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

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000
FXUS66 KMTR 172200
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
200 PM PST WED DEC 17 2014

.SYNOPSIS...SHOWERS WILL LINGER OVER THE REGION THROUGH TONIGHT
BEFORE A BRIEF LULL IN PRECIPITATION ON THURSDAY. OUR NEXT SYSTEM
WILL BRING RAIN BACK TO THE REGION LATE THURSDAY THROUGH
FRIDAY...YET RAINFALL AMOUNTS ARE EXPECTED TO GENERALLY BE LIGHT. A
RIDGE OF HIGH PRESSURE WILL THEN BUILD OVER MUCH OF THE STATE AND
RESULT IN DRY...SEASONAL WEATHER CONDITIONS.

&&

.DISCUSSION...AS OF 01:58 PM PST WEDNESDAY...LINGERING SHOWERS
CONTINUE TO INCREASE IN COVERAGE THIS AFTERNOON AS A WEAK
MID/UPPER LEVEL DISTURBANCE APPROACHES THE REGION. THIS WILL ALLOW
FOR ISOLATED TO SCATTERED SHOWERS TO CONTINUE THROUGH THE EVENING
WITH GENERALLY LIGHT RAINFALL AMOUNTS. ADDITIONAL RAINFALL AMOUNTS
OF 0.10" TO 0.15" IN URBAN AREAS WITH THE COASTAL RANGES PICKING
UP AS MUCH AS 0.25" TO 0.50" OF RAIN THROUGH TONIGHT. A BIT OF A
LULL IN PRECIPITATION IS EXPECTED ON THURSDAY ON THE BACK SIDE OF
THE EXITING MID/UPPER LEVEL TROUGH.

CHANCES FOR PRECIPITATION ONCE AGAIN INCREASE THURSDAY NIGHT INTO
FRIDAY AS THE NEXT PACIFIC SYSTEM APPROACHES THE PACIFIC NORTHWEST.
THIS FEATURE WILL PUSH ANOTHER FRONTAL BOUNDARY INTO THE NORTH BAY
LATE THURSDAY NIGHT AND THEN SOUTHWARD DURING THE DAY ON FRIDAY.
PWAT VALUES ARE FORECAST TO BE JUST ABOVE THE 1 INCH MARK...YET THE
MID/UPPER LEVEL SUPPORT WILL NOT BE ALL THAT STRONG. WITH THAT
SAID...ONLY EXPECTING WIDESPREAD RAINFALL AMOUNTS TO BE AROUND 0.50"
TO 1.00" IN THE NORTH BAY...GENERALLY BELOW 0.50" OVER THE SAN
FRANCISCO BAY AREA AND 0.25" OR LESS SOUTH OF THE SANTA CRUZ
MOUNTAINS. A FEW SHOWERS MAY LINGER OVER THE NORTH BAY THROUGH
SATURDAY...YET A MAJORITY OF THE REGION IS FORECAST TO BEGIN A
DRYING TREND.

BY EARLY NEXT WEEK...A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE
EASTERN PACIFIC AND BRING DRY CONDITIONS TO THE REGION. DAYTIME
TEMPERATURES WILL ALSO WARM SLIGHTLY UNDER PARTLY CLOUDY CONDITIONS.
THE RIDGE IS FORECAST TO REMAIN IN PLACE THROUGH MIDWEEK AND WILL
ALLOW FOR SOME DRYING OF THE VERY SATURATED SOILS CAUSED BY THE
MUCH NEEDED RECENT RAINFALL. THE FORECAST MODELS THEN DIVERGE LATE
NEXT WEEK ON THE UPPER LEVEL PATTERN. THE ECMWF AND GEM PUSH A
STRONGER MID/UPPER LEVEL SYSTEM INTO THE PACIFIC NORTHWEST WITH A
COLD AIRMASS DROPPING SOUTHWARD. MEANWHILE...THE GFS DOES BREAK DOWN
THE RIDGE SLIGHTLY...YET PUSHES THE MUCH COLDER AIR MASS DOWN INTO
THE CENTRAL PLAINS. OVERALL...NO MAJOR WEATHER CONCERNS ANTICIPATED
ACROSS THE REGION FOR CHRISTMAS.

&&

.AVIATION...AS OF 10:00 AM PST WEDNESDAY...THE IR SATELLITE IS
SHOWING A WEAK STORM SYSTEM PUSHING TOWARDS THE COAST THIS
MORNING. SOUTHEASTERLY WINDS ARE EXPECTED TO PREVAIL AHEAD OF THIS
SYSTEM BECOMING MORE SOUTHERLY OVERNIGHT. LIGHT RAIN SHOULD REACH
THE TERMINALS BY LATE MORNING EARLY AFTERNOON. A PERIOD OF
MODERATE RAIN IS ANTICIPATED AS THE STORM SYSTEM PASSES OVER THE
TERMINALS BETWEEN 0200 AND 0600Z TONIGHT.

VICINITY OF KSFO...ADVANCED THE TIMING OF RAINFALL TO BE A FEW
HOURS EARLIER THAN PREVIOUS FORECAST. STEADY SHOWERS ARE
ANTICIPATED TO BEGIN AROUND 2100Z WITH A PERIOD OF MODERATE RAIN
ANTICIPATED BETWEEN 0200 AND 0600Z THIS EVENING. SOUTHEASTERLY
WINDS ARE ANTICIPATED TO PREVAIL WITH THIS SYSTEM REACHING 8 TO 12
KT AS THE SYSTEM DRAWS CLOSER.

CONFIDENCE IS MODERATE.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR IS ANTICIPATED TO PERSIST INTO
THE AFTERNOON HOURS WITH SHOWERS POSSIBLE BY LATE MORNING. LIGHT
RAIN AND MVFR CIGS ARE ANTICIPATED TO BEGIN AROUND 2300Z WITH A
PERIOD OF MODERATE RAIN EXPECTED BETWEEN 0200 AND 0600Z. SOUTHERLY
WINDS ARE ANTICIPATED TO REACH 5 TO 10 KT AS THE STORM SYSTEM
PASSES OVER THE AREA.

CONFIDENCE IS MODERATE.

&&

.MARINE...AS OF 09:43 AM PST WEDNESDAY...WEST AND NORTHWEST WINDS
WILL PREVAIL ALONG THE CENTRAL COAST TODAY AS A COLD FRONT EXITS
THE REGION. WINDS WILL BECOME MORE SOUTHERLY AS ANOTHER STORM
SYSTEM APPROACHES THE REGION. MODERATE NORTHWEST TO WEST SWELLS
WILL IMPACT THE COASTAL WATERS THROUGH THURSDAY. A LONG PERIOD
NORTHWEST SWELL WILL INCREASE FRIDAY AND NEXT WEEKEND.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PIGEON PT TO PT PINOS 0-10 NM UNTIL 10 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM UNTIL 10 PM
             SCA...PIGEON PT TO PT PINOS 10-60 NM UNTIL 10 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM UNTIL 10 PM
             SCA...PT ARENA TO PT REYES 0-10 NM UNTIL 10 PM
             SCA...PT ARENA TO PT REYES 10-60 NM UNTIL 10 PM
             SCA...PT REYES TO PIGEON PT 10-60 NM UNTIL 10 PM
             SCA...PT REYES TO PIGEON PT 0-10 NM UNTIL 1 AM
             SCA...ROUGH BAR ADVISORY FOR SF BAR UNTIL 3 PM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION/MARINE: LARRY/MM

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