Area Forecast Discussion
Issued by NWS Los Angeles, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 211736
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1036 AM PDT SUN SEP 21 2014

.SYNOPSIS...

A WARMING TREND IS EXPECTED THROUGH EARLY NEXT WEEK AS UPPER LEVEL
LOW PRESSURE MOVES EAST AND HIGH PRESSURE RETURNS. HIGH PRESSURE
WILL ALSO SHRINK THE MARINE LAYER AND FORCE THE NIGHT THROUGH
MORNING LOW CLOUDS AND FOG OUT OF SOME VALLEYS EARLY NEXT WEEK.
COOLER WEATHER WILL RETURN LATER NEXT WEEK AS A BROAD TROUGH OF LOW
PRESSURE APPROACHES FROM THE WEST.

&&

.SHORT TERM (TODAY-TUE)...ANOTHER DEEP MARINE LYR DAY, AROUND 3000`
DOWN SOUTH AND 2500` UP NORTH. RAOBS AND PROFILERS SHOW LITTLE
CHANGE IN THE LOWER LAYERS BUT WARMING ABOVE 500 MB AS THE UPPER LOW
STARTS TO FILL AND LIFT NORTHEAST. GRADIENTS ARE A HAIR STRONGER
ONSHORE THIS MORNING AND MODELS PROJECTING A SIMILAR TO SLIGHTLY
STRONGER ONSHORE GRADIENT THIS AFTERNOON AS YESTERDAY. SO THOSE
FACTORS ARE POINTING TOWARDS A SIMILAR TO EVEN SLIGHTLY COOLER DAY.
HOWEVER, PROBABLY THE OVERRIDING FACTOR TODAY WILL BE THE MARINE
LAYER`S RESPONSE TO THE LOW MOVING NORTHEAST AND THE SUBSIDENCE AND
WARMING BEHIND IT WHICH MAY OFFSET ALL THOSE COOLING FACTORS AND
RESULT IN EARLIER CLEARING, ESPECIALLY INLAND. COMPARING THE VISIBLE
IMAGE TODAY WITH YESTERDAY AT THIS TIME WE`RE ALREADY SEEING
SIGNIFICANT THINNING OF THE CLOUDS ACROSS THE SAN FERNANDO VALLEY
AND OVER THE COASTAL WATERS. BASED ON THESE FACTORS THE ODDS FAVOR A
SLIGHTLY WARMER DAY TODAY WITH EARLIER CLEARING. FORECAST MAY STILL
BE A TOUCH ON THE WARM SIDE BUT PROBABLY IN THE BALL PARK.

***FROM PREVIOUS DISCUSSION***

HGTS CONTINUE TO RISE MONDAY AND THIS WILL SHRINK THE MARINE LAYER
SOME. THE INVERSION WILL BE A LITTLE STRONGER SO EXPECT THE BEACHES
TO CONTINUE TO STRUGGLE TO CLEAR. AWAY FROM THE BEACHES TEMPS WILL
BUMP UP ANOTHER FEW DEGREES.

A 592 DM UPPER SIT WILL SIT ATOP OF SOCAL TUESDAY IT WILL BE
CENTERED OVER SAN DIEGO. HGTS SHOULD BE HIGH ENOUGH TO SMOOSH THE
MARINE LAYER OUT OF MOST OF THE VLYS. AGAIN MAX TEMPS WILL RAISE A
FEW MORE DEGREES. TUESDAY WILL BE THE WARMEST DAY OF THE NEXT 7 DAYS.

.LONG TERM (WED-SAT)...
ALL MDLS AGREE THAT A DECENT SIZED PAC NW UPPER LOW/TROF WILL SET UP
ACROSS THE WEST COAST THURSDAY. COULD BE A TRICKY FORECAST DOWN HERE
BASED ON WHEN THE TROF MOVES CLOSE ENOUGH TO AFFECT THE WEATHER DOWN
HERE. RIGHT NOW WILL GO WITH AN EARLY ENOUGH ARRIVAL TIME TO
INCREASE THE MARINE LAYER AND COOL TEMPS EVERYWHERE. THIS IS NOT THE
HIGHEST CONFIDENCE FCST AND IT COULD BE SUNNIER AND WARMER THAN FCST
IF THE TROF IS A LITTLE LATE TO THE PARTY.

MDLS BEGIN TO DIVERGE BY FRIDAY BUT NOT ENOUGH TO REALLY LOWER FCST
CONFIDENCE. THE TROF WILL SLOWLY MOVE CLOSER AND CLOSER TO THE
COAST. SW FLOW WILL ALOFT WILL INCREASE. LOOK FOR AN INCREASE IN THE
MARINE LAYER EACH DAY AND A SUBSEQUENT DECREASE IN TEMPERATURES.

FORECAST IS A LITTLE MURKIER SATURDAY. THE GFS AND GEM MDLS ARE MORE
PROGRESSIVE WITH THE TROF AND MOVE IT ON OUT INTO NV...BUT THE EC
HANGS THE TROF BACK AND STRENGTHENS IT. THE EC SOLN WOULD RESULT IN
A RATHER GLOOMY FCST WITH A DOSE OF DRIZZLE FOR GOOD MEASURE. WENT
WITH A RATHER VANILLA FCST WITH A DECENT MARINE LAYER AND BLO NORMAL
TEMPS.

&&

.AVIATION...21/1800Z.

MID/UPPER LEVEL TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC AND
RIDGE OF HIGH PRESSURE CENTERED SOUTHEAST OF THE AREA WILL PERSIST.
UPPER LEVEL MODERATE SOUTHWEST WINDS AND MID LEVEL LIGHT SOUTHEAST
WINDS WILL PREVAIL OVER THE AREA. LOW LEVEL CLOUD TOPS WERE
APPROXIMATELY 2.8KFT THIS MORNING AND WILL DIFFER BY MINUS 1KFT
MONDAY MORNING. THE CLOUD FIELD WAS RELATIVELY ORGANIZED THIS
MORNING AND WILL PROBABLY DIFFER LITTLE MONDAY MORNING. WEAK TO
MODERATE ONSHORE PRESSURE GRADIENT THROUGH 22/04Z AND AFTER
22/19Z...OTHERWISE A WEAK MIXED ONSHORE AND NORTHERLY GRADIENT IS
EXPECTED.

KLAX...CHANCE SCATTERED 027 BY 21/21Z. CHANCE CIGS 013-015 BETWEEN
22/07-22/17Z AND CIGS 025 BETWEEN 22/17-22/21Z.

KBUR...SKC LIKELY BY 21/19Z THEN CHANCE CIGS 012 BY 22/11Z.

VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS


&&

.MARINE...21/900 AM.

THERE IS A CHANCE SMALL CRAFT ADVISORY CONDITIONS WILL EXIST IN
THE VICINITY OF THE CHANNEL ISLANDS THIS EVENING AND AGAIN MONDAY
AND TUESDAY EVENING. THERE IS A CHANCE SMALL CRAFT ADVISORY
CONDITIONS WILL EXIST NORTH OF POINT CONCEPTION TO POINT SAL MONDAY
AND MONDAY NIGHT. THERE IS A CHANCE THE NORTHWEST WINDS WILL
INCREASE TO GALES FRIDAY IN THE VICINITY OF THE NORTHERN ISLANDS TO
SAN NICOLAS ISLAND. SWELLS ORIGINATING FROM A FAST MOVING AND SHORT
LIVED GULF OF ALASKA STORM A FEW DAYS AGO ON THURSDAY FROM 295-305
DEGREES AND WILL PEAK THIS AFTERNOON. A LOW PRESSURE SYSTEM IS
LIKELY TO DEVELOP OVER THE EASTERN PACIFIC MONDAY THROUGH TUESDAY.
SWELLS GENERATED BY STORM FORCE WINDS ARE EXPECTED TO ARRIVE FROM
300-310 DEGREES WEDNESDAY EVENING AND PEAK THURSDAY AND LINGER
THROUGH FRIDAY AND SMALL CRAFT ADVISORY CONDITIONS FOR HAZARDOUS
SEAS WILL LIKELY EXIST.

&&

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

&&

$$

PUBLIC...MW/RORKE
AVIATION/MARINE...30
SYNOPSIS...SUKUP

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.