SPC AC 171727

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1227 PM CDT SAT OCT 17 2015

   VALID 181200Z - 191200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM NORTHWEST AZ INTO SOUTHERN
   NV AND SOUTHWEST UT...

   ...SUMMARY...
   A FEW STRONG TO SEVERE STORMS ARE POSSIBLE FROM NORTHWEST ARIZONA
   INTO SOUTHERN NEVADA AND SOUTHWEST UTAH SUNDAY AFTERNOON AND
   EVENING.

   ...SYNOPSIS...
   A SPLIT-FLOW REGIME IS EXPECTED TO BECOME ESTABLISHED ACROSS THE
   WESTERN STATES FROM TODAY THROUGH DAY 2.  A DEEP PACIFIC TROUGH WILL
   CONTINUE TO BECOME REMOVED FROM THE NORTHERN STREAM ON SUNDAY...
   TRACKING INTO THE GREAT BASIN AND SOUTHERN CA/LOWER CO VALLEY BY 12Z
   MONDAY.  MEANWHILE...THE DEEP LONG-WAVE TROUGH ACROSS THE EASTERN
   STATES WILL MOVE OFFSHORE AS UPSTREAM FLOW EAST OF THE ROCKIES
   BECOME QUASI-ZONAL. 

   TSTM COVERAGE WILL AGAIN BE THE GREATEST ACROSS THE INTERMOUNTAIN
   WEST...WITH NO CHANGES NEEDED AT THIS POINT FOR THE MARGINAL SEVERE
   RISK AREA EXTENDING FROM NORTHWEST AZ INTO SOUTHERN NV AND SOUTHWEST
   UT.  

   ...NORTHWEST AZ/SOUTHERN NV/SOUTHWEST UT...
   A CORRIDOR OF GENERALLY WEAK INSTABILITY IS EXPECTED TO EXTEND
   POLEWARD FROM SOUTHERN/WESTERN AZ AND THE LOWER CO VALLEY INTO
   SOUTHERN NV AND SOUTHWEST UT SUNDAY AFTERNOON INTO THE EARLY
   EVENING.  MODELS SUGGEST TWO SHORTWAVE TROUGHS WILL MOVE ACROSS THE
   MARGINAL RISK AREA SUNDAY AFTERNOON THROUGH THE EVENING...WITH THE
   LEAD ONE BEING WEAKER AS A MORE VIGOROUS SHORTWAVE TROUGH ADVANCES
   ACROSS CENTRAL CA INTO SOUTHERN NV.

   SHOWERS AND TSTMS MAY BE ONGOING AT THE START OF DAY 2 ATTENDANT TO
   FORCING FOR ASCENT WITH THE LEAD IMPULSE/SPEED MAX...WITH THIS
   ACTIVITY PERSISTING INTO THE AFTERNOON.  GREATER TSTM COVERAGE AND
   STORM INTENSITY ARE EXPECTED LATER SUNDAY AFTERNOON INTO SUNDAY
   EVENING AS STRONGER FORCING FOR ASCENT AND HEIGHT FALLS SPREAD
   EASTWARD INTO SOUTHERN NV...NORTHWEST AZ AND SOUTHWEST UT. 
   STRENGTHENING MIDLEVEL WINDS ACCOMPANYING THE APPROACHING CENTRAL CA
   SHORTWAVE TROUGH WILL AID IN STRONGER DEEP-LAYER SHEAR REACHING THE
   MARGINAL RISK AREA AFTER 18/21Z...SUCH THAT THE CONFIDENCE FOR
   ORGANIZED STORMS INCREASES INTO THE EARLY EVENING.  WEAK INSTABILITY
   SHOULD LIMIT THE COVERAGE OF SEVERE STORMS...PRECLUDING THE
   INTRODUCTION OF HIGHER SEVERE PROBABILITIES.

   ..PETERS.. 10/17/2015

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z