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

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FXUS66 KMTR 030536
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1036 PM PDT SUN AUG 2 2015

.SYNOPSIS...A SUBTLE COOLING TREND IS FORECAST TO CONTINUE THROUGH
TUESDAY AS ONSHORE FLOW AND THE MARINE INFLUENCE INCREASES. MODEST
WARMING IS THEN FORECAST FOR WEDNESDAY AND THURSDAY. ASIDE FROM
PATCHY COASTAL DRIZZLE AND FOG DURING THE OVERNIGHT AND EARLY
MORNING HOURS...DRY WEATHER CONDITIONS ARE EXPECTED TO PERSIST
THROUGH THE FORECAST PERIOD.

&&

.DISCUSSION...AS OF 09:00 PM PDT SUNDAY... AFTERNOON TEMPERATURES
PEAKED A FEW TO UP TO FIVE DEGREES COOLER ACROSS MOST LOCATIONS
TODAY. THIS AIDED IN DROPPING MOST LOCATIONS WITHIN RANGE OF THEIR
NORMAL AFTERNOON TEMPERATURES FOR THIS TIME OF THE YEAR... WHICH
COMES AFTER SEVERAL DAYS OF ABOVE AVERAGE TEMPERATURES FOR THE
REGION. THE AREA HAS ALSO SEEN A SLIGHT DRYING OF THE ATMOSPHERE
OVER THE COURSE OF THE DAY... ESPECIALLY SO AT THE LOW TO MID
LEVELS. PRECIPITABLE WATER VALUES HAVE FALLEN TWENTY PERCENT FROM
1.0" TO 0.8" OVER THE PREVIOUS 24 HOURS. MODEL DATA AND SOUNDINGS
SHOW A RATHER DRY LAYER SITUATED DIRECTLY ATOP THE MARINE LAYER
THIS EVENING WHICH IS INHIBITING TYPICAL SUMMER EVENING COASTAL
STRATUS DEVELOPMENT. VISIBLE SATELLITE SHOWS A STRATUS FREE
COASTLINE AS FAR NORTH AS POINT ARENA SO FAR THIS EVENING.
HOWEVER... COASTAL STRATUS IS EXPECTED TO DEVELOP LATER TONIGHT
AND PUSH INLAND BY MORNING.

AS HIGH PRESSURE SHIFTS DOWNSTREAM... A CLOSED LOW SITUATED
AROUND 500 MILES WEST OF NORTHERN CALIFORNIA IS GRADUALLY TRENDING
ATMOSPHERIC HEIGHTS AND TEMPERATURES LOWER ACROSS THE REGION.
TEMPERATURES ARE EXPECTED TO DWINDLE FURTHER MONDAY AND TUESDAY AS
ONSHORE FLOW AND MARINE INFLUENCE INCREASES. TEMPERATURES WILL
BE AT OR BELOW NORMAL ON MONDAY AND TUESDAY AFTERNOONS WITH
TUESDAY BEING THE COOLEST DAY OF THE WEEK. FUTHERMORE... THIS
FEATURE IS SENDING PULSES OF ENERGY AND MOISTURE TOWARDS CALIFORNIA
FROM THE SOUTHWEST. MODELS HINT CONVECTION MAY BE POSSIBLE FURTHER
NORTH AND EAST OF OUR FORECAST AREA GIVEN THE RIGHT COMBINATION
OF ENERGY AND MOISTURE...BUT SLIM TO UNLIKELY HERE. DRIZZLE ALONG
THE COAST TOMORROW MORNING LOOKS LIKE OUR BEST CHANCE FOR ANY
PRECIPITATION... BUT CAN NOT COMPLETELY RULE OUT A STRAY SHOWER OR
TWO ADVANCING INLAND FROM THE WEST.

TEMPERATURES REBOUND WEDNESDAY AND THURSDAY AS THE WEATHER PATTERN
RETROGRADES UPSTREAM... FORCING THE CLOSED LOW FURTHER WEST AND
PAVING THE WAY FOR THE DESERT SOUTHWEST RIDGE TO ENCROACH INTO THE
REGION.

&&

.PREV DISCUSSION...AS OF 01:30 PM PDT SUNDAY...AFTER A CLOUDY START TO
THE TODAY...MUCH OF THE BAY AREA CLEAR OUT...EVEN SOME COASTAL
LOCATIONS. DESPITE THE CLEARING TEMPERATURES TODAY ARE RUNNING A
FEW COOLER THAN YESTERDAY. THIS IS MOST LIKELY DUE TO THE FILTERED
SUNSHINE FROM HIGH CLOUDS OVERHEAD AND SLIGHTLY COOLER AIRMASS.

THE LONG WAVE PATTERN CONTINUES TO SHOW AN UPPER LEVEL RIDGE
COVERING MUCH OF THE WEST. HOWEVER...A CLOSED UPPER LOW AND BROAD
TROUGH REMAIN PARKED WEST OF 130W. THE CIRCULATION ASSOCIATED WITH
THE TROUGH/LOW IS HELPING TO STREAM THE UPPER LEVEL CLOUDS OVER
THE BAY AREA. LATEST GUIDANCE SHOWS THE RIDGE WEAKENING WITH THE
LOW REMAINING NEARLY STATIONARY THROUGH MID WEEK. THEREFORE...DAY
TO DAY CHANGE OF SENSIBLE WEATHER WILL BE SMALL. NIGHT AND MORNING
CLOUDS WILL BE COMMON WITH AFTERNOON SUNSHINE. TEMPERATURES WILL
REMAIN SEASONABLY COOL WITH HIGHS IN THE 60S/70S COAST AND 80S/LOW
-MID 90S INLAND.

TEMPERATURES WILL WARM UP BRIEFLY FOR WEDNESDAY AND THURSDAY AS
SHORTWAVE RIDGING DEVELOPS OVER THE REGION THANKS TO A DEEPENING
UPPER LOW TO THE WEST. COASTAL CLOUDS WILL KEEP TEMPERATURES IN
CHECK...BUT INLAND AREAS WILL BE MORE SEASONABLE WITH MORE
LOCATIONS IN THE 90S.

TEMPERATURES MODERATE ON THURSDAY BUT COOL DOWN FRIDAY AND OVER
THE WEEKEND. ANOTHER UPPER LOW IS FORECAST TO DEVELOP OFF THE
COAST LATE IN THE WEEK AND GRADUALLY MOVE INLAND...THE REASON FOR
THE COOL DOWN. IN ADDITION...SOME OF THE MODEL GUIDANCE SUGGESTS
POSSIBLE PRECIPITATION FOR PORTIONS OF CA. MOISTURE AND
INSTABILITY LOOK MARGINAL AT THIS POINT FOR THE BAY AREA. BETTER
CHANCE NORTH OF THE CWA. GIVEN THAT TIME PERIOD IS STILL SEVERAL
DAYS AWAY AND GUIDANCE IS NOT THE BEST...WILL NOT INCLUDE ANY
MENTION OF PRECIP. HOWEVER...A BIG HOWEVER...WILL HAVE TO WATCH
THIS CLOSELY GIVEN RECENT FIRE WEATHER CONCERNS AROUND THE STATE.
ESPECIALLY FROM A POSSIBLE CONVECTION STANDPOINT IMPACTING CURRENT
FIRE FIGHTING EFFORTS.

&&

.AVIATION...AS OF 10:29 PM PDT SUNDAY...SURFACE WINDS HAVE BECOME
LIGHT IN MOST AREAS AND SKIES HAVE REMAINED VFR THIS EVENING.
HOWEVER SATELLITE IS STARTING TO SHOW A BAND OF STRATUS EDGING
EASTWARD OVER THE COASTAL WATERS APPROACHING THE SONOMA COUNTY TO
SANTA CRUZ COUNTY COASTLINE. GENERALLY EXPECTING THE STRATUS TO
INCREASE INTO MONDAY MORNING. A WEAK AND DRY MID LEVEL SHORTWAVE
TROUGH CAUGHT UP IN THE S-SW SUB-TROPICAL FLOW ALOFT MAY HELP TO
STIR UP SOME PATCHY LIGHT COASTAL DRIZZLE MONDAY MORNING.

VICINITY OF KSFO...MVFR CIGS REDEVELOP OVERNIGHT WITH CLEARING BY
18Z MONDAY. ONSHORE WINDS CONTINUE DURING THE PERIOD.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...GRADUAL RETURN TO STRATUS LATE
TONIGHT WITH IFR CEILINGS FORECAST...CLEARING BY LATE MONDAY
MORNING.

&&

.MARINE...AS OF 8:56 PM PDT SUNDAY...GENERALLY LIGHT WINDS WILL
CONTINUE ACROSS THE COASTAL WATERS THROUGH TUESDAY EXCEPT OVER
THE SAN FRANCISCO BAY WATERS NORTH OF THE BAY BRIDGE WINDS WILL
BE GUSTY AGAIN MONDAY AFTERNOON AND EVENING. NORTHWEST WINDS WILL
STRENGTHEN MID TO LATE WEEK OVER THE COASTAL WATERS AS HIGH
PRESSURE BUILDS NEAR THE NORTHERN CALIFORNIA COAST. MIXED
NORTHWEST SWELL AND A LONG PERIOD SOUTH TO SOUTHWEST SWELL WILL
CONTINUE TONIGHT INTO MONDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...SF BAY UNTIL 10 PM

&&

$$

PUBLIC FORECAST: DRP
AVIATION/MARINE: CANEPA


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