Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 240341
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
840 PM PDT TUE SEP 23 2014

.SYNOPSIS...
WARM AND DRY CONDITIONS WILL PREVAIL ACROSS SOUTHERN CALIFORNIA
THROUGH THURSDAY UNDER HIGH PRESSURE.  A SHALLOW MARINE LAYER WILL
BRING AREAS OF DENSE FOG TO THE COASTAL MESAS AND WESTERN VALLEYS...
AND COULD IMPACT SOME COASTAL AIRPORTS AS WELL THE NEXT COUPLE OF
MORNINGS.  A TROUGH OF LOW PRESSURE WILL THEN MOVE INLAND ACROSS
CALIFORNIA FRIDAY INTO THE WEEKEND BRINGING COOLING...AND GUSTY
WINDS OVER THE MOUNTAINS AND DESERTS. A DEEPENING MARINE LAYER WILL
ALSO BRING MORE WIDESPREAD LOW CLOUDS WEST OF THE MOUNTAINS.

&&

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

SKIES WERE CLEAR ACROSS THE REGION THIS EVENING...EXCEPT FOR A FEW
PATCHES OF MARINE CLOUDS OVER THE COASTAL WATERS. DEWPOINTS WERE IN
THE LOWER TO MIDDLE 60S ALONG THE COAST...AND 50S FARTHER INLAND.
THE 00Z MIRAMAR SOUNDING HAD A WEAK 4 DEGREE C MARINE INVERSION
BASED NEAR 1200 FT. WEAK ONSHORE GRADIENTS WERE HOLDING TO THE
DESERTS AT 8 PM PDT.

MODELS SHOW HIGH PRESSURE ALOFT OVER SOCAL PEAKING OVERNIGHT...THEN
SLIDING NE OVER THE ROCKIES THROUGH THU...BUILDING A MASSIVE RIDGE
OVER THE EASTERN TWO-THIRDS OF THE NATION. AS THE RIDGE TAKES
SHAPE...A LONG-WAVE TROUGH WILL DEEPEN OVER THE EASTPAC AND SLOWLY
DRIFT EAST OVER CA THIS WEEKEND. IT WILL BRING RAIN TO NORTHERN
CA...AND COOLER DAYS FRI THROUGH SUN WITH GUSTY WINDS OVER THE
MOUNTAINS AND DESERTS. AT THIS TIME IT DOES NOT APPEAR THE TROUGH
WILL BRING ANY RAIN THIS FAR SOUTH...BUT A DEEP MARINE LAYER MAY
LEAK SOME PATCHY DRIZZLE BY SAT OR SUN MORNING.

AREAS OF DENSE FOG WILL BE THE MAIN WEATHER CONCERN FOR THE NEXT
COUPLE OF NIGHTS. DEWPOINTS ARE HIGH IN THE SHALLOW MARINE LAYER
ALONG THE COASTAL STRIP...SO AS TEMPERATURES DROP...FOG IS LIKELY TO
DEVELOP. SOME AREAS OF DENSE FOG ARE LIKELY BY MORNING SO A DENSE
FOG ADVISORY HAS BEEN ISSUED FOR THE COASTAL STRIP...EXTENDING INTO
THE WESTERN VALLEY AREAS. SEE LAXNPWSGX FOR DETAILS.

THE LATEST AVAILABLE GLOBAL MODEL OPERATIONAL RUNS HAVE FLIP-FLOPPED
FROM YESTERDAY WITH THE HANDLING OF THE TROUGH MOVING ACROSS THE
WEST THIS COMING WEEKEND. THE GFS CLOSES OFF AN UPPER LOW...WHILE
THE ECMWF KEEPS THE WAVE OPEN AND MOVING FASTER. IN EITHER CASE...
BROAD CYCLONIC FLOW DOMINATES THE WEST EARLY NEXT WEEK...KEEPING
ONSHORE FLOW ACROSS SOCAL...ALONG WITH DRY AND SEASONALLY MILD TO
WARM DAYS INLAND.

&&

.AVIATION...
240330Z...COAST/VALLEYS...AREAS OF STRATUS/FOG WILL DEVELOP NEAR THE
COAST BETWEEN 05Z AND 09Z AND COULD REACH 15-20 MI INLAND BY 12Z.
BASES WILL MOSTLY BE UNDER 1000 FT MSL...LOCALLY BELOW 600 FT
MSL...WITH A CHANCE OF CIGS BELOW 300 FT AGL AT SOME COASTAL MESA
AIRPORTS INCLUDING KCRQ...KMYF AND KSDM. AREAS OF VISIBILITY BELOW 3
MI WILL OCCUR MAINLY 07Z-16Z WITH LOCAL VISIBILITY BELOW 1/2
MI...MAINLY OVER HIGHER COASTAL TERRAIN AND SAN DIEGO COUNTY COASTAL
MESAS. CONFIDENCE OF TIME OF ARRIVAL OF LOW CIGS/LOW VIS IS LOW.
MOST AREAS SHOULD CLEAR BY 17Z. MOST OF THE VALLEYS WILL STAY CLEAR
TONIGHT/WED. STRATUS/FOG COULD DEVELOP AGAIN NEAR THE COAST WED
NIGHT.

MOUNTAINS/DESERTS...MOSTLY CLEAR SKIES WITH UNRESTRICTED VISIBILITY
WILL CONTINUE THROUGH WED NIGHT.

&&

.MARINE...
830 PM...NO MARINE WEATHER HAZARDS ARE EXPECTED THROUGH THURSDAY.
STRONGER NORTHWEST WINDS FRIDAY AND SATURDAY IN THE OUTER WATERS
COULD REACH SMALL CRAFT ADVISORY CRITERIA.

&&

.SKYWARN...
SPOTTER ACTIVATION WILL NOT BE NEEDED ON WEDNESDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...DENSE FOG ADVISORY FROM 3 AM TO 9 AM PDT WEDNESDAY FOR THE
     ORANGE COUNTY COASTAL AREAS...SAN DIEGO COUNTY COASTAL
     AREAS...SAN DIEGO COUNTY VALLEYS.

PZ...NONE.

&&

$$

PUBLIC...JAD
AVIATION/MARINE...BM









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