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000
FXUS66 KSGX 151010
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
310 AM PDT WED MAY 15 2013

.SYNOPSIS...
A LOW PRESSURE TROUGH DEVELOPING OVER THE WEST COAST WILL BRING
COOLING THROUGH FRIDAY ALONG WITH GUSTY WINDS IN THE MOUNTAINS AND
DESERTS. A DEEPENING MARINE LAYER WILL SPREAD FARTHER INTO THE
VALLEYS EACH NIGHT...REACHING THE LOWER COASTAL SLOPES OF THE
MOUNTAINS FRIDAY MORNING. THE DEEP MARINE LAYER MAY LEAK SOME
DRIZZLE OR LIGHT RAIN SHOWERS FRIDAY AND SATURDAY ALONG AND WEST OF
THE MOUNTAINS. BY THE WEEKEND...BUILDING HIGH PRESSURE WILL BRING
DRYING AND WARMING WITH A SHALLOWER MARINE LAYER...LIMITING CLOUDS
TO COASTAL AREAS.

&&

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

STRONG ONSHORE PRESSURE GRADIENT TRENDS OVERNIGHT SUPPORTED AN
EXPANDING AND DEEPENING MARINE LAYER AND GUSTY WESTERLY WINDS
THROUGH THE MOUNTAINS AND INTO THE DESERTS. A WIND ADVISORY  EXPIRED
AT 3 AM PDT. GUSTY WINDS SHOULD REDEVELOP AGAIN LATER TODAY...
TONIGHT...AND AGAIN ON THU PM WHICH MAY REQUIRE ADVISORIES IN WIND
PRONE AREAS OF THE MTNS AND DESERTS. AT 3 AM PDT...THE STRATUS LAYER
WAS EXPANDING WELL INTO THE VALLEYS.

LOCAL WRFEMS AND NAM12 SHOW AN EDDY DEVELOPING BY MORNING AND
PERSISTING THROUGH THU. THE EDDY WILL CONTINUE TO DEEPEN THE MARINE
LAYER IN CONJUNCTION WITH FALLING HEIGHTS AND ONSHORE FLOW. CLOUDS
WILL REACH WELL INTO THE VALLEYS BY MORNING...BUT SHOULD CLEAR BACK
TO THE COAST BY AFTERNOON. IT WILL BE PROGRESSIVELY COOLER EACH DAY
THROUGH SAT AS THE MARINE LAYER DEEPENS AND SPREADS FARTHER INLAND.

THE ATMOSPHERE WILL TRANSITION ACROSS N.A. FROM A PROGRESSIVE
WESTERLY FLOW TODAY...TO A BLOCKED UP PATTERN NEXT WEEK. HIGH
PRESSURE OVER THE CANADIAN PROVINCES WILL SPLIT THE POLAR JET WITH
ONE BRANCH SUPPORTING STORMS ACROSS THE FAR NORTH...WHILE ANOTHER
UNDERCUTS THE RIDGE TO THE SOUTH...CARVING OUT UPPER LOW PRESSURE
CENTERS OVER THE MISSISSIPPI VALLEY AND OVER THE PACNW BY WED.

FOR CALIFORNIA...A BROAD...LONG-WAVE TROUGH WILL SLOWLY DEVELOP OVER
THE WEST THROUGH FRI...MAINTAINING THE MARINE LAYER AND PRODUCING
GUSTY WINDS IN THE MOUNTAINS AND DESERTS LATE EACH DAY AND
OVERNIGHTS. MODELS DIFFER IN INTENSITY AND SPEED OF THE TROUGH WITH
THE 00Z GFS/NAM SOLUTIONS LOOKING A BIT STRONGER. COOLER...WITH A
CHANCE OF SOME LIGHT PRECIP FRI AND SAT FROM A DEEP MARINE LAYER
MOVING UP THE COASTAL SLOPES AND INTO THE PASSES. THE TROUGH WILL
MOVE EAST OVER THE UPCOMING WEEKEND...ALLOWING A DRYING NW FLOW TO
DEVELOP ACROSS CA. SOME WARMING IS EXPECTED...HOWEVER LATEST MODEL
TRENDS ARE FLATTENING THE STRONG EASTPAC RIDGE AS IT TRIES TO EXPAND
EAST OVER THE REGION EARLY NEXT WEEK AHEAD OF THE DEEP LOW SLATED TO
DROP SOUTH ALONG THE WEST COAST OF CANADA.

ONLY FORECAST CHANGE WAS TO INTRODUCE LOW POPS TO THE FORECAST FOR
FRI/SAT. 00Z WRFEMS/NAM12 RUN...AS WELL AS THE 00Z ECMWF RUN SHOW
SOME LIGHT PRECIP W OF THE MTNS UNDER A DEEP MARINE LAYER. EXPECT
THE FOCUS OF ANY PRECIP THAT DOES FALL TO SHIFT FROM COASTAL AREAS
FRI AM...TO THE COASTAL SLOPES ON SAT AM.

&&

.AVIATION...
150900Z...LOW CLOUDS WILL CONTINUE MOVING INLAND THIS MORNING ENOUGH
TO NEARLY FILL THE COASTAL BASIN. CLOUD BASES WILL BE AROUND 1800
FEET ASL WITH NO VIS ISSUES EXCEPT IN THE HIGHER INLAND VALLEYS.
THIS WILL CLEAR TO THE COAST BY 17-18Z. LOW CLOUDS WITH SIMILAR
CLOUD BASES WILL MOVE ASHORE THIS EVENING AND INTO COASTAL AIRPORTS
BETWEEN 01-04Z AND SPREAD INLAND OVERNIGHT TO KONT BY AROUND 10Z.

&&

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

PZ...NONE

&&

$$

PUBLIC...JAD
AVIATION/MARINE...MM