Flash Flood and Hail in California, August 15, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
415 AM PDT MON AUG 15 2005

.SYNOPSIS...A WEAK UPPER LOW OVER THE SOUTHERN CALIFORNIA BIGHT AND
RESIDUAL MONSOONAL MOISTURE WILL BRING SCATTERED THUNDERSTORMS
THROUGH THIS EVENING...MAINLY IN THE MOUNTAINS AND DESERTS. DRIER
SOUTWEST FLOW ALOFT WILL REDUCE THE CHANCES FOR THUNDERSTORMS
WEDNESDAY INTO THE WEEKEND. OVERNIGHT LOW CLOUDS WILL EXTEND INLAND
INTO THE VALLEYS FOR MUCH OF THE WEEK.

&&

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

THUNDERSTORMS HAVE CONTINUED TO DEVELOP MUCH OF THE NIGHT ACROSS
SOUTHERN CALIFORNIA IN THE MOIST...UNSTABLE...DIFLUENT AREA TO THE
NORTHEAST OF A WEAK UPPER LOW CENTERED OVER THE SOUTHERN CALIFORNIA
BIGHT. GREATEST ACTIVIY THE PAST COUPLE OF HOURS HAS BEEN ACROSS LOS
ANGELES AND WESTERN SAN BERNARDINO COUNTIES. NEW CELLS CONTINUE TO
DEVELOP AND SPREAD NORTHWARD WITH CELLS EXTENDING AS FAR SOUTH AS
THE SANTA ANA MOUNTAINS. FLASH FLOOD WATCH HAS BEEN ISSUED UNTIL 8
PM FOR THE MOUNTAINS AND DESERTS OF SAN BERNARDINO COUNTY. WHILE
RELATIVELY FAST CELL MOVEMENT AND MODERATE PWS WOULD TEND TO REDUCE
THE POTENTIAL FOR FLASH FLOODING...CELLS HAVE TRAINED OVERNIGHT AND
MAY CONTINUE TO DO SO TODAY GIVEN THE UPPER FORCING. WHILE MOST GAGE
REPORTS HAVE BEEN LESS THAN ONE HALF INCH OVERNIGHT...AN AUTOMATED
SENSOR IN THE SUMMIT VALLEY...EAST OF CAJON PASS...RECORDED 1.73
INCHES. CROSS SECTIONS SHOW DRYING FOR TUESDAY...BUT PERHAPS WITH
STILL ENOUGH RESIDUAL MOISTURE FOR AFTERNOON THUNDERSTORMS.
ALSO...ENOUGH VERTICAL SHEARING FOR AT LEAST AN ISOLATED THREAT FOR
SEVERE THUNDERSTORMS...WIND AND HAIL. VERTICAL SHEAR PROFILE COULD
SUPPORT ISOLATED TORNADO FORMATION IN UPPER DESERT AREAS LATER TODAY.

MODERATELY DEEP MARINE LAYER WILL CONTINUE WEST OF THE MOUNTAINS FOR
MUCH OF THE WEEK WITH OVERNIGHT LOW CLOUDS EXTENDING INLAND INTO THE
VALLEYS. THIS WILL CONTINUE TO MODERATE TEMPERATURES WEST OF THE
MOUNTAINS. BY THE WEEKEND INTO NEXT WEEK...HIGH PRESSURE MAY BEGIN
TO BUILD AND EXPAND WESTWARD ACROSS SOUTHERN CALIFORNIA. THIS SHOULD
BRING WARMING AND A DECREASE IN THE MARINE LAYER. IT MIGHT ALSO
BRING A RETURN OF THE MONSOON.

&&

.AVIATION...UPPER LOW MOVING IN FROM WEST ATOP THE MONSOON AIR MASS
COMING IN FROM THE EAST. AND BELOW ALL THAT IS A 3000 FT MARINE
LAYER TRYING TO MOVE INLAND. LOW CLOUDS ARE ALREADY STARTING TO BE
ERODED BY THE MONSOON. BIGGEST LIGHTNING SHOW THIS SIDE OF TEXAS
CONTINUES IN THE INLAND EMPIRE...THE MOUNTAINS...AND THE UPPER
DESERTS. EXPECT NUMEROUS THUNDERSTORMS AND TURBULENT FLYING
CONDITIONS AS THE UPPER LOW CONTINUES TO MOVE INTO SOUTHERN
CALIFORNIA...INCREASING THE INSTABILITY. STRATUS BASE AT THE COAST
IS ABOUT 2000 FEET MSL WITH TOPS TO 3000 FEET. DESPITE THE DEPTH OF
THE MARINE LAYER...EXPECT IT TO CLEAR BY 17Z.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 8 PM MONDAY FOR CAZ055-CAZ060.

&&

PUBLIC...MARTIN
AVIATION...MACKECHNIE

HAZARDOUS WEATHER OUTLOOK...UPDATE
NATIONAL WEATHER SERVICE SAN DIEGO CA
845 PM PDT SUN AUG 14 2005

CAZ042-043-151100-
ORANGE COUNTY COASTAL AREAS-
SAN DIEGO COUNTY COASTAL AREAS-
400 PM PDT SUN AUG 14 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR
COASTAL AREAS
IN EXTREME SOUTHWESTERN CALIFORNIA.

.DAY ONE... TONIGHT.
NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN... MONDAY THROUGH SATURDAY.

LARGE SOUTH SWELL WILL CAUSE ABOVE NORMAL SURF ALONG WITH STRONG AND
DANGEROUS RIP CURRENTS WEDNESDAY THROUGH FRIDAY. HIGH TIDES OF OVER
7 FEET DURING THE EVENINGS...COMBINED WITH THE LARGER SURF...COULD
CAUSE MINOR TIDAL OVERFLOW AND BEACH EROSION WEDNESDAY THROUGH
FRIDAY.

.SPOTTER INFORMATION STATEMENT...
SKYWARN WEATHER SPOTTER ACTIVATION IS NOT REQUESTED FOR THIS AREA...
HOWEVER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

CAZ055-056-058-060-061-062-151100-
SAN BERNARDINO COUNTY MOUNTAINS-
RIVERSIDE COUNTY MOUNTAINS-
SAN DIEGO COUNTY MOUNTAINS-
APPLE AND LUCERNE VALLEYS-
COACHELLA VALLEY-
SAN DIEGO COUNTY DESERTS-
845 PM PDT SUN AUG 14 2005

THIS HAZARDOUS OUTLOOK IS FOR THE MOUNTAINS AND DESERTS OF
SOUTHWESTERN CALIFORNIA.

.DAY ONE... TONIGHT.
ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED OVERNIGHT OVER THE
APPLE AND LUCERNE VALLEYS AND SAN BERNARDINO COUNTY MOUNTAINS. LOCAL
HEAVY RAINS...FLASH FLOODING...DANGEROUS LIGHTNING...HAIL AND GUSTY
WINDS WILL BE THREATS.

.DAYS TWO THROUGH SEVEN... MONDAY THROUGH SATURDAY. SCATTERED TO
POTENTIALLY WIDESPREAD THUNDERSTORMS WILL OCCUR MONDAY...MAINLY IN
THE AFTERNOON INTO EARLY EVENING. THE GREATEST THREAT WILL BE IN SAN
BERNARDINO COUNTY. HEAVY RAINS...FLOODING...DANGEROUS
LIGHTNING...HAIL AND GUSTY WINDS WILL BE THREATS.

THERE IS A MODERATE FLASH FLOOD POTENTIAL RATING MONDAY.
THUNDERSTORMS WITH ISOLATED FLASH FLOODING ARE POSSIBLE.

.SPOTTER INFORMATION STATEMENT...
SKYWARN ACTIVATION MAY BE NEEDED MONDAY AFTERNOON.
WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

NOTE...THE HAZARDOUS WEATHER OUTLOOK NOW INCORPORATES THE FLASH
FLOOD POTENTIAL INDEX THAT WAS ISSUED SEPARATELY IN PREVIOUS YEARS.
THE FLASH FLOOD POTENTIAL INDEX WILL BE INCLUDED IN THE HAZARDOUS
WEATHER OUTLOOK IF IT EXCEEDS THE LOW CATEGORY IN THE FIRST TWO
DAYS. THIS PRODUCT WILL BE UPDATED DAILY AT 4 AM AND 4 PM OR AS
NEEDED THROUGH SEPTEMBER 30.

MAXWELL