Dense Fog in California, December 22 to 25, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
300 AM PST FRI DEC 22 2006

.SHORT TERM...FOR THE CENTRAL CALIFORNIA INTERIOR...SATELLITE AND
RADAR LOOPS SHOW THE BACK EDGE OF THE FRONTAL BAND MOVING THROUGH
THE HANFORD WARNING/FORECAST AREA...WITH PRECIPITATION ENDING FROM
THE NORTHWEST. THE STORM DUG A BIT DEEPER THAN EXPECTED...BRINGING
MODERATE RAIN AS FAR SOUTH AS LOST HILLS. RAINFALL AMOUNTS IN THE
CENTRAL AND SOUTHERN SAN JOAQUIN VALLEY AS OF 08Z /MIDNIGHT/ RANGED
FROM 0.01 INCH AT BAKERSFIELD TO 0.46 INCH AT MERCED AIRPORT /KMCE/.
FRESNO/S RAINFALL FOR THE 21ST WAS 0.35 INCH. THE DECEMBER RAINFALL
AT FRESNO YOSEMITE INTERNATIONAL AIRPORT THROUGH THE 20TH WAS ONLY
0.48 INCH.

RADAR LOOPS SHOWED THE PRECIPITATION ENDING OVER YOSEMITE NATIONAL
PARK AT 09Z...WITH DECREASING ACTIVITY OVER THE FRESNO AND MADERA
COUNTY MOUNTAINS. WILL DROP THE SNOW ADVISORY FOR THAT AREA.

THE 00Z/06Z MODELS ARE IN GOOD AGREEMENT WITH THE UPPER-LEVEL TROUGH
MOVING EAST OF CALIFORNIA THIS MORNING...WITH AN UPPER-LEVEL RIDGE
BUILDING INTO THE STATE BEHIND IT. THE FORECAST PROBLEM THIS MORNING
WILL BE LOW CLOUDS BANKED ALONG THE EAST SIDE AND SOUTH END OF THE
SAN JOAQUIN VALLEY...PUSHING INTO THE SIERRA NEVADA FOOTHILLS AND
ONTO THE NORTH SLOPES OF THE TEHACHAPI MOUNTAINS.

FOR TONIGHT...LOW-LEVEL MOISTURE LIKELY WILL BE SUFFICIENT TO KEEP
MOST CENTRAL AND SOUTHERN SAN JOAQUIN VALLEY AREAS ABOVE FREEZING
DUE TO HIGHER DEW POINTS. THIS ALSO WILL LEAD TO THE POTENTIAL FOR
THE DEVELOPMENT OF AREAS OF DENSE FOG...LINGERING WELL INTO SATURDAY
MORNING.

THE MODELS CONTINUE TO FORECAST A WEAK SHORT-WAVE TO MOVE THROUGH
THE PACIFIC NORTHWEST SATURDAY AFTERNOON...FLATTENING THE RIDGE. AS
THE SHORT-WAVE MOVES INTO IDAHO SATURDAY NIGHT...AND A DEEPER TROUGH
DIGS ALONG 140W IN THE EAST PACIFIC...THE RIDGE WILL REBUILD OVER
CALIFORNIA FOR ANOTHER NIGHT OF VALLEY FOG. OTHERWISE...DRY WEATHER
WILL PREVAIL THROUGH THE PERIOD.

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...THE UPPER RIDGE OVER
CALIFORNIA FLATTENS SUNDAY NIGHT AS A LOW PRESSURE SYSTEM MOVES INTO
THE PACIFIC NORTHWEST. ZONAL FLOW WILL BRING THE ASSOCIATED FRONT
AND MOISTURE OVER NORTH CALIFORNIA MONDAY. EXPECT A MINIMAL THREAT
OF PRECIPITATION MONDAY IN CENTRAL CALIFORNIA AS THE BEST THREAT OF
PRECIPITATION SHOULD REMAIN IN NORTH CALIFORNIA NEAR THE STALLED
FRONT. ANOTHER PACIFIC STORM SYSTEM QUICKLY FOLLOWS INTO OREGON AND
NORTH CAL TUESDAY. MOST OF THE MODELS INDICATE THE UPPER TROUGH WILL
DIG FURTHER SOUTH INTO THE CENTRAL CALIFORNIA AREA. ALTHOUGH THIS
SYSTEM IS FAST MOVING BOTH EURO AND GFS MODELS BRING SUFFICIENT
MOISTURE INTO THE CENTRAL CALIFORNIA. HENCE MAY NEED TO INCREASE THE
THREAT OF PRECIPITATION FOR TUESDAY. DRY THEREAFTER WITH A THREAT OF
TULE FOG IN THE SAN JOAQUIN VALLEY AS AN THE UPPER RIDGE BUILDS BACK
OVER THE AREA. TEMPERATURES DO NOT VENTURE TO FAR AWAY FROM CLIMO,
SO WENT WITH THE BIAS CORRECTED GRID VALUES AND ONLY MADE SOME MINOR
ADJUSTMENTS TO CURRENT TEMP FORECAST.

&&

.AVIATION...MVFR CONDITIONS IN THE SAN JOAQUIN VALLEY MAINLY DUE TO
LOW CLOUDS THROUGH 02Z...VISIBILITIES DECREASING AFTER 08Z SATURDAY
TO MVFR LEVELS WITH LCL IFR DUE TO MIST AND FOG. UPSLOPE CLOUDS
PROVIDING MOUNTAIN OBSCURATIONS UNTIL 02Z SATURDAY OVER THE
TEHACHAPI MOUNTAINS AND SIERRA FOOTHILLS. OTHERWISE VFR CONDITIONS
REMAINING IN THE KERN COUNTY DESERTS THROUGH 12Z SATURDAY.
FOR SPECIFIC DETAILS...PLEASE REFER TO THE TAFS FOR
KMCE...KFAT AND KBFL...AND TWEB ROUTES 421 AND 423.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

WEATHER.GOV/HANFORD

SANGER/VASQUEZ