Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 042057
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
200 PM PDT MON MAY 4 2015

.SYNOPSIS...
A LOW PRESSURE SYSTEM MOVING THROUGH SOUTHERN CALIFORNIA WILL BRING
ISOLATED THUNDERSTORMS TO THE MOUNTAINS AND DESERTS THIS
AFTERNOON...ENDING EARLY THIS EVENING. THERE WILL BE LOCALLY GUSTY
WEST WINDS IN THE DESERTS TONIGHT. SLIGHT WARMING WILL OCCUR INLAND
TUESDAY AFTER THE LOW PRESSURE SYSTEM MOVES EAST OUT OF THE
REGION...BUT THEN ANOTHER TROUGH OF LOW PRESSURE WILL BUILD OVER THE
WEST COAST WEDNESDAY THROUGH FRIDAY AND BRING MORE COOL WEATHER AND
A CHANCE OF PRECIPITATION THURSDAY AND FRIDAY. NIGHT AND MORNING LOW
CLOUDS WILL BE WIDESPREAD WEST OF THE MOUNTAINS THROUGH
FRIDAY...WITH ONLY PARTIAL AFTERNOON CLEARING EACH DAY. FAIR WEATHER
SHOULD RETURN OVER THE WEEKEND.

&&

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

ISOLATED THUNDERSTORMS WERE OCCURRING OVER THE MOUNTAINS...MAINLY
FROM THE SANTA ROSA MOUNTAINS SOUTH THROUGH THE SAN DIEGO COUNTY
MOUNTAINS. THESE SHOULD CONTINUE UNTIL LATE AFTERNOON...OR AT THE
VERY LATEST EARLY THIS EVENING. RAINFALL AMOUNTS SHOULD NOT COVER
MUCH TERRITORY. SOME STRATOCUMULUS CONTINUED IN COASTAL
AREAS...ESPECIALLY IN SAN DIEGO COUNTY. TEMPERATURES WERE
5-10 DEG F BELOW NORMAL...MOSTLY IN THE 60S TO
LOWER 70S WEST OF THE MOUNTAINS WITH LOWER TO MID 80S IN THE DESERTS.

THE UPPER LOW WAS NOW OVER SOUTHEASTERN CALIFORNIA...MOVING
EAST. AFTER THE LOW MOVES EAST OUT OF THE AREA...FAIR WEATHER WILL
RETURN FOR LATER TONIGHT/TUESDAY...THOUGH THE MARINE LAYER WILL BE
DEEP WEST OF THE MOUNTAINS WITH LOCAL WRF SHOWING A LOT OF CLOUD
COVER...EVEN IN SOME AREAS TUE AFTERNOON...AND AGAIN WED AFTERNOON.
THERE COULD BE DRIZZLE AT NIGHT...ESPECIALLY WED MORNING WITH A
SHORT WAVE MOVING THROUGH. WHILE SLIGHT WARMING WILL OCCUR INLAND
TUESDAY...TEMPS WILL OVERALL CONTINUE BELOW NORMAL THE NEXT SEVERAL
DAYS...INCLUDING WHEN THE NEXT TROUGH BUILDS OVER THE WEST COAST
WEDNESDAY THROUGH FRIDAY. THIS COULD BRING MORE PRECIP
THURSDAY/FRIDAY...AND WITH THE MOSTLY OPEN TROUGHING AND NORTH-SOUTH
GRADIENTS...GUSTY WINDS TO THE MOUNTAINS/DESERTS. THE UPPER LOW WILL
BE CLOSEST ON FRIDAY...AND THAT COULD BRING SNOW LEVELS DOWN TO 5500-
6000 FEET THEN...SO THE HIGHER MOUNTAINS COULD HAVE SOME LIGHT SNOW.
SO FAR...THE GFS AND ECM BOTH HAVE LOW QPF VALUES...MOSTLY LESS
THAN ONE-QUARTER INCH OF PRECIP. AFTER THE TROUGH MOVES EAST...FAIR
WEATHER WILL RETURN OVER THE WEEKEND WITH TEMPERATURES RECOVERING TO
NEAR NORMAL BY SUNDAY.

&&

.AVIATION...
042005Z...COAST/VALLEYS...THROUGH 05/0000 UTC...UNRESTRICTED VIS
WITH WITH FEW-SCT CLOUDS 2500-3500 FT MSL AND FEW-SCT CLOUDS AOA
10000 FT MSL. LOCALLY BKN CLOUDS 2500-3500 FT MSL POSSIBLE. 05/0000-
1500 UTC...STRATUS MOVING BACK INLAND DEEP INTO THE VALLEYS...WITH
BASES 2000-3000 FT MSL...AND TOPS 3500-4500 FT MSL. MARINE LAYER
INVERSION OF 5 DEG C EXPECTED. STRATUS GRADUALLY CLEARING OUT DURING
THE 05/1600-2000 UTC. FORECAST CONFIDENCE MODERATE-TO-HIGH.

MTNS/DESERTS...MTN OBSCURATION OF COASTAL SLOPES BELOW 4500 FT MSL
ELEVATION DUE TO LOW CLOUDS INTERSECTING TERRAIN WILL DEVELOP AGAIN
TONIGHT INTO TUESDAY MORNING. SCT-BKN CLOUDS BETWEEN 7000 AND 15000
FT MSL...WITH EMBEDDED SHOWERS OVER THE MOUNTAINS AND DESERTS...WITH
THE POSSIBILITY OF THUNDERSTORMS/HEAVY SHOWERS. CB TOPS 25000-30000
FT MSL. THUNDERSTORMS/SHOWERS SHOULD DISSIPATE AFTER 05/0000
UTC...WITH UNRESTRICTED VIS AND MOSTLY SKC EXPECTED THEREAFTER.
AFTER 05/0000 UTC...20-25 KT WEST WINDS WITH GUSTS TO 35 KT OVER MTN
RIDGES...THROUGH AND BELOW CANYONS/PASSES...ALONG DESERT SLOPES AND
INTO ADJACENT LOWER DESERT AREAS...WILL PRODUCE MOD-STG UDDFS/LLWS
OVER AND EAST OF THE MTNS.

&&

.MARINE...
105 PM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SATURDAY.
HOWEVER...BREEZY NORTHWEST WINDS...WITH GUSTS OF 20 TO LOCALLY 25
KT...ARE POSSIBLE IN THE AFTERNOONS AND EVENINGS WEDNESDAY THROUGH
FRIDAY...MAINLY IN THE OUTER WATERS NEAR SAN CLEMENTE ISLAND.
ALSO...A TROUGH MOVING ACROSS THE REGION WILL CREATE A SLIGHT CHANCE
OF SHOWERS THURSDAY AND FRIDAY.

&&

.BEACHES...
105 PM...NEARSHORE BUOY REPORTS SHOW SOUTH-SOUTHWEST SWELLS HOLDING
STEADY THIS AFTERNOON...WITH A SIGNIFICANT WAVE HEIGHT OF 5 FT WITH
A PERIOD OF 20 SECONDS...AND LIFEGUARD REPORTS AND SURFLINE SURF
OBSERVATIONS SHOW 6 TO 12 FOOT SURF IN ORANGE COUNTY...5 TO 8 FOOT
SURF ALONG FAVORED BEACHES IN SAN DIEGO COUNTY...AND 15 TO 18 FOOT
SURF AT THE WEDGE. THESE SWELLS WILL HOLD STEADY THROUGH THE REST OF
TODAY...RESULTING IN CONTINUED HAZARDOUS SWIMMING CONDITIONS AT THE
LOCAL BEACHES...WITH LARGE SURF IN ORANGE COUNTY AND NORTHERN SAN
DIEGO COUNTY...IN ADDITION TO POWERFUL RIP AND LONGSHORE
CURRENTS...BEACH EROSION AND POSSIBLE MINOR TIDAL FLOODING OF LOW-
LYING VULNERABLE COASTAL AREAS DURING THE EVENING HIGH TIDES. IN
PARTICULAR...SEAL BEACH IS LIKELY TO EXPERIENCE SOME MINOR COASTAL
FLOODING AGAIN THIS EVENING WITH THE CONTINUED LARGE SURF AND A HIGH
TIDE AROUND 5.9 TO 6 FEET. THE SMALLER ENERGY SWELL SHOULD DROP-OFF
ON TUESDAY...BUT THE LARGER SWELL WILL STILL BE GOING STRONG...AT 4-
5 FT/16-17 SECONDS...AND SO HIGH SURF SHOULD CONTINUE THAT DAY. IT
IS NOT UNTIL WEDNESDAY THAT THE SWELL IS EXPECTED TO DROP BELOW 4
FEET...WITH SURF FALLING AS WELL. THE SWELL WILL THEN CONTINUE TO
FALL INTO THE END OF THE WORK-WEEK. A HIGH SURF ADVISORY IS IN
EFFECT THROUGH TUESDAY EVENING. PLEASE SEE LAXCFWSGX FOR FURTHER
DETAILS.


&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY UNTIL 11 PM PDT TUESDAY FOR ORANGE COUNTY
     COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.

PZ...NONE.

&&

$$

PUBLIC...MAXWELL
AVIATION/MARINE/BEACHES...HARRISON


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