Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 282256 AAA
AFDSGX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN DIEGO CA
356 PM PDT TUE JUL 28 2015

UPDATED FOR ISSUANCE OF BEACH HAZARDS STATEMENT. W/W/A SECTION
AND BEACHES SECTION UPDATED.

.SYNOPSIS...
HIGH PRESSURE BUILDING WESTWARD INTO CALIFORNIA WILL BRING WARMER
DAYS...HIGHER HUMIDITIES AND A SHALLOWER MARINE LAYER THROUGH
FRIDAY. INCREASING MONSOONAL MOISTURE WILL BRING SCATTERED AFTERNOON
AND EVENING THUNDERSTORMS TO THE MOUNTAINS AND DESERTS THROUGH THE
MIDDLE OF NEXT WEEK. SOME STORMS MAY DRIFT INTO THE INLAND VALLEYS
WEDNESDAY AND THURSDAY.

&&

.PREVIOUS DISCUSSION...ISSUED AT 145 PM...FOR EXTREME SOUTHWESTERN
CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND
SOUTHWESTERN SAN BERNARDINO COUNTIES...

THE DRIVING FORCE BEHIND WHAT WILL BE A PROLONGED PERIOD OF MONSOON
FLOW IS A 594 DM HIGH CENTERED OVER OKLAHOMA TODAY. THIS UPPER HIGH
WILL DRIFT WEST OVER NEW MEXICO THURSDAY AND THEN BECOME ANCHORED
OVER THE FOUR CORNERS REGION FRIDAY THROUGH NEXT WEDNESDAY.
SOUTHEAST FLOW AROUND THE UPPER HIGH WILL CONTINUE TO DRAW MIDLEVEL
MONSOONAL MOISTURE INTO THE SOUTHWEST.

MONSOON MOISTURE REACHED THE LOWER COLORADO RIVER VALLEY THIS
AFTERNOON WHERE INTEGRATED PRECIPITABLE WATER VALUES ROSE STEADILY
THIS MORNING. AT 12Z THE YUMA PRECIPITABLE WATER WAS 1.02"...AND BY
18Z IT HAD RISEN TO 1.39". THE 12Z PWAT AT THE BRAWLEY SENSOR (NEAR
EL CENTRO) WAS LESS THAN AN INCH...BUT BY 18Z IT HAD RISEN TO 1.3".
THIS SURGE OF MONSOON MOISTURE WILL CONTINUE MOVING WESTWARD INTO
THE SOUTHERN CALIFORNIA MOUNTAINS AND DESERTS TONIGHT AND WEDNESDAY.

THE 12Z WRF MODEL SHOWS PWATS APPROACHING 2.00" IN THE LOWER DESERTS
WEDNESDAY AFTERNOON THROUGH THURSDAY. MUCAPE INCREASES TO 500 J/KG
OVER THE MTNS AND DESERTS DURING THIS TIME WHEN THUNDERSTORMS ARE
MOST LIKELY. THE STORMS WILL DRIFT NORTHWEST IN THE 15KT 500-700 MB
SOUTHEAST FLOW ALOFT AND MAY VERY WELL REACH THE INLAND VALLEYS.

EVEN HIGHER CAPE IS PROJECTED FOR THURSDAY WHEN THUNDERSTORMS WILL
BE MORE WIDESPREAD. STEERING FLOW ALOFT REMAINS SOUTHEASTERLY SO
STORMS MAY ONCE AGAIN DRIFT INTO THE VALLEYS. STORMS MAY ALSO FIRE
ALONG THE ELSINORE CONVERGENCE ZONE WEDNESDAY AFTERNOON...WITH EVEN
BETTER CHANCES ON THURSDAY AFTERNOON WHEN MOISTURE AND CONVERGENCE
PARAMETERS ARE MAXIMIZED.

FRIDAY AND SATURDAY...PWATS DECREASE SLIGHTLY AND THUNDERSTORM
COVERAGE LOOKS LIKE IT WILL BE LESS WIDESPREAD AND MAINLY CONFINED
TO THE MOUNTAINS AND DESERTS DUE TO THE MORE SOUTHERLY STEERING FLOW
ALOFT.

SUNDAY THROUGH WEDNESDAY...THE MONSOONAL FLOW PATTERN WILL PERSIST
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK WITH DIURNAL AFTERNOON AND
EVENING THUNDERSTORMS MAINLY OVER THE MOUNTAINS AND DESERTS EACH
DAY.

THE MARINE LAYER WILL TURN SHALLOWER THIS WEEK AS THE UPPER HIGH
BUILDS. 500 MB HTS OVER SAN DIEGO THIS MORNING WERE 589DM...AND THEY
WILL INCREASE TO 592 DM BY THE WEEKEND. WARMING ALOFT WILL INCREASE
THE INVERSION STRENGTH WHICH IN TURN MAY RESULT IN SLOWER CLEARING
OF THE LOW CLOUDS AT THE COAST.

&&

.AVIATION...
282030Z...COAST/VALLEYS...AFTER THE LATE STRATUS SURGE THIS
MORNING...LOW CLOUDS CLEARED OUT RAPIDLY...LEAVING MOSTLY CLEAR
SKIES ACROSS THE AREA THIS AFTERNOON. STRATUS WILL RETURN TO THE
COASTAL AIRPORTS AFTER 29/04Z AND SPREAD 15-20 MI INLAND OVERNIGHT.
BASES WILL BE SLIGHTLY LOWER TONIGHT...GENERALLY AROUND 1000-1400 FT
MSL. OTHERWISE...INCREASING CLOUDS AOA 15000 FT MSL EARLY WED
MORNING WITH UNRESTRICTED VIS.

MTNS/DESERTS...INCREASING CLOUDS AOA 15000 FT MSL EARLY WED MORNING
AND UNRESTRICTED VIS PREVAILING.

&&

.MARINE...
130 PM...THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER
THE COASTAL WATERS WEDNESDAY NIGHT THROUGH EARLY THU AFTERNOON AND
AGAIN LATE THU NIGHT INTO FRI MORNING. OTHERWISE...NO HAZARDOUS
MARINE WEATHER IS EXPECTED THROUGH SATURDAY.

&&

.BEACHES...
400 PM...THERE IS A SLIGHT CHANCE OF THUNDERSTORMS AT
THE BEACHES WEDNESDAY NIGHT INTO EARLY THU AFTERNOON AND AGAIN LATE
THU NIGHT INTO FRI MORNING...THOUGH EXACT TIMING IS UNCERTAIN.
LIGHTNING WILL POSE A THREAT TO BEACH-GOERS SHOULD ANY THUNDERSTORMS
DEVELOP.

ALSO...A LONG-PERIOD SOUTHWEST SWELL IS PEAKING HIGHER THAN FORECAST
BY THE WAVE WATCH 3...NEAR 4 FEET/17 SECONDS. THIS IS RESULTING IN
ELEVATED SURF OF 4-6 FEET AT THE SOUTHERN ORANGE COUNTY BEACHES AND
MOST OF THE SAN DIEGO COUNTY BEACHES THIS AFTERNOON...WITH LARGE AND
POWERFUL RIP CURRENTS BEING REPORTED. A BEACH HAZARDS STATEMENT HAS
BEEN ISSUED...AND CONTINUES THROUGH WEDNESDAY EVENING. BY
THURSDAY...THE SWELL SHOULD HAVE LOWERED ENOUGH WHERE CONDITIONS
WILL IMPROVE.

&&

.SKYWARN...
SKYWARN ACTIVATION MAY BE REQUESTED WEDNESDAY AND THURSDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...BEACH HAZARDS STATEMENT THROUGH WEDNESDAY EVENING FOR ORANGE
     COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.
PZ...NONE.

&&

$$

PUBLIC...MOEDE
AVIATION/MARINE...TS
BEACHES...TS/HARRISON
UPDATE...HARRISON



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