Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 032032
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
132 PM PDT THU SEP 3 2015

.SYNOPSIS...
COOLING WILL CONTINUE THROUGH FRIDAY...WITH A DEEP MARINE LAYER
REMAINING IN PLACE...DUE TO A TROUGH OF LOW PRESSURE ALONG THE WEST
COAST. GUSTY WINDS IN THE MOUNTAINS AND DESERTS WILL OCCUR DURING
THE LATE AFTERNOONS AND EVENINGS TODAY AND FRIDAY. THE TROUGH WILL
WEAKEN...AND HIGH PRESSURE WILL SLOWLY BUILD ALOFT...RESULTING IN
WARMING AND LESS EXTENSIVE LOW CLOUDS THIS WEEKEND THROUGH MOST OF
NEXT WEEK.

&&

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

VISIBLE SATELLITE SHOWS THAT STRATUS HAS CLEARED NICELY THIS
AFTERNOON...ALTHOUGH IT WAS A LITTLE SLOW TO DO SO. HE 12Z MIRAMAR
SOUNDING SHOWED A 7 DEG C MARINE LAYER INVERSION AT AROUND 2500
FEET...AND AIRCRAFT SOUNDINGS INDICATED MARINE LAYER DEPTH AT
AROUND 2600-3500 FEET ABOVE MSL.

WATER VAPOR IMAGERY SHOWS A LARGE LOW PRESSURE SYSTEM OVER BRITISH
COLUMBIA...WITH THE ASSOCIATED TROUGH ALONG THE WEST COAST AND
STRETCHING INTO SOUTHERN CALIFORNIA...WHILE A RIDGE REMAINS FAR TO
THE EAST OVER TEXAS. THIS TROUGH WILL MOVE SOUTH AND EAST THROUGH
LATE FRIDAY...RESULTING IN CONTINUED LOWER HEIGHTS ALOFT OVER OUR
AREA. ONSHORE FLOW IS STRENGTHENING AS WELL...WITH ONSHORE PRESSURE
GRADIENTS FROM SAN DIEGO TO LAS VEGAS UP TO 7.8 MB...COMPARED TO 6.8
MB AT THIS TIME YESTERDAY. WITH ONSHORE FLOW STRENGTHENING AND
LOWERING 500 MB HEIGHTS...THE COOLING TREND IS CONTINUING...AS
TEMPERATURES ARE CURRENTLY ABOUT 3 TO 6 DEGREES LOWER THAN 24 HOURS
AGO FOR MOST LOCATIONS. FRIDAY LOOKS TO BE THE COOLEST DAY...WITH
DAY-TIME HIGHS REACHING 10 TO 20 DEGREES BELOW NORMAL ON FRIDAY.
THIS SHOULD ALSO CAUSE THE MARINE LAYER TO DEEPEN TO 4000-4500 FEET
ABOVE MSL BY LATE TONIGHT...WHICH WOULD RESULT IN LOW CLOUDS FILLING
THE COASTAL BASIN AGAIN AND ALSO REACHING INTO THE LOWER MOUNTAIN
SLOPES AND THROUGH THE PASSES. THE CLOUD LAYER MAY THICKEN UP ENOUGH
TO BRING SOME DRIZZLE AS WELL. FINALLY...THE STRONGER ONSHORE FLOW
WILL ALSO RESULT IN GUSTY SOUTHWEST TO WEST WINDS ALONG THE DESERT
SLOPES AND THROUGH AND BELOW MOUNTAIN PASSES/CANYONS DURING THE LATE
AFTERNOON AND EVENING HOURS TODAY AND FRIDAY. GUSTS TO 45 MPH...AND
LOCALLY 55 MPH...WILL BE POSSIBLE IN THESE AREAS.

BY FRIDAY NIGHT...THE TROUGH TO THE NORTH WILL HAVE WEAKENED...AND
RIDGING TO THE EAST WILL NUDGE INTO THE AREA. THE RIDGE WILL SLOWLY
BUILD OVER THE AREA THROUGH MOST OF NEXT WEEK...BRINGING A WARMING
TREND AND A SHALLOWER...PATCHY MARINE LAYER. ONSHORE FLOW WILL
WEAKEN AS WELL. EVEN WITH THE WARMING TREND...DAY-TIME HIGHS MAY
ONLY REACH NEAR TO SLIGHTLY BELOW NORMAL BY THE MIDDLE OF NEXT WEEK.
ANY MONSOONAL OR TROPICAL MOISTURE LOOKS TO MOSTLY REMAIN TO OUR
EAST...WITH THE GFS BEING THE MODEL THAT BRINGS SOME TROPICAL
MOISTURE CLOSEST TO OUR AREA...ALTHOUGH EVEN WITH THAT THE
PRECIPITABLE WATER ONLY INCREASES TO 1 INCH. THE FORECAST REMAINS
DRY FOR NOW.

&&

.AVIATION...
032000Z...COAST/VALLEYS...SCT TO LOCALLY BKN CLOUDS WITH BASES 3000-
3500 FT MSL WILL THICKEN AFTER 00Z ALONG THE COASTAL STRIP AND
SPREAD INLAND OVERNIGHT WITH WIDESPREAD BASES 2500-3000 FT MSL AND
TOPS 4000-4500 FT MSL BY FRI MORNING. VIS WILL BE GENERALLY
UNRESTRICTED...EXCEPT ALONG THE HIGHER COASTAL TERRAIN AND FAR INLAND
ALONG THE LOWER COASTAL SLOPES AND FOOTHILLS WHERE THE TERRAIN MAY
BE OBSCURED AT TIMES. CLEARING MAY BE LIMITED ON FRI IN SOME
AREAS...BUT VFR CONDITIONS ARE EXPECTED MUCH OF THE DAY WITH BROKEN
CLOUD BASES LIFTING ABOVE 3000 FEET.

MOUNTAINS/DESERTS...FEW-SCT CLOUDS AOA FL150 AND UNRESTRICTED VIS
THROUGH FRI.

&&

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

&&

.BEACHES...
100 PM...A LONG PERIOD SOUTH-SOUTHWEST WILL BEGIN TO MOVE INTO THE
COASTAL WATERS SATURDAY...PEAKING SUNDAY AT 3 FEET/19-20 SEC. SURF
WILL BUILD TO 3-5 FEET BY EARLY SUNDAY...WITH SOME SETS TO 7 FEET
ALONG SOUTH-SOUTHWEST FACING BEACHES BY SUN EVENING. THE SURF WILL
REMAIN ELEVATED THROUGH MON WITH A COMBO OF SOUTHWEST AND SOUTH
SWELLS. STRONG RIP AND LONGSHORE CURRENTS WILL ACCOMPANY THE HIGHER
SURF...CREATING DANGEROUS SWIMMING CONDITIONS OVER THE HOLIDAY
WEEKEND. A BEACH HAZARD STATEMENT WILL BE IN EFFECT BEGINNING MID
MORNING ON SATURDAY THROUGH TUESDAY.

&&

.SKYWARN...
SKYWARN ACTIVATION WILL NOT BE NEEDED TODAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...BEACH HAZARDS STATEMENT FROM SATURDAY MORNING THROUGH TUESDAY
     EVENING FOR ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY
     COASTAL AREAS.

PZ...NONE.
&&

$$

PUBLIC...HARRISON
AVIATION/MARINE/BEACHES...JAD



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