Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 061702
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
930 AM PDT WED MAY 6 2015

.SYNOPSIS...
A DEEP MARINE LAYER WILL CONTINUE THE COOL WEATHER TODAY WITH AREAS
OF LOW CLOUDS LINGERING THROUGH THE AFTERNOON WEST OF THE MOUNTAINS.
PATCHY FOG WILL CONTINUE IN THE MOUNTAINS THROUGH FRIDAY. GUSTY WEST
WINDS WILL OCCUR IN THE MOUNTAINS AND DESERTS THROUGH FRIDAY. A COLD
LOW PRESSURE SYSTEM WILL BRING PERIODS OF SHOWERS THURSDAY THROUGH
FRIDAY NIGHT. THERE WILL ALSO BE A SLIGHT CHANCE OF THUNDERSTORMS
THURSDAY NIGHT THROUGH FRIDAY...AND THERE COULD BE SOME SNOW IN THE
HIGHER MOUNTAINS...MAINLY IN SAN BERNARDINO COUNTY. DRY AND WARMER
WEATHER WILL RETURN OVER THE WEEKEND AS HIGH PRESSURE ALOFT MOVES
THROUGH...BUT THEN SOME COOLING WILL OCCUR BY NEXT TUESDAY AS
ANOTHER LOW APPROACHES.

&&

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

WIDESPREAD STRATUS WAS OCCURRING WEST OF THE MOUNTAINS DUE TO A 5000-
5500 FOOT DEEP MARINE LAYER. WITH THE UNSTABLE LAYER BELOW THE
INVERSION...THERE WILL BE AREAS OF CLOUDS REFORMING WHERE THE SUN
POKES THROUGH THIS AFTERNOON. THE STRONG THERMAL AND PRESSURE
GRADIENTS BETWEEN THE COOL VALLEYS AND THE SOMEWHAT WARM DESERTS
WILL CONTINUE STRONG GUSTY WINDS IN THE MOUNTAINS AND DESERTS...WITH
LOCAL GUSTS OVER 55 MPH AT TIMES ESPECIALLY TONIGHT AND THURSDAY
NIGHT. A WIND ADVISORY WILL GO INTO EFFECT FOR THE DESERTS AT 4 PM
THIS AFTERNOON.

THE UPPER LOW IS CURRENTLY OVER WASHINGTON/OREGON AND WILL DIVE DOWN
INTO CENTRAL CALIFORNIA THURSDAY AND INLAND SOUTHERN CALIFORNIA
THURSDAY NIGHT. MODELS HAVE MOSTLY BEEN CONSISTENT ON TRACKING AND
TIMING...AND THIS LOW SHOULD GIVE ENOUGH INSTABILITY...ONSHORE LOW-
LEVEL TRAJECTORY AND MOISTURE...MOSTLY BELOW 700 MB...TO GIVE
PRECIPITATION. MOST MODEL RUNS ARE SHOWING AVERAGE PRECIP AROUND ONE-
QUARTER INCH WEST OF THE MOUNTAINS WITH UP TO AN INCH IN THE
MOUNTAINS...MAINLY THE OROGRAPHIC W/SW SLOPES. THERE COULD BE A FEW
THUNDERSTORMS THU NIGHT/FRI...AND THIS WOULD BRING LOCALLY HIGHER
AMOUNTS...AND I WOULD NOT BE SURPRISED TO SEE A LOCAL 1.5 TO 2 INCH
AMOUNT OVER HIGHER TERRAIN IN SAN BERNARDINO COUNTY CLOSE TO THE
COLD CORE. MOSTLY LIGHT PRECIP FROM MOIST ONSHORE FLOW WILL OCCUR
LATE TONIGHT/THU...THEN THE MORE VARIABLE AND BRIEFLY HEAVY PRECIP
WILL OCCUR THU NIGHT INTO FRIDAY. ANOTHER WAVE ON THE BACK SIDE OF
THE CLOSED LOW COULD PROLONG PRECIP INTO FRIDAY NIGHT...MAINLY BASED
ON THE 12Z NAM SOLUTION. WITH THE COLDER AIR IN PLACE...AND 850 MB
TEMPS DOWN AS LOW AS 2-3 DEG C...WE COULD GET SNOW LEVELS DOWN TO
ABOUT 5500 FEET IN SAN BERNARDINO COUNTY...AND A FEW INCHES OF SNOW
COULD FALL THERE.

AFTER THE LOW MOVES EAST SATURDAY...FAIR WARMER CONDITIONS WILL
OCCUR...THOUGH WITH SOME NIGHT AND MORNING LOW CLOUDS IN COASTAL
AREAS. TEMPS SHOULD PEAK NEAR OR JUST A BIT ABOVE NORMAL SUN/MON
BEFORE ANOTHER TROUGH BRINGS COOLING AND PROBABLY A DEEPER MARINE
LAYER TUESDAY.

&&

.AVIATION...
061500Z...LOW CLOUDS FILLING THE COASTAL BASIN WILL CONTINUE WITH
ONLY PARTIAL CLEARING IN TIME AND SPACE. BASES WILL BE AROUND 3500
FEET MSL WITH TOPS TO 5500 FEET MSL. LOCAL MOUNTAIN OBSCURATION
THROUGH 18Z WITHIN THAT LAYER. LOW CLOUDS WILL FILL THE COASTAL
BASIN THIS EVENING WITH SIMILAR BASES AND TOPS...SPREADING INLAND TO
TOUCH THE COASTAL SLOPES OVERNIGHT. STRONG AND GUSTY WESTERLY WINDS
WILL CONTINUE IN THE MOUNTAINS AND DESERTS MAINLY THIS AFTERNOON
THROUGH TONIGHT. POSSIBLE UPDRAFTS AND LLWS OVER AND EAST OF THE
MOUNTAINS AT TIMES.

&&

.MARINE...
800 AM...THERE IS A CHANCE OF THUNDERSTORMS AND ISOLATED CLOUD-TO-
WATER LIGHTNING STRIKES OVER THE COASTAL WATERS THURSDAY NIGHT INTO
FRIDAY. OTHERWISE...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH
SUNDAY.

&&

.BEACHES...
800 AM...SURF WILL CONTINUE RATHER HIGH TODAY ALONG WITH STRONG RIP
CURRENTS ESPECIALLY IN ORANGE COUNTY. SOUTHERLY SWELL AND SURF WILL
FADE SLOWLY TODAY AND THURSDAY. FOR SURF DETAILS SEE THE BEACH
HAZARDS STATEMENT (LAXCFWSGX) AND THE SURF ZONE FORECAST (LAXSRFSGX).

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 3 AM PDT FRIDAY FOR
     APPLE AND LUCERNE VALLEYS-SAN DIEGO COUNTY DESERTS-SAN
     GORGONIO PASS NEAR BANNING.

     BEACH HAZARDS STATEMENT THROUGH THIS EVENING FOR ORANGE COUNTY
     COASTAL AREAS.

PZ...NONE.

&&

$$

PUBLIC...MAXWELL
AVIATION/MARINE/BEACHES...MM


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