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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1058 AM PDT SAT SEP 20 2014

.SYNOPSIS...ANOTHER PLEASANT DAY IN STORE FOR THE FORECAST AREA
TODAY. THIS PLEASANT WEATHER IS EXPECTED TO PERSIST INTO THE
FIRST PART OF NEXT WEEK. A PACIFIC STORM SYSTEM WILL BRING A
POSSIBILITY OF RAIN AND THE FIRST LARGE NORTHWEST SWELL OF THE
SEASON TO THE AREA BY MIDWEEK.  

&&

.DISCUSSION...AS OF 8:20 AM PDT SATURDAY...THE FIRST LOW LIGHT
VISIBLE SATELLITE IMAGE OF THE DAY IS SHOWING LOW CLOUDS ALONG THE
COAST STRETCHING INTO THE INTERIOR VALLEYS. CLOUD BASES ARE
RUNNING BETWEEN 600 AND 1200 FEET WITH THE FORT ORD PROFILER
INDICATING A MARINE LAYER APPROXIMATELY 1600 FEET DEEP. THE 1200Z
KOAK SOUNDING IS SHOWING A SLIGHTLY DEEPER MARINE LAYER AT
APPROXIMATELY 1800 FEET WITH AND INVERSION TOPPING OUT AT 2600
FEET...INDICATING WARM TEMPERATURES ALONG THE HIGHER TERRAIN LAST
NIGHT. NAM12 BUFR FORECAST SOUNDINGS ARE INDICATING THAT THE LOW
CLOUDS WILL BURN OFF BY LATE MORNING...LEAVING BEHIND MOSTLY SUNNY
SKIES INTO THE EARLY EVENING HOURS. 

AN AREA TO WATCH TODAY WILL BE THE HILLS/MOUNTAINS OF SAN BENITO
COUNTY. THERE IS ENOUGH MOISTURE AND INSTABILITY IN THIS AREA TO
SUPPORT A POSSIBILITY OF A THUNDERSTORM THIS AFTERNOON. NAM12
FORECAST PROXIMITY SOUNDINGS ARE SHOWING CAPE VALUES 600 AND 1000
J/KG AND LIFTED IDICES BETWEEN -1.6 AND -3.0...INDICATING
INSTABILITY. SOME FORCING WILL AVAILABLE FROM THE DEPARTING LOW
NOW CENTERED OFF OF THE LA COAST.

THE CURRENT SATELLITE WATER VAPOUR IMAGE IS SHOWING A TROUGH OF
LOW PRESSURE IN THE GULF OF ALASKA AND A LOW PRESSURE SYSTEM
CENTERED APPROXIMATELY 200 MILES SOUTHWEST OF LA. THE 0000Z ECMWF
AND 0600Z GFS40 HAVE INITIALIZED WELL WITH THESE FEATURES AND
REMAIN IN GOOD AGREEMENT WITH THE GENERAL SYNOPTIC PATTERN THROUGH
AT LEAST FRIDAY. BOTH MODELS DEVELOP A STRONG LOW PRESSURE SYSTEM OFF OF
THE BC COAST MONDAY INTO TUESDAY. THIS LOW WILL SAG SOUTH BRINGING
A POSSIBILITY OF RAIN TO THE FORECAST AREA BEGINNING WEDNESDAY
EVENING IN THE NORTH BAY SPREADING SOUTH TO MONTEREY BY THURSDAY
MORNING. THE POSSIBILITY OF RAIN WILL STICK AROUND THROUGH AT LEAST
FRIDAY. 45 TO 50 KT NORTHWEST WINDS ON THE BACK SIDE OF THE BC
LOW WILL ALSO GENERATE THE FIRST SIGNIFICANT NORTHWEST SWELL OF
THE SEASON WITH WAVES RANGING BETWEEN 10 TO 15 FEET ARRIVING TO
THE COAST AROUND WEDNESDAY EVENING.

&&

.AVIATION...AS OF 10:55 AM PDT SATURDAY...VERY RAPID CLEARING ON
SATELLITE RIGHT NOW WHICH WILL LEAD TO VFR CONDITIONS AT ALL
TERMINALS BY 19-20Z. WINDS WILL GENERALLY BE A NON-ISSUE AND STAY
WESTERLY UNDER 15 KT (EXPECT AT SFO). EXPECT A RETURN TONIGHT
AFTER 06Z. OVERALL MODERATE CONFIDENCE.

VICINITY OF KSFO...WAS WORRIED EARLIER THAT THE TAF MIGHT NOT
VERIFY, HOWEVER CLEARING IS HAPPENING VERY FAST WITH ALMOST THE
ENTIRE APPROACH NOW TO VFR. SHOULD STAY VFR THROUGH AT LEAST 06Z.
WINDS WILL PICK UP AND BE FROM 260 TO 280 UP TO 15 KT IN THE
AFTERNOON. MVFR RETURNS TONIGHT. MODERATE CONFIDENCE.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...CLOUDS BURNING OFF, SO SHOULD FLIP
OVER TO VFR CONDITIONS AROUND 19Z AND REMAIN THROUGH AT LEAST 02Z
THIS EVENING BEFORE MVFR RETURNS. WINDS 260 TO 280 UP TO 12 KT
THROUGH THE AFTERNOON AND EARLY EVENING. MODERATE CONFIDENCE.

&&

.MARINE...AS OF 10:55 AM PDT SATURDAY...LIGHT SOUTH TO
SOUTHWESTERLY WINDS ARE EXPECTED ACROSS THE NORTHERN COASTAL
WATERS THROUGH THE WEEKEND. ELSEWHERE...WEST TO NORTHWESTERLY
WINDS WILL PREVAIL AND PERSIST THROUGH THE FIRST HALF OF THE WEEK.
LIGHT SEAS WILL CONTINUE THROUGH THE FIRST HALF OF THE WEEK. A
LONGER PERIOD WEST TO NORTHWEST SWELL IS FORECAST TO IMPACT OUR
AREA STARTING ON WEDNESDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...NONE.

$$

PUBLIC FORECAST: LARRY
AVIATION/MARINE: BELL

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