SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 900 PM PDT SAT APR 28 2001
MARINE LAYER STUBBORN OVER LAX/VTU COUNTIES THIS EVENING. AS OF
03Z VBG/NKX SOUNDINGS...AND ACARS SOUNDINGS INDICATE THE MARINE
LAYER WAS NEAR 1200 FEET OVER SBA COUNTY AND 2000 TO 2500 FEET OVER
LAX COUNTY. AN EDDY SHOULD LINGER OVER THE INNER WATERS TONIGHT TO
HELP KEEP THE MARINE LAYER RELATIVELY DEEP WITH SOME DRIZZLE
POSSIBLE MANY AREAS...ALL THE WAY UP TO THE LOWER COASTAL SLOPES.
WITH A NORTHERLY FLOW OVER SBP/SBA COUNTIES...SKIES SHOULD AVERAGE
OUT PARTLY CLOUDY TONIGHT. SOME NORTHERLY CANYON WINDS ARE POSSIBLE
ACROSS THE S SBA COAST AS WELL...ESPECIALLY LATER TONIGHT.
VERY WEAK UPPER TROF TO MOVE OVER SOCAL LATER TONIGHT AND EARLY
SUNDAY. ONLY AFFECT WITH THIS FEATURE ARE A FEW HIGH CLOUDS...AND
AN INCREASE IN NORTH TO SOUTH GRADIENTS ACROSS THE DISTRICT. THE
EASTERN END OF AN UPPER HIGH WILL THEN BUILD INTO THE REGION SUN
AFTERNOON THRU MON. THE MESO-ETA SUGGESTS THE MARINE LAYER TO SOME
EXTENT WILL LINGER AT LEAST OVER LAX COUNTY COAST THRU MON. STRONG
NW FLOW OVER THE OUTER WATERS SHOULD KEEP THE EDDY GOING OVER THE
INNER WATERS THROUGH THE PERIOD AS WELL. MESO-ETA 950 MB TEMPS DO
INCREASE NICELY SUN TO MON...WITH DRYING AT THAT LEVEL...SUGGESTING
A SHRINKING MARINE LAYER. WE SHOULD SEE A BIT BETTER CLEARING OF
THE LOW CLOUDS OVER VTU/LAX COUNTIES SUN...WITH MOST AREAS SEEING
SUNSHING SUN AFTENROON. LOW CLOUDS SHOULD STAY OUT OF LAX/VTU
COUNTY VALLEYS SUN NITE...BUT AT LEAST PATCHY LOW CLOUDS AND FOG
STILL POSSIBLE FOR COASTAL AREAS. SLO/SBA COUNTIES SHOULD REMAIN
MOSTLY CLEAR WITH JUST SOME PATCHY LOW CLOUDS AND FOG. ON
MONDAY...ALL INLAND AREAS SHOULD WARM UP...WITH 80S TO POSSIBLY
AROUND 90 IN THE VALLEYS...AND 70S IN THE MOUNTAINS. SOME SLIGHT
OFFSHORE FLOW SHOULD ALLOW TEMPS TO WARM INTO THE 70S OVER COASTAL
AREAS OF SLO/SBA COUNTIES AS WELL...WITH TEMPS REMAINING RELATIVELY
COOL NEAR THE BEACHES ELSEWHERE.
CURRENT FORECAST...INCLUDING TEMPS...LOOKS GOOD OVERALL...BUT WILL
DO A ZONE UPDATE BY 945 PM FOR MINOR CHANGES IN FIRST PERIOD.
IN THE EXTENDED...UPPER RIDGE GIVES THE DISTRICT ANOTHER WARM DAY
TUE...THEN AN UPPER LOW DEVELOPS SOMEWHERE BETWEEN LAS VEGAS AND THE
FOUR CORNERS WED AND THU. THE UPPER LOW WILL PROVIDE THE DISTRICT
WITH BREEZY TO WINDY CONDITIONS AT TIMES...MAINLY NORTHERN ZONES
AND IN MOUNTAINS WED AND THU...ALONG WITH COOLER TEMPERATURES.
LAX 0000. SIRARD.
.LAX...GALE WARNING/SMALL CRAFT ADVISORY (SEE LAXCWFLAX).
EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 205 PM PDT SAT APR 28 2001
...SYNOPSIS...
ONSHORE FLOW AND A DEEP MARINE LAYER WILL CONTINUE LOW CLOUDS
TONIGHT WITH SOME PATCHY DRIZZLE LATE. BUILDING HIGH PRESSURE ALOFT
AND WEAKER ONSHORE FLOW WILL BRING WARMING AND LESS OF A MARINE
LAYER SUNDAY AFTERNOON THROUGH TUESDAY. COOLING IS EXPECTED INLAND
BY MID-WEEK AS LOW PRESSURE ALOFT DIVES SOUTH INTO THE DESERTS.
...DISCUSSION...
THE MARINE INVERSION IS AT AROUND 3000 FEET...THOUGH AFTER ACARS
SOUNDINGS SHOW THE STRENGTH DOWN TO ABOUT 5-6 DEG C DUE TO SOME
COOLING JUST BELOW 850 MB. THE EDDY RESULTED IN NORTHERN AREAS
HAVING TROUBLE CLEARING...MORE SPECIFICALLY ORANGE COUNTY...THE
ONTARIO AREA AND THE N COAST OF SAN DIEGO COUNTY. SOME DRIZZLE
OCCURRED THIS MORNING...AND WITH THE WEAK TROUGH MOVING THROUGH
SUNDAY MORNING...PROBABLY AROUND 18Z...SOME DRIZZLE COULD AGAIN
OCCUR THEN...ESPECIALLY ALONG THE COASTAL SLOPES.
HOWEVER...ONCE THE TROUGH MOVES THROUGH...OFFSHORE TRENDS WILL
OCCUR...BOTH AT THE SURFACE AND ESPECIALLY ALOFT. SO...THAT SHOULD
BE ENOUGH TO BRING BETTER CLEARING TO MOST AREAS SUNDAY AFTERNOON.
THIS APPEARS TO BE ENOUGH TO CLEAR EVEN COASTAL AREAS
MONDAY...THOUGH 12Z AVN HINTS AT A WEAK EDDY...SO AT LEAST THE USUAL
NIGHT/MORNING COASTAL LOW CLOUDS AND FOG SHOULD CONTINUE THEN.
INLAND AREAS SHOULD GET QUITE WARM TOO DUE TO A LOT OF WARMING
ALOFT. SINCE THE OFFSHORE FLOW WILL NOT MAKE IT TO THE
COAST...SEASONABLE TEMPS SHOULD OCCUR THERE.
THE LONGER RANGE MODELS VARY QUITE A BIT WITH THE SOLUTION OF THE
INSIDE SLIDER AND/OR CLOSED LOW FOR THE WED-FRI PERIOD. 12Z AVN IS
TRENDING A BIT MORE WITH A CLOSED LOW FROM THE MRF...THOUGH THE
CONFIDENCE IS QUITE LOW...ESPECIALLY GIVEN THAT ONE MRF ENSEMBLE
SOLUTION HAS A WEAK RIDGE THU. FOR NOW...I WILL GO WITH AN ECM/AVN
BLEND WITH THE CLOSED LOW A BIT FURTHER EAST...BUT STILL WITH
COOLING. THE LOW MAY BE CLOSE ENOUGH FOR SOME CLOUDS OVER THE MTNS/N
DESERTS...SO I WENT WITH PARTLY CLOUDY WORDING FOR THOSE
AREAS...THOUGH THE AVN SOLUTION WOULD HINT AT A VERY SLIGHT CHANCE
OF SHOWERS. SOME BREEZY CONDITIONS COULD OCCUR BELOW PASSES AND
CANYONS TOO SINCE WE WOULD HAVE THE RIGHT UPPER-LEVEL WIND DIRECTION
AND COLD AIR ADVECTION. ALSO...THOSE WHO ARE WEST OF THE MTNS WOULD
EXPERIENCE FEWER LOW CLOUDS WITH THIS REGIME.
SAN 0-00
.SAN...NONE.
MAXWELL