SPC AC 050054

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0754 PM CDT WED SEP 04 2013

   VALID 050100Z - 051200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE INTERIOR
   PACIFIC NORTHWEST...

   ...NORTHWEST...
   ISOLATED STRONG TO SEVERE TSTM DEVELOPMENT THROUGH THE AFTERNOON
   HOURS APPEARS TO HAVE BEEN DRIVEN PRIMARILY BY DIURNAL HEATING AND
   TERRAIN INFLUENCES. MUCH OF THE CONVECTION HAS SHOWN SOME DECREASE
   IN INTENSITY DESPITE CONTINUING PRESENCE OF POCKETS OF MODEST
   INSTABILITY /MUCAPE TO AROUND 800 J/KG PER BOI/OTX RAOBS/ AND BELT
   OF STRONGER 30-40KT DEEP-LAYER VERTICAL SHEAR SITUATED BETWEEN
   OFFSHORE TROUGH AND DOMINANT WRN U.S. UPPER RIDGE.

   LARGE SCALE ASCENT IS FORECAST TO STRENGTHEN ACROSS ORE/WA/WRN ID
   LATER TONIGHT AND ESPECIALLY THROUGH FRI MORNING AS A LOBE OF
   VORTICITY AND DPVA...CURRENTLY ROUNDING THE BASE OF THE OFFSHORE
   TROUGH PER WATER VAPOR IMAGERY...SPREADS INLAND AND NNEWD. DESPITE A
   TENDENCY FOR BOUNDARY LAYER TO STABILIZE WITH LOSS OF DAYTIME
   HEATING...SUFFICIENTLY STEEP MID-LEVEL LAPSE RATES AND CONTINUED
   MOISTENING/WARNING AROUND 700MB WILL CONTRIBUTE TO MUCAPE OF
   500-1000 J/KG AHEAD OF THE UPPER FORCING. CLOUD-BEARING SHEAR WILL
   REMAIN SUPPORTIVE OF UPDRAFT ENHANCEMENT AND STORM COVERAGE MAY
   INCREASE IN THE 0900-1200 UTC TIME FRAME AS VORTICITY LOBE/DPVA AND
   ASSOCIATED SPEED MAX DEVELOP INLAND. WILL MAINTAIN SLGT RISK
   PROBABILITIES WITH THE PROSPECT FOR A FEW STORMS BY EARLY MORNING
   CAPABLE OF PRODUCING SEVERE HAIL. DESPITE DECOUPLING OCCURRING
   OVERNIGHT...GENERALLY DRY/WARM SUB-CLOUD LAYER COULD ALSO CONTRIBUTE
   TO LOCALLY GUSTY WINDS.

   ...CNTRL/NRN HIGH PLAINS...
   JUXTAPOSITION OF SFC THERMAL/LEE TROUGH AND MOIST AXIS ALONG
   RESIDUAL/DECAYING FRONTAL SEGMENT NEAR SD/NEB BORDER HAS RESULTED IN
   A CORRIDOR OF GREATER INSTABILITY SAMPLED WELL BY EVENING RAOB FROM
   RAP. LOW LEVEL LIFT ALONG THE TROUGH AND FRONTAL SEGMENT...AS WELL
   AS WEAK UPSLOPE FLOW...HAVE SPURRED ISOLATED AND LOCALLY INTENSE
   CONVECTIVE DEVELOPMENT FROM THE NEB PNHDL NWWD TO ERN MT. WEAK LOW
   LEVEL ELY FLOW TOPPED BY 15-30KT MID-LEVEL FLOW PER RAOBS AND
   PROFILER DATA WAS RESULTING IN SUFFICIENT DIRECTIONAL/SPEED SHEAR
   FOR STORMS TO PERSIST AND POSE A THREAT FOR LARGE HAIL AND LOCALLY
   STRONG DOWNDRAFTS. GIVEN GENERALLY LIMITED/WEAK LARGE SCALE SUPPORT
   FOR DEEPER ASCENT NEAR THE CENTER OF LARGE UPPER LEVEL
   ANTICYCLONE...EXPECT SEVERE THREAT TO REMAIN TOO ISOLATED FOR HIGHER
   PROBABILITIES...ESPECIALLY AT THIS TIME OF DAY.

   ..CARBIN.. 09/05/2013

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