NWS Storm Prediction Center - Day 1 Convective Outlook

Jul 16, 2020 1300 UTC Day 1 Convective Outlook
Updated: Thu Jul 16 12:39:01 UTC 2020
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Overview Overview

 Forecast Discussion - Day 1 Convective Outlook


   SPC AC 161239

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0739 AM CDT Thu Jul 16 2020

   Valid 161300Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING FOR EASTERN OH INTO WESTERN PA/NY...ACROSS WEST
   CENTRAL AND NORTH CENTRAL NE...AND NORTHEAST MN...

   ...SUMMARY...
   Severe storms with damaging winds, isolated large hail, and a few
   tornadoes will be possible this afternoon/evening from eastern Ohio
   into western Pennsylvania and New York.  Large hail and damaging
   winds will also be possible this afternoon/evening across west
   central Nebraska and the Arrowhead region of Minnesota.

   ...Eastern OH to western PA/NY this afternoon/evening...
   A weak surface cyclone will move across the lower Great Lakes
   through tonight, in advance of a midlevel trough over the OH Valley
   that includes remnant MCVs from prior convection.  Moisture
   advection from the southwest and surface heating in cloud breaks
   will support moderate buoyancy in advance of a weak cold front that
   is now moving eastward into western OH.  Scattered thunderstorm
   development is expected in broken bands along and ahead of the front
   this afternoon, from eastern OH into western PA/NY.  MLCAPE
   approaching 1500 J/kg and effective bulk shear near 40 kt will be
   sufficient for supercells with an accompanying threat for damaging
   winds and isolated large hail.  In addition, boundary-layer
   dewpoints near 70 F and effective SRH of 250-400 m2/s2 (near the
   east edge of the more unstable warm sector) suggest that a few
   tornadoes will also be possible this afternoon/evening.

   ...West central to north central NE this afternoon/evening...
   A weak front will stall later this afternoon near the SD/NE border. 
   Boundary-layer dewpoints in the 60s across KS/southern NE will
   spread northward today, beneath a lingering plume of steep midlevel
   lapse rates.  MLCAPE near 2500 J/kg and weakening convective
   inhibition are expected along the front and lee trough from
   southwest NE across eastern CO by mid-late afternoon.  Forcing for
   ascent should remain rather weak and this area will be along the
   southern fringe of the stronger midlevel westerlies.  However,
   strong surface heating/deep mixing will likely allow widely
   scattered thunderstorm development along the surface boundaries and
   spreading into the open warm sector by this evening.  Effective bulk
   shear near 35 kt and the strong buoyancy/steep low-midlevel lapse
   rates will support the threat for large hail with supercells, and
   damaging winds with any clustering of storms by evening.

   ...Northeast MN and vicinity this afternoon/evening...
   An embedded shortwave trough over the eastern Dakotas will progress
   eastward to Lake Superior and Upper MI by tonight.  At the surface,
   a cold front will move eastward across northern/central MN by
   mid-late afternoon.  Boundary-layer dewpoints will increase to 60-62
   F with daytime heating/mixing in advance of the front (and in the
   wake of morning convection), where MLCAPE will increase to near 1500
   J/kg with weak convective inhibition.  Scattered thunderstorm
   development is expected along the front by mid-late afternoon, with
   a few supercells possible given relatively straight hodographs in
   the unstable warm sector, with effective bulk shear in excess of 45
   kt.  Occasional damaging winds and large hail will be the main
   threats.

   ...Southeast KS/northeast OK to KY this afternoon...
   An MCS now moving along the KS/OK border is expected to weaken by
   mid-late morning over southeast KS/northeast OK.  The remnant MCV
   from this convection will move slowly eastward toward southeast
   KS/northeast OK by mid afternoon, when additional storm development
   may  occur along a stalled front and/or remnant outflow.  Some
   enhancement to low-midlevel vertical shear with the MCV could be
   sufficient for some transient supercells capable of producing
   isolated damaging winds and large hail.  Farther east along the
   front, from AR to KY, vertical shear will be relatively weak. 
   Still, large buoyancy and precipitation loading could support
   isolated strong downburst winds with multicell clusters this
   afternoon/evening along the front.

   ..Thompson/Dial.. 07/16/2020

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z



Data courtesy the Storm Prediction Center
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