Dense Fog in California, February 2 to 5, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
829 PM PST MON FEB 2 2015

.SYNOPSIS...
HIGH PRESSURE ALOFT WILL DOMINATE THE WEATHER ACROSS SOUTHERN
CALIFORNIA THIS WEEK WITH FAIR SKIES AND ABOVE AVERAGE TEMPERATURES.
THE RIDGE WILL STEER ANY PRECIPITATION TO THE NORTH THROUGH AT LEAST
NEXT WEEKEND. A SHALLOW MARINE LAYER WILL BRING AREAS OF NIGHT AND
MORNING LOW CLOUDS AND FOG WITHIN TEN MILES OF THE COAST THROUGH
MIDWEEK.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

SATELLITE IMAGERY IS SHOWING PATCHY LOW CLOUDS DEVELOPMENT OVER THE
COASTAL WATERS THIS EVENING BENEATH THE HIGHER CLOUDS. SURFACE OBS
NEAR THE COAST VERIFY THE LOWER CLOUD DEVELOPMENT...ALONG WITH SOME
VISIBILITY REDUCTION. SURFACE PRESSURE GRADIENTS REMAINED WEAK
OFFSHORE FROM THE NE...AND WEAK ONSHORE TO THE EAST. 24-HOUR TRENDS
WERE WEAK AS WELL. THE 00Z MIRAMAR SOUNDING HAD LIGHT NORTH WINDS
BELOW 5K FT...AND WEAK NE ABOVE THROUGH 9K FT.

THE MAIN FORECAST ISSUE IN THE NEAR TERM WILL BE THE DEVELOPMENT OF
THE LOW CLOUDS AND FOG. SURFACE DEWPOINTS HAVE RISEN INTO THE LOWER
AND MIDDLE 50S ALONG THE COAST...EXTENDING SEVERAL MILES INLAND...
AND ASSOCIATED CLOUDS HAD COME IN WITH 700 FT BASES. THESE WILL
LIKELY LOWER OVERNIGHT. AS WEAK DRAINAGE WINDS DEVELOP...ANY FOG/LOW
CLOUDS MAY DRIFT BACK TOWARD...OR OFF THE COAST BY DAWN AS INDICATED
BY THE 00Z LOCAL WRFEMS. THIS SCENARIO SUGGESTS THE POSSIBILITY OF
SEVERAL HOURS OF COASTAL DENSE FOG LATE TONIGHT. WEAK GRADIENTS AND
HIGH PRESSURE ALOFT WILL SET THE STAGE FOR MORE OF THESE GAMES WITH
THE MARINE LAYER OVER THE NEXT COUPLE OF NIGHTS.

CONDITIONS WILL BE MONITORED CLOSELY. IF THE SURFACE DRAINAGE WINDS
AND THE NORTHERLY DRIFT IN THE BOUNDARY LAYER DO NOT OVERWHELM THE
SHALLOW MOIST LAYER EARLY ENOUGH...A DENSE FOG ADVISORY MAY BE
NEEDED ALONG THE COASTAL STRIP OVERNIGHT.

ASIDE FROM THE SHALLOW MARINE LAYER...THERE IS NOT MUCH WEATHER TO
DISCUSS. A BROAD RIDGE OF HIGH PRESSURE ALOFT...WILL REMAIN OVER THE
SW THROUGH NEXT WEEKEND KEEPING WINDS LIGHT AND TEMPERATURES ABOVE
AVERAGE. MOISTURE MOVING IN OFF THE EASTPAC ON SHORTWAVES WILL BE
SHUNTED OVER NORTHERN PORTIONS OF THE STATE AS THE RIDGE HOLDS.
MODELS SHOW THE RIDGE MORPHING BACK INTO A REX BLOCK AGAIN NEXT
WEEK. THE ASSOCIATED CUT-OFF LOW AND STRONGER SURFACE HIGH PRESSURE
OVER THE GREAT BASIN MAY TEAM UP TO CREATE ANOTHER ROUND OF SANTA
ANA CONDITIONS  BY THE MIDDLE OF THE WEEK. IN ANY CASE...THERE IS NO
SIGN OF ANY SIGNIFICANT PRECIPITATION OCCURRING OVER SOCAL THROUGH
MID FEBRUARY.

&&

.AVIATION...
030800Z...COAST...PATCHY LOW CLOUDS AND FOG WILL OCCUR THROUGH 17Z
OVER COASTAL PORTIONS OF ORANGE AND SAN DIEGO COUNTIES. LOCAL VIS
MAY FALL BELOW 1 SM AT TIMES...BUT EXPECT TAF SITES TO REMAIN
PRIMARILY 3 SM AND ABOVE THROUGH 17Z. CLOUD BASES WILL HOVER BETWEEN
400 AND 700 FT MSL AND CLOUD TOPS WILL RANGE FROM 700 TO 1000 FT
MSL. OVERALL CONFIDENCE IN LOW CLOUD/FOG DEVELOPMENT...COVERAGE...
AND PLACEMENT IS LOW. AFTER 17Z...FEW AOA 20000 AND UNRESTRICTED VIS
WILL PREVAIL INTO TUESDAY EVENING...WITH LOW CLOUDS/FOG POTENTIALLY
RETURNING TO THE COAST AFTER 03Z WEDNESDAY.

VALLEYS/MTNS/DESERTS...UNRESTRICTED VIS AND FEW CLOUDS AOA 20000 FT
MSL THROUGH TUESDAY EVENING.

&&

.MARINE...
800 PM...PATCHY DENSE FOG...WITH VISIBILITIES FALLING TO 1 NM OR
LESS...WILL BE POSSIBLE INTO TUESDAY MORNING OVER THE COASTAL
WATERS. OTHERWISE...NO HAZARDOUS MARINE WEATHER IS EXPECTED THOUGH
FRIDAY EVENING.

&&

CLIMATE...
THE RECORD WARM YEAR OF 2014 WAS FOLLOWED BY A VERY WARM START TO
THE NEW YEAR. JANUARY 2015 WAS ONE OF THE WARMEST JANUARY'S ON
RECORD AT SEVERAL LOCATIONS.

JANUARY 2015 WAS THE 8TH WARMEST JANUARY ON RECORD AT SAN DIEGO'S
LINDBERGH FIELD WITH AN AVERAGE TEMPERATURE OF 60.8. THE RECORD IS
61.7 SET IN 2003.

JANUARY 2015 WAS THE 5TH WARMEST JANUARY ON RECORD AT ALL OF THE
FOLLOWING STATIONS:

RIVERSIDE......58.8 (RECORD IS 61.9 SET IN 2003)
SANTA ANA......62.1 (RECORD IS 64.3 SET IN 2003)
PALM SPRINGS...62.3 (RECORD IS 66.1 SET IN 2003)
BIG BEAR.......38.2 (RECORD IS 41.8 SET IN 1986)

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

PUBLIC...JAD
AVIATION/MARINE...BA
CLIMATE...MOEDE