Area Forecast Discussion
Issued by NWS San Diego, CA

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000 FXUS66 KSGX 011319 CCA AFDSGX AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE SAN DIEGO CA 335 AM PDT WED OCT 1 2014 .SYNOPSIS... A WEAK COASTAL EDDY WILL BRING AREAS OF LOW CLOUDS TO COASTAL AREAS EARLY THIS MORNING. HIGH PRESSURE ALOFT AND OFFSHORE FLOW WILL BRING MUCH WARMER HIGH TEMPERATURES FOR THURSDAY THROUGH SUNDAY... ESPECIALLY WEST OF THE MOUNTAINS. THE OFFSHORE FLOW WILL ALSO BRING GUSTY NORTHEAST WINDS AT TIMES FOR THURSDAY INTO SATURDAY...STRONGEST THURSDAY. WEAK ONSHORE FLOW IS EXPECTED TO RETURN FOR SUNDAY THROUGH EARLY NEXT WEEK WITH SLOW COOLING SPREADING INLAND AND WITH A RETURN OF NIGHT AND MORNING COASTAL LOW CLOUDS AND FOG. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... AS CONSISTENTLY FORECAST BY THE HIGHER RESOLUTION MODELS FOR THE PAST FEW DAYS...A WEAK COASTAL EDDY HAS DEVELOPED WITH COASTAL LOW CLOUDS EXTENDING FROM THE COASTAL WATERS INLAND TO THE WESTERN VALLEYS. COVERAGE IS GREATER THAN RECENT NIGHTS...BUT STILL SOMEWHAT PATCHY WITH GREATEST COVERAGE FOR SAN DIEGO COUNTY COASTAL AREAS. SOME COVERAGE IS POSSIBLE AGAIN TONIGHT...MAINLY FOR SAN DIEGO COUNTY COASTAL AREAS WITH MORE RAPID CLEARING TOWARD THURSDAY MORNING AS OFFSHORE FLOW DEVELOPS AND STRENGTHENS. A TROUGH OF LOW PRESSURE WILL MOVE SOUTHEASTWARD THROUGH THE GREAT BASIN TODAY WITH SURFACE HIGH PRESSURE DEVELOPING BEHIND IT OVER THE GREAT BASIN FOR TONIGHT INTO THURSDAY AND FRIDAY. LOCAL NORTHEAST WINDS WILL DEVELOP TODAY...MAINLY ALONG THE COASTAL SLOPES OF THE SAN GABRIEL AND SAN BERNARDINO MOUNTAINS. MORE WIDESPREAD AND STRONGER WINDS ARE EXPECTED FOR LATE TONIGHT INTO THURSDAY MORNING WITH STRONGEST WINDS ALONG AND BELOW THE COASTAL SLOPES OF THE SAN BERNARDINO COUNTY MOUNTAINS AND THE SANTA ANA MOUNTAINS AND BELOW THE CAJON AND BANNING PASSES WITH WINDS NOT AS STRONG IN THE MOUNTAINS AND INLAND VALLEYS IN SAN DIEGO AND RIVERSIDE COUNTIES. IN THE WINDIER AREAS...WINDS COULD LOCALLY GUST TO NEAR THE LOW END OF WIND ADVISORY CRITERIA THURSDAY MORNING...AROUND 40 TO 45 MPH. OFFSHORE WINDS ARE EXPECTED TO GRADUALLY WEAKEN FOR FRIDAY AND SATURDAY. IN ADDITION TO THE OFFSHORE FLOW...HIGH PRESSURE ALOFT WILL STRENGTHEN THROUGH FRIDAY WITH SLIGHT WEAKENING SATURDAY AND SLOW WEAKENING FOR SUNDAY INTO EARLY NEXT WEEK AS A TROUGH OF LOW PRESSURE DEVELOPS OFF THE CALIFORNIA COAST BRINGING A RETURN OF WEAK ONSHORE FLOW. FOR TODAY...THE MARINE LAYER WILL KEEP AREAS NEAR THE COAST COOLER WHILE INLAND AREAS CONTINUE TO SLOWLY WARM. FOR THURSDAY...THE STRENGTHENING HIGH PRESSURE ALOFT COMBINED WITH THE OFFSHORE FLOW WILL BRING GREATER WARMING...ESPECIALLY WEST OF THE MOUNTAINS...WITH WARMEST TEMPERATURES WEST OF THE MOUNTAINS FROM INLAND COASTAL AREAS INTO THE WESTERN VALLEYS. THE WEAKENING OFFSHORE FLOW COMBINED WITH STRONGER HIGH PRESSURE ALOFT WILL BRING THE WARMEST TEMPERATURES FRIDAY FOR AREAS CLOSER TO THE COAST WITH HIGH TEMPERATURES WEST OF THE MOUNTAINS 10 TO 15 DEGREES ABOVE AVERAGE AND LOCALLY 20 DEGREES ABOVE AVERAGE. AS THE OFFSHORE FLOW CONTINUES TO WEAKEN SLOWLY AND HIGH PRESSURE ALOFT WEAKENS SLIGHTLY...MINOR COOLING MAY OCCUR NEAR THE COAST SATURDAY WITH AREAS FARTHER INLAND ABOUT AS HOT AS FRIDAY. FOR SUNDAY THROUGH EARLY NEXT WEEK...WEAK ONSHORE FLOW IS EXPECTED TO RETURN WITH GRADUAL DEEPENING OF THE MARINE LAYER INTO THE MIDDLE OF NEXT WEEK. SLOW COOLING NEAR THE COAST SUNDAY WILL SPREAD SLOWLY INLAND THROUGH EARLY NEXT WEEK. && .AVIATION... 010930Z...LOW CLOUDS WILL CONTINUE TO FORM ALONG THE COAST AND SPREAD LOCALLY INTO COASTAL VALLEYS. CIGS WILL BE AROUND 1200 FEET MSL WITH VIS ONLY AN ISSUE WHERE CLOUDS INTERSECT INLAND TERRAIN. SCATTER OUT WILL OCCUR BY 16-18Z. LOW CLOUDS WILL RETURN TO THE COAST MOSTLY LIKELY ONLY AROUND KSAN AND KCRQ BETWEEN 03-05Z THIS EVENING WITH BASES AROUND 700-900 FEET MSL. OTHERWISE...CLEAR AND VFR CONDITIONS WILL PREVAIL THROUGH TONIGHT. && .MARINE... 230 AM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SUNDAY. && .FIRE WEATHER... HIGH PRESSURE ALOFT AND OFFSHORE FLOW WITH LOCALLY GUSTY NORTHEAST WINDS WILL BRING MUCH WARMER AND DRIER CONDITIONS FOR THURSDAY THROUGH SUNDAY. STRONGEST WINDS...WITH LOCAL GUSTS TO AROUND 40 MPH...ARE EXPECTED FOR LATE TONIGHT INTO THURSDAY MORNING...FOLLOWED BY GRADUAL WEAKENING FRIDAY AND SATURDAY. FRIDAY AND SATURDAY WILL BE THE WARMEST DAYS...ESPECIALLY INLAND WHERE TEMPERATURES OF 95 TO 105 DEGREES ARE POSSIBLE. SLOW COOLING MAY BEGIN NEAR THE COAST ON SUNDAY AS WEAK ONSHORE FLOW RETURNS. HUMIDITIES WILL FALL THURSDAY... REACHING THE MID TEENS BY LATE MORNING FOR INLAND AREAS. EXPECT LOWEST DAYTIME HUMIDITIES OF 5 TO 10 PERCENT FOR INLAND AREAS FRIDAY AND SATURDAY WITH POOR OVERNIGHT RECOVERY. HUMIDITIES ARE EXPECTED TO SLOWLY RECOVER FOR SUNDAY INTO EARLY NEXT WEEK AS WEAK ONSHORE FLOW RETURNS. WHILE MORE WIDESPREAD AREAS MEETING RED FLAG WARNING CRITERIA IS NOT EXPECTED...WARNING CRITERIA COULD LOCALLY BE MET THURSDAY...MAINLY BELOW THE CAJON AND BANNING PASSES AND IN THE COASTAL FOOTHILLS OF THE SANTA ANA MOUNTAINS. REGARDLESS...THERE WILL BE AN ELEVATED THREAT FOR WILDFIRES FOR THURSDAY INTO SUNDAY. && .SKYWARN... SKYWARN ACTIVATION WILL NOT BE NEEDED TODAY. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...HEAT ADVISORY FROM 11 AM FRIDAY TO 8 PM PDT SATURDAY FOR THE ORANGE COUNTY COASTAL AREAS...RIVERSIDE COUNTY MOUNTAINS... SAN BERNARDINO COUNTY MOUNTAINS...SAN DIEGO COUNTY COASTAL AREAS...SAN DIEGO COUNTY MOUNTAINS INLAND OF THE BEACHES TO THE COASTAL MOUNTAIN SLOPES BELOW 4500 FEET. HEAT ADVISORY FROM 11 AM FRIDAY TO 8 PM PDT SUNDAY FOR THE SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE... SAN DIEGO COUNTY VALLEYS...SANTA ANA MOUNTAINS AND FOOTHILLS. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...17 AVIATION/MARINE...MM

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