SPC AC 082153

   Day 1 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0453 PM CDT Sat Jun 08 2019

   Valid 082150Z - 091200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   CENTRAL NEBRASKA INTO WESTERN/CENTRAL KANSAS AND NORTHEAST
   COLORADO...

   AMENDED FOR EXPANSION OF SLIGHT RISK ACROSS NORTHEAST COLORADO

   ...SUMMARY...
   The greatest potential for severe storms will be over parts of the
   central Great Plains and Red River of the North area, with large
   hail and severe gusts expected.

   Please reference MCD 1028 for discussion regarding increased severe
   threat across northeast Colorado.

   .PREV DISCUSSION... /ISSUED 233 PM CDT Sat Jun 08 2019/

   No appreciable change was made to the previous outlook.

   Primary severe threat continues to be over Nebraska and western
   Kansas where both large hail and damaging winds are possible this
   afternoon and evening.

   For more information see mesoscale discussion 1026.

   ..Grams.. 06/08/2019

   .PREV DISCUSSION... /ISSUED 1129 AM CDT Sat Jun 08 2019/

   ...Eastern ND/northwestern MN this afternoon...
   A pronounced northern stream shortwave trough will continue to
   progress eastward from the northern Rockies to the northern Plains
   through Sunday morning.  An associated surface cold front will
   likewise move eastward across the Dakotas into MN.  A narrow moist
   corridor east of the cold front extends northward from the central
   Plains to the northern Plains, where boundary-layer dewpoints are in
   the 60-65 F range this morning.  Surface heating in cloud breaks,
   low-level ascent along the front, and a remnant MCV moving
   north-northeastward across eastern SD will help focus thunderstorm
   development in a broken band along the front this afternoon.  Given
   messy observed wind profiles/hodographs and that the stronger flow
   aloft tends to lag the surface cold front, a mix of multicell
   clusters and marginal supercells will support threats for damaging
   winds and large hail this afternoon. 

   ...Central High Plains this afternoon into tonight...
   Lee cyclogenesis is expected today across eastern CO at the
   intersection of the cold front and lee trough, with faster
   southeastward motion of the front expected overnight.  This area
   will be along the southern fringe of the stronger mid-upper flow
   with the northern Rockies trough.  Deep-layer vertical shear will be
   sufficient for a couple of supercells near the triple point and a
   little northward along the front, with very large hail the main
   threat with the more discrete storms this afternoon/evening.  

   Overnight, the potential exists for storms to grow upscale into an
   MCS in the vicinity of northwest KS, where the surging cold front
   intersects a developing nocturnal low-level jet and the corridor of
   strongest buoyancy.  The convection should subsequently move
   southeastward toward central KS by the end of the period.  Lingering
   steep midlevel lapse rates and strong downdraft potential suggest
   the possibility of a corridor of damaging winds with this overnight
   convection.  However, uncertainty is high enough regarding MCS
   track/intensity and efficiency of the storms to produce damaging
   winds to hold off on introducing greater (30%) wind probabilities in
   this update. 

   ...Southern High Plains this afternoon/evening...
   Forcing for ascent will generally remain weak along a sharpening
   dryline this afternoon from southwest KS southward near the TX/NM
   border into southwest TX.  As temperatures warm into the 90s,
   convective inhibition will weaken in a narrow zone along the
   dryline, such that isolated storm development will be possible.  The
   deeply mixed environment with steep lapse rates and effective bulk
   shear of 30-35 kt will favor high-based supercells capable of
   producing isolated large hail and damaging gusts, prior to the
   storms weakening late evening.

   ...North FL/GA area this afternoon...
   A midlevel low over the TN Valley will move little as weak embedded
   speed maxima rotate around the southern and eastern periphery of the
   low.  Convection this morning is widespread along and off the
   northeast Gulf coast, and prior convection has left a residual cold
   pool across north FL.  There will be a window of opportunity for a
   few strong storms this afternoon in the zone of cloud breaks across
   west central and central GA, where moderate buoyancy and 25-30 kt
   south-southwesterly low-midlevel flow may support storms capable of
   producing isolated strong outflow gusts.  The widespread convection
   casts doubt on the degree of recovery across the FL Panhandle into
   north FL and south GA.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z