Area Forecast Discussion
Issued by NWS Los Angeles, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KLOX 240003 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
500 PM PDT TUE SEP 23 2014

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...
A SLIGHT WARMING TREND WILL CONTINUE THROUGH TOMORROW...THEN AS AN
UPPER LEVEL LOW PRESSURE SYSTEM MOVES INTO CALIFORNIA EXPECT COOLER
CONDITIONS INTO THE WEEKEND WITH AN INCREASE IN OVERNIGHT LOW CLOUDS
AND FOG. AFTER THE TROUGH PASSES SUNDAY...WARMER WEATHER IS EXPECTED
TO RETURN FOR NEXT WEEK.

&&

.SHORT TERM (WED-FRI)...A COUPLE MORE DAYS OF ABOVE AVERAGE TEMPS
BEFORE THE COOL DOWN KICKS IN THURSDAY. STRONG MERIDIONAL FLOW
PATTERN IN PLACE WITH THE DEEP FALL-LIKE UPPER TROUGH DIGGING OFF
THE PACIFIC NORTHWEST AND STRONG UPPER RIDGE OVER THE INTERMOUNTAIN
WEST. MOST AREAS HAVE WARMED COMPARED TO YESTERDAY AT THIS TIME DUE
TO A  SLIGHTLY LESS ONSHORE PRESSURE GRADIENT. MODELS TREND THIS
ONSHORE GRADIENT DOWNWARD SLIGHTLY MORE TOMORROW TO HELP WARM
AFTERNOON TEMPS A FEW MORE DEGREES. MARINE LAYER SHOULD REMAIN
FAIRLY SIMILAR TONIGHT AND HAVE GONE PERSISTENCE WITH STRATUS
COVERAGE. THE UPPER TROUGH BEGINS TO INFLUENCE THE AREA ON THURSDAY
WITH THE START OF THE COOLING TREND THAT WILL CONTINUE INTO THE
FIRST HALF OF THE WEEKEND. MODELS IN GOOD AGREEMENT THROUGH THURSDAY
ON THE PLACEMENT OF THE LOW AND SUBSEQUENT 500 MB HEIGHTS AND
THICKNESS VALUES OVER THE AREA ON THURSDAY. HIGHS WILLS STILL BE
ABOVE AVERAGE FOR ALL BUT NORTHERN SLO COUNTY ON THURSDAY DESPITE
THE COOLING...BUT THEN MOST OF THE AREA WILL BE BELOW NORMAL ON
FRIDAY WITH YET MORE COOLING AS THE SOUTHERN END OF THE TROUGH IS
WELL INTO SOCAL BY FRIDAY. MODELS HAVE BEEN CONSISTENT IN KEEPING
THE ASSOCIATED COOL FRONT DRY AS IT MOVES THROUGH SOMETIME THURSDAY.
EXPECT GUSTY SOUTHWEST WINDS BEHIND THE FRONT IN THE ANTELOPE VALLEY
FRIDAY AFTERNOON.

.LONG TERM (SAT-TUE)...
MODELS HAVE COME INTO GOOD AGREEMENT ON THE SPEED AND INTENSITY OF
THE UPPER TROUGH. THE TROUGH AXIS SHOULD SWING BY THE AREA SOMETIME
SATURDAY TO RESULT IN THE COOLEST DAY OF THE FORECAST ALONG WITH THE
DEEPEST MARINE LAYER. THE ANTELOPE VALLEY SHOULD HAVE ANOTHER BREEZY
AFTERNOON ON SATURDAY AS WELL. THE LOW EXITS THE AREA ON SUNDAY AND
THERE SHOULD BE A FEW DEGREE WARMUP AS A RESULT...BUT NOT MUCH. GFS
SHOWS MORE RIDGING BEHIND THE LOW THAN THE ECMWF WHICH MAINTAINS A
COOLER NORTHWEST FLOW. MONDAY AND TUESDAY SHOULD BRING ADDITIONAL
WARMING DUE TO WEAK OFFSHORE FLOW AND A SHRINKING MARINE LAYER.

&&

.AVIATION...23/2355Z...MODERATE CONFIDENCE OVERALL IN THE 00Z TAFS
DUE TO UNCERTAINTIES WITH TIMING AND EXTENT OF LOW CLOUDS TONIGHT
INTO WED MORNING FOR THE COASTAL AIRFIELDS. HOWEVER... THERE IS
GENERALLY HI CONFIDENCE THAT LOW CLOUDS AND LIFR/IFR CONDITIONS WILL
AFFECT THESE AIRFIELDS AT TIMES DURING THE PERIOD. THE EXPECTED
ONSET OF LOW CLOUDS WILL RANGE FROM 03Z AT KSMX TO 11Z AT KSBA. THE
TIMING OF THE ONSET OF THE LOW CLOUDS MAY BE OFF PLUS/MINUS 1-2
HOURS. THE LOW CLOUDS WILL LIKELY SCATTER OUT LATE WED MORNING...
ALTHO THERE IS ALSO UNCERTAINTY TO THE TIMING OF THE LOW CLOUDS
SCATTERING WHICH MAY BE OFF PLUS/MINUS AN HOUR OR SO. OTHERWISE...
VFR CONDITIONS CAN BE EXPECTED AT THE SWRN CA AIRFIELDS THRU WED.

KLAX...MODERATE CONFIDENCE OVERALL IN THE 00Z TAF DUE TO
UNCERTAINTIES WITH TIMING OF LOW CLOUDS LATE TONIGHT AND WED
MORNING. THE LOW CLOUDS WITH IFR CIGS SHOULD DEVELOP AROUND 08Z THEN
LINGER THRU ABOUT 17Z WED. THE TIMING OF THE ONSET AND DISSIPATION
OF THE LOW CLOUDS MAY BE OFF PLUS/MINUS 1-2 HOURS. OTHERWISE...VFR
CONDITIONS CAN BE EXPECTED AT THE AIRFIELD THRU WED EVENING.

KBUR...GENERALLY HI CONFIDENCE IN THE 00Z TAF WITH VFR CONDITIONS
EXPECTED THRU WED AFTERNOON.

&&

.MARINE...23/200 PM...

FOR THE OUTER WATERS...MODERATE CONFIDENCE IN LOW-END SMALL CRAFT
ADVISORY WINDS THIS AFTERNOON AND TONIGHT. SO...WILL CONTINUE WITH
ADVISORY WITH THE AFTERNOON FORECAST. THE NORTHWEST WINDS WILL BEGIN
TO INCREASE ON THURSDAY AND WILL CONTINUE TO STRENGTHEN THROUGH THE
WEEKEND. SO...HIGH CONFIDENCE IN STRONG SMALL CRAFT ADVISORY
CONDITIONS THIS WEEKEND...WITH A CHANCE OF GALE WARNINGS BEING
NEEDED.

FOR THE INNER WATERS...WINDS ARE ANTICIPATED TO REMAIN BELOW
ADVISORY LEVELS THROUGH THURSDAY (ALTHOUGH THE WESTERN PART OF THE
SANTA BARBARA CHANNEL COULD GET SOME LOCAL 25 KNOT GUSTS IN THE
AFTERNOON/EVENING HOURS). WITH THE STRENGTHENING FLOW THIS WEEKEND
THERE IS A BETTER CHANCE OF ADVISORY LEVEL WINDS ACROSS WESTERN
SECTIONS OF THE WATERS.

A LARGE LONG-PERIOD NORTHWEST SWELL WILL MOVE INTO THE COASTAL
WATERS WEDNESDAY NIGHT...PEAK ON THURSDAY THEN LINGER THROUGH
FRIDAY.


&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&
$$

PUBLIC...JACKSON
AVIATION...SIRARD
MARINE...RAT
SYNOPSIS...KJ

WWW.WEATHER.GOV/LOSANGELES





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.