Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 212016
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
116 PM PDT SUN SEP 21 2014

.SYNOPSIS...
LOW PRESSURE ALOFT WILL BEGIN TO EXIT THE REGION LATER TODAY AS HIGH
PRESSURE BUILDS FROM THE SOUTH. THIS WILL LOWER OUR MARINE LAYER
THROUGH WEDNESDAY FOR LESS EXTENSIVE NIGHT AND MORNING LOW CLOUDS
WEST OF THE MOUNTAINS. DAYTIME HIGHS WILL GRADUALLY WARM TO 5 TO 10
DEGREES ABOVE AVERAGE BY MIDWEEK. MUCH COOLER FOR THE END OF THE
WEEK AS A DEEP TROUGH DEVELOPS ACROSS CALIFORNIA...BRINGING RAIN TO
NORTHERN PORTIONS OF THE STATE...AND BLUSTERY...AUTUMN-LIKE WEATHER
ACROSS THE SOUTHLAND.

&&

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

WEATHER TRENDS THIS WEEK...PROGRESSIVELY LESS EXTENSIVE MARINE
CLOUDINESS BUT MORE FOG WEST OF THE MOUNTAINS TUESDAY THROUGH
THURSDAY MORNINGS...A WARMING TREND BEGINNING MON BRINGING
TEMPERATURES BACK ABOVE AVERAGE THROUGH MIDWEEK...MUCH COOLER
WEATHER BY NEXT WEEKEND.

MARINE STRATUS WAS SLOW TO BURN OFF AGAIN THIS MORNING IN THE INLAND
EMPIRE...OTHERWISE SKIES CLEARED BY MID MORNING. SURFACE PRESSURE
GRADIENTS WERE RUNNING 3-5 MBS ONSHORE TO THE DESERTS...AND WIND
SPEEDS WERE GENERALLY UNDER 15 MPH AT MIDDAY.

THE BROAD CUT-OFF LOW DOMINATING OUR WEATHER AGAIN TODAY WAS HEADED
INTO NV THIS AFTERNOON...AND WILL BE ABSORBED INTO THE WESTERLIES ON
MON. HIGH PRESSURE WILL BUILD IN ALOFT FROM THE SOUTH IN THE WAKE OF
THE LOW...AND PEAK OVER THE REGION ON WED. THIS TRANSITION WILL
PROGRESSIVELY LOWER THE MARINE LAYER FOR LESS EXTENSIVE LOW
CLOUDS...BUT MAY RESULT IN MORE AREAS OF FOG OVER COASTAL AND
WESTERN VALLEY AREAS EACH MORNING. MODELS SHOW THE SURFACE FLOW
REMAINING ONSHORE THROUGH THIS EVENT...SO SOME MARINE INFLUENCE WILL
REMAIN WEST OF THE MOUNTAINS...HELPING THE TEMPERATURES TO REMAIN
BELOW VALUES OBSERVED LAST WEEK.

THE MORNING GLOBAL MODEL RUNS ARE SHOWING BETTER AGREEMENT HANDLING
THE DEEP TROUGH ACROSS THE EASTPAC THIS WEEK. THE TROUGH WILL BEGIN
TO AFFECT NW PORTIONS OF THE STATE BY WED...AND WILL SWING SLOWLY
EAST TO COVER SOCAL BY SAT. THERE REMAINS TIMING DIFFERENCES BETWEEN
MODELS...BUT THE SLOWER GEM/ECMWF SOLUTIONS ARE PREFERRED. THESE
MODELS HAVE BEEN CUTTING OFF THE LOW OVER CA AS WELL THE PAST COUPLE
OF RUNS...WHICH IS PLAUSIBLE GIVEN THE STRENGTH OF THE MASSIVE RIDGE
THAT IS PUMPED UP ACROSS THE EASTERN HALF OF THE CONUS. THE ECMWF
ENSEMBLE MEAN STILL KEEPS THE WAVE OPEN...BUT IS MUCH SLOWER AND
MORE NEGATIVELY TILTED WITH THE WAVE AXIS.

THE EXTENDED PERIOD OF THE FORECAST REFLECTS THE LOW END OF TEMP
GUIDANCE WITH A SLOWER AND DEEPER TROUGH. EVEN THOUGH EARLY SEASON
RAINS ARE LIKELY ACROSS THE NORTHERN HALF OF THE STATE...IT APPEARS
SOCAL WILL STAY DRY...EXCEPT PERHAPS FOR SOME MARINE LAYER DRIZZLE.
SOME MID-LEVEL MOISTURE WILL INCREASE AHEAD OF THIS TROUGH
MIDWEEK...BUT LOOKS TO BE ONLY SUFFICIENT FOR SOME CU OVER OUR
MOUNTAINS AT THIS TIME. JUST TO THE EAST THOUGH...MODELS DO INDICATE
SIGNIFICANT SHWR/TSTM DEVELOPMENT OVER THE LOWER COLORADO RIVER
VALLEY AND POINTS NE. ONSHORE WINDS WILL RAMP UP AHEAD OF THIS
TROUGH AND MAY BE ADVISORY WORTHY BY LATE THU/FRI OVER THE MTNS/
DESERTS.

&&

.AVIATION...
212100Z...COASTS/VALLEYS...PATCHES OF LOW CLOUDS LINGER OVER
PORTIONS OF ORANGE COUNTY...OTHERWISE CLEAR WITH UNRESTRICTED VIS
THIS AFTERNOON. LOW CLOUDS WILL RETURN THIS EVENING WITH BASES
1700-2300 FT MSL...MOVING INTO THE COASTAL AIRPORTS BETWEEN 03Z AND
06Z...SPREADING ABOUT 25 MI INLAND OVERNIGHT. LIKELY REACHING KONT
AROUND 12Z MON. EXPECT CLEARING BETWEEN 15Z AND 17Z MON.

MOUNTAINS/DESERTS...MOSTLY CLEAR WITH UNRESTRICTED VISIBILITY
THROUGH MONDAY.

&&

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

&&

.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...PG












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