Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 012050
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
150 PM PDT FRI AUG 1 2014

.SYNOPSIS...
ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER THE MOUNTAINS
AND DESERTS THROUGH THIS EVENING.  THE INCREASE IN SUBTROPICAL
MOISTURE WILL CONTINUE THROUGH SUNDAY...AS AN UPPER LEVEL
DISTURBANCE MOVES OVER SOUTHERN CALIFORNIA.  THEREFORE...THE THREAT
OF SHOWERS AND THUNDERSTORMS WILL INCREASE DURING THE DAY ON
SATURDAY...BUT ESPECIALLY FOR SATURDAY NIGHT AND SUNDAY...EVEN ALONG
THE COAST.  AS THIS DISTURBANCES LIFTS OUT OF THE AREA...A TROUGH OF
LOW PRESSURE WILL DEVELOP ALONG THE CALIFORNIA COAST...WITH DRIER
CONDITIONS PREVAILING.

&&

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

WATER VAPOR IMAGERY CONTINUES TO SHOW THE RIDGE AXIS SHIFTING TO OUR
NORTH THIS AFTERNOON...WITH A CLEAR MOISTURE DELINEATION OVER
SOUTHERN CALIFORNIA.  AT THIS TIME...ISOLATED THUNDERSTORMS ARE
FIRING OVER THE HIGHER MOUNTAIN PEAKS...AND ARE CAPABLE OF PRODUCING
FREQUENT LIGHTNING...BRIEF HEAVY RAIN...AND LOCALIZED FLASH
FLOODING.  THE THUNDERSTORM THREAT WILL DECREASE THOUGH AFTER
SUNSET.  THE MODELS ARE HINTING AT AN EDDY SPINNING UP TONIGHT OVER
THE BIGHT...SO EXPECT THE MARINE LAYER TO DEEPEN SLIGHTLY AS WELL AS
PUSH BACK INTO THE SAN DIEGO COUNTY VALLEYS TONIGHT.

WATER VAPOR IMAGERY ALSO A CLEAR UPPER LEVEL CIRCULATION OVER
CENTRAL BAJA THIS AFTERNOON.  IT WILL COMBINE WITH A WEAKER
DISTURBANCE CURRENTLY OVER NORTHERN MEXICO ON SATURDAY...WHICH WILL
TRACK OVER SOUTHERN CALIFORNIA LATE SATURDAY AND INTO SUNDAY.  THE
12Z MODELS STILL VARY ON THE TRACK OF THIS LOW...BUT THE BRUNT OF
THE MODELS ARE LEANING TOWARDS A TRACK OVER SAN DIEGO COUNTY OR
SLIGHTLY OFF THE COAST.  FOR THIS REASON...THINK THAT THE THREAT OF
SHOWERS AND THUNDERSTORMS WILL INCREASE FOR SATURDAY THROUGH
SUNDAY.  MY ONE CONCERN FOR SATURDAY MAY BE THE FACT THAT A CLOUD
SHIELD COULD LIMIT THUNDERSTORM DEVELOPMENT.  HOWEVER...AS THE VORT
MAX TRACKS OVER THE REGION SATURDAY NIGHT...THINK THAT SOME ELEVATED
INSTABILITY WILL BE DRIVE THE SHOWER AND THUNDERSTORM
DEVELOPMENT...EVEN ALONG THE COAST.  WITH PW VALUES INCREASING TO
BETWEEN 1.5 AND 2 INCHES...DEPENDING ON THE MODEL...BELIEVE SMALL
STREAM AND URBAN FLOODING MAY BE POSSIBLE AS WELL AS FLASH
FLOODING.  FOR NOW...THE MODELS REALLY FAVOR THE COASTAL AREAS OF
SAN DIEGO COUNTY...COMPARED TO THAT OF ORANGE COUNTY...JUST BASED
OFF THE TRACK OF THE UPPER LEVEL LOW.  HOWEVER...CANNOT RULE OUT
COASTAL STORMS IN ORANGE COUNTY AT THIS TIME.

AS THIS DISTURBANCES LIFTS OFF TO OUR EAST OR NORTHEAST ON
SUNDAY...THE THREAT OF UNSETTLED WEATHER WILL DECREASE FROM SOUTH TO
NORTH AS WELL AS WEST TO EAST DURING THE DAY.  OTHERWISE...JUST
EXPECT A GRADUAL COOLING TREND FOR THE WEEKEND...WITH PARTLY TO
MOSTLY CLOUDY SKIES.

MUCH DRIER WEATHER SHOULD RETURN BY MONDAY...AS ANOTHER UPPER LEVEL
TROUGH DEVELOPS ALONG THE WEST COAST.  THIS MEANS THAT THE UPPER
LEVEL FLOW WILL BE SOUTHWESTERLY OR WESTERLY...AND THE MODELS SHOW
THE PWS FALLING BELOW AN INCH BY MONDAY AFTERNOON.  THIS TROUGH WILL
SHIFT INLAND BY MIDWEEK...WITH GENERAL TROFINESS REMAINING OVER
THE REGION THROUGH FRIDAY.  THEREFORE...EXPECT DRY CONDITIONS AND
ONSHORE FLOW TO PREVAIL DURING THIS TIME...WITH TEMPERATURES NEAR OR
BELOW NORMAL FOR THE WEEK.  THE MARINE LAYER WILL DEEPEN AS
WELL...WITH MORE COASTAL LOW CLOUDS AND FOG POSSIBLE EACH NIGHT.
SOME LOCALLY GUSTY WEST WIND WILL BE POSSIBLE THROUGH AND BELOW THE
FAVORED CANYONS AND PASSES EACH AFTERNOON.

&&

.AVIATION...
012000Z...THUNDERSTORMS OVER MOUNTAINS THROUGH 00Z THIS AFTERNOON
AND LESS POSSIBLE OVER ADJACENT DESERTS THROUGH 02Z. THEY WILL NOT
BE NUMEROUS...BUT WHERE THEY OCCUR BASES WILL BE AROUND 9000 FEET
ASL WITH TOPS UP TO 35000 FEET. EXPECT GUSTY ERRATIC WINDS AROUND
ANY TSTORM. OTHERWISE...INCREASING CLOUDS AOA 15000 FEET SATURDAY
AND MORE NUMEROUS TSTORMS AFTER 18Z.

LOW CLOUDS WILL RETURN TO COASTAL AIRPORTS THIS EVENING BETWEEN
04-08Z AT AROUND 1000 FEET ASL WITH TOPS TO 1600 FEET. THESE WILL
DISSIPATE SATURDAY MORNING BY 16Z.

&&

.MARINE...
100 PM...THERE WILL BE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS
FOR THE COASTAL WATERS SATURDAY NIGHT THROUGH SUNDAY MORNING. THESE
STORMS WILL BE CAPABLE OF PRODUCING BRIEF HEAVY RAIN...CLOUD TO
WATER LIGHTNING AND BRIEF GUSTY WINDS. OTHERWISE...NO MARINE HAZARDS
ARE EXPECTED THROUGH WEDNESDAY.

&&

.FIRE WEATHER...
ISOLATED AFTERNOON AND EVENING THUNDERSTORMS WILL BE POSSIBLE TODAY
OVER THE MOUNTAINS AND DESERTS.  THESE THUNDERSTORMS ARE CAPABLE OF
PRODUCING WETTING RAINS...LOCALIZED FLASH FLOODING...AND FREQUENT
LIGHTNING.  A DISTURBANCE WILL MOVE OVER SOUTHERN CALIFORNIA LATE
SATURDAY AND INTO SUNDAY...INCREASING THE THREAT OF SHOWERS AND
THUNDERSTORMS...WITH NOCTURNAL THUNDERSTORMS POSSIBLE ON SATURDAY
NIGHT.  AN ADDITIONAL SURGE OF MOISTURE WILL COMPANY THIS
DISTURBANCE...INCREASING THE CHANCES OF FLASH FLOODING AS WELL.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC/FIRE WEATHER...PALMER
AVIATION/MARINE...MM





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