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

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000
FXUS66 KMTR 252155
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
255 PM PDT SAT OCT 25 2014

.SYNOPSIS...A PACIFIC STORM WILL MOVE EAST OF THE AREA LATER
TONIGHT AND SUNDAY WITH A COOLER AND DRIER AIRMASS OVER THE AREA
SUNDAY. HIGH PRESSURE WILL BUILD OVER THE STATE FROM MONDAY
THROUGH MIDWEEK WITH A WARMING TREND EXPECTED. THE NEXT PACIFIC
STORM SHOULD REACH THE COAST BY LATE FRIDAY OR SATURDAY WITH
AN INCREASING CHANCE OF RAIN.

&&

.DISCUSSION...AS OF 02:28 PM PDT SATURDAY...LIGHT SHOWERS CONTINUE
TO DEVELOP OVER THE COASTAL MOUNTAINS ESPECIALLY NORTH BAY. EVEN A
COUPLE SHOWERS SHOWING UP IN THE MONTEREY BAY AND SPREADING
EASTWARD. NOTED ONLY ONE LIGHTNING STRIKE SO FAR IN SONOMA
COUNTY...BUT POTENTIAL EXISTS THROUGH THE EARLY EVENING FOR
ADDITIONAL STRIKES FROM ABOUT THE SANTA CRUZ MOUNTAINS NORTHWARD.
IN ADDITION...OFFSHORE SHOWERS APPROACHING MARIN COUNTY AND NORTH
BAY COULD EVEN IMPACT CENTRAL AND NORTHERN SF BAY OVER THE NEXT
FEW HOURS. NOT EXPECTING ANY HEAVY AMOUNTS FROM THESE
SHOWERS...BUT COULD SEE A QUICK TENTH OF AN INCH OF SO FROM
STRONGER CELLS. MOST AREAS WILL SEE ONLY LIGHT PRECIPITATION IF ANY.

HRRR GUIDANCE SHOWS SURFACE WIND SHIFT WITH TROF AXIS MOVING
ONSHORE AROUND 02Z THIS EVENING. SUSPECT GREATEST CONCENTRATION OF
CONVECTION SHOULD OCCUR WITH THIS AXIS AS IT MOVES ONSHORE AND
THRU THE BAY AREA. HIT AND MISS SHOWERS WITH AN OUTSIDE CHANCE OF
A LATE AFTERNOON OR EVENING THUNDERSTORM SHOULD COME TO AN END BY
MIDNIGHT MOST AREAS.

DRIER AND COOLER AIRMASS WILL SET UP OVER THE CENTRAL COAST AREA
SUNDAY WITH 850 MB TEMPERATURES ONLY AROUND 6C. THE RIDGE
GRADUALLY BUILDS OVER CALIFORNIA INTO MIDWEEK WITH A WARMING
TREND. ATMOSPHERIC RIVER ENERGY SHOULD REMAIN NORTH OF OUR
FORECAST AREA WITH THE CLOSEST BRUSH WITH SONOMA COUNTY LATE
TUESDAY AND WEDNESDAY. KEEPING FORECAST DRY FOR NOW.

MAIN CONCERN IS NEXT PACIFIC TROF MOVING INTO THE AREA FRIDAY AND
SATURDAY. MODELS COMING INTO BETTER AGREEMENT ON PROGRESSING A
COLD FRONT THROUGH THE AREA. THERE ARE MINOR TIMING DIFFERENCES
WITH THE ECMWF FASTEST AND WEAKEST FORCING A COLD FRONT THROUGH
THE AREA FRIDAY. GFS SLIGHTLY SLOWER AND STRONGER WITH THE FRONT
FRIDAY NIGHT OR EARLY SATURDAY. GEM IS IN BETWEEN THE TWO OTHER
MODELS. THIS TROF IS DEEPER AND COLDER AND SHOULD BRING MUCH
NEEDED PRECIPITATION A LITTLE FURTHER SOUTH. STILL SEVERAL DAYS
AWAY SO DETAILS MAY CHANGE WITH FUTURE MODEL RUNS.

&&

.AVIATION...AS OF 4:45 AM PDT SATURDAY...A PRE-FRONTAL BOUNDARY
CONTINUES TO PUSH INLAND THIS MORNING WITH LIGHT RAIN IMPACTING
THE MONTEREY BAY AREA TERMINALS. FURTHER NORTH...RAIN SHOWERS ARE
DEVELOPING ALONG THE COLD FRONT THAT WILL PUSH INLAND THROUGH THE
AFTERNOON. IN ADDITION...A FEW THUNDERSTORMS WILL BE POSSIBLE
OVER THE NORTH BAY TERMINALS THIS AFTERNOON AND EVENING. WINDS
WILL INCREASE SLIGHTLY THIS AFTERNOON AND SHIFT TO THE NORTHWEST
IN WAKE OF THE FRONTAL PASSAGE. PRECIPITATION CHANCES DIMINISH
THROUGH THE LATE EVENING.

VICINITY OF KSFO...VFR WITH BRIEF MVFR CONDITIONS THROUGH THE
AFTERNOON/EVENING BENEATH SHOWER ACTIVITY. WIND SPEEDS WILL LIKELY
INCREASE THIS AFTERNOON AND BECOME MORE WESTERLY THROUGH THE
EVENING. MODERATE CONFIDENCE.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...VFR WITH BRIEF MVFR CONDITIONS
THROUGH THE LATE MORNING BENEATH SHOWER ACTIVITY. VFR CONDITIONS
EXPECTED AFTER 21Z WITH A SLIGHT INCREASE IN WESTERLY WIND SPEEDS.
WINDS BECOME LIGHT OVERNIGHT WITH PATCHY STRATUS POSSIBLE...YET
WILL KEEP SCT CLOUDS AT THIS TIME. MODERATE CONFIDENCE.

&&

.MARINE...AS OF 02:50 PM PDT SATURDAY...WEST TO NORTHWEST WINDS
WILL CONTINUE TO DIMINISH THROUGH TONIGHT AS A STRONG SURFACE LOW
PRESSURE PULLS AWAY FROM THE REGION. IN ADDITION...A LARGE
WESTERLY SWELL MOVING THROUGH THE WATERS WILL SLOWLY SUBSIDE
OVERNIGHT. WIND SPEEDS WILL THEN INCREASE AGAIN SUNDAY AFTERNOON
AND EVENING OVER THE COASTAL WATERS AS HIGH PRESSURE BUILDS OFF
THE CALIFORNIA COAST.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...SF BAY SOUTH OF THE BAY BRIDGE UNTIL 3 PM
             SCA...PT REYES TO PIGEON PT 0-10 NM UNTIL 3 PM
             SCA...PIGEON PT TO PT PINOS 0-10 NM UNTIL 3 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM UNTIL 3 PM
             SCA...PIGEON PT TO PT PINOS 10-60 NM UNTIL 3 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM UNTIL 3 PM
             SCA...SF BAY NORTH OF THE BAY BRIDGE UNTIL 9 PM
             SCA...PT ARENA TO PT REYES 0-10 NM UNTIL 9 PM
             SCA...PT ARENA TO PT REYES 10-60 NM UNTIL 9 PM
             SCA...PT REYES TO PIGEON PT 10-60 NM UNTIL 9 PM
             SCA...ROUGH BAR ADVISORY FOR SF BAR UNTIL 9 PM

&&

$$

PUBLIC FORECAST: KBB
AVIATION/MARINE: RGASS

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