Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000 FXUS66 KLOX 192100 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 201 PM PDT FRI SEP 19 2014 .SYNOPSIS... WEAK UPPER LEVEL LOW PRESSURE WILL BRING BELOW NORMAL TEMPERATURES TO MUCH OF THE REGION THROUGH THE WEEKEND. TEMPERATURES WILL LIKELY WARM TO NEAR NORMAL EARLY NEXT WEEK AS THE UPPER LOW MOVES EAST AND HIGH PRESSURE BRIEFLY RETURNS. ANOTHER TROUGH OF LOW PRESSURE WILL BRING A COOLING TREND FOR THE SECOND HALF OF NEXT WEEK. && .SHORT TERM (SAT-MON)...MAIN WEATHER FEATURE OVER THE NEXT COUPLE OF DAYS WILL BE THE CLOSED UPPER LOW THAT CONTINUES TO SPIN JUST NORTHWEST OF POINT CONCEPTION AT THIS TIME...BRINGING A DEEP MARINE LAYER...COOLER TEMPERATURES...AND A SLIGHT CHANCE OF CONVECTION IN SOME MOUNTAIN AREAS. OVERNIGHT AND MORNING STRATUS COVERAGE FORECAST IS A LITTLE TRICKY BUT AM COMFORTABLE WITH ESSENTIALLY A PERSISTENCE FORECAST FOR TONIGHT AND TOMORROW MORNING. UPPER LOW WILL DISRUPT STRATUS IN SOME AREAS SO DON`T EXPECT A SOLID CLOUD COVER...BUT EXPECT A SIMILAR INLAND INTRUSION DUE TO SIMILAR CONTROLLING FACTORS TONIGHT AS LAST NIGHT. SEEING SOME CONVECTIVE CLOUD BUILDUPS OVER THE VTU AND SBA COUNTY MOUNTAINS THIS AFTERNOON BUT SO FAR NOTHING SIGNIFICANT AND THEY LOOK FAIRLY FLAT. 18Z NAM CONSISTENT WITH EARLIER RUNS SHOWING LIFTED INDICIES BETWEEN -2 AND -3 BY LATER THIS AFTERNOON (SUPPORTED BY BY SOME NEAR ZERO LI`S IN THE LATEST GOES SOUNDER DATA) AND THE POOLING MOISTURE AT 850 MB. DON`T EXPECT ANY WIDESPREAD CONVECTION THIS AFTERNOON BUT BELIEVE ENOUGH FAVORABLE FACTORS IN PLACE FOR A FEW CELLS TO DEVELOP BY LATER THIS AFTERNOON. FOR TOMORROW`S POPS...OTHER THAN THE FACT THAT MOISTURE IS NOT AS FAVORABLE...THE UPPER LOW SHOULD PROVIDE SOME FORCING FOR AT LEAST A SLIGHT CHANCE OF CONVECTION...AGAIN OVER THE VTU AND SBA MOUNTAINS...POSSIBLY WITH MORE OVER THE SBA MOUNTAINS COMPARED TO TODAY DUE TO MORE FAVORABLE CONVECTIVE FACTORS. MOISTURE LACKING FURTHER SOUTH OVER LOS ANGELES COUNTY MOUNTAINS SO DO NOT EXPECT ANY DEVELOPMENT THERE. TEMPERATURES WILL WARM JUST SLIGHTLY TOMORROW THOUGH STILL REMAIN BELOW NORMAL ACROSS MOST AREAS. THE UPPER LOW THEN EJECTS OUT OF THE AREA BY SATURDAY EVENING WITH A SHORT WAVE RIDGE MOVING IN FOR SUNDAY AND MONDAY. FOR NOW HAVE A SIMILAR STRATUS FORECAST FOR SUNDAY MORNING...BUT WOULD NOT BE SURPRISED TO SEE A SLIGHTLY WEAKER MARINE LAYER AND A LITTLE LESS INLAND INTRUSION. TEMPERATURES FURTHER WARM SUNDAY AFTERNOON TO AROUND NORMAL AND ANY CONVECTIVE CHANCES ASSOCIATED WITH THE LOW WILL BE WELL EAST OF THE AREA BY THAT TIME. CONTINUED WARMING EXPECTED FOR MONDAY WITH ALL BUT THE IMMEDIATE COAST BACK UP TO ABOVE NORMAL FOR THIS TIME OF YEAR. MARINE LAYER SHOULD SHRINK SOME MONDAY. .LONG TERM (TUE-FRI)...PRETTY GOOD MODEL TO MODEL AND RUN TO RUN CONSISTENCY FOR GFS AND ECMWF OVER THE EXTENDED...AT LEAST THROUGH THURSDAY BEFORE DIFFERENCES APPEAR BY FRIDAY. THE SHORT WAVE RIDGE HANGS AROUND THROUGH MIDWEEK THEN THE WELL ADVERTISED LONG WAVE TROUGH MOVES INTO THE WEST COAST THURSDAY. TUESDAY AND WEDNESDAY SHOULD BE FAIRLY SIMILAR WITH ABOVE NORMAL HIGH TEMPS AND SIMILAR MARINE LAYER DEPTHS. THURSDAY WILL COOL DOWN SOME AND THEN AGAIN ON FRIDAY. THE GFS IS FASTER AND DEEPER WITH THIS TROUGH VERSUS THE ECMWF...A TREND THAT IT HAS SHOWN FROM ITS PREVIOUS RUNS AND A SOLUTION THAT AGREES WELL WITH ITS ENSEMBLE SOLUTION....SO WILL FAVOR THE GFS FOR NOW AND STICK WITH ADDITIONAL COOLING ON FRIDAY...ESPECIALLY AWAY FROM COASTAL AREAS. && .AVIATION...19/1800Z. MID/UPPER LEVEL LOW PRESSURE SYSTEM CENTERED SOUTHWEST OF POINT CONCEPTION WILL SHIFT NORTHEAST. UPPER LEVEL STRONG SOUTHWEST WINDS WILL BECOME MODERATE SOUTHWEST BY 21/00Z WHILE MID LEVEL LIGHT SOUTHEAST WINDS BECOME MODERATE SOUTHEAST AFTER 20/08Z OVER THE AREA. ISOLATED THUNDERSTORMS BETWEEN 19/23-20/03Z OVER VENTURA AND SANTA BARBARA COUNTY MOUNTAINS WITH TOPS 45KFT AND STORMS WILL MOVE NORTH APPROXIMATELY 15KT. LOW LEVEL CLOUD TOPS WERE APPROXIMATELY 3KFT ALONG THE CENTRAL COAST TO 3KFT OVER THE BIGHT. THE CAPPING INVERSION WAS WEAK AND WILL LIKELY DIFFER LITTLE SATURDAY MORNING FROM THIS MORNING. THE CLOUD FIELD WAS DISORGANIZED...BROKEN OVER THE BIGHT AND SCATTERED ON THE CENTRAL COAST AND WILL LIKELY CONTINUE DISORGANIZED SATURDAY MORNING. WEAK ONSHORE PRESSURE GRADIENT BECOMING MODERATE ONSHORE AFTER 20/19Z. KLAX...LIKELY SCATTERED 035 BY 19/20Z. CHANCE CIGS 015 BETWEEN 20/09-20/17Z AND CIGS 027 BETWEEN 20/17-20/19Z. KBUR...LIKELY SCATTERED 025 BY 19/20Z. CHANCE CIGS 017 BY 20/10Z. VIRTUALLY CERTAIN - 95-100% VERY LIKELY - 80-95% LIKELY - 60-80% CHANCE - 30-60% VERY UNLIKELY - 20% OR LESS && .MARINE...19/200 PM THERE IS A CHANCE SMALL CRAFT ADVISORY CONDITIONS IN THE VICINITY OF THE NORTHERN CHANNEL ISLANDS WILL DEVELOP THIS AFTERNOON AND END LATE TONIGHT. THERE IS A CHANCE SMALL CRAFT ADVISORY CONDITIONS WILL REDEVELOP EACH EVENING AND EXIST SEVERAL HOURS EACH DAY SUNDAY THROUGH TUESDAY. THERE IS A CHANCE THE NORTHWEST WINDS WILL INCREASE TO GALES FRIDAY IN THE VICINITY OF THE NORTHERN ISLANDS TO SAN NICOLAS ISLAND. A MIXED WEST NORTHWEST SWELL AND SOUTH SOUTHWEST SWELL WILL CONTINUE TO SUBSIDE AND LINGER THROUGH SATURDAY. SWELLS ORIGINATING FROM A FAST MOVING AND SHORT LIVED GULF OF ALASKA STORM ON THURSDAY ARE EXPECTED TO ARRIVE SUNDAY FROM 295-305. THERE IS A CHANCE THE SWELL WILL PEAK SUNDAY NIGHT AND LINGER THROUGH TUESDAY. A LOW PRESSURE SYSTEM IS LIKELY TO DEVELOP OVER THE EASTERN PACIFIC NEXT WEEK MONDAY THROUGH TUESDAY AND GUIDANCE HAD TRENDED DEEPER WITH THE SYSTEM. SWELLS GENERATED BY STORM FORCE WINDS ARE EXPECTED TO ARRIVE FROM 300-310 DEGREES WEDNESDAY EVENING AND PEAK THURSDAY AND LINGER THROUGH FRIDAY. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...JACKSON AVIATION/MARINE...30 SYNOPSIS...SUKUP WWW.WEATHER.GOV/LOSANGELES

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