SPC AC 140621
   
   DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0121 AM CDT SAT MAY 14 2005
   
   VALID 161200Z - 171200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL /
   SRN HIGH PLAINS...
   
   ...SYNOPSIS...
   LARGE UPPER TROUGH SHOULD PERSIST OVER THE ERN THIRD OF THE CONUS
   THIS PERIOD...WHILE ASSOCIATED COLD FRONT LINGERS FROM OFF THE
   ATLANTIC COAST SWWD ACROSS NRN FL INTO THE NRN GULF.
   
   MEANWHILE...LARGE TROUGH NEAR THE W COAST AT THE START OF THE PERIOD
   SHOULD SHIFT EWD ACROSS THE INTERMOUNTAIN WEST THROUGH THE
   PERIOD...WHILE TAKING ON AN INCREASING NEGATIVE TILT.  COLD FRONT
   ASSOCIATED WITH THIS TROUGH IS FORECAST TO MOVE EWD ACROSS THE GREAT
   BASIN DURING THE DAY...AND ATTM IS PROGGED TO EXTEND FROM DEEPENING
   MT LOW SWWD ACROSS WRN WY INTO UT / SRN NV BY 17/00Z.
   
   BETWEEN THESE TWO UPPER TROUGHS...A SHARP RIDGE SHOULD SHIFT SLOWLY
   EWD ACROSS THE PLAINS.
   
   ...CENTRAL HIGH PLAINS...
   WEAK LEAD SHORT-WAVE TROUGH AHEAD OF STRONGER WRN U.S. TROUGH MAY
   MOVE ACROSS THE HIGH PLAINS THROUGH MEAN RIDGE DURING THE
   DAY...ABOVE CENTRAL / SRN PLAINS AIRMASS WHICH SHOULD BECOME
   MODERATELY UNSTABLE BY AFTERNOON.
   
   CAP SHOULD WEAKEN THROUGH THE DAY...WITH CONVERGENCE INVOF DRYLINE /
   LEE TROUGH -- AIDED BY WEAK SHORT-WAVE TROUGH -- LIKELY SUFFICIENT
   TO ALLOW SCATTERED TO ISOLATED STORM DEVELOPMENT BY LATE AFTERNOON. 
   GREATEST STORM COVERAGE APPEARS LIKELY FROM FAR ERN CO / NERN NM EWD
   ACROSS WRN KS / THE TX OK PANHANDLES.  ACROSS THIS REGION...MODERATE
   SELY LOW-LEVEL WINDS BENEATH 20 KT WSWLY MID-LEVEL FLOW IS
   EXPECTED...RESULTING IN SHEAR SUFFICIENT FOR SUPERCELLS.  LARGE HAIL
   WOULD LIKELY BE THE PRIMARY SEVERE THREAT...THOUGH LOCALLY DAMAGING
   WINDS OR AN ISOLATED TORNADO WOULD ALSO BE POSSIBLE.  THOUGH THREAT
   SHOULD BE LIMITED BY CAP WHICH SHOULD SUPPRESS CONVECTIVE
   DEVELOPMENT ACROSS MUCH OF THE REGION...WILL INTRODUCE SLIGHT RISK /
   15% SEVERE PROBABILITIES ATTM.
   
   ...PARTS OF THE GREAT BASIN / INTERMOUNTAIN WEST...
   STEEPENING LAPSE RATES ALOFT ASSOCIATED WITH APPROACHING UPPER
   TROUGH COMBINED WITH DAYTIME HEATING SHOULD YIELD AT LEAST MARGINAL
   DIURNAL AIRMASS DESTABILIZATION...AHEAD OF EWD-MOVING COLD FRONT. 
   STORMS SHOULD INCREASE FROM NV / UT NWD ACROSS ERN ID / WRN MT / S
   CENTRAL MT DURING THE AFTERNOON...AIDED BY DIFFLUENT FLOW ALOFT.
   
   MODELS FORECAST MODERATE LOW-LEVEL FLOW AHEAD OF FRONT...ALONG WITH
   60 TO 80 KT SWLY MID / UPPER JET AHEAD OF TROUGH.  ASSUMING
   SUFFICIENT DESTABILIZATION CAN OCCUR...DEGREE OF SHEAR WOULD SUPPORT
   ORGANIZED CONVECTION -- EITHER IN THE FORM OF SMALL LINES OR
   ISOLATED ROTATING STORMS.  THOUGH LIMITED INSTABILITY SUGGESTS ONLY
   MARGINAL HAIL...STRENGTH OF FLOW ALOFT INDICATES THE POTENTIAL FOR
   DAMAGING WINDS ACROSS THIS REGION.  
   
   ATTM...WILL INTRODUCE 5% SEVERE PROBABILITY ACROSS PARTS OF THE
   GREAT BASIN / NRN ROCKIES...BUT AREA COULD REQUIRE SLIGHT RISK
   UPGRADE IN LATER OUTLOOKS.
   
   ..GOSS.. 05/14/2005
   
   ...NOTICE...
   THE STATION RELATIVE POINTS IN THIS PRODUCT ARE NOW AVAILABLE
   SEPARATELY UNDER THE WMO HEADINGS WUUS01 PTSDY1...
   WUUS02 PTSDY2...WUUS03 PTSDY3.  THE INCLUSION OF POINTS
   IN THIS DISCUSSION WILL BE DISCONTINUED AFTER THE 2005
   CONVECTIVE SEASON.  A PUBLIC NOTIFICATION STATEMENT (PNS)
   WILL PROVIDE DETAILS ON THE TRANSITION.
   
   CLICK TO GET WUUS03 PTSDY3 PRODUCT

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z