Flash Flood Watch 10, NWS San Diego, CA

330 
WGUS66 KSGX 220240
FFASGX

FLOOD WATCH
NATIONAL WEATHER SERVICE SAN DIEGO CA
740 PM PDT TUE AUG 21 2012

...SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED...

.ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORMS WILL
DEVELOP TONIGHT AND CONTINUE INTO WEDNESDAY. HOWEVER...THE
THREAT FOR FLASH FLOODING HAS GREATLY DIMINISHED.

CAZ055-056-058-060>062-220345-
/O.EXP.KSGX.FF.A.0010.000000T0000Z-120822T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
SAN BERNARDINO COUNTY MOUNTAINS-RIVERSIDE COUNTY MOUNTAINS-
SAN DIEGO COUNTY MOUNTAINS-APPLE AND LUCERNE VALLEYS-
COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS-
740 PM PDT TUE AUG 21 2012

...FLASH FLOOD WATCH WILL EXPIRE AT 8 PM PDT THIS EVENING...

THE FLASH FLOOD WATCH FOR A PORTION OF SOUTHWEST CALIFORNIA WILL
EXPIRE AT 8 PM PDT THIS EVENING. THE THREAT FOR FLASH FLOODING
HAS GREATLY DIMINISHED.

A FEW STRONG TO SEVERE THUNDERSTORMS BROUGHT VERY HEAVY RAIN TO
PARTS OF THE DESERT SLOPES IN SAN DIEGO AND RIVERSIDE COUNTY
TODAY. SCATTERED SHOWERS AND THUNDERSTORMS TONIGHT AND INTO
WEDNESDAY MORNING ARE EXPECTED TO BRING BRIEF HEAVY RAIN IN
LOCALIZED AREAS.

$$

TARDY

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN DIEGO CA
810 AM PDT TUE AUG 21 2012

UPDATED WWA SECTION...ROUTINE MID MORNING ISSUANCE WILL FOLLOW LATER

.SYNOPSIS...
A TROUGH OF LOW PRESSURE OFF THE CALIFORNIA COAST WILL MOVE SLOWLY
INLAND THROUGH THURSDAY. THIS WILL INTERACT WITH MONSOONAL MOISTURE
TO BRING SCATTERED AFTERNOON AND EARLY EVENING THUNDERSTORMS TO THE
MOUNTAINS AND DESERTS THROUGH WEDNESDAY. THERE IS ALSO A SLIGHT
CHANCE OF THUNDERSTORMS FOR THE SAN BERNARDINO COUNTY MOUNTAIN AND
DESERT AREAS LATE TONIGHT INTO WEDNESDAY MORNING AND AGAIN LATE
WEDNESDAY NIGHT. THE TROUGH OF LOW PRESSURE WILL BRING A GREATER
RETURN AND DEEPENING OF THE MARINE LAYER THROUGH THURSDAY FOR SLOW
COOLING WEST OF THE MOUNTAINS AND MORE LATE NIGHT AND EARLY MORNING
COASTAL LOW CLOUDS AND FOG. DRIER SOUTHWEST FLOW ALOFT WILL PREVAIL
FOR THURSDAY THROUGH EARLY NEXT WEEK.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

.SHORT TERM (TODAY THROUGH THURSDAY)...
MONDAY WAS ANOTHER RELATIVELY INACTIVE CONVECTIVE DAY WITH THE MAIN
ACTIVITY ONCE AGAIN FOCUSED OVER THE HIGHEST TERRAIN...MAINLY AROUND
BIG BEAR...WITH SOME LESSER ACTIVITY IN THE UPPER DESERTS AND THE
RIVERSIDE COUNTY MOUNTAINS.

MODELS ARE IN MUCH CLOSER AGREEMENT IN THE TIMING AND DETAILS OF A
TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC THAT WILL CLOSE OFF
AS IT APPROACHES THE CALIFORNIA COAST...THEN MOVE SLOWLY INLAND
THROUGH CENTRAL AND SOUTHERN CALIFORNIA WEDNESDAY AND EARLY
THURSDAY.

THIS TROUGH OF LOW PRESSURE WILL INTERACT WITH MONSOONAL MOISTURE TO
GENERATE SCATTERED AFTERNOON AND EARLY EVENING THUNDERSTORMS TODAY
WITH GREATEST COVERAGE OVER THE MOUNTAINS AND UPPER DESERTS. SIMILAR
OR GREATER COVERAGE IS EXPECTED FOR WEDNESDAY AFTERNOON AND EARLY
EVENING WITH SOME ACTIVITY ALSO EXTENDING INTO PORTIONS OF THE LOWER
DESERTS. THERE IS A SMALL POSSIBILTY FOR NOCTURNAL CONVECTION LATE
TONIGHT INTO WEDNESDAY MORNING FOR PORTIONS OF CENTRAL AND SOUTHERN
CALIFORNIA IN THE DIFLUENT AREA EAST OF THE CENTER OF THE UPPER LOW.
FOR SOUTHWEST CALIFORNIA...THIS WOULD MOST LIKELY AFFECT THE SAN
BERNARDINO COUNTY MOUNTAIN AND DESERT AREAS IF IT OCCURS AT ALL.

THE 00Z ECWMF AND 06Z GFS ARE SIMILAR IN MOVING THE CENTER OF THE
UPPER LOW TO NEAR LAS VEGAS AT 18Z THURSDAY...LATE THURSDAY MORNING.
THIS IS FAST ENOUGH EASTWARD PROGRESS TO BRING ENOUGH DRYING TO
SOUTHERN CALIFORNIA TO KEEP MOST CONVECTION FOR THURSDAY CONFINED TO
AREAS OF THE EASTERN DESERTS OF SOUTHERN CALIFORNIA EASTWARD.

WITH THE APPROACH AND PASSAGE OF THE TROUGH...COASTAL STRATUS WILL
GRADUALLY INCREASE IN COVERAGE AND THE MARINE LAYER DEEPEN. COVERAGE
OVER THE SOUTHWEST CALIFORNIA COASTAL WATERS IS ONCE AGAIN QUITE
PATCHY EARLY THIS MORNING...BUT SLIGHTLY GREATER THAN 24 HOURS AGO.
WHILE SOME DEEPENING IS EXPECTED FOR TONIGHT INTO WEDNESDAY
MORNING...THE LINGERING INFLUENCE OF MONSOONAL MOISTURE WILL
PROBABLY KEEP THE COVERAGE STILL SOMEWHAT PATCHY AND EXTENDING NO
FARTHER INLAND THAN THE WESTERN VALLEYS. THE TROUGH PASSAGE
WEDNESDAY NIGHT WILL BRING GREATER DRYING ALOFT AND STRONGER ONSHORE
FLOW. THIS SHOULD BRING MORE EXTENSIVE COVERAGE AND GREATER
DEEPENING WITH STRATUS POSSIBLY EXTENDING INTO THE FAR INLAND
VALLEYS BY THURSDAY MORNING.

THE INCREASING MARINE INFLUENCE WILL BRING SLOW COOLING WEST OF THE
MOUNTAINS...BUT THE RELATIVELY WARM SEA SURFACE TEMPERATURES OVER
THE COASTAL WATERS SHOULD MUTE THE DEGREE OF COOLING SOMEWHAT
RELATIVE TO THE DEGREE OF COOLING THAT WOULD BE EXPECTED FROM A
SIMILAR TROUGH PASSAGE IN MAY OR JUNE.

&&

.LONG TERM (FRIDAY THROUGH MONDAY)...
NCEP HPC LEANS TOWARD THE ECMWF AND ECMWF ENSEMBLE MEAN THROUGH THE
PERIOD. THIS WOULD MAINTAIN A DRY SOUTHWEST FLOW PATTERN ACROSS
SOUTHERN CALIFORNIA WITH TEMPERATURES NEAR TO SLIGHTLY BELOW
SEASONAL AVERAGES. THE MARINE LAYER AND WEAK ONSHORE FLOW WILL
MAINTAIN AREAS OF LATE NIGHT AND EARLY MORNING LOW CLOUDS AND FOG
EXTENDING LOCALLY INLAND.

&&

.AVIATION...
COAST/VALLEYS...LOW CLOUDS ALONG THE COAST WILL BE PATCHY AT AROUND
1000 FEET ASL. CIGS WILL BE RANDOM AT COASTAL AIRPORTS BUT MOST
LIKELY BETWEEN 11-15Z. EXPECT MORE HOURS OF COVERAGE AT COASTAL
AIRPORTS LATE TONIGHT INTO WEDNESDAY MORNING ROUGHLY 06-15Z.

MOUNTAINS/DESERTS...AFTER 18Z TODAY CUMULUS WILL DEVELOP AND
GROW INTO CUMULONIMBUS WITH SCATTERED TSTMS OVER THE MOUNTAINS THIS
AFTERNOON 19Z-01Z. CLOUD TOPS 45-50KFT. SCATTERED DEBRIS CLOUDS AOA
12000 FEET THEREAFTER.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...UPDATED
CA...FLOOD WATCH UNTIL 8 PM PDT THIS EVENING FOR THE APPLE AND
     LUCERNE VALLEYS...COACHELLA VALLEY...RIVERSIDE COUNTY
     MOUNTAINS...SAN BERNARDINO COUNTY MOUNTAINS...SAN DIEGO
     COUNTY DESERTS...SAN DIEGO COUNTY MOUNTAINS.

PZ...NONE.

&&

PUBLIC/FIRE WEATHER...17/BALFOUR
SHORT TERM WARNINGS...HARRISON
AVIATION/MARINE...MM/JJT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN DIEGO CA
748 AM PDT TUE AUG 21 2012

CAZ055-056-058-060>062-220100-
SAN BERNARDINO COUNTY MOUNTAINS-RIVERSIDE COUNTY MOUNTAINS-
SAN DIEGO COUNTY MOUNTAINS-APPLE AND LUCERNE VALLEYS-
COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS-
748 AM PDT TUE AUG 21 2012

...FLOOD WATCH IN EFFECT THROUGH THIS EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME
SOUTHWESTERN CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT
THUNDERSTORMS WITH HEAVY DOWNPOURS ARE POSSIBLE TODAY. THERE IS A
SLIGHT CH ACNE THAT THUNDERSTORMS MAY CONTINUE OVERNIGHT...MAINLY
ACROSS THE SAN BERNARDINO COUNTY MOUNTAINS AND DESERTS. THE FLASH
FLOOD POTENTIAL IS MODERATE TO HIGH. FLASH FLOODING IS POSSIBLE
FROM LATE MORNING THROUGH THIS EVENING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY
THUNDERSTORMS ARE POSSIBLE THROUGH LATE WEDNESDAY AFTERNOON.
FOR THURSDAY THROUGH MONDAY...NO SIGNIFICANT WEATHER IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...
SKYWARN WEATHER ACTIVATION IS REQUESTED FOR SAN BERNARDINO
COUNTY...RIVERSIDE COUNTY...AND SAN DIEGO COUNTY ACROSS THE
MOUNTAINS AND DESERT AREAS.

CAZ042-043-048-050-057-220100-
ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS-
SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-
SAN DIEGO COUNTY VALLEYS-SANTA ANA MOUNTAINS AND FOOTHILLS-
748 AM PDT TUE AUG 21 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME
SOUTHWESTERN CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT...
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS LATE THIS AFTERNOON
AND TONIGHT. THE FLASH FLOOD POTENTIAL IS LOW. HOWEVER BRIEF HEAVY
DOWNPOURS ARE POSSIBLE AND MAY LEAD TO MINOR FLOODING OF LOW
LYING URBAN AREAS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS WEDNESDAY.
FOR THURSDAY THROUGH MONDAY...NO HAZARDOUS WEATHER IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...
SKYWARN WEATHER ACTIVATION IS NOT REQUESTED AT THIS TIME...HOWEVER
SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER.

BALFOUR