Flash Flood Warning 13, NWS San Diego, CA

EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
230 PM PDT MON JUL 12 1999

                          ...SYNOPSIS...

A FLASH FLOOD WATCH IS IN EFFECT FOR THE MOUNTAINS AND DESERTS OF
EXTREME SOUTHWESTERN CALIFORNIA UNTIL 9 PM THIS EVENING. A MOIST
UNSTABLE AIR MASS WILL CONTINUE TO CAUSE SCATTERED AFTERNOON AND
EVENING SHOWERS OR THUNDERSTORMS IN THE MOUNTAINS AND DESERTS.
SOME SHOWERS COULD DRIFT WEST OF THE MOUNTAINS TODAY AND TUESDAY.
THUNDERSTORMS HAVE DANGEROUS LIGHTNING AND MAY HAVE HEAVY RAIN...
STRONG GUSTY WINDS AND SMALL HAIL. OTHERWISE...WEAKENING HIGH
PRESSURE ALOFT WILL KEEP THE WEATHER FAIR. SLIGHTLY COOLER...BUT
CONTINUED HOT INLAND.

                         ...DISCUSSION...

MOSTLY CLEAR SKIES OVER CWA THIS AM WITH JUST A FEW CU OVER
MOUNTAINS. TCU FORMING OVER MOUNTAINS BY LATE MORNING AND ISOLATED
THUNDERSTORMS BY EARLY AFTERNOON. 12Z NKX SOUNDING STILL FAIRLY
MOIST AND UNSTABLE BUT WEAKER ELY FLOW AT MID LEVELS THAN
YESTERDAY. OFFSHORE GRADIENTS FROM N AND WEAK ONSHORE TO E WITH
LESS THAN 2 MB SAN-IPL.

MODELS CONTINUE TO DIFFER ON DETAILS BUT ALL AGREE TO KEEP ENOUGH
RH AROUND FOR CONTINUED THREAT OF THUNDERSTORMS...MAINLY MOUNTAINS
AND DESERTS IN THE AFTERNOONS/EVES. ETA INDICATES VORT MAX/ELY WAVE
INTO TUE THEN STARTS TO SHIFT IT OUT TO NE WED. ETA HAS BEEN
HANDLING THESE SMALLER DETAILS BETTER AND IS PREFERRED. THIS SHOULD
HELP CONCENTRATE MOST THUNDERSTORM ACTIVITY TO NRN ZONES.
HOWEVER...MOISTURE MOVING UP FROM SW SO THUNDERSTORMS WILL BE
FAIRLY EVENLY DISTRIBUTED IN MOUNTAINS WITH FEWER IN DESERTS. SO
WILL CONTINUE FLASH FLOOD WATCH. NO SIGNIFICANT DRYING FOR TUE AND
IN FACT SOME INCREASE IN RH INDICATED AND MIGHT HAVE BETTER CHANCE
OF SHOWERS W OF MOUNTAINS. TROF MOVES PAST TO N WED INTO THU WITH
SOME INDICATIONS OF DRIER SW FLOW DEVELOPING ALOFT...BUT NOT VERY
RAPID DRYING AT OUR LAT AND WILL NOT BE IN ANY HURRY TO PULL OUT
THUNDERSTORMS FROM MOUNTAINS/ DESERTS. PATCHY LATE NIGHT/EARLY
MORNING LOW CLOUDS/FOG...MAINLY S COAST. TODAY WAS THE WARMEST DAY
IN MOST AREAS. SLIGHTLY COOLER TUE/WED AS HEIGHTS/THICKNESS START
TO COME DOWN AND SEA BREEZE INCREASES.

LONGER RANGE PROGS INDICATE DRIER SW FLOW ALOFT LATER PART OF WEEK.

SAN 0110

.SAN...FLASH FLOOD WATCH...SEE LAXFFASAN

ATKIN