Rip Current and High Surf in California, February 13, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
331 AM PST SAT FEB 13 2010

.DISCUSSION...AS OF 3:00 AM PST SATURDAY...GENERALLY DRY THE NEXT
SEVEN DAYS WITH THE MAIN FORECAST CHALLENGE REVOLVING AROUND FOG.
POSSIBLE PATTERN CHANGE AFTER NEXT WEEK.

ALTHOUGH A FEW SPRINKLES WERE RECORDED EARLY THIS MORNING RADAR
RETURNS HAVE BEEN VIRTUALLY NIL AND ALL SIGNS POINT TO A DRY DAY
TODAY AS A RIDGE OF HIGH PRESSURE STARTS TO BUILD OVER THE WEST
COAST. SATELLITE FOG PRODUCT DOES SHOW POSSIBLE PATCHY FOG OVER THE
SALINAS VALLEY AND INTO THE MONTEREY BAY. SURFACE OBS DO BRING SOME
CREDENCE TO THIS AS MONTEREY DROPPED DOWN TO 1/4 MILE A COUPLE OF
HOURS AGO. KSTS HAS ALSO DROPPED TO UNDER A MILE. WOULD EXPECT
REPORTS OF FOG OVER THE NORTH AND EAST BAY DURING THE MORNING HOURS
ALTHOUGH WIDESPREAD FOG IS NOT ANTICIPATED. HIGHS WILL IN MANY CASES
BE A FEW DEGREES WARMER TODAY COMPARED TO YESTERDAY AS HEIGHTS RISE
AND 850MB TEMPS GO UP 1-2C. EXPECT MOSTLY UPPER 50S TO UPPER 60S WITH
LOWER 70S POSSIBLE OVER INLAND SPOTS IN THE SOUTHERN THIRD OF THE
CWA.

MODELS CONTINUE TO BE IN GOOD AGREEMENT FOR THE FIRST HALF OF NEXT
WEEK. THEY DEPICT A RIDGE ALTERNATING BETWEEN THE WEST COAST AND THE
ROCKIES WITH THE STORM TRACK SHIFTED WELL TO THE NORTH OF OUR
AREA. PRECIPITATION LOOKS VERY UNLIKELY WITH THIS TYPE OF PATTERN
WITH ONLY THE FAR NORTHERN PORTION OF THE CWA UNDER THE GUN FOR
SOME LIGHT RAIN AS THE SOUTHERN END OF FRONTS ATTEMPT TO BREAK
DOWN THE RIDGE. 20-30 POPS WERE LEFT IN FOR A FEW PERIODS...
ALTHOUGH ANY RAINFALL LOOKS EXTREMELY LIGHT. BIGGER STORY WILL BE THE
FOG WHICH MAY BECOME MORE WIDESPREAD DUE TO THE PERSISTENCE OF THE
RIDGE. PLENTY OF BOUNDARY LAYER RH COMBINED WITH LIGHT WINDS
OVERNIGHT SHOULD PRODUCE AREAS OF FOG IN THE FAVORED REGIONS PLUS
EVEN DOWN THROUGH THE SANTA CLARA VALLEY. THIS COULD ALSO BE A SETUP
WHERE ENOUGH MIXING OCCURS OVER THE NORTH BAY DUE TO WEAK FRONTAL
PASSAGES THAT THEY END UP GETTING LESS FOG THAN OTHER AREAS. HIGHS
WILL MOSTLY BE IN THE UPPER 50S TO MID 60S WITH LOWS IN THE 40S.

ALTHOUGH LOOKING MORE THAN 7 DAYS OUT CAN BE TRICKY AND OFTEN WITH
MUCH LESS ACCURACY...A POTENTIAL PATTERN CHANGE IS WORTH NOTING AS
THE OPERATIONAL RUNS OF THE GFS/GEM/ECMWF ALL SHOW A RETURN TO A MORE
ZONAL FLOW AS ENERGY FROM WELL OUT IN THE PACIFIC BREAKS THROUGH THE
RIDGE AND MOVES TO OUR AREA. WHAT IS ALSO NOTABLE ABOUT THIS IS THE
MJO HAD UNTIL THE PAST DAY BEEN IN THE FAVORABLE 6 AND 7 REGIONS
WHICH WOULD SUGGEST ENERGY MAKING IT HERE A WEEK OR SO DOWN THE ROAD.
IN ADDITION THE ECMWF ENSEMBLES OUT FOR THE END OF NEXT WEEK BEGIN TO
SHOW A LARGE SPREAD INDICATING THE MODELS ARE PICKING UP ON THE
POTENTIAL TRANSITION. IF...AND THIS IS A BIG IF...THIS PATTERN CHANGE
DOES OCCUR...IT WOULD MEAN A RETURN TO MUCH WETTER WEATHER FOR THE
FINAL FULL WEEK OF FEBRUARY WITH MULTIPLE SYSTEMS ABLE TO MOVE INTO
THE AREA. WE WILL CONTINUE TO KEEP A CLOSE EYE ON THIS AND ANY
POTENTIAL HYDROLOGIC IMPACTS THAT THIS COULD LEAD TO.
&&

.AVIATION...AS OF 3:30AM PST SATURDAY...AMPLE LOW LEVEL MOISTURE
WITH HIGH PRESSURE BUILDING OVERHEAD WILL HELP TO PRODUCE LOWER CIGS
AND SOME PATCHY FOG.  CIGS GENERALLY IN THE MVFR TO IFR RANGE...WITH
POCKETS OF LIFR.  BURN OFF WILL BE SOMEWHAT SLOW GIVE SUN ANGLE AND
HIGH LEVEL CLOUDS.

VICINITY OF KSFO...RECENT TRENDS THIS MORNING SHOW A DEVELOPING
STRATUS LAYER OVER THE BAY.  LOOKS LIKE IT COULD IMPACT KSFO CLOSE
TO 1K FT. THEREFORE...TEMPO OVC010 WILL BE USED THROUGH 16Z.

KSFO BRIDGE APPROACH...CIGS CLOSE TO 1K FEET WILL LIKELY PERSIST
THROUGH THE MORNING HOURS.

MRY BAY AREA TERMINALS...TRANSIENT FOG AND LOW CLOUDS WILL CAUSE
PROBLEMS AROUND MRY BAY.  IN FACT...KSNS IS ACTUALLY REPORTING VIS
BELOW 1 MILE. WILL KEEP IFR TO LIFR CONDITIONS THROUGH THE MORNING
HOURS.  LESS CERTAIN FOR CIGS/VIS AT KMRY.

&&

.MARINE...AS OF 3:00 AM PST SATURDAY...ENP CONTINUES TO SHOW
SWELLS OF UP TO 18 FEET HITTING THE COAST THROUGH TONIGHT WITH
PERIODS OF 16 TO 17 SECONDS SO THE HIGH SURF ADVISORY (SFOCFWMTR) WAS
CONTINUED.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...ALL COASTAL WATERS
          ...SCA FOR ROUGH BAR
          ...HIGH SURF ADVISORY...MOST COASTAL ZONES

PUBLIC FORECAST: BELL
AVIATION/MARINE: MEHLE/BELL

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO