Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 261527
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
826 AM PDT SAT JUL 26 2014

.SYNOPSIS...
HIGH PRESSURE TO THE EAST WILL BRING SEASONALLY WARM SUMMER WEATHER
THROUGH NEXT WEEK. MONSOONAL MOISTURE WILL BRING PERIODS OF ISOLATED
TO SCATTERED THUNDERSTORMS THROUGH MONDAY OVER THE MOUNTAINS AND
DESERTS...MAINLY IN THE AFTERNOONS AND EARLY EVENINGS. THE MARINE
LAYER WILL KEEP COASTAL AREAS COOLER WITH AREAS OF NIGHT AND MORNING
LOW CLOUDS AND FOG EXTENDING LOCALLY INTO THE WESTERN VALLEYS. THE
MARINE LAYER WILL BECOME MORE SHALLOW NEXT WEEK...WITH NIGHT AND
MORNING CLOUDS MAINLY OVER COASTAL AREAS.

&&

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

A MIX OF HIGH AND LOW CLOUDS WAS PREVALENT OVER THE REGION THIS
MORNING WITH PATCHY DENSE FOG IN SOME AREAS AROUND SUNRISE.
THUNDERSTORMS WERE OCCURRING ABOUT 200 MILES SW OF SAN DIEGO AT 8 AM
PDT...BUT SKIES WERE DRY OVER SOCAL. THE 12Z MIRAMAR SOUNDING
INDICATED A LOWERING OF THE MARINE LAYER FROM YESTERDAY TO AROUND
1300 FT...CAPPED BY A 7 DEGREE C INVERSION. ABOVE THE INVERSION
WINDS WERE LIGHT SW TO AROUND 10K FT BEFORE TURNING S-SE. THE PW WAS
MEASURED AT 1.52 INCH WITH ABOUT 1000 J/KG OF CAPE ABOVE 11K FT.
WEAK ONSHORE SFC PRESSURE GRADIENTS WERE PRESENT.

A STRONG SUBTROPICAL HIGH WAS CENTERED OVER NEW MEXICO THIS MORNING.
THE HIGH HAD AN EAST-WEST ORIENTED AXIS THAT WILL GRADUALLY BECOME
TILTED MORE NW-SE THROUGH MON. FLOW AROUND THE HIGH WILL CONTINUE
TO ADVECT MONSOONAL MOISTURE AND WEAK INSTABILITY OVER SOCAL WITH A
THREAT OF MAINLY AFTERNOON CONVECTION OVER THE MOUNTAINS AND
DESERTS. AFTER MON...THE HIGH CENTER DRIFTS SW AND GRADUALLY SHUTS
OFF THE MOISTURE FLOW INTO SOCAL. THIS SHOULD SHUT DOWN THE CHANCE
FOR CONVECTION NEXT WEEK. HEIGHTS/THICKNESS WILL REMAIN ELEVATED
THROUGH NEXT WEEK SO WARM SUMMER WEATHER WILL CONTINUE.

LITTLE CHANGE IS LIKELY WITH THE SFC PRESSURE PATTERN. A SEASONAL
THERMAL LOW WILL REMAIN OVER THE LOWER COLORADO RIVER VALLEY AND
CONTINUE WEAK ONSHORE FLOW. THIS SHOULD ALSO MAINTAIN A SHALLOW
MARINE LAYER ALONG THE COAST WITH PERIODS OF NIGHT AND MORNING LOW
CLOUDS AND FOG.

CONVECTION OUTLOOK...MOISTURE STILL LOOKS PLENTIFUL OVER THE
IMPERIAL VALLEY AND ALONG THE EAST SLOPES OF THE MOUNTAINS THIS
MORNING BASED ON GPS PW ESTIMATES. IT IS A BIT DRIER FARTHER WEST
BUT STILL SUFFICIENT MOISTURE FOR CONVECTION TO BUILD OVER THE
ELEVATED HEAT SOURCES. WINDS ARE 10 KT OR LESS IN THE MID-LEVELS AND
WITH CAPE BUILDING THROUGH MIDDAY...EXPECT TO SEE CUMULUS DEVELOP
SHORTLY OVER THE MOUNTAINS AND BLOSSOM INTO ISOLATED/SCATTERED
THUNDERSTORMS BY AFTERNOON. THE MEAN UPPER-LEVEL RIDGE IS IN PLACE
ACROSS THE REGION TODAY SO THIS MAY HELP TO KEEP CONVECTION SOMEWHAT
LIMITED.

FOR SUNDAY...THE RIDGE AXIS SHIFTS NORTH...AND BOTH THE ECMWF/GFS
MODELS INDICATE A WEAK EASTERLY WAVE MOVING THROUGH OR APPROACHING
THE AREA BY AFTERNOON FROM THE SOUTH. MID-LEVEL STEERING WINDS WILL
BE STRONGER...SO STRONG HEATING WILL BE NECESSARY TO MAINTAIN DEEP
CONVECTION. BUT GIVEN THE ADDED INSTABILITY AND DEEP MOISTURE IN
PLACE...THERE IS MORE POTENTIAL FOR WIDESPREAD MTN/DESERT
CONVECTION.

&&

.AVIATION...
261515Z...COAST/VALLEYS...AREAS OF STRATUS WITH BASES FROM 800-1200
FT AND TOPS TO 1600 FT WILL CLEAR TO THE COAST 16-17Z WITH MOST VIS
ABOVE 5 MI BY 16Z. OTHERWISE...SCT-BKN CLOUDS AT/ABOVE 15000 FT MSL
WILL OCCUR TODAY. AREAS OF STRATUS WILL GRADUALLY DEVELOP AGAIN
TONIGHT 05-08Z WITH SIMILAR BASES/TOPS. LOCAL VIS BELOW 2 MI WILL
OCCUR 11-15Z SUNDAY OVER HIGHER COASTAL TERRAIN AND THE SAN DIEGO
COUNTY MESAS/COASTAL VALLEYS. MOST AREAS WILL CLEAR BY 16-17Z SUNDAY.

MTNS/DESERTS...ISOLATED TO SCATTERED THUNDERSTORMS WILL OCCUR THIS
AFTERNOON/EARLY THIS EVENING...MOST NUMEROUS IN RIVERSIDE AND SAN
DIEGO COUNTIES. A THUNDERSTORM COULD REACH KPSP...WITH GREATEST
THREAT BEING LIGHTNING. LOCAL VIS OF 3 MI WILL OCCUR WITH HEAVIER
SHOWERS. BASES OF THE BKN-OVC CLOUDS WILL BE AT/ABOVE 8000 FT WITH
ISOLATED TOPS TO 35000 FT MSL.

&&

.MARINE...
800 AM PDT...NO HAZARDOUS MARINE WEATHER THROUGH WEDNESDAY.
&&

.SKYWARN...
SKYWARN ACTIVATION MAY BE NEEDED THIS AFTERNOON DUE TO POSSIBLE
THUNDERSTORMS. SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT
WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...JAD
AVIATION/MARINE...MAXWELL







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