Flash Flood Warning 19, NWS San Diego, CA

EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
830 AM PDT TUE AUG 29 2000

                              ...SYNOPSIS...
ABUNDANT MOISTURE WILL KEEP SOUTHWEST CALIFORNIA MOSTLY CLOUDY TODAY
WITH SCATTERED SHOWERS...BELOW NORMAL TEMPERATURES...AND A CHANCE OF
AFTERNOON THUNDERSTORMS IN THE MOUNTAINS AND DESERTS. MID LEVEL
MOISTURE WILL REMAIN ON WEDNESDAY WITH A GREATER CHANCE OF AFTERNOON
THUNDERSTORMS IN THE MOUNTAINS AND DESERTS. FOR THURSDAY THROUGH
SATURDAY...A TROUGH OF LOW PRESSURE WILL DEVELOP ALONG THE WEST
COAST WITH DRIER AND A LITTLE COOLER WEATHER IN THE MOUNTAINS AND
DESERTS AND  EXTENSIVE NIGHT AND MORNING COASTAL LOW CLOUDS.

                             ...DISCUSSION...
A FAIRLY DEEP MARINE LAYER WITH TOPS AROUND 3000 FEET OVER THE CWFA.
ABOVE THE MARINE LAYER...A FAIRLY THICK LAYER OF MID AND HIGH CLOUDS
COVER THE CWFA. SATELLITE IR LOOP INDICATES THE HIGHER CLOUDS WERE
THINNING OUT OVER THE CWFA AND THE LATEST VISIBLE IMAGERY SHOWS A
LARGE HOLE OVER THE MOUNTAINS AND DESERTS OF THE CWFA. 12Z NKX
SOUNDING REMAINS UNSTABLE WITH A LIFTED OF MINUS 1 AND PCP WATER OF
1.35 INCHES. YUMA SOUNDING IS MORE UNSTABLE WITH A LIFTED OF MINUS 3
AND A PCP WATER OF NEARLY 1.5 INCHES.  WIND PROFILE FROM THE YUMA
88D SHOWS A DEEP SOUTHERNLY FLOW UP TO ABOUT 11 THOUSAND FEET
STREAMING INTO THE SOUTHERN DESERTS. THIS IS ALSO SUPPORTED BY THE
YUMA SOUNDING.

ETA STILL APPEARS TO BE THE MODEL OF CHOICE WITH THE PATTERN OVER
SOUTHERN CALIFORNIA AND WILL LEAN TOWARDS THE ETA SOLUTION. THE ETA
INITIALIZES A CUTOFF LOW NEAR 35N/129W WITH ANOTHER LOW NEAR
31N/120W AND A S/WV TROUGH TRAILING SOUTHEAST TO CENTRAL BAJA. THE
S/WV TROUGH MOVES EAST THROUGH TONIGHT THEN BEGINS TO SHIFT
NORTHWARD WEDNESDAY MORNING WHILE THE SECOND LOW MINORS OUT AS IT
SHIFTS NORTHEAST TOWARDS SOUTHERN CALIFORNIA TODAY. IF THE ETA IS
CORRECT...THE S/WV THROUGH SWINGS THROUGH WEDNESDAY MORNING SHOULD
BE THE LAST ONE TO IMPACT THE AREA AS THE CUT OFF LOW FURTHER
OFFSHORE CONTINUES TO SLIDE SOUTH TO WEST OF THE SOUTHERN CALIFORNIA
COAST AND PUSHES A SOUTHWEST FLOW ALOFT OVER THE AREA ON THURSDAY.
THE CUTOFF LOW THEN BEGINS TO LIFT OUT TO THE NORTHEAST THURSDAY
AFTERNOON WITH A SOUTHWEST FLOW REMAINING OVER SOUTHERN CALIFORNIA.

A LITTLE CONCERNED ABOUT THE DECREASE IN THE HIGH LEVEL MOISTURE
SINCE THIS IS ALLOWING MORE SUN INTO THE MOUNTAINS AND DESERTS WHICH
SHOULD AID IN CONVECTION FOR LATER TODAY. WITH THE MOISTURE IN
PLACE...WOULD NOT BE SURPRISED TO SEE AN INCREASE IN THE
THUNDERSTORM ACTIVITY FOR LATER THIS AFTERNOON. ALSO...A FLASH FLOOD
WATCH SHOULD NOT BE RULED OUT.

MEDIUM RANGE MODELS SWING A S/WV TROUGH ACROSS THE PACIFIC NORTHWEST
AND NORTHERN CALIFORNIA TOWARDS THE WEEKEND WHICH SHOULD MAINTAIN
THE SOUTHWEST FLOW OVER SOUTHERN CALIFORNIA INTO THE WEEKEND. THIS
SHOULD M{AINTAIN A DEEP MARINE LAYER AS WELL AS BRING BELOW NORMAL
TEMPERATURES TO THE AREA.

SAN 110

.SAN...MARINE WEATHER STATEMENT FOR MINOR TIDAL OVERFLOW
       (SEE LAXMWSSAN).

HORTON