Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 311113
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
338 AM PDT FRI JUL 31 2015

.SYNOPSIS...THERE WILL BE SLIGHT CHANCE OF THUNDERSTORMS ACROSS THE
MOUNTAINS...THE ANTELOPE VALLEY AND INTERIOR SECTIONS OF SAN LUIS
OBISPO AND SANTA BARBARA COUNTIES TODAY...THEN ANY THUNDERSTORMS
THIS WEEKEND SHOULD BE CONFINED TO THE MOUNTAINS OF LOS ANGELES AND
VENTURA COUNTIES AND THE ANTELOPE VALLEY. MORE STABLE SOUTHWESTERLY
FLOW ALOFT WILL SET UP MONDAY THROUGH THURSDAY...WITH DRY WEATHER
EXPECTED...AND GENERALLY NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES.

&&

.SHORT TERM (TODAY-SUN)...SOME STRATUS HAS DEVELOPED ACROSS THE
COASTAL WATERS...AND CLOUDS HAVE PUSHED INTO COASTAL SECTIONS OF
L.A. COUNTY AND THE CENTRAL COAST. THE MARINE LAYER WAS AROUND 1200
FEET DEEP...AND WITH A GOOD ONSHORE PUSH...CLOUDS SHOULD BE ABLE TO
SPREAD INTO AT LEAST THE SAN GABRIEL VALLEY BY DAYBREAK. LOW CLOUDS
SHOULD CLEAR IN MOST AREAS BY LATE MORNING.

THE FORECAST AREA WILL CONTINUE TO BE AFFECTED BY ITS LOCATION
BETWEEN UPPER LEVEL HIGH PRESSURE OVER THE FOUR CORNERS AREA AND AN
UPPER LOW WELL OFF THE COAST OF POINT CONCEPTION. THE MID AND UPPER
LEVEL FLOW WILL BECOME A BIT MORE SLY TODAY...BUT SHOULD STILL HAVE
A SLIGHT EASTERLY COMPONENT. THE WRF SHOWS VERY GOOD INSTABILITY
ACROSS THE MTNS OF SBA...VTU AND L.A. COUNTIES AND THE ANTELOPE
VALLEY LATE THIS MORNING AND THIS AFTERNOON AS SFC HEATING TAKES
PLACE. HOWEVER...THERE WILL NOT BE AS MUCH IN THE AVAILABLE
MOISTURE...WITH PW VALUES DOWN TO ABOUT 1.5 TO 1.6 INCHES THIS
MORNING...DOWN FROM 2 INCHES ON THU. IN ADDITION...THE WRF SHOWS
SOME DRYING DURING THE AFTERNOON...ESPECIALLY ACROSS SRN
SECTIONS...WITH PW VALUES DROPPING TO BETWEEN 1.0 AND 1.2 BY LATE
AFTERNOON. STILL...THE SLIGHT CHANCE OF SHOWERS AND TSTMS LOOKS
REASONABLE FOR THE MTNS AND ANTELOPE VALLEY. DESPITE SOMEWHAT LESS
IN THE WAY OF INSTABILITY ACROSS SLO COUNTY AND THE CUYAMA
VALLEY...THERE WILL BE MORE IN THE WAY OF MOISTURE THERE ALL
DAY...SO THE SLIGHT CHANCE OF TSTMS LOOKS GOOD THERE AS WELL.

WITH THE DECREASING MOISTURE CONTENT THROUGH THE ATMOSPHERE...THERE
IS NOT AS MUCH CONFIDENCE IN HEAVY RAINFALL WITH THE STORMS.
THEREFORE...HAVE REFRAINED FROM ISSUING A FLASH FLOOD WATCH AT THIS
TIME. HOWEVER...STEERING FLOW IS MARGINALLY WEAK...AND IF ANY HIGH
PRECIP PRODUCING STORMS DEVELOP...ISOLATED FLASH FLOODING IS A
POSSIBILITY.

WITH INCREASING ONSHORE GRADIENTS...SLIGHT THICKNESS FALLS...AND
SLIGHT COOLING AT 850 AND 950 MB TODAY...EXPECT A BIT OF COOLING IN
MOST AREAS TODAY.

THE FOUR CORNERS HIGH WILL WEAKEN SOMEWHAT OVER THE WEEKEND...AND
THE MID AND UPPER FLOW WILL BECOME SLY ON SAT...THEN SWLY ON SUNDAY.
THERE WILL BE A DECREASING CHANCE OF CONVECTION OVER THE WEEKEND.
WAS TEMPTED TO REMOVE POPS...BUT HAVE DECIDED TO LEAVE JUST SLIGHT
CHANCE POPS FOR THE AFTERNOON AND EVENING HOURS FOR THE MTNS OF L.A
AND VTU COUNTIES AND THE ANTELOPE VALLEY. THE WRF SHOW SOME INCREASE
IN LOW LEVEL RH VALUES...WITH NIGHT THROUGH MORNING STRATUS MOST
LIKELY ACROSS THE CENTRAL COAST AND SANTA YNEZ VALLEY...AND THE L.A.
COUNTY COAST AND THE SAN GABRIEL VALLEY. MAX TEMPS SAT AND SUN
SHOULD BE QUITE SIMILAR TO THOSE TODAY.

.LONG TERM (MON-THU)...THE UPPER LOW WELL OFF THE COAST OF PT
CONCEPTION WILL KEEP SWLY FLOW ALOFT ACROSS THE REGION MON THRU THU
AS IT SLOWLY APPROACHES THE COAST. IT IS EXPECTED TO BE DRY THROUGH
THE PERIOD. NIGHT THRU MORNING LOW CLOUDS AND FOG WILL LIKELY AFFECT
MOST COASTAL AND SOME VLY AREAS THROUGH THE PD. MAX TEMPS WILL
GENERALLY BE NEAR TO SLIGHTLY BELOW NORMAL THROUGH THE PD.


&&

.AVIATION...31/1045Z...

AT 0854Z...THE MARINE INVERSION AT KLAX WAS BASED AT 1200 FEET. THE
TOP OF THE INVERSION WAS 3100 FEET WITH A TEMPERATURE OF 25 DEGREES
CELSIUS.

OVERALL...MODERATE CONFIDENCE IN 12Z TAF PACKAGE. RATHER CHAOTIC LOW
CLOUD PATTERN THIS MORNING...LEADING TO LOW CONFIDENCE FORECASTS FOR
ALL COASTAL TAF SITES. WHEREVER CIGS DEVELOP THIS MORNING...FLIGHT
CATEGORIES SHOULD RANGE FROM MVFR TO IFR. LOW CLOUDS WILL DISSIPATE
BY AFTERNOON...WITH VFR CONDS ALL SITES THROUGH THIS EVENING.
OVERNIGHT...EXPECT A BIT MORE ORGANIZED LOW CLOUD PATTERN ESPECIALLY
ACROSS THE CENTRAL COAST AND LOS ANGELES/VENTURA COUNTY COASTS.

WITH LINGERING MOISTURE AND INSTABILITY...THERE WILL BE THE CHANCE
OF THUNDERSTORMS AROUND KPMD/KWJF THIS AFTERNOON/EVENING. SO WILL
INCLUDE VCTS REMARKS.

KLAX...MODERATE CONFIDENCE IN 12Z TAF. MODERATE CONFIDENCE IN LOW
CLOUDS ARRIVING 12Z-13Z THIS MORNING. CIGS WILL LIKELY RANGE IN THE
MVFR CATEGORY WITH A SLIGHT CHANCE OF IFR CIGS...AND SHOULD
DISSIPATE BY LATE MORNING. FOR TONIGHT...MODERATE CONFIDENCE IN
RETURN OF LOW CLOUDS...BUT LOW CONFIDENCE IN TIMING.

KBUR...MODERATE CONFIDENCE IN 12Z TAF. HIGH CONFIDENCE IN VFR CONDS
THRU THIS EVENING. OVERNIGHT...THERE IS A 30% CHANCE OF MVFR/IFR
CIGS DEVELOPING AFTER 08Z.

&&

.MARINE...31/330 AM...

FOR THE OUTER WATERS...MODERATE TO HIGH CONFIDENCE IN CURRENT
FORECAST. FOR THE SOUTHERN TWO OUTER WATERS...MODERATE CONFIDENCE IN
NORTHWEST GUSTS REACHING SMALL CRAFT ADVISORY LEVELS THIS
AFTERNOON/EVENING...WITH WINDS REMAINING BELOW SCA LEVELS ELSEWHERE.
NORTHWEST WINDS WILL INCREASE A BIT ON SATURDAY...AND REMAIN
MODERATE THROUGH TUESDAY. THERE IS A GOOD CHANCE THAT SMALL CRAFT
ADVISORIES WILL BE NEEDED FOR ALL OR PART OF THE OUTER WATERS
SATURDAY THROUGH TUESDAY.

FOR THE INNER WATERS...MODERATE TO HIGH CONFIDENCE IN CURRENT
FORECAST. HIGH CONFIDENCE IN WESTERLY WINDS REMAINING BELOW SMALL
CRAFT ADVISORY LEVELS THROUGH SATURDAY. FOR SUNDAY THROUGH TUESDAY
THE WINDS ARE EXPECTED TO INCREASE...WITH A CHANCE OF SMALL CRAFT
ADVISORY CONDITIONS EACH AFTERNOON AND EVENING ACROSS THE INNER
WATERS OFF THE COAST OF SAN LUIS OBISPO COUNTY AS WELL AS THE
WESTERN PORTION OF THE SOUTHERN INNER WATERS.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).

&&

$$

PUBLIC...DB
AVIATION/MARINE...RAT

WWW.WEATHER.GOV/LOSANGELES


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