Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 282134
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
133 PM PST SAT FEB 28 2015

.SYNOPSIS...LOW PRESSURE MOVING SOUTH ALONG THE CALIFORNIA COAST
WILL WILL BRING COOLER WEATHER AND PERIODS OF SHOWERS INTO EARLY
TUESDAY...DECREASING TUESDAY AFTERNOON. THERE WILL BE STRONG GUSTY
WEST WINDS IN THE MOUNTAINS AND LOCALLY INTO THE DESERTS INTO THIS
AFTERNOON. DRY AND WARMER FOR THE LATTER HALF OF THE WEEK WITH
PERIODS OF LOCALLY GUSTY NORTHEAST WINDS AT TIMES.

&&

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

ZONE FORECAST UPDATED TO REDUCE CLOUD COVER WEST OF THE MTS TODAY
AND LOWER POPS SLIGHTLY.

SATELLITE IMAGERY AT MIDDAY SHOWED PATCHY CLOUDS EXTENDING WELL OUT
TO SEA...MOVING INLAND. CLOUDS WERE THICKEST OVER THE MTS WITH WAVE
CLOUDS EXTENDING OUT OVER THE LOWER DESERTS. THE WESTERLY WINDS WERE
DROPPING OFF A BIT...BUT GUSTS OF 40-45 MPH WERE STILL OCCURRING AT A
FEW WIND-PRONE AREAS OF THE MOUNTAINS...AND WAVE CLOUDS FARTHER EAST
INTO THE DESERTS SUGGEST THE POSSIBILITY OF STRONG GUSTS SURFACING
LOCALLY OUT OVER THE DESERT FLOOR.

THROUGH 1:30 PM PST...RADAR HAD A SMATTERING OF SHOWERS DRIFTING
EAST OFF THE COASTAL WATERS. THEY WERE MOSTLY LIGHT...BUT A FEW HAD
SMALL MODERATE CORES. PRECIP AMOUNTS FOR THE PAST 12 HOURS WERE
MOSTLY UNDER ONE-TENTH OF AN INCH...EXCEPT FOR A FEW CHOICE SPOTS ON
THE COASTAL SLOPES WHERE 0.25-0.50 INCH AMOUNTS HAVE BEEN RECORDED.

SURFACE LOW PRESSURE INLAND WILL WEAKEN THIS EVENING AS A BROAD...
SW-NE ORIENTED LOW PRESSURE TROUGH DRIFTS SOUTH TOWARD POINT
CONCEPTION. MOUNTAIN SLOPE WINDS WILL DECREASE BY EVENING AS THE
PRESSURE GRADIENT RELAXES. SCATTERED...MOSTLY LIGHT SHOWERS ARE
LIKELY TO CONTINUE AS THE LOW APPROACHES AND COOLER AIR ALOFT
CONTINUES TO DESTABILIZE THE ATMOSPHERE.

LATEST GLOBAL MODELS SHOW THE TROUGH SLOWLY WEAKENING AND BECOMING
MORE NORTH-SOUTH ORIENTED AS IT DRIFTS SOUTH ALONG THE COAST THROUGH
MONDAY. AT THE SAME TIME...ANOTHER STRONG WAVE WILL DROP SOUTH ALONG
THE COAST...READY TO REINFORCE THE COLD AIR ALOFT AND CONTINUE THE
SHOWER/TSTM THREAT INTO TUE. HEIGHTS/THICKNESS WILL GRADUALLY RISE
AFTER TUE AS THE RIDGE OFFSHORE BUILDS BACK OVER CA BRINGING A
RETURN OF OFFSHORE FLOW AND FAIR...WARMER WEATHER FOR THE LATTER
HALF OF THE WEEK.

WIND...A WIND ADVISORY WILL EXPIRE OVER THE MTS/DESERTS BY 4 PM.
GUSTS OF 40 TO 50 MPH WILL CONTINUE IN WIND-PRONE AREAS...MAINLY
THROUGH THE SAN GORGONIO PASS AND DESERT MTN SLOPES UNTIL THEN.

PRECIP...SCATTERED SHOWERS INTO THIS EVENING WITH AN EMPHASIS OVER
THE COASTAL SLOPES DUE TO UPSLOPE FLOW. THE SNOW LEVEL WAS 5500 TO
6000 FT THIS AFTERNOON AND SHOULD DROP TONIGHT TO AROUND 5000 FEET.
AN INCREASE IN THE PRECIP RATE IS POSSIBLE LATE TONIGHT OR ON SUN AS
COLDER AIR AND BETTER DYNAMICS ALOFT DEVELOP. HOWEVER...IT LOOKS
LIKE THE BEST ORGANIZED LIFT MAY WAIT UNTIL SUN NIGHT/MON AS THE
MAIN TROUGH AND VORTICITY AXIS SWING INLAND. MODELS ALSO SUGGEST THE
HEAVIEST PRECIP COULD FALL SOUTH OF THE BORDER. THE SHOWERS WILL
BECOME MORE NUMEROUS WITH HEAVIER RAINFALL RATES POSSIBLE SUN NIGHT
THROUGH TUE MORNING AS THE COLDEST AIR ALOFT OVERSPREADS THE REGION.
WE SHOULD ALSO SEE THE EMPHASIS FOR CONSISTENTLY HEAVIER PRECIP
AMOUNTS MOVE AWAY FROM THE MTNS AND TOWARD THE COASTAL AREAS WITH
TIME.

ALL OF EXTREME SOUTHERN SAN DIEGO COUNTY HAS A CHANCE TO GET MORE
RAINFALL THAN CURRENTLY FORECAST IF THE MOISTURE AND ENERGY FORECAST
TO MOVE OVER NORTHERN BAJA CLIPS THAT REGION AS INDICATED BY THE
LATEST 12 MODEL RUNS. EXPECT RAIN AND SNOWFALL AMOUNTS TO BE HIGHLY
VARIABLE AS OROGRAPHIC INFLUENCES DIMINISH AND CONVECTION DOMINATES
THE PRECIP PROCESS.

ALL THE LATEST MODELS NOW KEEP THE SECOND AMPLIFYING WAVE AND BULK
OF THE ASSOCIATED PRECIP OFFSHORE TUE...SO POPS HAVE BEEN DECREASED
ACCORDINGLY.

SNOWFALL...A WINTER STORM WARNING IS IN EFFECT ABOVE 5000 FT FROM
LATE THIS AFTERNOON THROUGH MON AFTERNOON...WITH THE SNOW LEVEL
FALLING TO 4800 TO 5200 FT. THE WARNING MAY BE PREMATURE WITH THE
LATEST MODEL RUNS NOT INDICATING MUCH PRECIP OVERNIGHT...BUT SOME
SNOW AND FREEZING CONDITIONS ARE STILL LIKELY. HEAVIER CONVECTIVE
SNOWFALL LOOKS LIKE A BETTER BET LATER SUN THROUGH MON. LATEST CIPS
ANALOGS FOR THIS TYPE OF SYSTEM STILL FAVOR 8 INCH AMOUNTS IN THE
HIGHER MTS BY LATE TUE. NO PLANS TO ALTER THE WARNING...BUT AMOUNTS
HAVE BEEN CLIPPED FROM VALUES PUBLISHED IN EARLIER GRIDS.


&&

.AVIATION... 282230Z...A MIX OF SCT-OVC CLOUD LAYERS WITH BASES
BETWEEN 2500-6000 FT MSL WILL PERSIST ALONG AND WEST OF THE
MOUNTAINS THROUGH THE OVERNIGHT HOURS. ISOLATED SHOWERS WILL ALSO
OCCUR TODAY...WITH BRIEF VIS REDUCTIONS TO 3 SM AND CIGS AS LOW AS
1500 FT MSL IN THE HEAVIEST SHOWERS. SHOWERS WILL BECOME MORE
NUMEROUS AFTER 10Z SUNDAY. WEST WINDS WILL CONTINUE OVER THE
REGION...WITH THE STRONGEST WINDS OVER THE MOUNTAIN RIDGES AND THE
DESERTS SLOPES THROUGH 06Z. PATCHY BLOWING DUST WILL BE POSSIBLE
OVER THE COACHELLA VALLEY AND LOWER DESERTS THROUGH 03Z SUNDAY.
MODERATE UDDFS/LLWS ARE POSSIBLE OVER AND EAST OF THE MTNS. WINDS
WILL GRADUALLY WEAKEN THIS EVENING AND OVERNIGHT.

&&

.MARINE...130 PM...WEST-NORTHWEST WINDS WILL CONTINUE TO WEAKEN OVER
THE COASTAL WATERS THIS AFTERNOON...WITH WINDS BECOMING 5-10 KT BY
LATE THIS EVENING. A SHORT PERIOD SWELL AT 4-6 FT AND 7-9 SECONDS
WILL CONTINUE TO PRODUCE CHOPPY SEAS INTO EARLY SUNDAY MORNING. DUE
TO THE DOWNWARD TREND IN WINDS...THE SMALL CRAFT ADVISORY HAS BEEN
ALLOWED TO EXPIRE. PERIODS OF SHOWERS WILL OCCUR THROUGH MONDAY
NIGHT...WITH ISOLATED THUNDERSTORMS POSSIBLE SUNDAY THROUGH MONDAY
NIGHT. FOR FORECAST DETAILS...SEE LAXCWFSGX.

&&

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR COACHELLA VALLEY-
     RIVERSIDE COUNTY MOUNTAINS-SAN DIEGO COUNTY DESERTS-SAN
     DIEGO COUNTY MOUNTAINS-SAN GORGONIO PASS NEAR BANNING.

     WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM PST MONDAY
     FOR RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO COUNTY
     MOUNTAINS-SAN DIEGO COUNTY MOUNTAINS ABOVE 5000 FEET.

PZ...NONE.

&&

$$

PUBLIC...JAD
AVIATION/MARINE...BA



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