SPC AC 270651

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0151 AM CDT Sun Aug 27 2017

   Valid 291200Z - 301200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE TEXAS AND LOUISIANA GULF COAST...

   ...SUMMARY...
   Risk for a couple of tornadoes may persist across portions of the
   western Gulf Coast region, dependent upon increasingly uncertain
   movement of Harvey.

   ...Synopsis...
   No major change in the overall upper flow field is forecast for
   Tuesday, with a ridge remaining over the West and a trough in the
   East.  As short-wave troughing within the broader cyclonic flow
   field over the eastern U.S. shifts northeast across the mid-Atlantic
   region, a deepening low is forecast to shift north-northeast away
   from the NC coast through the period.  Meanwhile, a weak cool front
   may move inland across the Pacific Northwest ahead of a trough
   advancing across the northeast Pacific.  Finally, Harvey will likely
   linger in the vicinity of coastal Texas through the period.

   ...Parts of the Texas and Louisiana Gulf Coast areas...
   The broad circulation around the center of Harvey will likely
   continue to support low-level shear sufficient for some rotation
   within stronger convective cells Tuesday, along with
   corresponding/limited risk for brief/weak tornadoes.  The areal
   coverage of this risk becomes increasingly uncertain with time into
   the forecast period, as large variation in solutions exists among
   various models.  Based on the latest official forecast from the NHC,
   Harvey will remain over the middle Texas Coastal Plain through
   Tuesday, which would keep the main risk for brief tornadic spin-ups
   across the middle and upper Texas coast and into portions of coastal
   Louisiana.

   ..Goss.. 08/27/2017

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