Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 170345
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
845 PM PDT THU APR 16 2015

.SYNOPSIS...HIGH PRESSURE WILL MAINTAIN WARM AND DRY CONDITIONS
THROUGH FRIDAY. A LONG PERIOD OCEAN SWELL WILL RESULT IN HAZARDOUS
BEACH CONDITIONS THROUGH FRIDAY. COOLER WEATHER IS EXPECTED OVER
THE WEEKEND AS A MARINE LAYER REDEVELOPS AND ONSHORE FLOW
STRENGTHENS. FOR NEXT WEEK...AN UPPER LEVEL DISTURBANCE WILL BRING
THE POSSIBILITY OF SHOWERS BEGINNING ABOUT TUESDAY.

&&

.DISCUSSION...AS OF 8:45 PM PDT THURSDAY...AN UPPER LEVEL RIDGE
STRENGTHENED OVER CALIFORNIA TODAY AND LIGHT OFFSHORE FLOW
PERSISTED THROUGH THE EARLY AFTERNOON HOURS. THE RESULT WAS A WARM
DAY ACROSS OUR ENTIRE REGION WITH AFTERNOON HIGHS MOSTLY RANGING
FROM THE MID 70S TO MID 80S...ABOUT 10 TO 15 DEGREES WARMER THAN
NORMAL FOR MID-APRIL. A FEW LOCATIONS CAME CLOSE TO THEIR DAILY
HIGH TEMPERATURE RECORDS...BUT IN THE END NO RECORDS WERE TIED OR
SET TODAY.

LITTLE CHANGE IS EXPECTED IN THE STRENGTH AND POSITION OF THE
UPPER RIDGE INTO FRIDAY. THIS WILL MEAN CONTINUED WARM CONDITIONS
ACROSS INLAND AREAS. HOWEVER...A WEAK SHORTWAVE TROUGH GLIDING
OVER THE TOP OF THE RIDGE AND INTO THE PAC NW WILL TRIGGER AN
INCREASE IN ONSHORE FLOW WHICH WILL RESULT IN SLIGHT COASTAL
COOLING TOMORROW. THE SHORTWAVE IS THEN FORECAST TO DROP SOUTH
OVER CA DURING THE WEEKEND AS THE UPPER RIDGE AXIS RETREATS
OFFSHORE. THIS WILL RESULT IN A COOLING TREND ACROSS THE ENTIRE
REGION OVER THE WEEKEND. HOWEVER...THE MAGNITUDE OF THIS COOLING
IS EXPECTED TO BE MODEST FOR INLAND AREAS AND TEMPERATURES THERE
ARE FORECAST REMAIN ABOVE NORMAL THROUGH SUNDAY. PERSISTENT
ONSHORE FLOW BEGINNING LATE TOMORROW SHOULD RESULT IN THE
DEVELOPMENT OF A MARINE LAYER BY LATE FRIDAY NIGHT...AND SO WE CAN
EXPECT AT LEAST PATCHY NIGHT AND MORNING LOW CLOUDS AND FOG IN
COASTAL AREAS OVER THE WEEKEND.

A WEAK UPPER LOW IS FORECAST TO DEVELOP OFF THE CENTRAL CA COAST
BY LATE SUNDAY OR MONDAY. SOME RECENT MODEL RUNS HAVE INDICATED
THAT THIS LOW WOULD TRIGGER ISOLATED SHOWER/THUNDERSTORM ACTIVITY
OVER THE SOUTHERN PORTION OF OUR AREA AS EARLY AS MONDAY.
HOWEVER...MODEL CONSENSUS AT THIS POINT INDICATES THAT THERE WILL
NOT YET BE SUFFICIENT MOISTURE AND INSTABILITY FOR CONVECTIVE
PRECIP ON MONDAY. WILL WAIT FOR ALL 00Z MODEL DATA BEFORE DECIDING
IF SLIGHT SHOWER/THUNDERSTORM CHANCES NEED TO BE ADDED FOR MONDAY.
PRECIPITATION CHANCES INCREASE BY TUESDAY AS AN UPPER TROUGH
APPROACHES FROM THE NORTHWEST. THIS TROUGH IS THEN FORECAST TO
FORM A CUTOFF LOW SOMEWHERE OVER OR NEAR CENTRAL/SOUTHERN CA BY
MIDWEEK. ALTHOUGH THIS SYSTEM WILL BE SHORT ON MOISTURE...THERE
SHOULD BE MORE THEN ENOUGH INSTABILITY FOR SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS FROM LATE TUESDAY THROUGH WEDNESDAY NIGHT.
CONFIDENCE IN THE FORECAST FOR THIS TIME PERIOD REMAINS RELATIVELY
LOW GIVEN DIFFERENCES IN THE MODELS AND THE FACT THAT CUTOFF LOWS
ARE DIFFICULT TO PREDICT...PARTICULARLY DURING THE SPRING MONTHS.

&&

.AVIATION...AS OF 5:00 PM PDT THURSDAY...HIGH PRESSURE WILL
MAINTAIN CLEAR SKIES ACROSS AREA TERMINALS THROUGH THE FORECAST
PERIOD. MODERATE WINDS WILL EASE OVERNIGHT BECOMING LIGHT AND
LOCALLY VARIABLE.

VICINITY OF KSFO...VFR. MODERATE SEA BREEZE WILL EASE THIS EVENING
BECOMING LIGHT OVERNIGHT.

HIGH CONFIDENCE.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR. MODERATE SEA BREEZE WILL EASE
THIS EVENING BECOMING LIGHT OVERNIGHT.

HIGH CONFIDENCE.

&&

...BEACH HAZARD STATEMENT IN EFFECT THROUGH FRIDAY EVENING...

.BEACHES...AS OF 2:40 PM PDT THURSDAY...A HIGH ENERGY/LONG PERIOD
WESTERLY SWELL TRAIN IS EXPECTED TO ARRIVE TO THE COAST THIS
EVENING. THE 2:00 PM BUOY OBSERVATION FROM BUOY 46014 LOCATED JUST
NORTH OF PT ARENA IS REPORTING AN 8 FOOT SWELL WITH A DOMINANT
PERIOD OF 21 SECONDS...INDICATING THAT THE SWELL IS JUST A FEW
HOURS AWAY. THESE FAST MOVING LONG PERIOD WAVES WILL ARRIVE DURING
A PERIOD OF LIGHT OFFSHORE WINDS PROMOTING GLASSY WAVE CONDITIONS
SUPPORTIVE OF LARGE BREAKING WAVES. THESE STRONG WAVES WILL
PROMOTE HAZARDOUS BEACH CONDITIONS INCLUDING STRONG RIP
CURRENTS...LARGE SURF AND SNEAKER WAVES.

VISITORS/DIVERS/SURFERS HEADING TO THE BEACH SHOULD REMAIN ALERT
FOR RAPIDLY CHANGING SEA CONDITIONS. FISHERMEN SHOULD AVOID
FISHING FROM ROCKS AND JETTIES AND BEACH VISITORS SHOULD REFRAIN
FROM CLIMBING ON ROCKS OR VISITING STEEP BEACHES. NEVER TURN YOUR
BACK TO THE OCEAN WHEN VISITING THE BEACH. IF YOU SEE SOMEONE
BEING WASHED INTO THE OCEAN BY A WAVE DO NOT ATTEMPT TO RESCUE
THEM ON YOUR OWN...YOU COULD BECOME A VICTIM YOURSELF. INSTEAD CALL
911 IMMEDIATELY FOR ASSISTANCE AND KEEP A CLOSE EYE ON THE VICTIM
UNTIL HELP ARRIVES.

&&

.CLIMATE...RECORD HIGH TEMPERATURES FOR FRIDAY (4/17)
ALONG WITH THE MOST RECENT DATE IT OCCURRED.

SF BAY AREA
.LOCATION.................4/17
 KENTFIELD...............89/1999
 SAN RAFAEL..............88/1954
 NAPA....................88/1954
 SAN FRANCISCO...........79/1954
 SFO AIRPORT.............82/1954
 OAKLAND (DOWNTOWN)......78/1977
 OAKLAND AIRPORT.........87/1954
 RICHMOND................86/1954
 LIVERMORE...............90/1966
 MOFFETT FIELD...........83/1954
 SAN JOSE................92/1999
 GILROY..................92/1999

MONTEREY BAY AREA
.LOCATION.................4/17
 MONTEREY................80/1952
 SANTA CRUZ..............84/1938
 SALINAS.................81/1999
 SALINAS AIRPORT.........87/1952
 KING CITY...............98/1954

&&

.MARINE...AS OF 02:25 PM PDT THURSDAY...A WEAK SURFACE PRESSURE
GRADIENT WILL MAINTAIN GENERALLY LIGHT WINDS ACROSS THE COASTAL
WATERS THROUGH FRIDAY. WINDS WILL BECOME GUSTY ALONG THE IMMEDIATE
COAST WITH THE AFTERNOON SEA BREEZE. A LONG PERIOD WESTERLY SWELL
WILL MOVE INTO THE COASTAL WATERS LATER THIS EVENING AND SPREAD
SOUTHWARD ALONG THE COAST OVERNIGHT. THESE LONG PERIOD WAVES ARE
EXPECTED TO STICK AROUND THROUGH FRIDAY AND WILL RESULT IN LARGE
BREAKERS ALONG OFFSHORE REEFS AND SAND BARS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...ROUGH BAR ADVISORY FOR SF BAR

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION: CW
MARINE: LARRY
CLIMATE: HENDERSON/BELL

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