Small Craft Advisory 175, NWS San Francisco Bay Area, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1002 AM PST WED DEC 23 2015

.SYNOPSIS...DRY CONDITIONS WITH MOSTLY SUNNY SKIES AND
TEMPERATURES A BIT ON THE COOL SIDE WILL PREVAIL TODAY. THE
NEXT...AND COLDER...STORM SYSTEM WILL SWEEP THROUGH THE DISTRICT
FROM THE NORTH ON THURSDAY. IT WILL BRING LIGHT TO LOCALLY
MODERATE RAINFALL AT LOWER ELEVATIONS AND SNOW TO THE HIGHER
ELEVATIONS IN THE HILLS. CHILLY TEMPERATURES AND DIMINISHING
SHOWERS ARE EXPECTED FOR CHRISTMAS DAY. DRY CONDITIONS AND BELOW
NORMAL TEMPERATURES ARE THEN PROJECTED FOR FRIDAY NIGHT THROUGH
THE UPCOMING WEEKEND.

&&

.DISCUSSION...AS OF 09:15 AM PST WEDNESDAY...SKIES ARE NOW MOSTLY
CLEAR ACROSS THE DISTRICT ASIDE FROM A FEW AREAS OF CLOUDINESS
OVER THE MOUNTAINS OF MONTEREY AND SAN BENITO COUNTIES. THE NEXT
WEATHER SYSTEM TO AFFECT US IS PRESENTLY JUST BEGINNING TO DEVELOP
IN THE SOUTHEASTERN GULF OF ALASKA...WITH IT NOW BEING CENTERED
NEAR 50N 140W AND MOVING RAPIDLY EAST SOUTHEASTWARD.

LATEST MODEL OUTPUT REMAINS CONSISTENT IN PROJECTING IT TO DIVE
DOWN THE CALIFORNIA COAST ON THURSDAY...WITH SHOWER CHANCES
BEGINNING LATE TONIGHT IN THE NORTH BAY AND THE MAIN RAIN BAND
MOVING THROUGH THE SF BAY AREA THURSDAY MORNING. AFTER A BIT OF
BREAK...A SECONDARY DISTURBANCE AND ASSOCIATED SHOWERS LOOK TO
MOVE THROUGH THE SF BAY AREA IN THE LATE THURSDAY AFTERNOON/EARLY
EVENING TIME FRAME. SHOWER ACTIVITY SHOULD THEN DIMINISH FROM THE
NORTH LATER THURSDAY NIGHT AND FRIDAY WITH DRY CONDITIONS
DISTRICTWIDE BY FRIDAY EVENING...AND THEN CONTINUING THROUGH THE
WEEKEND.

ALTHOUGH STRONGER DYNAMICALLY THAN OUR LAST STORM...ASSOCIATED
MOISTURE CONTENT AND DURATION OF PRECIPITATION ARE BOTH EXPECTED
TO BE MUCH MORE LIMITED. RAINFALL TOTALS LOOK TO BE IN THE 1/3 TO
2/3 OF AN INCH RANGE AT LOWER ELEVATIONS AND PERHAPS AS HIGH AS
1.5 TO 2 INCHES WETTEST SPOTS IN THE COASTAL HILLS.

THIS NEXT WEATHER SYSTEM WILL ALSO BE MUCH COLDER...WITH MODELS
PROJECTING 850 MB TEMPS WILL FALL DOWN INTO THE -2C TO -3C RANGE
THURSDAY AFTERNOON. AS A RESULT...SNOW LEVELS IN THE HILLS ARE
EXPECTED TO DROP TO AROUND 2500 FT AND PERHAPS LOCALLY EVEN A BIT
LOWER THAN THAT. TEMPERATURES AT MIDTROPOSPHERIC LEVELS WILL ALSO
DECREASE DRAMATICALLY AND RESULT IN THE POTENTIAL FOR APPRECIABLE
SURFACE BASED CAPE...AND THUS THE POSSIBILITY OF THUNDERSTORM
DEVELOPMENT. WILL ALSO NEED TO KEEP AN EYE ON WINDS IN THE NORTH
AND EAST BAY HILLS IN THE THURSDAY AFTERNOON AND EVENING TIME
FRAME. LATEST NAM MODEL OUTPUT BRINGS 925 MB WIND SPEEDS UP TO THE
35 TO 38 KT RANGE IN THAT TIME FRAME...SUGGESTING SOME RISK OF
SURFACE WINDS REACHING WIND ADVISORY LEVELS UP IN THE HIGHER
HILLS.

&&

.AVIATION...AS OF 10:00 AM PST WEDNESDAY...VFR CONDITIONS
EXPECTED AT ALL TERMINALS THROUGH THE EVENING. WESTERLY WINDS
WILL PREDOMINATE AT ALL SPOTS. RAIN MOVES IN FROM THE NORTH LATE
IN THE TAF PERIOD. HIGH CONFIDENCE.

VICINITY OF KSFO...VFR WITH WINDS OF 280 TO 300 OF 15 TO 20 KT
WITH GUSTS OCCASIONALLY TO 25 KT THROUGH 02Z. WINDS SLOWLY DIMINISH
AFTER SUNSET. RAIN RETURNS AROUND 15Z WITH MVFR CIGS AND VIS
EXPECTED. HIGH CONFIDENCE THROUGH 02Z.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR THROUGH THE PERIOD WITH 270 TO
290 WINDS WITH HIGHER SPEEDS AT KMRY. HIGH CONFIDENCE.

&&

.MARINE...AS OF 09:53 AM PST WEDNESDAY...HIGH PRESSURE WILL
CONTINUE OFF THE CALIFORNIA COAST THROUGH CHRISTMAS THEN WEAKEN
OVER THE WEEKEND. A SYSTEM WILL BRING ANOTHER ROUND OF RAIN AND
POSSIBLE THUNDERSTORMS TO OUR WATERS ON THURSDAY. NORTHWEST WINDS
WILL CONTINUE TO BE MODERATE BUT WILL DECREASE SATURDAY AND
SUNDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...MRY BAY UNTIL 2 PM
             SCA...PT ARENA TO PT REYES 0-10 NM UNTIL 2 PM
             SCA...PT REYES TO PIGEON PT 0-10 NM UNTIL 2 PM
             SCA...PIGEON PT TO PT PINOS 0-10 NM UNTIL 2 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM UNTIL 2 PM
             SCA...PT ARENA TO PT REYES 0-10 NM FROM 2 PM
             SCA...PT REYES TO PIGEON PT 0-10 NM FROM 2 PM
             SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 2 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 2 PM
             SCA...PT ARENA TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM
             SCA...ROUGH BAR ADVISORY FOR SF BAR UNTIL 2 PM

&&

PUBLIC FORECAST: BLIER
AVIATION: BELL
MARINE: BELL

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