High Plains southward to the southern
   Rockies/southern High Plains region.  As isolated afternoon storms
   develop -- largely near higher terrain -- and then shift
   southward/southeastward, risk for locally gusty winds will be
   possible with a couple of the strongest storms.  As such, a
   large/broad 5% wind risk area has been introduced at this time, for
   diurnal convection evolving across this region.

   ...Florida...
   Latest forecasts from the National Hurricane Center continue to show
   Hurricane Isaias shifting northwestward toward the eastern Florida
   coast Saturday, reaching a position just offshore southeast of
   Melbourne by the end of the Day 2 period (12Z Sunday 8-2).  This
   forecast track -- keeping the center of the storm east of the coast
   through the period -- would be generally unfavorable for inland
   tornado risk, so no probabilities have been included at this time.

   ..Goss.. 07/31/2020

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