EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 155 AM PST SUN MAR 19 2000
...SYNOPSIS...
THE MARINE LAYER WILL DEEPEN AGAIN AS ANOTHER EDDY SPINS UP AND PERSISTS
THROUGH TONIGHT. AN UPPER LEVEL TROUGH WILL MOVE TO THE FOUR CORNERS
AREA AND DEVELOP INTO A MAJOR STORM SYSTEM FOR THE SOUTHERN ROCKY
MOUNTAIN REGION. STRONG NORTHERLY WINDS ON THE WEST SIDE OF THIS SYSTEM
MAY SOUTHWEST CALIFORNIA LATE TONIGHT...MAINLY OVER THE DESERTS...
MOUNTAINS... AND HIGH VALLEYS. HGIH WINDS ARE MORE LIKELY MONDAY INTO
TUESDAY. HIGH WIND WATCHES ARE IN EFFECT FOR DAMAGING WINDS GUSTING AS
HIGH AS 80 MPH. THE VERNAL EQUINOX...ALSO KNOWN AS THE OFFICIAL START
OF SPRING... OCCURS TONIGHT...1135 PM PST...AS THE SUN MOVES NORTH
ACROSS THE EQUATOR.
...DISCUSSION...
AFTER TAKING INTO ACCOUNT MEDIUM RANGE MODEL GUIDANCE DID NOT HANDLE
THE DEVELOPMENT OF THE LOW CURRENTLY OVER THE CENTRAL UNITED STATES AND
WAVE LENGTH CONSIDERATIONS BETWEEN IT AND THE SHORT WAVE CURRENTLY
DROPPING SE THROUGH THE PACIFIC NORTHWEST STATES...A FURTHER EASTWARD
PROGRESSION AND STALLING OF THIS SHORT WAVE IS A MORE LIKELY SOLUTION
THAN CONTINUING TO DIG CLOSER TO SW CALIFORNIA. THIS IS WHAT THE
CANADIAN MODEL COMES UP WITH WHICH HAS BEEN CONSISTENTLY SHOWING A LOW
DEVELOPING IN THE VICINITY OF THE FOUR CORNERS REGION AND THEN REMAINING
QUASI-STATIONARY. SINCE THE HIGH WIND WATCH IS ALREADY UP AND NO ONE
KNOWS FOR CERTAIN WHAT THE EXACT TRACK WILL BE... PLAN TO MODIFY BY
DROPPING AND/OR DELAYING ONSET OF WINDS FOR LATE TONIGHT/MONDAY MORNING.
FOR THE COASTS AND THE MAJORITY OF THE INLAND VALLEYS...ANOTHER/SAME
COASTAL EDDY WILL BE THE CONTROLLING FACTOR. VAD WINDS FROM KNKX WSR-88D
AGAIN SHOW SE 20 KTS IN THE LOWER LAYERS BUT NOW ALL GREEN UP TO 11000
FEET...HOWEVER AM BEGINNING TO SUSPECT BIRD CONTAMINATION...POSSIBLY
SWALLOWS RETURNING. NONETHELESS ACARS WINDS GENERALLY SUPPORTIVE. THEY
EITHER SHOW LIGHT AND VARIABLE IN LOWER 15000 FEET OR IN CASE OF AN 0452
UTC FLIGHT NEAR KPSP...SE 10 KT OR LESS. SHORT TERM SATELLITE MOTION OF
CLOUDS HAS STRATUS PULLING AWAY FROM THE COAST...THE KAVX METAR DEWPOINT
WAS NEGATIVE SO THESE TWO FATORS WEIGH AGAINST A DEEP MARINE LAYER BUT
NOCTURNAL COOLING SHOULD SATURATE AIR MASS AND RETURN DENSE FOG TO THE
COASTS AND SAN DIEGO COUNTY VALLEYS THIS MORNING. ORIENTATION OF MID
LEVEL FLOW AND DEVELOPING SURFACE LOW LATER TODAY/TONIGHT IN THE
VICINITY OF S ARIZONA/NEW MEXICO WILL INCREASE/STRENGTHEN ONSHORE FLOW
THROUGH MONDAY ACROSS SW CALIFORNIA. THUS ANY MOUNTAIN WAVE ACTION
GENERATED BY THE STRONG NORTHERLY WINDS AROUND THE UPPER LOW WILL HAVE
A TOUGH TIME REACHING THE VALLEY FLOORS. THIS REASONING HOWEVER DOES NOT
HOLD FOR THE DESERTS AND/OR APPLE/YUCCA AND COACHELLA VALLEYS. NWSO SGX
LOCAL WIND SCHEME COMPUTES GUSTS NEAR 80 MPH FOR WIND PRONE AREAS. SINCE
LAST PRECIPITATION EVENT WAS ABOUT 10 DAYS AGO AND EVAPOTRANSPIRATION
HAS BEEN AT A MAXIMUM SINCE...ANTECEDENT GROUND CONDITIONS AND FUEL
MOISTURE POINT TO HIGH FIRE DANGER AS ANOTHER CONSIDERATION BELOW SNOW
MELT LINE IN THE MOUNTAINS AND BLOWING SAND/DUST ACROSS DESERTS/HIGH
VALLEYS.
IN THE MEDIUM RANGE ALL MODELS EVENTUALLY HAVE THE UPPER FOUR CORNERS
LOW RETROGRADING AND THIS MAY COME BACK TO AFFECT SW CALIFORNIA TOWARDS
THE END OF THE WEEK BY ENHANCING CONVECTION IN THE TROPICAL UPPER
TROPOSPHERIC TROUGH THAT IS PROGGED TO PHASE WITH A SHORT WAVE DROPPING
SOUTHEAST DOWN THE CALIFORNIA COAST THURSDAY. THIS IS DEPICTED IN THE
ECMWF SOLUTION AND HINTED AT BY THE OTHER MEDIUM RANGE MODELS. SPRING
MAY BE SPRUNG...BUT CHANCES OF PRECIPITATION WOULD BE OPTIMIZED FOR
SOUTHERN CALIFORNIA IF THIS COMES TO PASS.
SAN 000
.SAN...HIGH WIND WATCH MOUNTAINS/DESERTS/HIGH VALLEYS LATE TONIGHT
THROUGH MONDAY...AND DELAYED UNTIL MONDAY FOR COASTS AND REMAINDER
INLAND VALLEYS.
BALFOUR