EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 300 AM PST TUE MAR 7 2000
...SYNOPSIS...
SKIES WILL BE PARTLY CLOUDY TODAY WITH A CHANCE OF SHOWERS OVER
SOUTHERN COASTAL AREAS IN THE MORNING...AND OVER THE MOUNTAINS ALL
DAY. THE LATEST IN THE SERIES OF PACIFIC STORMS TO IMPACT CALIFORNIA
WILL MOVE TO NEAR THE NORTHERN CALIFORNIA COAST BY THURSDAY MORNING.
THIS WILL BRING ANOTHER ROUND OF RAIN AND MOUNTAIN SNOW TO SOUTHWEST
CALIFORNIA LATE TONIGHT AND WEDNESDAY WITH A SECOND ROUND LATE
WEDNESDAY NIGHT AND THURSDAY. SOME DRYING IS POSSIBLE FRIDAY WITH
MORE RAIN POSSIBLE SATURDAY OR SUNDAY.
...DISCUSSION...
AVN HAS BEEN THE CONSISTENT MDL OF CHOICE THE PAST THREE WEEKS OR SO
WITH STORMS AFFECTING SW CA AND WL BE FOLLOWED AGAIN IN THE SHORT
TERM. AVN KPS ONE AREA OF LWR LVL MSTR AND ASSOCD SHOWERS MOSTLY S OF
THE FORECAST AREA TODAY WITH A SECOND AREA OF LOW LVL MSTR ALG THE
CNTRL CST GRADUALLY EXPANDING SOUTHWARD AND EASTWARD TODAY. A FEW
SHOWERS ARE POSSIBLE TODAY OVR THE HIGHER TERRAIN...ESPECIALLY NRN
RANGES...BY LATE AFTERNOON AS CENTRAL CST MSTR SPREADS INTO NRN
RANGES LATE IN THE DAY AND IS LIFTED OROGRAPHICALLY AS SW LOW LVL
FLOW GRADUALLY INCREASES. NKX 88D VAD WINDS AND ACARS SOUNDINGS SHOW
A WK WARM ADVECTION PATTERN AT LOW LVLS THIS EARLY MORNING. IN
COMBINATION WITH RESIDUAL LOW LCL MSTR...LIGHT SHOWERS HAVE
DEVELOPED OVR THE IMMEDIATE CSTL WTRS...MOVG ONSHR INTO SRN CSTL
SXNS. WITH FOG PRODUCT SHOWING ENHANCEMENT IN THE LOW CLOUD FIELD
JUST OFF THE CST FM SRN LOS ANGELES COUNTY S...HAVE ADDED
CHANCE/SLIGHT CHANCE POPS FOR CST/VLYS THIS MORNING AND KEPT
CHANCE/SLIGHT CHANCE POPS FOR THE MTNS ALL DAY. SHORT WAVE RDGG ALG
SHOULD PUT AN END TO SHOWERS FOR CST/VLYS BY AFTERNOON...BUT A FEW
SHOWERS COULD LINGER IN THE MTNS ALL DAY.
AREA OF RAIN AND MTN SNOW SHOULD SPREAD SOUTHEASTWARD ACROSS SRN CA
TONIGHT PER AVN 850 MB RH...REACHING ORANGE COUNTY AROUND 06Z AND
SAN COUNTY BY 12Z. SHOWERS SHOULD LINGER WED AFTERNOON WITH ANOTHER
ROUND OF RAIN AND MTN SNOW FOR LATE WED NIGHT AND THU...AGAIN PER
AVN 850 MB RH. SNOW LVLS WL NOT BE AS LOW AS DURG THE PAST TWO
DAYS...GENERALLY 4500 TO 5000 FEET...LCL 4000 FEET TONIGHT AND
WEDNESDAY. RHEA OROGRAPHIC QPF GUIDANCE FROM THE AVN LOOKS
REASONABLE FOR NRN RANGES...A LTL HIGH FOR SRN RANGES. THIS COULD
RESULT IN SNOWFALL IN THE ADV...BORDERLINE WARNING AMOUNTS ABV 5000
FEET LATE TONIGHT AND WEDNESDAY. DAY SHIFT MAY WANT TO ISSUE A SNOW
ADV FOR SOME MTN AREAS... ESPECIALLY NRN RANGES...FOR TONIGHT AND
WED.
EXTENDED...WHILE MDLS WANT TO BUILD HEIGHTS SOME OVR SRN CA DURG THE
WEEKEND...IT SHOULD BE NOTED THAT MDLS TRIED TO DO THAT TWO WEEKS OR
SO AGO. THAT TIME...THE MDLS WERE BUILDING RDGG INTO SRN CA EVEN
MORE STRONGLY THAN AT PRESENT WITH THE MDLS ADVERTISING A SHIFT OF
THE STORM TRACK N INTO THE PAC NW. IN REALITY...THE TRACK SHIFTED NORTH
ONLY INTO NRN AND CNTRL CA. IN THAT CASE...WHEN THE EXTENDED MDLS
WERE ADVERTISING THE GREATEST NORTHWARD SHIFT OF THE STORM TRACK...A
NEW RUN OF THE AVN WAS STRONGER AND FARTHER S WITH ONE IN THE SERIES
OF STORMS MOVG ACROSS THE ERN PAC. THIS PORTENDED A LESSER SHIFT OF
THE STORM TRACK TO THE N (NRN AND CNTRL CA VERSUS THE PAC NW).
TONIGHT'S AVN IS STRONGER WITH THE SHORTWAVE ALG 140 W AT 72 HOURS
(00Z FRI) THAN PREVIOUS MDL RUNS. THIS MAY WELL PORTEND LESS
BUILDING OF HEIGHTS OVR SRN CA FOR THE WEEKEND. HENCE...HAVE DOUBTS
THAT WEEKEND WL BE ENTIRELY DRY WITH AT LEAST SOME RETURN OF RAIN...
THOUGH NOT NECESSARILY HVY...BY SAT OR SUN.
SAN 468
.SAN...NONE.
MARTIN