Flood in California, July 6, 2001

EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
900 AM PDT FRI JUL 6 2001

                             ...SYNOPSIS...
MOIST SOUTHERLY FLOW WILL CONTINUE TO BRING WARM...HUMID WEATHER TO
THE REGION THROUGH TONIGHT. AN UPPER LEVEL LOW PRESSURE SYSTEM WEST
OF BAJA WILL BRING THE THREAT FOR SHOWERS AND THUNDERSTORMS...AND
HEAVY RAIN IS POSSIBLE OVER THE MOUNTAINS AND DESERTS. A FLASH FLOOD
WATCH IS IN EFFECT FOR THESE AREAS UNTIL 9 PM. BUILDING HIGH
PRESSURE AND A SHIFT TO SOUTHWEST FLOW ALOFT WILL BRING A DRYING
TREND SUNDAY AND MONDAY.

                             ...DISCUSSION...
CLOUD COVER FROM THE THUNDERSTORM COMPLEX THAT DEVELOPED SOUTH OF
THE BORDER THIS MORNING DRIFTED NORTH AND COVER MOST OF THE CWA.
LIMITED SUN TODAY WILL PREVENT ANY STRONG CONVECTION FROM DEVELOPING
AT LEAST THROUGH LATE MORNING. HOWEVER...IT IS STILL POSSIBLE FOR
SURFACE HEATING LATER THIS AFTERNOON AS THERE WAS A LARGE AREA OF
CLEAR SKIES IN NORTHERN MEXICO THAT IS MOVING SLOWLY NORTH.

THE MAIN FORECAST CONCERN INVOLVES THE FLASH FLOOD THREAT TODAY. THE
12Z NKX SOUNDING PRECIPITABLE WATER WAS 1.78 INCHES...AND THE MODELS
CONTINUE TO FORECAST DEEP MOISTURE OVER THE REGION THROUGH TONIGHT.
VORTICITY MAXIMUM JUST WEST OF CENTRAL BAJA THIS MORNING WILL TRACK
NORTH THIS AFTERNOON AND TONIGHT AND WILL PROVIDE SUFFICIENT
INSTABILITY FOR SHOWERS TO FORM JUST ABOUT ANYWHERE ACROSS THE
REGION.

AS FOR THE SEVERE WEATHER THREAT...THE NKX SOUNDING INDICATED 50 KT
250 MB WINDS. IF THE CLOUDS BREAK UP AND WE GET SOME SURFACE
HEATING...FAVORABLE JET DYNAMICS COULD TRIGGER STRONG AFTERNOON AND
EVENING CONVECTION.

ON SATURDAY...SOUTHWEST FLOW WILL BEGIN TO ADVECT DRIER AIR INTO
SOCAL AND THIS WILL BRING DRIER AND LESS HUMID WEATHER SUNDAY.

.SAN...FLASH FLOOD WATCH UNTIL 9 PM FOR MOUNTAINS AND DESERTS
       CAZ055>058-060>062...SEE FFASAN.

MOEDE