SPC AC 021948

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0248 PM CDT Fri Jun 02 2017

   Valid 022000Z - 031200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER EASTERN NORTH
   DAKOTA INTO NORTH-CENTRAL SOUTH DAKOTA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
   HIGH PLAINS TO THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...

   ...SUMMARY...
   Isolated severe hail and wind may accompany thunderstorms through
   tonight across parts of the northern Great Plains and upper
   Mississippi Valley.  In addition, a few strong-to-severe storms will
   be possible over the central high plains of western Nebraska and
   eastern Colorado.

   ...20z Update...

   Storms were starting to develop ahead of the cold front across
   western/central South Dakota along the surface trough. Additional
   development further north into North Dakota is expected within the
   next few hours as forcing and shear increase toward evening.
   Modification of the 12z RAOB at BIS with current surface obs in the
   central ND vicinity indicate capping has eroded and visible
   satellite shows an expanding cumulus field southward across South
   Dakota. Given these trends in observations, the previous outlook
   appears on track, and no changes have been made.  Reference MCD 939
   for more details.

   ..Leitman.. 06/02/2017

   .PREV DISCUSSION... /ISSUED 1124 AM CDT Fri Jun 02 2017/

   ...Northern Plains into the central High Plains...
   Satellite imagery shows a short wave trough progressing eastward
   across parts of Montana and Wyoming late this morning.  The primary
   energy with this system is forecast to lift into the Canadian
   Prairie provinces as a surface cold front advances eastward into the
   central Dakotas by this evening.  The air mass ahead of the front is
   warming and destabilizing as moisture increases northward into the
   Dakotas with surface dew points currently near 60F within the moist
   axis.  Forecast soundings indicate steep low-mid level lapse rates
   developing with an axis of MLCAPE up to 1500-2000 J/kg expected this
   afternoon, especially in parts of central/eastern North Dakota.

   As the front moves eastward into the unstable environment, the cap
   will weaken with a few thunderstorms expected to develop by mid-late
   afternoon along the front. Although vertical shear will be weak
   suggesting potential for hybrid pulse storm modes, a dry and
   relatively deep sub-cloud layer /large values of DCAPE/ will promote
   strong downdrafts with potential for localized damaging wind gusts. 
   In addition, steep low-mid level lapse rates will also support large
   hail with the stronger updrafts.  These storms will spread slowly
   northeast into parts of northern Minnesota during the evening hours.

   Other storms are expected to develop southward along a lee trough
   into parts of western Nebraska and eastern Colorado where steep
   lapse rates and sufficient moisture will support higher-based
   convection.  Again, vertical shear will be weak limiting storm
   organization, but strong wind gusts and isolated hail will be
   possible with stronger primarily pulse cells from mid-afternoon into
   the evening hours.

   ...Upper Mississippi Valley...
   As storms spread from eastern North Dakota into northern Minnesota
   this evening, a strengthening southwesterly low-level jet is
   expected to develop across the area.  This will result in stronger
   warm advection lift along and north of the northwest-southeast
   oriented warm front over the upper Mississippi Valley, which will
   support a continuation of strong /primarily elevated/ thunderstorms
   from northeast Minnesota into parts of western Wisconsin during the
   overnight hours.  The stronger storms will have potential to produce
   occasional hail.

   ...Parts of Western and Central Texas...
   A complex convective pattern is in place over this region in advance
   of a southern-stream vorticity maxima over northern Mexico.  Earlier
   convection has resulted in the development of at least two MCVs,
   with one over southwest Texas south of MAF and another near the
   Texas/New Mexico border west of LBB.  These features may focus new
   convective development this afternoon and evening.  However,
   previous storms have modified/stabilized the thermodynamic
   environment and may limit the coverage of stronger cells.  Coupled
   with generally weak westerly flow aloft, the overall severe threat
   is likely to remain limited.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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