SPC AC 230736

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0236 AM CDT Sun Sep 23 2018

   Valid 251200Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   EASTERN MISSOURI NORTHEASTWARD TO THE LAKE ERIE VICINITY...

   ...SUMMARY...
   Severe risk -- mainly in the form of damaging winds -- is forecast
   to evolve Tuesday from the Ozarks vicinity northeastward to the
   Lower Great Lakes.

   ...Synopsis...
   A long-wave upper trough is progged to reside over central NOAM at
   the start of the period, with a shorter-wavelength trough embedded
   therein to advance slowly eastward with time.

   In conjunction with short-wave progression aloft, a seasonably
   strong surface cold front -- initially expected to lie from the
   Upper Great Lakes southwestward to the southern Rockies -- will
   likewise advance eastward/southeastward, and should extend from
   roughly the Lake Erie vicinity southwestward in an arcing manner
   across the Mid-South, and then to central Texas.  

   Elsewhere, upper-level ridging will flank the large area of cyclonic
   flow, while corresponding surface high pressure prevails both east
   and west of the advancing surface front.

   ...The Ozarks vicinity northeastward to the Lower Great Lakes...
   As a surface cold front sweeps across the Upper Great Lakes/Midwest
   region during the day Tuesday, modest pre-frontal boundary-layer
   heating/destabilization is expected.  Robust large-scale ascent --
   focused near the surface front -- should allow development of a
   frontal or pre-frontal convective band, which will likely grow
   upscale into an at least loosely continuous squall line through late
   afternoon/early evening.  With moderately strong west-southwest flow
   aloft supporting both locally organized updrafts and fast storm
   motion, locally damaging winds will likely affect a broad portion of
   the Midwest vicinity as the system advances quickly eastward.  

   With the strongest flow over northern fringes of the outlook area,
   some risk for damaging winds appears evident despite more limited
   availability of CAPE with northward extent.  Later, as instability
   diminishes diurnally across the entire risk area, severe threat
   should gradually decrease through the overnight hours.

   ..Goss.. 09/23/2018

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