Flood in California, December 20 to 21, 2002

NORTHWEST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE EUREKA CA
830 PM PST FRI DEC 20 2002

RADAR PROBLEMS SEEM TO HAVE SETTLED DOWN FOR NOW. NEW MODEL RUNS
TAKE SYSTEM NEAR 35N 130W SOUTHEASTWARD TOWARDS CENTRAL CALIFORNIA.
THIS IS REFLECTED IN THE CURRENT SATELLITE IMAGES. AIR MASS OVER THE
AREA WILL BE STABLIZING AS A RIDGE DEVELOPS OVER THE NORTHEAST
PACIFIC. GOES SOUNDINGS SHOW LIFTED INDICES GREATER THAN 10 IN THE
UP STREAM AIR SO SHOWERS WILL BE ON DECREASE LATER TONIGHT AND INTO
SATURDAY. THE CURRENT PRECIPITATION FORECAST FOR SATURDAY MAY HAVE
TO BE TAKEN DOWN A LITTLE. IN THE MARINE...SWELL HAS BEGUN TO EASE
AS PER FORECAST SO HAVE ADJUSTED THE WORDING TO REFLECT IT. NO MAJOR
CHANGES PLANNED. LOVEGROVE

.PREVIOUS DISCUSSION...

.SHORT TERM...
CATEGORICAL POPS FOR SHOWERS WILL CONTINUE OVERNIGHT IN DEEP
WESTERLY FLOW...ALTHOUGH OVERALL DYNAMICS WILL WEAKEN AFTER 06Z AS
UPPER JET CONTINUES TO SAG SOUTHWARD AND SURFACE LOW FILLS. WEAK
OFFSHORE BOUNDARY LOSES ITS DEFINITION BY 12Z SAT WITH EVENTUAL
SHEARED UPPER TROF PASSAGE AROUND 21Z. SHOWERS SHOULD DIMINISH IN
COVERAGE/INTENSITY DURING SAT...ALTHOUGH AIR ALOFT WILL REMAIN COLD
ENOUGH FOR SCATTERED COVERAGE INTO SAT NIGHT...ESPECIALLY NORTH.
SNOW LEVELS WILL FLUCTUATE LATE TONIGHT THRU SAT NIGHT...AND PERHAPS
FALL DOWN TO 2000FT IN ZONE 4 AGAIN AND WILL INSERT A FEW INCHES OF
ACCUMULATION THERE IN SNOW SHOWERS. MODELS FAIRLY CONSISTENT IN
BRINGING IN RIDGE OVER NW CA BY EARLY SUN THROUGH MON AS SPLIT FLOW
ACROSS EASTERN PACIFIC FOCUSES ENERGY OVER SOCAL FOR AWHILE. DRY
FORECAST WILL REMAIN INTACT WITH TEMPERATURES CREEPING BACK TO
SEASONAL NORMALS.

.LONG TERM...
12Z AVN CONTINUES RECENT TREND OF AVN/GFS MODEL RUNS IN BEING
FASTEST TO BRING NEXT EASTERN PACIFIC TROF TO COAST BY 12Z TUE.
CANADIAN AND ESPECIALLY NOGAPS ARE SLOWER WITH NATIONAL 6-10 DAY
GUIDANCE INDICATING BELOW AVERAGE CONFIDENCE IN THIS TIME-FRAME.
BASED ON COORDINATION...WILL BEGIN CHANCE POPS EARLY TUE AND
CONTINUE THRU FRIDAY. LATEST INDICATIONS AND ENSEMBLE MEANS FAVOR
THE FIRST SHOT SLIDING SOUTHWARD ALONG THE COAST...AS IS PLAUSIBLE
UNDER THE SPLIT FLOW. THEREAFTER...CONSENSUS IS TO FLATTEN FLOW AND
AIM PACIFIC ZONAL JET INTO NW CA FOR A FEW DAYS AT THE END OF NEXT
WEEK. EVENTS FOR MID/LATE NEXT WEEK DO NOT CONTAIN HUGE AMOUNTS OF
TROPICAL MOISTURE...AND UPPER JET STRENGTH IS MODERATE FOR THIS TIME
OF YEAR. TRAJECTORY WOULD BRING SNOW LEVELS DOWN TO LOCAL PASS
LEVELS...BUT NOT OUTRAGEOUSLY LOW. THEREFORE...HOLIDAY WEATHER
LOOKING INCLEMENT/YET NOT AS INTENSE AS RECENT DAYS.

POPS CEC 8751 ACV/EKA 8740 UKI 8630

SOROKA

.EKA...SMALL CRAFT ADVISORY PT ST GEORGE TO CAPE MENDOCINO 0-60 NM.
    ...HIGH SURF ADVISORY...CAZ001-002
    ...WINTER STORM WARNING...ABOVE 3000FT...CAZ003-004

CAZ001>004-076-201800-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE EUREKA CA
500 AM PST FRI DEC 20 2002

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHWEST CALIFORNIA

.DAY ONE...TODAY

...WINTER STORM WARNING ABOVE 3000 FEET FOR DEL NORTE...HUMBOLDT
...TRINITY AND MENDOCINO COUNTIES THROUGH LATE TONIGHT...
SEE SFOWSWEKA FOR DETAILS

...WIND ADVISORY FOR THE REDWOOD COAST THROUGH MIDDAY...

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED.

.INSTRUCTIONS TO SPOTTERS...
WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.