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000
FXUS66 KSGX 011133
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
430 AM PDT FRI AUG 1 2014

.SYNOPSIS...
MONSOON MOISTURE WILL INCREASE THIS WEEKEND AND COMBINE WITH LOW
PRESSURE ALOFT TO BRING SHOWERS AND THUNDERSTORMS AT TIMES TO THE
MOUNTAINS AND DESERTS. SOME THUNDERSTORMS MAY DRIFT WEST OF THE
MOUNTAINS. INCREASING CLOUDS AND HIGHER HUMIDITIES WILL KEEP
TEMPERATURES A LITTLE LOWER. THE UPPER LOW WILL EXIT THE REGION
MONDAY FOLLOWED BY DRIER WEATHER AND LOWER HUMIDITIES NEXT WEEK.

&&

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

WATER VAPOR LOOP THIS MORNING SHOWS A BROAD CIRCULATION CENTER OVER
SOUTHERN BAJA MOVING SLOWLY NORTH. MOISTURE IS STREAMING NORTH FROM
THIS FEATURE WILL COMBINE WITH ADDITIONAL MONSOONAL MOISTURE FROM
THE SOUTHEAST TO BRING HIGH PRECIPITABLE WATER VALUES INTO SOUTHERN
CALIFORNIA THIS WEEKEND. STEADY MOISTURE ADVECTION WILL RAISE PWATS
TO ABOUT 1.20" OVER THE MTNS AND 1.75" OVER THE LOWER DESERTS THIS
AFTERNOON...HIGH ENOUGH FOR A FEW THUNDERSTORMS TO FORM OVER THE
MTNS OR DESERTS WITH DAYTIME HEATING. AT 4 AM...A SHALLOW MOISTURE
SURGE WAS EVIDENT WITH A DEWPOINT OF 69F AT THERMAL AND WAS 75F AT
IMPERIAL.

A MORE SIGNIFICANT MOISTURE SURGE TONIGHT AND SATURDAY WILL RAISE
PWATS TO 1.5" IN THE MOUNTAINS AND TO 2.20" IN THE DESERTS. PRECIP
CHANCES WERE TRENDED UPWARD OVER THE WEEKEND BASED ON THIS DEEP
MOISTURE SURGE AND THE BETTER DYNAMICS WITH THE UPPER LOW OVER BAJA
MOVING INTO SOCAL SATURDAY. THE POTENTIAL ALSO EXISTS FOR SHORTWAVES
AND OUTFLOW BOUNDARIES FROM ANY MCS THAT FORMS OVER SONORA MEXICO TO
MOVE INTO SE CALIFORNIA IN THE EASTERLY FLOW ALOFT.

ON SATURDAY THE MIDLEVEL EASTERLY WINDS INCREASE TO 20-25 KT...SO
ANY SHOWERS AND THUNDERSTORMS THAT FORM WILL LIKELY DRIFT WEST INTO
THE VALLEY AND COASTAL ZONES. SOME CELLS MAY EVEN REACH THE COASTAL
WATERS. THE ONE CAVEAT IS THE CLOUD COVER WHICH COULD BE A LIMITING
FACTOR FOR STRONG CONVECTION. BUT WITH SUCH HIGH MOISTURE CONTENT
THE CHANCES FOR RAIN ARE QUITE GOOD. SOUNDING FORECASTS OVER THE
MOUNTAINS SATURDAY NIGHT AND SUNDAY MORNING SHOW NEAR SATURATION IN
THE 850-500 MB LAYER...SO THE FLASH FLOOD THREAT WILL BE HIGHER THAN
IT HAS BEEN IN A WHILE. THE WRF MODEL SHOWS AN ELSINORE CONVERGENCE
ZONE IN THE INLAND EMPIRE SATURDAY AND SUNDAY AFTERNOONS. CONVECTION
ALONG THIS BOUNDARY WOULD BE LIMITED IF THE CLOUD COVER IS TOO
GREAT.

MID LEVEL SHEAR INDUCED BY THE UPPER LOW INTERSECTING WITH TERRAIN
DRIVEN CONVERGENCE BOUNDARIES OR SEA BREEZE FRONTS THAT SET UP COULD
TRIGGER ISOLATED STRONG STORMS WITH HAIL AND STRONG GUSTY WINDS. BUT
AGAIN THIS IS HIGHLY DEPENDENT ON SOLAR HEATING. A MID LEVEL CLOUD
DECK WOULD LIMIT STORM POTENTIAL.

OUTLOOK FOR NEXT WEEK...THE UPPER LOW SLOWLY LIFTS NORTHEAST INTO
NEVADA SUNDAY NIGHT AND MONDAY WITH DRIER WESTERLY FLOW AND ALOFT
BRINGING AN END TO THE PRECIP. HUMIDITIES WILL BE LOWER NEXT WEEK.
INCREASING ONSHORE FLOW WILL DEEPEN THE MARINE LAYER WITH NIGHT AND
MORNING STRATUS SPREADING FARTHER INLAND EACH NIGHT THROUGH
THURSDAY.

&&

.AVIATION...
010930Z...COASTS/VALLEYS...STRATUS WITH BASES 900-1200 FT MSL AND
TOPS 1500 FT MSL HAVE PUSHED 8-15 SM INLAND...AFFECTING
KSNA...KCRQ...AND KSNA. THESE LOW CLOUDS WILL ERODE TO THE COAST BY
1530Z THIS MORNING. VISIBILITY MAY BE LOCALLY REDUCED TO 1 MILE OR
LESS WHERE THE CLOUDS ARE INTERSECTING THE TERRAIN ON THE LOWER
COASTAL MESAS. FEW/SCT MID AND HIGH LEVEL CLOUDS AT OR ABOVE 15000
FT MSL WILL MOVE OVER THE AREA THROUGH THE AFTERNOON FRIDAY. ANOTHER
STRATUS DECK...SLIGHTLY DEEPER...WILL MOVE FROM THE COAST INLAND AFT
02/0400Z.

MOUNTAINS/DESERTS...SCT CUMULUS DEVELOPMENT WITH BASES AROUND
9000 FT ABOVE MEAN SEA LEVEL AFT 01/1800Z...WITH TOPS RISING UP TO
35000 FT MSL WHERE THUNDERSTORMS DEVELOP OVER THE MOUNTAINOUS
TERRAIN. OTHERWISE...INCREASING HIGH CLOUDS AT OR ABOVE 15000 FT MSL.

&&

.MARINE...
230 AM PDT...THERE WILL BE A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS FOR THE COASTAL WATERS SATURDAY NIGHT THROUGH SUNDAY
EVENING AS A SUB-TROPICAL LOW PRESSURE SYSTEM MOVES OVER SOUTHERN
CALIFORNIA. THESE STORMS WILL BE CAPABLE OF PRODUCING BRIEF HEAVY
RAIN, CLOUD TO WATER LIGHTNING, AND BRIEF GUSTY WINDS.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED TODAY. SKYWARN ACTIVATION MAY BE
REQUESTED SATURDAY.

&&

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

&&

$$

PUBLIC...MOEDE
AVIATION/MARINE...JT