Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 042031
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
128 PM PDT SAT JUL 4 2015

.SYNOPSIS... SOLID ONSHORE FLOW AT THE SURFACE AND INCREASING
SOUTHWESTERLY FLOW ALOFT WILL GUARANTEE SOME FINE SUMMER WEATHER
ACROSS THE SOUTHLAND THROUGH NEXT WEEK. A DEEP MARINE LAYER WILL
BRING LOW CLOUDS EACH NIGHT AND MORNING WELL INTO THE VALLEYS...
WHICH AND MAY LINGER NEAR THE BEACHES INTO THE AFTERNOONS. THIS WILL
MEAN COOLER THAN AVERAGE SUMMER DAYS NEXT WEEK. THERE REMAINS A
SMALL CHANCE OF ISOLATED THUNDERSTORM ACTIVITY NEAR THE MOUNTAINS
THIS WEEKEND...AND PATCHY DRIZZLE FROM THE MARINE LAYER SOME DAYS...
OTHERWISE THE WEATHER WILL BE DRY.

&&

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

MARINE CLOUDS WERE STILL EXTENSIVE AT MIDDAY OVER THE CA COASTAL
WATERS...BUT HAD BURNED OFF INLAND TO THE COASTAL STRIP. HIGH CLOUDS
COVERED PORTIONS OF FAR EASTERN CA AND MUCH OF AZ. A FEW CUMULUS HAD
DEVELOPED OVER THE MTS OF SOCAL AS WELL. SURFACE PRESSURE GRADIENTS
WERE RUNNING 5-8 MBS ONSHORE TO THE DESERTS...WITH A WEAK ONSHORE
TREND. THE WINDIEST DESERT PASSES HAD GUSTS TO 25 MPH AT NOON PDT.
TEMPERATURES W OF THE MTS AT NOON PDT WERE RUNNING SOME 2 TO 8
DEGREES F LOWER THAN YESTERDAY NOON....BUT IT WAS STILL QUITE HOT IN
THE DESERTS.

A REX BLOCK OVER THE FAR EAST PACIFIC THIS AFTERNOON IS NOT EXPECTED
TO BREAK DOWN UNTIL THE MIDDLE OF NEXT WEEK. MEANTIME...A SOUTHERLY
FLOW ALOFT AROUND HIGH PRESSURE CENTERED OVER THE FOUR CORNERS AREA
WILL CONTINUE TO ADVECT MONSOONAL MOISTURE NORTHWARD INTO EASTERN
CA...AZ...AND NV. THE EDGE OF THIS DEEPER MOISTURE IS FORECAST TO
REMAIN JUST EAST OF THE CWA...BUT IS CLOSE ENOUGH SO THAT WEAK
DISTURBANCES IN THE FLOW ALOFT COULD TAP SOME OF IT AND RESULT IN
ISOLATED MTN/DESERT SHWRS/TSTMS. FOR THE NOW...THE MODELS SUPPORT A
DRY SOLUTION...BUT WITH TCU OVER THE MTS MUCH OF THE DAY...INCLUDED
A SLIGHT CHANCE INTO THIS EVENING THERE.

ANY UNCERTAINTY REGARDING SHWR/TSTM DEVELOPMENT WILL BE SWEPT AWAY
BY THE MIDDLE OF NEXT WEEK AS THE BLOCK BREAKS DOWN OVER THE
EASTPAC...AND THE LOW APPROACHES THE COAST WITH INCREASING...DRY SW
FLOW ALOFT. THIS PATTERN ALSO FAVORS SOLID ONSHORE FLOW DEEP INTO
THE INTERIOR FOR A DEEPER THAN AVERAGE MARINE LAYER AND COOLER THAN
NORMAL DAYS. THE MODELS BEGIN TO REBUILD THE SUBTROPICAL HIGH BACK
OVER NEW MEXICO AND THE FOUR CORNERS AREA AFTER NEXT WEEK. EXPECT
WARMER WEATHER WITH A SHALLOWER MARINE LAYER THEN.

IN THE MEANTIME...MODELS SHOW THE MARINE LAYER DEEPENING SUNDAY...
WHICH COULD PUT IT CLOSE TO 3K FT DEEP. SOME FLUCTUATIONS ARE LIKELY
THROUGH NEXT WEEK...BUT THE PATTERN SUGGESTS IT WILL REMAIN NEAR
2500 FT. THIS WILL BRING NOCTURNAL CLOUDS/FOG DEEP INTO THE VALLEYS
EACH NIGHT/MORNING...AND HOLD MAX TEMPS BELOW AVERAGE. DEPENDING ON
THE INVERSION STRENGTH...THIS COULD RESULT IN LIMITED CLEARING NEAR
THE BEACHES SOME DAYS.

&&

.AVIATION... 042000Z...COAST/VALLEYS...LOW CLOUDS...WITH BASES FROM
1600-1900 FT MSL AND TOPS TO 2400 FT MSL...WILL LIKELY LINGER ALONG
THE SAN DIEGO COUNTY COAST THIS AFTERNOON DUE TO AN 11 DEG C MARINE
LAYER INVERSION. STRATUS WILL BECOME MORE BKN/OVC LATE THIS
AFTERNOON ELSEWHERE ALONG THE COAST...AND PUSH AROUND 40 SM INLAND
BY EARLY SUN MORNING...WITH SLIGHTLY HIGHER TOPS AND BASES. VIS OF 2-
4 SM BR WILL BE POSSIBLE TONIGHT WHERE STRATUS NEARS HIGHER TERRAIN.
SIMILAR CLEARING IS EXPECTED SUN MORNING. OTHERWISE SCT-BKN CLOUDS
AOA 15K FT MSL AND UNRESTRICTED VIS THROUGH SUN MORNING. FORECASTER
CONFIDENCE IN STRATUS FORECAST IS MODERATE TO HIGH.

MTNS/DESERTS...SCT-BKN CLOUDS AOA 15K FT MSL AND UNRESTRICTED VIS
THROUGH SUN MORNING. LOCAL WEST SFC WINDS GUSTING 30-40 KT THROUGH
THE SAN GORGONIO PASS AND ALONG THE DESERT MOUNTAIN SLOPES THIS
AFTERNOON AND EVENING WITH THE NORMAL SEA BREEZE. SLIGHT CHANCE OF A
LIGHT SHOWER OVER THE HIGHEST PEAKS THIS AFTERNOON.

&&

.MARINE... 100 PM...NO HAZARDOUS WEATHER IS EXPECTED THROUGH
WEDNESDAY.

&&

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

&&

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

$$

PUBLIC...JAD
AVIATION/MARINE...JJT



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