SPC AC 170727

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0227 AM CDT Thu Oct 17 2019

   Valid 191200Z - 201200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE SOUTHEAST...

   ...SUMMARY...
   A few severe storms may occur over portions of the southeastern U.S.
   coastal areas, and into parts of the Florida Peninsula on Saturday.

   ...Synopsis...
   As upper troughing over the central U.S. early Saturday weakens as
   it shifts northeastward toward/into the Great Lakes/Northeast with
   time, a second area of troughing initially near the British
   Columbia/Pacific Northwest coasts is expected to dig southeastward
   across the Intermountain West, gradually amplifying as it does so. 
   Elsewhere, a weaker, southern-stream trough is expected to cross the
   Southeast states.

   At the surface, a cold front progged to initially lie near/just west
   of the Mississippi Valley, is expected to undergo frontolysis with
   time, as its parent upper trough deamplifies ahead of the
   second/digging western trough.  Late in the period, a second area of
   low pressure/frontal development is expected over the northern High
   Plains, in response to the western trough's advance.

   Meanwhile, low pressure initially in the vicinity of the
   central/eastern Gulf Coast region is expected to move across the
   Southeast -- though substantial model differences exist with respect
   to timing of the low's progression.  Despite this however, the
   evolution of this surface system will likely result in at least
   isolated severe potential with associated convection, as it
   traverses the GA/FL/SC vicinity.

   ...Portions of Florida northward into the coastal Carolinas...
   As low pressure advances inland/across the Southeast U.S. Saturday,
   the combination of a moist warm sector spreading across the area,
   coupled with substantial shear -- especially at low-levels in the
   northeast quadrant of the low -- suggests at least local severe
   risk, including potential for a few tornadoes.  The substantial
   model discrepancies evident with respect to timing of the low's
   advance currently preclude a detailed assessment of location/degree
   of risk at this point, hence only the initial inclusion of a MRGL/5%
   risk area.  With that said however, upgrade in risk category --
   including tornado potential -- may be necessary for parts of this
   area in future outlooks, as evolution of the surface low becomes
   more certain over time.

   ..Goss.. 10/17/2019

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