SPC AC 211952

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0252 PM CDT Fri Jun 21 2019

   Valid 212000Z - 221200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE MID MS/LOWER OH/TN VALLEYS AND VICINITY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE EASTERN DAKOTAS...AND OVER PARTS OF NORTHEAST CO...NORTHWEST
   KS...AND SOUTHWESTERN NE...

   ...SUMMARY...
   Severe storms capable of damaging winds are expected to affect the
   mid Mississippi, Lower Ohio, and Tennessee Valleys.  Other severe
   storms may occur over parts of eastern Colorado and the Dakotas.

   ...Discussion...
   With current forecast reasoning still reflective of the ongoing
   convective evolution, and expectations for future development, no
   substantive changes to the outlook areas are being made in this
   update.

   The greatest adjustment has been to trim the ENH risk area from
   areas in the wake of the ongoing/bowing MCS now crossing Illinois. 
   Otherwise, expect severe risk to continue across the mid MS/lower
   OH/TN Valleys, and over both the eastern Dakotas, and central high
   Plains region where storm development is currently underway.

   ..Goss.. 06/21/2019

   .PREV DISCUSSION... /ISSUED 1115 AM CDT Fri Jun 21 2019/

   ...Middle MS Valley into TN...
   A long-lived mature linear MCS is tracking across eastern MO into
   western IL.  This activity has resulted in several reports of
   damaging winds, and will likely persist through the afternoon as it
   moves into portions of IN and northern KY.  The air mass will become
   progressively less unstable farther east, so it is unclear how far
   up the Ohio valley the damaging wind threat will persist.  But due
   to uncertainties and the significant mesoscale organization of the
   system, have expanded the MRGL/SLGT risk areas farther east into
   central/eastern Kentucky.

   A second mature linear MCS over western MO is immediately following
   the first, and has also produced several reports of wind damage. 
   This line appears to be taking a slightly more southerly trajectory,
   and is tapping a very moist and very unstable air mass.  It appears
   likely that this MCS will become dominant through the day and track
   across parts of southern MO, southern IL and eventually into KY/TN. 
   Have expanded the ENH risk eastward into these regions to account
   for this scenario.  It is unclear how far southeast this activity
   will maintain severe intensity.  However, based on a few CAM
   solutions, have extended SLGT risk to the mountains of east TN for
   tonight.

   ...CO/KS...
   Northerly boundary layer winds are present this morning over much of
   eastern CO, with dewpoints only in the 30s and 40s.  Model solutions
   are consistent that low-level cyclogenesis will occur over central
   CO this afternoon, backing winds and aiding upslope flow in the
   Denver and Palmer Divide areas.  This will likely result in
   scattered thunderstorm development along the front range and
   foothills.  Instability is limited, but strong shear profiles and
   steep midlevel lapse rates will promote supercell storm structures
   capable of large hail.  One or two of these cells may persist into
   the plains during the evening and progress into northwestern KS
   before weakening.

   ...Dakotas...
   A N-S surface boundary extends across central and western SD/ND
   today.  Abundant clouds are currently limiting
   heating/destabilization in this area.  However, increasing
   large-scale ascent from the west and slow moistening of the boundary
   layer may be sufficient for a few strong to severe storms to develop
   this afternoon along the boundary.  These storms will track
   northeastward across the SLGT risk area, with hail and damaging
   winds possible.

   ...Western CO...
   Water vapor imagery shows considerable midlevel moisture along the
   jet axis from southern UT into CO.  Relatively strong shear profiles
   are present in this region, and models are consistent in the
   development of a few organized storms this afternoon and evening. 
   The strongest cells could produce hail and gusty winds.

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