164 FXUS66 KLOX 100306 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 800 PM PDT SAT JUN 9 2012 .SYNOPSIS... OFFSHORE WINDS WILL DEVELOP ACROSS INTERIOR SECTIONS OVERNIGHT INTO SUNDAY MORNING BRINGING A WARMING AND DRYING TREND TO THE REGION. CONTINUED WARM TEMPERATURES ACROSS INLAND AREAS THROUGH MID WEEK...WITH TUESDAY THE WARMEST DAY. THE LATTER PART OF THE WEEK WILL HAVE A COOLING TREND WITH THE OVERNIGHT MARINE LAYER CLOUDS REACHING INTO THE VALLEYS. && .SHORT TERM (TONIGHT-TUESDAY)... UPPER LEVEL TROUGH MOVING EASTWARD INTO GREAT BASIN TONIGHT WILL GENERATE BUILDING HIGH PRESSURE AT THE SURFACE ACROSS THE INTERIOR DESERTS. AS THIS OCCURS...THERE WILL BE A RAPID OFFSHORE TREND IN THE PRESSURE GRADIENTS OVERNIGHT. CURRENTLY...THE LAX-DAG GRADIENT IS STRONGLY ONSHORE AT +7.9 MB BUT IS EXPECTED TO BE NEAR 0 OR SLIGHTLY NEGATIVE BY SUNDAY MORNING. WHILE THE ACTUAL LAX-DAG PRESSURE GRADIENT WILL NOT BE ALL THAT IMPRESSIVE...THE RAPID OFFSHORE TREND AND UPPER LEVEL WIND SUPPORT WILL BE. IN FACT...LATEST 00Z NAM MODEL INDICATES A LARGE AREA OF 40 TO 50 KNOT WINDS AT 850 MB LEVEL BETWEEN 09Z-15Z EARLY SUNDAY MORNING. EVEN IF THE NAM IS SLIGHTLY OVERDOING WITH THESE UPPER LEVEL WINDS...WE SHOULD EASILY SEE A GOOD BURST OF OFFSHORE WINDS IN THE MOUNTAINS DURING THIS TIME FRAME...WITH GUSTS GENERALLY IN THE 40 TO 50 MPH RANGE. WIND GUSTS TO AROUND 35 MPH CAN BE EXPECTED ACROSS THE SANTA CLARITA VALLEY. CURRENT WIND ADVISORIES FOR THESE AREAS LOOK GOOD. LATEST ACARS SOUNDING SHOWING MARINE LAYER DEPTH AROUND 1700 FEET ACROSS THE LA BASIN. WHILE THE MARINE LAYER DEPTH IS EXPECTED TO DECREASE SOMEWHAT OVERNIGHT INTO SUNDAY MORNING...APPEARS THAT GUSTY OFFSHORE WINDS OF ANY CONSEQUENCE WILL MAINLY BE CONFINED TO THE HIGHER VALLEY AND FOOTHILL AREAS...WITH LIGHTER BREEZES EVENTUALLY MAKING ITS WAY DOWN TO THE SAN FERNANDO VALLEY AND VENTURA COASTAL VALLEYS EARLY SUNDAY MORNING. PLEASE REFER TO FIRE SECTION BELOW FOR MORE DETAILS ON UPCOMING FIRE WEATHER THREAT. LOW CLOUDS AND FOG STILL EXPECTED TO MOVE INTO PORTIONS OF LOS ANGELES AND VENTURA COUNTIES THIS EVENING...AS WELL AS THE SBA CENTRAL COAST. HOWEVER...WITH INCREASING OFFSHORE INFLUENCE...SHOULD SEE MARINE LAYER DEPTH DECREASE LATER TONIGHT WITH LOW CLOUDS AND FOG GRADUALLY SCOURED OUT THROUGH THE EARLY MORNING HOURS. WARMING TREND ON TAP FOR MUCH OF THE REGION...WITH BIGGEST WARMING TRENDS EXPECTED FOR INTERIOR SECTIONS...WHERE SOME OF THE WARMEST VALLEYS WILL CLIMB OVER 90 DEGREES. *** FROM PREVIOUS DISCUSSION *** GENERALLY TROUGHY ALOFT MONDAY AND TUESDAY...BUT WEAKER EACH DAY...WHICH WILL ALLOW THE AIR MASS TO WARM. MOUNTAINS AND INTERIOR VALLEYS WILL LIKELY RESPOND WITH WARMER TEMPERATURES...BUT COASTAL SECTIONS WILL REMAIN AT THE MERCY OF THE MARINE LAYER. WITH ONSHORE GRADIENTS INCREASING EACH DAY...THE MARINE LAYER WILL BE HERE TO STAY...AND IMAGINING THE LOW CLOUDS AND FOG WILL PENETRATE A LITTLE DEEPER INLAND EACH DAY. BREEZY ONSHORE WINDS LOOK TO RETURN TO THE MOUNTAINS AND DESERTS AS WELL. .LONG TERM (WEDNESDAY-SATURDAY)... TROUGHY PATTERN WILL CONTINUE THROUGH THE WEEK...BUT STARTING WEDNESDAY...THE TROUGH WILL DEEPEN THANKS TO A MORE POTENT LOW PRESSURE SYSTEM THAT WILL PUSH INTO THE PACIFIC NORTHWEST. THIS WILL BRING A GENERAL COOLING TREND...AND AN EXPANSION OF THE MARINE LAYER AND STRATUS. THIS SHOULD BRING MORE TYPICAL JUNE-LIKE CONDITIONS BY THURSDAY...WITH NEAR NORMAL TEMPERATURES...BREEZY ONSHORE WINDS...AND GLOOMY MORNINGS. && .FIRE... THE OFFSHORE WINDS WILL BRING HEIGHTENED FIRE WEATHER CONCERNS TO INTERIOR SECTIONS OF SOUTHWEST CALIFORNIA. THE GREATEST THREAT WILL OCCUR IN THE MOUNTAINS OF LOS ANGELES AND VENTURA COUNTIES AS WELL AS THE SANTA CLARITA VALLEY. THE ABOVE MENTIONED WINDS COMBINED WITH HUMIDITIES FALLING INTO SINGLE DIGITS BRING A SHORT PERIOD OF CRITICAL FIRE WEATHER CONDITIONS LATE TONIGHT THROUGH SUNDAY MORNING TO THESE LOCATIONS. PER COORDINATION WITH LOCAL AGENCIES...A RED FLAG WARNING WAS NOT ISSUED FOR THIS EVENT SINCE THE EXPECTED DURATION OF CRITICAL RED FLAG CONDITIONS WAS NOT SUFFICIENTLY LONG. && .AVIATION...08/2340Z. LOW CLOUDS LINGERING ACROSS IMMEDIATE COASTAL AREAS OF LA AND VENTURA COUNTIES LATE THIS AFTERNOON. WITH STRONG ONSHORE FLOW IN PLACE...LOOKING FOR EARLY RETURN OF MVFR CIGS ACROSS COASTAL AREAS THIS EVENING...SPREADING LOCALLY INTO THE VALLEYS. DURING THE OVERNIGHT HOURS...PRESSURE GRADIENTS EXPECTED TO TREND SHARPLY OFFSHORE WHICH WILL LIKELY RESULT IN MARINE LAYER BECOMING MORE SHALLOW WITH TIME. THIS TREND SHOULD ALSO ALLOW FOR AN EARLIER BURNOFF TIME OF LOW CLOUDS SUNDAY MORNING. GUSTY OFFSHORE BREEZES EXPECTED TO IMPACT KVNY...KPMD...AND KWJF ON SUNDAY MORNING WITH A CHANCE OF LLWS CONDITIONS. KLAX...WITH LOW CLOUDS LINGERING ACROSS SANTA MONICA BAY EXPECTING MVFR CIGS TO MOVE IN QUICKLY THIS EVENING AT KLAX. ALSO ANTICIPATING EARLIER BURNOFF OF LOW CLOUDS SUNDAY MORNING AND COULD END UP BEING EARLIER THAN PROJECTED 16Z TIME FRAME. KBUR...VFR CONDITIONS EXPECTED THROUGH PERIOD. SLIGHT CHANCE OF IFR CIGS LATER TONIGHT. HOWEVER AT THIS POINT EXPECTING OFFSHORE TRENDS TO KEEP LOW CLOUDS AND FOG SOUTH AND EAST OF KBUR. && .LOX WATCHES/WARNINGS/ADVISORIES... GALE WARNING (SEE LAXMWWLOX). SMALL CRAFT ADVISORY (SEE LAXMWWLOX). WIND ADVISORY (SEE LAXNPWLOX). && $$ PUBLIC...GOMBERG/KITTELL AVIATION...GOMBERG SYNOPSIS...SETO WWW.WEATHER.GOV/LOSANGELES