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

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000
FXUS66 KMTR 310048 CCA
AFDMTR

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
448 PM PST FRI JAN 30 2015

.SYNOPSIS...DRY CONDITIONS ARE EXPECTED TO CONTINUE INTO NEXT
WEEK WITH CHANCES OF RAIN ONLY OVER FAR NORTHERN CALIFORNIA.
TEMPERATURES WILL REMAIN SEVERAL DEGREES ABOVE NORMAL FOR THE NEXT
WEEK. THERE ARE INDICATIONS THAT RAIN MAY MOVE BACK INTO THE AREA
BY THE END OF NEXT WEEK.

&&

.DISCUSSION...AS OF 01:28 PM PST FRIDAY...
MORNING FOG HAS DISSIPATED AND GIVEN WAY TO ANOTHER MOSTLY SUNNY
DAY WITH A FEW CLOUDS LINGERING ALONG THE IMMEDIATE COASTLINE.
TEMPERATURES HAVE CLIMBED INTO THE 60S AND LOWER 70S IN YET
ANOTHER ABOVE NORMAL DAY. THE UPPER LOW IN SOUTHERN CALIFORNIA
WILL CONTINUE TO STRENGTHEN AND LIFT EASTWARD OVERNIGHT AS A
STRONG RIDGE OVER THE PACIFIC WILL BUILD BACK INTO THE AREA. THIS
WILL BRING IN SOME DRIER AIR AND WILL TEMPER THE EXTENT OF
OVERNIGHT FOG TONIGHT WITH MORE FAVORABLE CONDITIONS EXISTING
EARLIER OVERNIGHT. THE RIDGE WILL BUILD INTO THE AREA OVER THIS
WEEKEND AND BRING DRY AND SUNNY CONDITIONS ALONG WITH WELL ABOVE
NORMAL TEMPERATURES AGAIN. READINGS FROM THE MID 60S TO MID 70S
WILL BE COMMON ON SATURDAY AND SUNDAY WITH THE RIDGE OF HIGH
PRESSURE DOMINATING. THIS WILL BE A REPEATING THEME AS THERE WILL
BE A SHOT OF PRECIP AGAIN INTO FAR NORTHERN CALIFORNIA BUT UNABLE
TO MAKE IT SOUTH DUE TO THE RIDGE OF HIGH PRESSURE ON MONDAY. THE
RIDGE WILL HANG STRONG THROUGH THE END OF THE WEEK WITH DRY
WEATHER AND ABOVE NORMAL TEMPERATURES.

FINALLY SOME HOPE ON THE DISTANT HORIZON...AS THE ECMWF AND GFS
REMAIN WITH A FAIRLY CONSISTENT SOLUTION OF RAINFALL ARRIVING BY
LATE THURSDAY INTO FRIDAY. BOTH SHOW THE RIDGE BEING SUPPRESSED
WELL SOUTH AND THEN THE PATTERN BECOMING MORE CONDUCIVE FOR STORM
SYSTEMS TO PUSH INTO THE BAY AREA. HAVE INCREASED POPS
CONSIDERABLY IN THE FAR EXTENDED PERIODS AND IF THE SOLUTIONS
REMAIN CONSISTENT THIS COULD BE OUR FIRST RAIN IN QUITE A LONG
TIME. THE LAST MEASURABLE RAIN IN DOWNTOWN SAN FRANCISCO WAS DECEMBER
24 2014. WILL HAVE TO CONTINUE MONITORING THIS AS IT IS PROMISING
BUT THERE IS QUITE A WAYS TO GO UNTIL IT ARRIVES.

&&

.AVIATION...AS OF 4:48 PM PST FRIDAY...AREAS OF LOW CLOUDS ARE
BRUSHING THE IMMEDIATE COASTLINE THIS AFTERNOON WHILE SKIES ARE
CLEAR INLAND. THE WMC-SFO PRESSURE GRADIENT IS 7 MB DIRECTED
OFFSHORE WHILE THE ACV-SFO AND SFO-SAC GRADIENTS ARE 4.7 MB
NORTHERLY AND 1.1 MB ONSHORE RESPECTIVELY. THE NORTHERN EXTENT OF
THE COASTAL LOW CLOUDS IS JUST BARELY REACHING SAN FRANCISCO
PLACING THE CLOUD COVER PRECARIOUSLY CLOSE TO THE SAN BRUNO GAP
BUT THE DOMINANT ACV-SFO GRADIENT SHOULD BE SUFFICIENT TO HOLD THE
LOW CLOUDS OUT OF KSFO THIS EVENING. CWSU OAKLAND RESEARCH SHOWS
90% PROBALILITY OF "NO EARLY RETURN" WHEN THE SFO-ACV/SFO-SAC
RATIO IS LESS THAN OR EQUAL TO -1.1 MB...AND PRESENTLY IT`S -4.7
MB. ON A LARGER SCALE...SURFACE HIGH PRESSURE WILL BUILD OVER THE
GREAT BASIN TONIGHT AND EARLY SATURDAY MORNING RESULTING IN
SURFACE WINDS IN THE BAY AREA TRENDING MORE SOLIDLY OVER TO AN
OFFSHORE DIRECTION. THE 925 MB LEVEL RH`S DRY OUT APPRECIABLY ON
SATURDAY PER THE LATEST NAM MODEL...SUPPORTIVE OF A HIGH
CONFIDENCE VFR FORECAST ON SATURDAY.

VICINITY OF KSFO...WESTERLY WINDS PICKED UP AT THE TOP OF THE
HOUR WITH GUSTS JUST OVER 20 KNOTS...BUT HAVE SINCE SETTLED BACK.
THE OCEAN-LAND AFTERNOON TEMPERATURE DIFFERENTIAL COULD CAUSE A
FEW MORE BRIEF GUSTS BACK UP TO 20 KNOTS BUT ON THE AVERAGE IT
SHOULD HOLD BELOW. IT`S A MODERATE TO HIGH CONFIDENCE VFR FORECAST
FOR THE PERIOD.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...NW WINDS ARE MORE EFFICIENT AT
PRESSING LOW CLOUDS BACK IN OVER THE SOUTHERN MONTEREY BAY AREA.
THE FORECAST IS FOR A CONTINUATION OF MVFR CIGS AT KMRY AND KSNS
FOR TONIGHT AND SATURDAY MORNING. VFR IS FORECAST TO RETURN NO
LATER THAN LATE SAT MORNING. THE LOCALLY RUN 3 KM RESOLUTION WRF
MODEL HINTS AT A POSSIBLE EDDY CIRCULATION DEVELOPING OVER THE
MONTEREY BAY WATERS APPROX 2 AM - 5 AM SATURDAY THEN IT DISSIPATES.
IF IT ACTUALLY HANGS AROUND LONGER THEN MAYBE THE LOW CLOUDS WILL
MIX OUT A BIT QUICKER OVER THE NORTHERN SALINAS VALLEY WHILE
TENDING TO STAY LONGER OVER THE MONTEREY PENINSULA.

&

.MARINE...AS OF 01:28 PM PST FRIDAY...MODERATE NORTH WINDS WILL
CONTINUE OVER THE COASTAL WATERS THROUGH SATURDAY. THE STRONGEST
WINDS WILL BE AT LEAST 10 NAUTICAL MILES OFFSHORE OF THE COAST.
PATCHY DENSE FOG WILL LINGER ACROSS THE NORTH BAY AND WEST DELTA
THROUGH NOON TODAY. THE COMBINATION OF MODERATE WINDS AND SWELL
MAY RESULT IN SOMEWHAT CHOPPY SEAS AS WELL. WIND AND SEA
CONDITIONS ARE EXPECTED TO IMPROVE BY TOMORROW AFTERNOON.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...PT REYES TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PINOS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM

&&

$$

PUBLIC FORECAST: JOHNSON
AVIATION: CANEPA
MARINE: LARRY

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