Area Forecast Discussion
Issued by NWS San Diego, CA

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000 FXUS66 KSGX 200427 AFDSGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 930 PM PDT SUN OCT 19 2014 .SYNOPSIS... DRY AND SEASONAL WEATHER WILL CONTINUE THROUGH TUESDAY. HIGH PRESSURE ALOFT BUILD OVER THE REGION BY WEDNESDAY AND STRENGTHEN INTO FRIDAY. THE RIDGE AND WEAK OFFSHORE FLOW WILL BRING MUCH WARMER DAYS AND LESS MARINE LAYER CLOUDS THROUGH THE END OF THE WEEK. COOLER NEXT WEEKEND INTO EARLY NEXT WEAK AS THE RIDGE WEAKENS AND ONSHORE FLOW RETURNS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... PATCHY LOW CLOUDS WERE DEVELOPING OVER SAN DIEGO COUNTY AND THE COASTAL WATERS. OTHERWISE SKIES ARE CLEAR THIS EVENING. LOW CLOUDS WILL GRADUALLY FILL IN ALONG THE COAST AND INTO THE VALLEYS TONIGHT...AND CLEAR BY MID-MORNING. A TROUGH OFF THE WEST COAST AND ONSHORE FLOW WILL MAINTAIN FAIR AND SEASONAL WEATHER MONDAY. ONSHORE PRESSURE GRADIENTS WILL INCREASE DURING THE AFTERNOON AS THE TROUGH APPROACHES...GENERATING LOCALLY GUSTY WINDS IN THE MOUNTAINS AND DESERTS. THE TROUGH AXIS WILL MOVE THROUGH MONDAY NIGHT...WITH WEAKER ONSHORE FLOW AND COOL CONDITIONS CONTINUING INTO TUESDAY UNDER DRY NORTHWEST FLOW ALOFT. THE MARINE LAYER WILL REMAIN MODERATELY DEEP WITH LOW CLOUDS EXTENDING INTO THE INLAND VALLEYS MONDAY NIGHT INTO TUESDAY. FOR WED THROUGH SAT...AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD OVER SOUTHERN CALIFORNIA AND GRADUALLY AMPLIFY AND SHIFT EASTWARD OVER THE DESERT SOUTHWEST THROUGH THE PERIOD. SURFACE HIGH PRESSURE BUILDING OVER THE GREAT BASIN WILL GENERATE SOME OFFSHORE FLOW AS WELL. SURFACE PRESSURE GRADIENTS WILL BE WEAK...PEAKING AT ABOUT -6 MB SAN-TPH WED MORNING...WITH VIRTUALLY NO UPPER LEVEL SUPPORT. EXPECT JUST SOME LOCALLY BREEZY CONDITIONS IN THE WIND PRONE AREAS WITH GUSTS AROUND 25-30 MPH AT BEST. THERE MAY BE JUST ENOUGH OF AN OFFSHORE PUSH AT NIGHT TO KEEP ANY MARINE LAYER CLOUDS AND FOG THAT SURVIVES BEYOND WEDNESDAY MORNING OUT OF THE COASTAL AREAS. OVERALL WEATHER WILL REMAIN FAIR WITH A GRADUAL WARM UP AND DRIER CONDITIONS THROUGH FRIDAY. THE RIDGE WEAKENS BY SATURDAY AS ANOTHER LARGE TROUGH APPROACHES THE WEST COAST. THERE ARE STILL SOME TIMING DIFFERENCES BETWEEN THE MEDIUM RANGE MODELS WITH REGARDS TO WHEN THE TROUGH MOVES THROUGH...WITH THE GEM ON THE FASTER END...THE GFS SOMEWHERE IN THE MIDDLE BRINGING IT THROUGH SOMETIME SUNDAY...AND THE EC LAGGING BEHIND BY ABOUT 24 HOURS. EITHER WAY WILL SEE A COOLING TREND NEXT WEEKEND INTO EARLY NEXT WEEK WITH A RETURN OF ONSHORE FLOW AND COASTAL LOW CLOUDS. PRECIPITATION...IF ANY...WILL BE LIMITED TO MARINE LAYER DRIZZLE. && .AVIATION... 200410Z...COAST/VALLEYS...AREAS OF STRATUS WILL DEVELOP IN THE COASTAL AND VALLEY AREAS. TIME OF ARRIVAL AT AIRPORTS IS LOW CONFIDENCE DUE TO THE PATCHY NATURE OF THE STRATUS...BUT THE STRATUS WILL BECOME MORE WIDESPREAD AFTER 06-07Z...SO MOST AIRPORTS SHOULD HAVE A BROKEN CIG BETWEEN ABOUT 07Z AND 16Z MONDAY. BASES WILL BE 2000-2500 FT MSL WITH TOPS TO 3500 FT MSL...WITH TERRAIN LOCALLY OBSCURED. MOST VIS WILL REMAIN ABOVE 5 MI. MOSTLY SCT CONDITIONS WILL PREVAIL IN COASTAL/VALLEY AREAS AFTER 16Z MONDAY. STRATUS WILL DEVELOP AGAIN MONDAY NIGHT. MOUNTAINS/DESERTS...MOSTLY CLEAR SKIES WITH UNRESTRICTED VIS WILL PREVAIL THROUGH MONDAY NIGHT. && .MARINE... 900 PM...NORTHWEST WINDS WILL GUST TO NEAR 20 KT IN THE OUTER COASTAL WATERS NEAR SAN CLEMENTE ISLAND MONDAY EVENING. A LONG PERIOD NORTHWEST SWELL WILL ARRIVE TUESDAY MORNING...PEAKING IN THE OUTER WATERS WITH COMBINED SEAS OF 8 TO 10. NORTHWEST SWELL WILL DECREASE WEDNESDAY. && .BEACHES... 900 PM...THE LONG PERIOD NORTHWEST SWELL WILL AFFECT WEST FACING BEACHES SOUTH OF DEL MAR TUESDAY/TUESDAY EVENING. LOCAL SURF TO 8 FEET WILL BE POSSIBLE...MOST LIKELY TUESDAY AFTERNOON/EVENING WHEN THE SWELL WILL BE AT ITS PEAK. STRONG RIP CURRENTS WILL ACCOMPANY THE ELEVATED SURF. THE RIP CURRENT DANGER WILL BE GREATEST LATE TUESDAY MORNING DURING THE TRANSITION FROM HIGH TIDE TO LOW TIDE. && .FIRE WEATHER... NO FIRE WEATHER CONCERNS THROUGH TUESDAY. HOWEVER...THE WEATHER WILL TRANSITION TO WARMER AND DRIER FOR THE LATTER HALF OF THE WEEK. LOCALLY GUSTY EAST WINDS MAY DEVELOP AS EARLY AS WED MORNING IN THE WIND PRONE AREAS WITH LOCAL GUSTS OF 25 MPH POSSIBLE AT TIMES. EXCEPT IN THESE WIND PRONE AREAS NEAR THE FOOTHILLS AND PASSES...MOST AREAS SHOULD SEE WINDS 15 MPH OR LESS THIS PERIOD. INLAND FROM THE COASTAL STRIP...RH WILL DROP TO AROUND 15 PERCENT OR LESS EACH AFTERNOON WEDNESDAY THROUGH FRIDAY. COOLER WITH HIGHER HUMIDITY AND ONSHORE FLOW RETURNING BY SATURDAY. && .SKYWARN... SKYWARN ACTIVATION WILL NOT BE NEEDED ON MONDAY. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...SS AVIATION/MARINE/BEACHES...MAXWELL

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