SPC AC 180049

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0649 PM CST Wed Nov 17 2021

   Valid 180100Z - 181200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk for severe thunderstorms appears negligible across the U.S.
   through tonight.

   ...01Z Outlook Update...
   Strongest southerly low-level return flow is now focused across the
   lower Ohio Valley into lower Great Lakes region and Northeast, with
   low-level flow across the northwestern Gulf coast region into the
   Ozark Plateau generally modest to weak.  However, latest model
   output continues to suggest that a corridor of pre-frontal low-level
   moistening which has occurred across the Ozark Plateau vicinity into
   the lower Ohio Valley will be sufficient to contribute to scattered
   thunderstorm development overnight.  

   Warm mid-level temperatures are still contributing to inhibition
   above the corridor of most substantive low-level moistening, but as
   a significant short wave trough continues to gradually turn
   southeast/east of the middle Missouri Valley and central Great
   Plains, mid-level height falls and cooling should support the
   initiation of thunderstorm activity.  Large-scale ascent is already
   aiding increasing convection rooted in increasingly elevated
   moisture return to the northwest of the surface frontal zone, across
   northwestern Arkansas and southern/eastern Missouri into the Great
   Lakes.  It appears that strengthening lift in closer proximity to
   the front (but still to the cool side of it) will yield thunderstorm
   initiation within the next hour or two, which should tend to
   gradually spread southward with the advancement of the front.

   Otherwise, isolated thunderstorm development still appears possible
   near the front as it advances into Deep South Texas overnight,
   perhaps aided by weak forcing associated with an impulse within weak
   troughing across the northern Mexican Plateau and Rio Grande Valley.

   Further moistening on continuing southerly low-level flow, coupled
   with weak mid-level cooling, may also contribute to isolated
   thunderstorms overnight near or inland of the Louisiana Gulf coast.

   A weak perturbation migrating northeast of the western Caribbean may
   contribute to additional thunderstorm development along a remnant
   frontal zone, mostly south and southwest of the Florida Keys,
   overnight.

   ..Kerr.. 11/18/2021

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z