[Printable]
Links in the discussion text will open a (small) new browser window with more information inside.
A more complete Weather Glossary is Available Here
000 FXUS66 KLOX 190424 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 925 PM PDT THU SEP 18 2008 ...UPDATED AVIATION DISCUSSION... .SHORT TERM (TODAY-SUN)... THE MENTION OF SLIGHT CHANCE FOR THUNDERSTORMS FOR LA/VTU COUNTY MTNS AND THE ANTELOPE VALLEY HAS BEEN TAKEN OUT OF THE FORECAST FOR THIS EVENING AS PEAK DIURNAL HEATING HAS PASSED AND AIRMASS HAS STARTED TO DRY OUT ACROSS THE AREA AT THE MID LEVELS. NOT EXPECTING ANY CONVECTION THROUGH THE THE NEXT SEVERAL DAYS. OVERALL...TEMPS WERE NEAR NORMAL IN MOST LOCATIONS...GIVE OR TAKE A FEW DEGREES. LATEST AMDAR SOUNDING NEAR KLAX INDICATED A STRENGTHENING SHALLOW INVERSION NEAR 700 FT DEEP. WHILE MIRAMAR 00Z SOUNDING WAS NEAR 1500 FT. EXPECT MARINE LAYER TO DEEPEN TO NEAR 1000 FT ACROSS LA COUNTY OVERNIGHT. THIS SHOULD KEEP VALLEYS MOSTLY CLEAR. LATEST FOG PRODUCT IMAGERY SHOWED A PATCH OF STRATUS ALONG THE IMMEDIATE COAST NEAR SAN DIEGO. NAM/WRF HAS BEEN HAVING A TOUGH TIME HANDLING THE RH FIELD IN REGARDS TO THE MARINE LAYER OVER THE PAST FEW DAYS. SINCE THERE WAS A DECENT AMOUNT OF 850 MB MOISTURE ACROSS THE COASTAL WATERS OVER THE LAST 24-HOURS...THIS LIKELY HELPED TO DISRUPT THE MARINE LAYER. CONFIDENCE IF LOW THAT STRATUS WILL DEVELOP ACROSS LA/VTU COUNTY COASTAL AREAS...BUT A WEAK EDDY SHOULD DEVELOP OVERNIGHT...SO WILL LEAVE THE MENTION OF PATCHY LOW CLOUDS ACROSS LA COUNTY AFTER MIDNIGHT...BUT WILL KEEP VTU COUNTY CLEAR TONIGHT. THERE IS A MODERATE NORTHERLY GRADIENT BETWEEN SBA-SMX AT -3.6 MB THIS EVENING...THEREFORE SKIES SHOULD REMAIN CLEAR ACROSS THE SANTA BARBARA SOUTH COAST OVERNIGHT AS WELL. EXPECT SOME LOCAL NORTHWEST TO NORTH WINDS 15 TO 25 MPH WITH LOCALLY HIGHER GUSTS BELOW AND THROUGH PASSES AND CANYONS NEAR GAVIOTA AND MONTECITO THROUGH MIDNIGHT. FOR FRI...CUT-OFF LOW NEAR THE OR/CA COAST WILL BEGIN TO FILL IN AND MOVE ACROSS NRN CAL. THE ASSOCIATED WEAK TROF ASSOCIATED WITH THIS LOW WILL HELP TO LOWER TEMPS A DEGREE OR TWO ACROSS THE FORECAST AREA...ESPECIALLY AREAS N OF POINT CONCEPTION WHERE SOME INLAND AREAS COULD LOWER 5 DEGREES. HIGHS SHOULD BE IN THE LOWER TO MID 80S ACROSS THE INTERIOR VALLEYS OF SLO COUNTY...WHILE THE WARMEST LA/VTU VALLEY LOCATIONS SHOULD REACH" onClick="return popup(this, 'notes')">REACH 90 WITH MOST AREAS INTO THE MID 80S. EDDY SHOULD BE BETTER ESTABLISHED BY FRI NIGHT...WHICH SHOULD BRING IN BETTER AREAL LOW CLOUD COVERAGE FOR LA/VTU COUNTY COASTAL AREAS...AND POSSIBLY ADJACENT COASTAL VALLEYS. GRADIENTS BETWEEN SBA-SMX SHOULD STRENGTHEN ONCE AGAIN FRI EVE CREATING GUSTY NORTHWEST TO NORTHERLY WINDS 20 TO 30 MPH...WITH LOCALLY HIGHER GUSTS ACROSS THE USUAL WINDY PASSES AND CANYONS ACROSS THE SANTA YNEZ RANGE. A WIND ADVISORY MIGHT BE NEEDED FOR THE SBA COUNTY MTNS AND ADJACENT SOUTH COAST. AS THE TROF CONTINUES TO MOVE INLAND...A BROAD NW FLOW ALOFT WILL PERSIST THROUGH SUNDAY BRINGING NEAR NORMAL TEMPS TO THE REGION AND LITTLE FLUCTUATION IN TEMPS ACROSS THE REGION. MOST VALLEY AREAS WILL BE IN THE 80S BOTH DAYS...WHILE THE COASTAL AREAS REMAIN IN THE HIGHER 60S AND 70S. ...FROM PREVIOUS DISCUSSION... .LONG TERM (MON-THU)...A TROF MOVING THROUGH THE PAC NW WILL KEEP DAYTIME TEMPS ABOUT THE SAME MONDAY. BOTH THE ECMWF AND GFS MOVE THIS TROF RAPIDLY INLAND, BUT FOR SOME REASON THE GFS BUILDS A STRONG SURFACE HIGH OVER NEVADA AND CREATES A PRETTY STRONG OFFSHORE FLOW PATTER. GIVEN THE TRAJECTORY OF THE TROF THIS SEEMS WAY OVERDONE AND I HAVE MORE FAITH IN THE ECMWF WHICH INDICATES GRADIENTS NEAR NEUTRAL. BOTH MODELS DO SHOW HIGH PRESSURE BUILDING OVER THE AREA TUE-THU AND CONFIDENCE IS HIGH THAT WE`LL SEE A SIZABLE WARMING TREND DURING THIS PERIOD. && .AVIATION...19/0345Z. MAINLY CLEAR SKIES ACROSS THE FORECAST AREA OVERNIGHT...WITH SOME LOCAL IFR HZ POSSIBLE NEAR KSMX AFTER 10Z. CIGS COULD APPROACH THE CENTRAL COAST BY 10Z...BUT CONFIDENCE IS LOW FOR THIS. KLAX...HIGH CONFIDENCE WITH CAVU TAF. KBUR...HIGH CONFIDENCE WITH CAVU TAF && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...KAPLAN/WOFFORD AVIATION...KAPLAN WWW.WEATHER.GOV/LOSANGELES