Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 052027
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
127 PM PDT SUN JUL 5 2015

.SYNOPSIS... LOW PRESSURE OFF THE CENTRAL CALIFORNIA COAST...AND
HIGH PRESSURE OVER THE INTERIOR SOUTHWEST STATES KEPT A SOUTHERLY
FLOW OF MID-LEVEL MOISTURE OVER THE REGION TODAY. THE HIGHER
MOISTURE WILL DECREASE AS THE UPPER LOW APPROACHES THE COAST AND
MOVES INLAND THROUGH FRI...MAINTAINING A DEEP MARINE LAYER WITH
WIDESPREAD NIGHT AND MORNING LOW CLOUDS...AND BELOW AVERAGE DAYTIME
TEMPERATURES WEST OF THE MOUNTAINS. CLOUDS MAY NOT COMPLETELY CLEAR
SOME BEACHES EACH DAY.

&&

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

AT MIDDAY CUMULUS BUILD-UPS WERE PREVALENT FROM THE SAN DIEGO COUNTY
MTN CRESTS NORTHWARD TO THE HIGH DESERTS OF SAN BERNARDINO COUNTY.
RADAR INDICATED ISOLATED THUNDERSTORM CELLS OVER THE SAN GORGONIO
WILDERNESS. WEST OF THE MTS...MARINE STRATUS WAS STUBBORNLY HOLDING
OVER COASTAL AREAS AND OVER SOME WESTERN VALLEYS OF SAN DIEGO
COUNTY. SURFACE PRESSURE GRADIENTS WERE STRENGTHENING DIURNALLY WITH
3-7 MBS TO THE DESERTS AT MIDDAY...BUT STRONGEST WIND GUSTS REMAINED
AROUND 25 MPH.

THE CONVECTIVE CLOUDS AND ANY LATE-DAY SHOWERS OVER THE MOUNTAINS
WILL DISSIPATE RAPIDLY AROUND SUNSET AS THE MARINE STRATUS MOVES
INLAND...PUSHING DEEP INTO THE VALLEYS AGAIN BY MORNING. SOME PATCHY
DRIZZLE IS POSSIBLE AGAIN...AND THERE IS A SLIGHT CHANCE FOR MORE
SHOWERS IN THE SAN BERNARDINO COUNTY MTS/DESERTS...BUT THE CHANCE OF
SIGNIFICANT ACTIVITY IS LESS THAN TODAY AS DRIER AIR PUSHES IN FROM
THE SOUTHWEST. THE MARINE LAYER CLOUDS MAY CLEAR ONLY PARTIALLY
AGAIN TOWARD THE COAST ON MON...OTHERWISE FAIR AND SLIGHTLY COOLER.

THE OVERALL SYNOPTIC PATTERN FORECAST BY THE MODELS FOR THE WEEK
CONTINUES THE THEME OF BREAKING DOWN THE REX BLOCK OVER THE FAR EAST
PACIFIC AND ALLOWING THE WESTERLIES TO LIFT THE CUT-OFF LOW AT THE
BASE OF THE BLOCK NE THROUGH CENTRAL/NORTHERN CA BY FRI. THIS
PATTERN WILL LOCK OUT THE MONSOON OVER SOCAL...AND LOCK IN A DEEP
MARINE LAYER WITH COOLER THAN AVERAGE SUMMER DAYS AND EXTENSIVE
NIGHT AND MORNING LOW CLOUDS THIS WEEK. SOME PATCHY DRIZZLE IS
POSSIBLE NIGHTS AND MORNINGS AS WELL.

CONFIDENCE FOR NEXT WEEK DIMINISHES AS THE LATEST GFS/ECMWF MODEL
SOLUTIONS DIVERGE SLIGHTLY. THE 12Z GFS MODEL IS TRENDING MORE
TOWARD STRENGTHENING THE SUBTROPICAL RIDGE OVER THE ROCKIES EARLY
NEXT WEEK...BUT KEEPS A TROUGH AND SW FLOW ALOFT OVER CA. THE 12Z
ECMWF DEVELOPS A BROADER HIGH OVER THE SW WHICH RESULTS IN HIGHER
HEIGHTS/THICKNESS OVER SOCAL AND A RETURN OF SOME MONSOONAL MOISTURE
ALOFT. BOTH SOLUTIONS LOOK DRY...AND PLACE THE MEAN RIDGE
AXIS CLOSER TO THE ROCKIES.

&&

.AVIATION... 052015Z...COAST/VALLEYS...BKN/OVC STRATUS WILL CONTINUE
THIS AFTERNOON IN MOST AREAS WITHIN 5-10 MILES OF THE COAST WITH
BASES 1300-2000 FT MSL AND TOPS TO 2500 FT MSL. KSAN AND KCRQ WILL
LIKELY STAY BKN/OVC...BUT KSNA COULD HAVE SCT CONDITIONS FOR A FEW
HOURS. STRATUS WILL SPREAD FURTHER INLAND AFTER 01Z AND COVER MOST
VALLEYS OVERNIGHT...WITH CLOUD BASES MOSTLY 1200-1700 FT MSL AND
TOPS 2500-3000 FT MSL. LOCALLY LOWER CLOUD BASES WILL BE POSSIBLE
11Z-17Z MONDAY WITH LOCAL DRIZZLE. PATCHY VIS 2-4 MI WILL OCCUR IN
FOG AND/OR DRIZZLE. CLEARING WILL AGAIN BE SLOW MONDAY...16-18Z IN
THE VALLEYS AND LIKELY AFTER 19Z...IF AT ALL...AT COASTAL AIRPORTS.

MTNS/DESERTS...ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER
THE MOUNTAINS...ESPECIALLY VCNTY KL35...AND HIGH DESERTS THROUGH
01Z...WITH BASES MOSTLY 9000 FT MSL AND TOPS TO 40000 FT MSL. LOCAL
WEST SFC WINDS 15-25 KT WITH GUSTS TO 35 KT WILL OCCUR THROUGH SAN
GORGONIO PASS AND DESERT MOUNTAIN SLOPES LATE THIS
AFTERNOON/EVENING. OTHERWISE...CLOUDS AT/ABOVE 12000 FT MSL AND
UNRESTRICTED VIS WILL CONTINUE THROUGH MONDAY MORNING.

&&

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

&&

.SKYWARN... SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER...
THUNDERSTORMS ARE ACTIVE OVER PORTIONS OF THE AREA AND ACTIVATION IS
POSSIBLE. WEATHER 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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