SPC AC 311230

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0730 AM CDT SAT MAY 31 2014

   VALID 311300Z - 011200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN AND
   CNTRL HIGH PLAINS...

   ...SUMMARY...
   ISOLATED TO SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED ACROSS
   PORTIONS OF THE NORTHERN AND CENTRAL HIGH PLAINS FOR SATURDAY
   AFTERNOON AND EVENING.

   ...SYNOPSIS...

   THE PRIMARY FEATURE OF INTEREST DURING THE DAY ONE PERIOD IS A
   POSITIVELY TILTED SHORT-WAVE TROUGH WHICH WILL SLOWLY PROGRESS
   THROUGH THE NRN INTER-MOUNTAIN REGION AND GREAT BASIN. AT THE
   SURFACE...A LEE CYCLONE WILL DEEPEN TODAY OVER N-CNTRL WY WHILE AN
   ASSOCIATED WEAK FRONT DEVELOPS NWD THROUGH WY AND WRN SD. A LEE
   TROUGH WILL EXTEND GENERALLY SWD FROM THE LOW THROUGH ERN PARTS OF
   WY...CO...AND NM BY MID TO LATE AFTERNOON. 

   ...NRN/CNTRL HIGH PLAINS THIS AFTERNOON AND EVENING...

   THE DEEPENING LEE CYCLONE WILL PROMOTE THE NWWD ADVECTION OF AN
   INCREASING MOIST BOUNDARY LAYER THROUGH ERN INTO CNTRL MT WHERE
   DEWPOINTS WILL CLIMB THROUGH THE 40S INTO LOW 50S. THIS PROCESS WILL
   OCCUR BENEATH AN EML/STEEP MIDLEVEL LAPSE RATE PLUME...YIELDING
   AFTERNOON MLCAPE VALUES APPROACHING 1000-2000 J/KG FROM SERN MT SWD
   ALONG/E OF THE LEE TROUGH.

   INCREASING HEIGHT FALLS/DCVA ASSOCIATED WITH THE MIGRATORY
   SHORT-WAVE TROUGH COUPLED WITH DEEPENING TERRAIN-INDUCED
   CIRCULATIONS...LOW-LEVEL UPSLOPE FLOW N OF THE SURFACE CYCLONE...AND
   CONVERGENCE ALONG THE LEE TROUGH WILL FOSTER WIDELY SCATTERED TSTMS
   BY MID AFTERNOON FROM WRN/CNTRL MT SWD INTO CNTRL/ERN WY AND NERN
   CO. THE DEEP-LAYER FORCING FOR ASCENT WILL BE FURTHER AUGMENTED BY
   THE DIVERGENT LEFT EXIT REGION OF AN UPPER-LEVEL JET STREAK MOVING
   INTO THE CNTRL ROCKIES. INITIAL STORM MODE WILL LIKELY BE
   SUPERCELLULAR GIVEN THE FAVORABLE OVERLAP OF MODERATE INSTABILITY
   AND VERTICALLY VEERING WIND PROFILES WITH 30-40 KT OF EFFECTIVE BULK
   SHEAR. LARGE HAIL APPEARS TO BE THE MOST PROBABLE HAZARD WITHIN THE
   FIRST FEW HOURS OF STORM INITIATION. A TORNADO OR TWO IS
   POSSIBLE...THOUGH RELATIVELY WEAK LOW-LEVEL SHEAR IS EXPECTED TO
   PRECLUDE A MORE SUBSTANTIAL THREAT.

   AGGREGATING STORM-SCALE OUTFLOWS WILL LIKELY LEAD TO UPSCALE
   CONVECTIVE GROWTH INTO ONE OR MORE TSTM COMPLEXES BY THIS EVENING
   INTO TONIGHT WITH DAMAGING WINDS BECOMING THE PRIMARY HAZARD. THIS
   SCENARIO IS WELL SUPPORTED BY CONVECTION-ALLOWING MODEL GUIDANCE
   ACROSS ERN MT WHERE STORM-RELATIVE INFLOW WILL BE ENHANCED BY THE
   ESELY LOW-LEVEL WINDS.

   ...UPPER MS VALLEY THIS AFTERNOON...

   TSTMS ONGOING FROM ERN SD INTO CNTRL MN WILL LIKELY PERSIST TODAY AS
   LARGE-SCALE FORCING FOR ASCENT/DCVA IS ENHANCED BY A SHORT-WAVE
   TROUGH MOVING THROUGH THE MID-MO VALLEY. WHERE BREAKS IN THE CLOUDS
   CAN OCCUR...THE PRESENCE OF BOUNDARY LAYER DEWPOINTS IN THE LOWER
   60S WILL SUPPORT POCKETS OF MODERATE INSTABILITY /I.E. MLCAPE
   APPROACHING 1000-1500 J PER KG/ AND THE POTENTIAL FOR ISOLATED
   SEVERE STORMS CAPABLE OF STRONG WIND GUSTS AND SOME HAIL.

   ...SERN U.S...INCLUDING FL THIS AFTERNOON...

   HEATING ALONG THE HIGH TERRAIN OF THE SRN APPALACHIANS AND
   CONVERGENCE ALONG THE SWWD-MOVING SYNOPTIC FRONT AND DEVELOPING SEA
   BREEZE FRONTS WILL SERVE AS FOCI FOR SCATTERED AFTERNOON TSTM
   DEVELOPMENT. WHILE VERTICAL SHEAR WILL REMAIN WEAK...THE PRESENCE OF
   A MOIST AND MODERATELY UNSTABLE AIR MASS WILL PROMOTE A FEW STRONG
   TO BRIEFLY SEVERE STORMS CAPABLE OF LOCALLY DAMAGING WINDS AND
   PERHAPS SOME HAIL.

   ..MEAD/ROGERS.. 05/31/2014

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