SPC AC 151437

   Day 3 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0937 AM CDT Sat Sep 15 2018

   Valid 171200Z - 181200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE UPPER MIDWEST/UPPER MISSISSIPPI VALLEY...

   CORRECTED FOR PROBABILITY GRAPHIC

   ...SUMMARY...
   A few severe storms may occur across parts of the upper
   Midwest/upper Mississippi Valley area.

   ...Synopsis...
   Southward suppression of the upper ridge over the U.S. is forecast
   Monday, as a belt of stronger westerly flow shifts gradually
   southward.  While short-wave troughing should continue to eject
   east-northeast across southern Canada, the main trough should remain
   just off the West Coast.  

   As short-wave troughing crosses southern Canada, a surface front
   will continue to advance slowly southeastward across the Great Lakes
   and northern/central Plains.  Meanwhile, remnants of Florence are
   expected to be turning more eastward -- shifting across the upper
   Ohio Valley and central Appalachians through the period.

   ...Southeast South Dakota to western Wisconsin...
   The slow advance of a frontal zone across the north-central U.S. may
   focus an area of thunderstorm development by late afternoon/evening,
   despite a somewhat benign upper pattern.  Much of the convection is
   progged to occur north of the front within a zone of isentropic
   ascent, with the warm sector likely to remain capped across much of
   the area.  However, some potential for a few surface-based storms
   appears to exist, from far northeast Nebraska and southeast South
   Dakota eastward to western Wisconsin.  Here, a combination of
   moderate destabilization above the cap and the southern fringe of
   stronger mid-level westerlies expanding atop the surface frontal
   zone suggest conditional risk for severe weather, should storms
   develop.  Given this potential, a low-probability/MRGL risk area is
   being added to the forecast at this time.

   ..Goss.. 09/15/2018

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z