Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000 FXUS66 KLOX 210410 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 910 PM PDT MON APR 20 2015 .SYNOPSIS... LOW CLOUDS...FOG...AND POSSIBLE DRIZZLE ARE EXPECTED BY TUESDAY MORNING...MOSTLY ALONG THE COAST AND VALLEYS. THE LOW PRESSURE SYSTEM WILL CONTINUE TO BRING A SLIGHT CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS TO MAINLY VENTURA AND LOS ANGELES COUNTIES ON TUESDAY...THEN ANYWHERE WEDNESDAY AFTERNOON THROUGH FRIDAY NIGHT. && .UPDATE... INFRARED SATELLITE IMAGERY INDICATE A TROUGH OF LOW PRESSURE ABOUT 300 MILES SOUTHWEST OF LOS ANGELES. ALL MODEL SOLUTIONS INDICATE THIS TROUGH MOVING INTO THE SOUTH COAST BASIN THROUGH TUESDAY MORNING WHILE DEEPENING SLIGHTLY. WITH THE TROUGHS CUTOFF NATURE...MOVEMENT CAN BE SOMEWHAT UNPREDICTABLE DESPITE MODEL AGREEMENT. MODELS TEND TO FOCUS THE BEST MOISTURE AND INSTABILITY OVER VENTURA COUNTY...BUT IT IS POSSIBLE THAT THE SYSTEM COULD DRIFT FARTHER SOUTH AND PUT LOS ANGELES COUNTY INTO THE MIX. POPS AND CLOUD COVER HAVE BEEN BUMPED UP FOR AREAS SOUTH OF POINT CONCEPTION ALONG WITH MENTIONS FOR A SLIGHT CHANCE OF SHOWERS AND THUNDESTORMS. WITH MODERATELY STRONG ONSHORE FLOW IN PLACE...A DEEP MARINE LAYER NEAR 2000 FEET THIS EVENING SHOULD DEEPEN TO BETWEEN 2500 AND 3000 FEET THROUGH TUESDAY MORNING. ENOUGH INSTABILITY WITH THE TROUGH COULD LIFT THE MARINE LAYER STRATUS DECK AND SQUEEZE OUT DRIZZLE OR LIGHT SHOWERS. MENTIONS OF PATCHY DRIZZLE HAS BEEN EXPANDED ACROSS THE AREA TONIGHT AND INTO TUESDAY MORNING IN THE CURRENT PACKAGE FOR ALL COASTAL AND VALLEY AREAS. INSTABILITY MOVING OVER THE AREA AROUND 12Z COULD SQUEEZE OUT SOMETHING OUT OF THE MARINE LAYER. NAM BUFR TIME HEIGHT SECTIONS INDICATE MEASURABLE DRIZZLE FOR A MAJORITY OF AIRPORT LOCATIONS THROUGHOUT SOUTHERN CALIFORNIA. && .PREV DISCUSSION... SHORT TERM...WEDNESDAY AND THURSDAY WILL SEE A MORE UNIFORM NORTH FLOW ACROSS THE AREA BUT WEAK DISTURBANCES WILL ROTATE SOUTH FROM THE SIERRA AND ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE FOR THE VENTURA AND LA MOUNTAINS EACH AFTERNOON. TEMPERATURES WILL BE STUNTED NEAR OR SLIGHTLY BELOW NORMAL THROUGH MOST OF THE WEEK AS THIS UNSETTLED PATTERN LINGERS AND ONSHORE GRADIENTS REMAIN STRONG. LONG TERM...INCREASING MODEL AGREEMENT OF ANOTHER FAST-MOVING SYSTEM DROPPING DOWN THE COAST DEEPENING THE TROUGH OVER CALIFORNIA ON FRIDAY. THERE IS EVEN SIGNS OF ANOTHER CUT-OFF LOW FORMING ACROSS THE SAN JOAQUIN VALLEY LATE FRIDAY. THIS WILL CONTINUE A THREAT OF MOUNTAIN SHOWERS AND POSSIBLY THUNDERSTORMS THROUGH FRIDAY. SATURDAY WILL LIKELY BE A TRANSITION DAY BETWEEN THE EXITING TROUGH AND BUILDING HIGH PRESSURE AND THE START OF A WARMING TREND. HIGH PRESSURE RIDGE WILL CONTINUE TO BUILD THROUGH MONDAY WITH TEMPERATURES EDGING TOWARD 80 DEGREES OR SO IN THE WARMER VALLEYS AND ANTELOPE VALLEY. && .AVIATION...21/0028Z. AT 2335Z...THE MARINE LAYER WAS 1900 FEET DEEP AT KLAX AND THE TOP OF THE INVERSION WAS 2700 FEET WITH A TEMPERATURE OF 16 DEGREES C. MVFR CONDITIONS WILL SPREAD INTO MOST COASTAL AND VALLEY TERMINALS THROUGH 09Z. THERE IS A CHANCE OF IFR CONDITIONS BETWEEN 10Z AND 16Z IN DRIZZLE. MVFR CONDITIONS WILL LIKELY LINGER LATER ON TUESDAY. THERE IS A CHANCE OF MVFR CONDITIONS THROUGHOUT THE DAY AT COASTAL AND VALLEY TERMINALS. KLAX...VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 04Z. THERE IS A 30 PERCENT CHANCE OF MVFR CONDITIONS BETWEEN 02Z AND 04Z. MVFR CONDITIONS SHOULD SPREAD IN BETWEEN 04Z AND 06Z. THERE IS A 40 PERCENT CHANCE OF IFR CONDITIONS BETWEEN 10Z AND 16Z DUE TO POSSIBLE DRIZZLE. MVFR CONDITIONS WILL LINGER THROUGH AT LEAST 20Z. THERE IS A 30 PERCENT OF MVFR CONDITIONS LINGER THROUGHOUT TUESDAY AFTERNOON. KBUR...VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 07Z. THERE IS A 30 PERCENT CHANCE OF MVFR CONDITIONS BETWEEN 06Z AND 08Z. MVFR CONDITIONS SHOULD SPREAD AROUND 08Z. THERE IS A 40 PERCENT CHANCE OF IFR CONDITIONS BETWEEN 10Z AND 16Z DUE TO POSSIBLE DRIZZLE. MVFR CONDITIONS WILL LINGER THROUGH AT LEAST 18Z. THERE IS A 30 PERCENT OF MVFR CONDITIONS LINGER THROUGHOUT TUESDAY AFTERNOON. && .MARINE...20/900 PM. HIGH CONFIDENCE THAT WINDS WILL REMAIN BELOW SCA THRESHOLDS THROUGH TUESDAY AFTERNOON...ASIDE FROM THE POSSIBILITY OF A FEW GUSTS UP TO 25 KNOTS NEAR POINT CONCEPTION THIS EVENING. HIGH PRESSURE 1000 NM WEST OF SAN FRANCISCO WITH A WEAK UPPER LOW MOVING OVER THE COASTAL WATERS TONIGHT INTO TUESDAY. NORTHWEST WINDS ARE EXPECTED TO INCREASE TO NEAR-SCA SPEEDS TUESDAY NIGHT INTO WEDNESDAY...THEN DIMINISH AGAIN ON THURSDAY AS ANOTHER WEAK UPPER LOW CROSSES THE AREA. NORTHWEST WINDS ARE EXPECTED TO INCREASE MORE STRONGLY OVER THE OUTER WATERS FRIDAY INTO SATURDAY AS THE EAST PACIFIC HIGH MOVES CLOSER TO THE CALIFORNIA COAST. && .LOX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ PUBLIC...HALL/BOLDT AVIATION...HALL MARINE...SMITH SYNOPSIS...B/HALL WWW.WEATHER.GOV/LOSANGELES

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