SPC AC 200919
   
   DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0419 AM CDT WED AUG 20 2003
   
   VALID 221200Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS NERN  U.S....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS INTERIOR NWRN U.S....
   
   ...SYNOPSIS...
   LARGE UPPER HIGH CENTERED OVER CO MOVES LITTLE DURING FORECAST
   PERIOD WHILE RIDGE EXTENDING NWD INTO CANADA GRADUALLY SHIFTS EWD.
   DEEP TROUGH OVER SERN CANADA AMPLIFIES SOME INTO NERN U.S. ALLOWING
   COLD FRONT TO MOVE OFFSHORE NEW ENGLAND BY FRIDAY NIGHT.  INCREASING
   SWLY FLOW SPREADS ACROSS PAC NW INTO NRN ROCKIES  AHEAD OF EJECTING
   S/WV TROUGH CURRENTLY OFF CA COAST.
   
   ...NERN U.S...
   COLD FRONT WILL BE MOVING ACROSS MUCH OF NERN U.S. DURING THE
   DAY...FRIDAY...PRECEEDED BY A VERY WARM AND MOIST  AIR MASS. WHILE
   THE DEEP LAYER SHEAR IS MARGINAL FOR SEVERE STORMS...THE EXPECTED
   CAPE UPWARDS OF 3000 J/KG DOES SUPPORT A SEVERE THUNDERSTORM THREAT
   ALONG AND AHEAD OF THE COLD FRONT. LAPSE RATES WILL BE WARM AND
   GENERALLY AROUND 6C/KM WITH PRIMARY SEVERE MODE BEING WIND DAMAGE
   AND MARGINALLY SEVERE HAIL.
   
   ...NWRN U.S...
   AS TROUGH MOVES NEWD ACROSS PAC NW INTO NRN ROCKIES THE MOIST
   MONSOON FLOW WILL BE SHUNTED ACROSS ERN OR/SERN WA AND ID INTO SWRN
   MT DURING THE DAY.  THE MID LEVEL COOLING ACCOMPANYING THE TROUGH
   WILL AID IN THE DESTABILIZATION PROCESS WHICH COUPLED WITH THE MDT
   SWLY FLOW OF 30-4O KT WILL RESULT IN FAVORABLE CONDITIONS FOR STRONG
   TO SEVERE THUNDERSTORMS BY AFTERNOON.  PRIMARY THREAT WOULD LIKELY
   BE DOWNBURST WINDS GIVEN THE STEEP LAPSE RATES OF 8C/KM AND GREATER
   AND STILL SOMEWHAT DRY LOW LEVELS.
   
   ..HALES.. 08/20/2003
   
   ...NOTICE...
   FOR USERS DECODING THE POINTS PARAGRAPH HEREIN...LATITUDE AND
   LONGITUDE POINTS FOR THE CATEGORICAL AND PROBABILISTIC OUTLOOK
   GRAPHICS ALSO ARE LOCATED IN A SEPARATE PRODUCT UNDER THE WMO
   HEADINGS WUUS01 PTSDY1...WUUS02 PTSDY2...AND WUUS03 PTSDY3.  THE
   INCLUSION OF POINTS IN THIS PRODUCT WILL EVENTUALLY BE DISCONTINUED.
   
   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED FOR 1200Z