Re: OMG!!!

AREA FORECAST
DISCUSSION


FXUS66 KLOX 240433
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
930 PM PDT SUN JUL 23 2006

...EXCESSIVELY HOT ACROSS SOUTHWESTERN CALIFORNIA FOR AT LEAST
ANOTHER DAY...

.SHORT TERM...DESPITE SOME EARLY CLOUD COVER IN SOME AREAS WHICH DID
KEEP TEMPERATURES IN THOSE AREAS FROM HITTING NEAR ALL-TIME RECORD
HIGHS...WE STILL WERE ABLE TO COMPILE A RATHER LONG LIST OF DAILY
RECORD HIGHS AGAIN TODAY (SEE LAXRERLOX). THUNDERSTORM ACTIVITY DIED
OFF AT THE MORE USUAL EARLY EVENING TIME-FRAME AND LATEST SATELLITE
PICTURES SHOW THE CLOSEST CONVECTION NEAR DEATH VALLEY. AIRMASS
STILL FAIRLY UNSTABLE AND QUITE MOIST...SO IT WOULD NOT TAKE MUCH TO
TOUCH OFF A FEW SHOWERS OR THUNDERSTORMS OVERNIGHT JUST ABOUT
ANYWHERE. SO I LEFT THE SLIGHT CHC OF SHRA/TSRA IN THE FORECAST
OVERNIGHT WITH WEAK UPPER LEVEL VORTICITY CENTERS MOVING WEST ON THE
SOUTHERN PERIPHERY OF THE UPPER LEVEL HIGH.

SFC PRESSURE GRADIENTS ARE TRENDING WEAKLY ONSHORE AND THE LAX
PROFILER DATA DOES INDICATE A SLIGHTLY COOLER AIRMASS MOVING ONTO
THE COAST. MODELS PREDICT THE UPPER LEVEL HIGH OVER THE GREAT BASIN
TO WEAKEN A LITTLE MONDAY. HOWEVER...LOWER LEVEL THICKNESSES AND 950
MB AND 850 MB TEMPS DO NOT REALLY SHOW ANY COOLING. IN FACT...THEY
SHOW SOME WARMING IN WRF MODEL. I TAKE THIS TO MEAN THAT THERE MAY
BE A FEW DEGREES OF COOLING ESPECIALLY CLOSE TO THE COAST ON
MONDAY...BUT INLAND AREAS WILL LIKELY BE PRETTY CLOSE TO WHAT THEY
WERE LIKE ON SUNDAY. THE EXCEPTION BEING THE LA VALLEYS WHERE CLOUD
COVER TODAY KEPT THEM COOLER THAN EXPECTED. AS A RESULT...THE SAN
FERNANDO AND SAN GABRIEL VALLEYS MAY ACTUALLY BE A LITTLE WARMER ON
MONDAY. WITH HIGHS INLAND EXPECTED TO RANGE ONCE AGAIN FROM 100 TO
112...AND THE RELATIVELY HIGH HUMIDITY HANGING AROUND...AN EXCESSIVE
HEAT WATCH REMAINS IN EFFECT FOR MONDAY AFTERNOON. I EXPANDED THE
WATCH TO INCLUDE THE SANTA YNEZ VALLEY AND THE MOUNTAINS (SEE
LAXNPWLOX). THIS WATCH WILL LIKELY BE UPGRADED TO A WARNING BY THE
TIME WE ISSUE THE 330 AM ZONE FORECAST PACKAGE.

...FROM PREVIOUS DISCUSSION...

THE CENTER OF THE UPPER LEVEL HIGH OVER THE GREAT BASIN SHIFTS
SLIGHTLY SOUTH TOMORROW BUT WILL STILL BE IN A POSITION TO KEEP OUR
MOIST SOUTHEASTERLY FLOW AROUND. VORTICITY RIPPLES WILL ALSO
CONTINUE TO ROTATE AROUND TO PROVIDE SOME FORCING FOR SHOWERS AND
THUNDERSTORMS.

MODEL STILL SHOWING THAT RIDGE IS KNOCKED DOWN JUST SLIGHTLY ON
TUESDAY AS AN UPPER LEVEL TROUGH SQUEEZES THROUGH INTO THE PACIFIC
NORTHWEST. OUR UPPER FLOW COULD IN FACT TURN ON SHORE FOR A
WHILE...AND CONTINUING INTO WEDNESDAY. EXPECT THUNDERSTORM CHANCES
TO BE LESS EACH DAY FOR TUESDAY INTO WEDNESDAY.

.LONG TERM...LATEST GFS RUN IS ADVERTISING A RETURN OF THE
SUBTROPICAL MOISTURE DURING THE SECOND HALF OF THE WEEK.
PRECIPITABLE WATER AMOUNTS...WHICH BRIEFLY DIPS DOWN TO MORE
REASONABLE LEVELS WEDNESDAY AND EARLY THURSDAY...CLIMB BACK UP TO
OVER AN INCH AND A HALF BY THE WEEKEND. AN INTERESTING FACTOR MAY BE
WHAT EMILIA DECIDES TO DO. GFS BRINGS MOISTURE FROM THIS STORM NORTH
INTO THE AREA BY THE WEEKEND.

&&

.AVIATION...TAF SITES SHOULD SEE VFR CONDS FOR MUCH OF THE PERIOD.
EXCEPTIONS BEING SOME 3-5SM HZ AT COASTAL TAFS LATE TONIGHT...AND
SOME HIT OR MISS SHRA/TSRA AT ANY TIME IN THE NEXT 6 TO 24 HOURS.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
EXCESSIVE HEAT WATCH (SEE LAXNPWLOX).

&&





PUBLIC...MOYER/JACKSON
AVIATION...MOYER