SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 850 AM PDT SUN APR 20 2003
THE RACE IS ON. LIGHT OFFSHORE TRENDS THIS MORNING ARE EXPECTED TO
QUICKLY REVERSE THIS AFTERNOON, BRINGING A COOL SEA BREEZE ONSHORE.
THE ONLY QUESTION IS WILL THIS SEA BREEZE ARRIVE BEFORE TEMPS PEAK
WELL ABOVE SATURDAY'S LEVELS? THIS ANSWER IS PROBABLY NOT INLAND, BUT
PERHAPS RIGHT ALONG THE COAST. ACARS SOUNDING AND SURFACE OBS ALL SHOW
GOOD WARMING TODAY WITH TEMPS AS MUCH AS 15 DEGREES WARMER THAN
YESTERDAY AT THIS TIME. THE LARGEST OF THESE TRENDS IS IN THE MTNS.
HOWEVER, A NEGATIVELY TILTED TROF IS APPROACHING CALIFORNIA THIS
MORNING AND THIS WILL INITIATE A RETURN TO STRONG ONSHORE FLOW AND
MUCH COOLER TEMPERATURES. FOR THE MOST PART, THE CURRENT FORECAST IS
RIGHT ON TRACK, KEEPING HIGHS TODAY NEAR OR SLIGHTLY ABOVE SATURDAY'S
LEVELS, THEN STARTING A MAJOR COOLING TREND MONDAY AND CONTINUING INTO
TUESDAY.
THIS FIRST UPPER TROF IS NOT IMPRESSIVE AS FAR AS MOISTURE GOES, BUT
WE DO EXPECT IT TO DEEPEN THE MARINE LYR ENOUGH TO GENERATE SOME
DRIZZLE MONDAY NIGHT INTO TUESDAY, ESPECIALLY NEAR THE MTNS. THEN
PROBABLY NOT A LOT OF CLEARING TUESDAY AFTERNOON WITH TEMPS SEVERAL
DEGREES COOLER THAN NORMAL FOR LATE APRIL. THE MODELS DO SHOW A FAIR
AMOUNT OF PVA ENTERING THE NRN MTN AREAS MON NT AND TUES, AND I STILL
WOULDN'T BE SURPRISED TO SEE A SHOWER OR TWO DEVELOP THERE WITH THE
UPSLOPE FLOW AND CLOUDS BANKING UP IN THE SRN SJ VALLEY. WILL CONSIDER
THROWING IN SOME POPS WITH THE AFTERNOON PACKAGE AFTER COORDINATION
WITH SURROUNDING OFFICES.
WED STILL LOOKS LIKE THE NICEST DAY NEXT WEEK AS A VERY TEMPORARY AND
WEAK UPPER RIDGE MOVES OVER SO CAL. WE SHOULD SEE DAYTIME HIGHS
JUMPING AT LEAST A FEW DEGREES OVER TUESDAY.
FORECAST STILL QUITE UNCERTAIN FOR THE THURS-SAT TIME FRAME. HAVEN'T
SEEN THE 12Z RUN OF THE GFS YET, BUT THE LAST COUPLE OF RUNS HAVE BEEN
CONSISTENTLY SHOWING ANOTHER UPPER LOW DROPPING SOUTH INTO CA WITH A
FRONTAL BAND MOVING THROUGH THURS INTO EARLY FRI. EURO MODELS IN
REASONABLE AGREEMENT AS WELL, THOUGH THERE ARE DIFFERENCES IN TIMING
AND STRENGTH. IF THE 12Z GFS RUN CONTINUES THE PREVIOUS TRENDS, I'LL
LIKELY ADD IN A CHANCE OF RAIN TO THE AREA LATE THURS AND POSSIBLY
INTO FRI AND SAT AS WELL. IT CERTAINLY WON'T RAIN DURING THAT WHOLE
TIME, BUT WE'LL BE ABLE TO REFINE THE TIMING AS WE GET CLOSER. IT'S
NOT A HUGE RAIN MAKER, BUT IT WILL BE COOL AND UNSTABLE WITH SHOWERS
POSSIBLE AT TIMES.
LAX 000. WOFFORD
.LOX...SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
$$