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

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS66 KMTR 050056
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
556 PM PDT SAT JUL 4 2015

.SYNOPSIS...A PREDOMINATE MARINE LAYER AND ONSHORE FLOW WILL
RESULT IN LATE NIGHT/EARLY MORNING LOW CLOUDS...PATCHY FOG AND
POSSIBLE DRIZZLE ALONG COASTAL LOCATIONS THROUGH EARLY NEXT WEEK.
OTHERWISE...DRY WEATHER CONDITIONS WILL PERSIST WITH TEMPERATURES
NEAR OR SLIGHTLY BELOW SEASONAL AVERAGES.

&&

.DISCUSSION...AS OF 01:42 PM PDT SATURDAY...GENERALLY QUIET
WEATHER CONDITIONS PERSIST OVER THE REGION TODAY AS AN UPPER
LEVEL LOW PRESSURE SYSTEM LINGERS WEST OF CALIFORNIA.
MEANWHILE...SHOWERS AND THUNDERSTORMS ARE ONCE AGAIN OCCURRING
OVER THE SIERRA AS MONSOONAL MOISTURE ADVECTS ACROSS THAT REGION.
BACK NEAR THE COAST...A MARINE LAYER AROUND 1500 FEET REMAINS IN
PLACE AND LOW LEVEL CLOUDS APPEAR TO BE MAKING A PUSH BACK TOWARD
THE COASTLINE. THIS TREND WILL LIKELY CONTINUE THROUGH THE LATE
AFTERNOON AND EVENING WITH LOW CLOUDS SPREADING INLAND INTO MOST
VALLEY LOCATIONS LATE TONIGHT. IN ADDITION...PATCHY FOG AND
DRIZZLE WILL BE LIKELY DURING THE OVERNIGHT AND EARLY MORNING
HOURS INTO SUNDAY.

LITTLE CHANGE IS EXPECTED THROUGH EARLY NEXT WEEK WITH THE
MID/UPPER LEVEL LOW FORECAST TO REMAIN OFF OF THE WEST COAST. A
SLIGHT COOLING TREND IS EXPECTED FOR THE FIRST HALF OF THE
UPCOMING WEEK AS THE RIDGE OVER THE GREAT BASIN WEAKENS AND THE
AFOREMENTIONED LOW PRESSURE SYSTEM BEGINS TO APPROACH THE COAST.
OVERALL...THE BEST MOISTURE AND INSTABILITY FOR ANY CONVECTION
WILL REMAIN OVER THE INTERIOR PORTIONS OF THE STATE.
MEANWHILE...THE UPPER LEVEL FEATURE WILL HELP TO MAINTAIN A STRONG
MARINE LAYER ALONG THE COAST AND SUPPORT OVERNIGHT/MORNING LOW
CLOUDS ALONG WITH PATCHY FOG AND DRIZZLE THROUGH EARLY NEXT WEEK.

DRY WEATHER CONDITIONS AND NEAR SEASONAL TEMPERATURES ARE
CURRENTLY FORECAST FOR THE LATTER HALF OF THE FORECAST PERIOD WITH
THE REGION UNDER A BROAD MID/UPPER LEVEL TROUGH.

&&

.AVIATION...AS OF 5:47 PM PDT SATURDAY...A NEARLY STATIONARY UPPER
LEVEL LOW PRESSURE AREA WAS LOCATED 650 MILES SW OF THE BIG SUR
COAST. A SUBTLE LOWERING /COOLING/ OF THE 500 MB GEOPOTENTIAL
HEIGHTS...LOWER BY LESS THAN 1 DECAMETER...IS EXPECTED OVER NORTHERN
CA TONIGHT FOLLOWED BY SLIGHTLY HIGHER HEIGHTS /WARMING/ SUNDAY. A
VERY GRADUAL COOLING BY APPROX 1-2 CELSIUS IS FORECAST AT THE 850 MB
LEVEL FROM TONIGHT THROUGH SUNDAY.

THE MARINE LAYER IS PRESENTLY 1500-1700 FEET DEEP AND MAY TEND TO
COMPRESS BY A FEW HUNDRED FEET FROM LATE TONIGHT THROUGH SUNDAY AS
MID TROPOSPHERIC RIDGING RETURNS PER SLIGHTLY RISING /WARMING/ 500
MB HEIGHTS. THE AFOREMENTIONED LOWER TO MID LEVEL COOLING IS NOT
ENOUGH TO GREATLY DISRUPT OR WEAKEN THE MARINE LAYER TO THE POINT
OF MIXING OUT.

BRIEF RIDGING OVER CA ON SUNDAY COMBINED WITH A SOMEWHAT COMPRESSED
MARINE LAYER AND A RETURN OF A ROBUST SFO-SAC ONSHORE PRESSURE GRADIENT
NEAR 4 MB WILL PRODUCE GUSTY WESTERLY WINDS IN THE AFTERNOON AND EVENING.
A SIMILAR SCENARIO LEADING TO GUSTY AFTERNOON AND EVENING WINDS IS
EXPECTED ON MONDAY.

VICINITY OF KSFO...WESTERLY WIND GUSTS TO THE MID TO UPPER 20 KNOT
RANGE ARE FORECAST TIL 04Z. IT`S LOW TO MODERATE CONFIDENCE REGARDING
THE RETURN OF CLOUD CEILINGS TONIGHT. DON`T HAVE A GREAT FEEL FOR THE
RETURN TIMING AND DECIDED TO LEAVE THE INHERITED FORECAST AS IS.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...THE STRATUS LAYER IS MOVING IN A BIT
QUICKER THAN USUAL DESPITE THE MONTEREY BAY BUOY WINDS 250 DEGREES
AT ONLY 7 KNOTS AND KMRY WINDS AVERAGING FROM A 220-240 DEGREES
/DOWNSLOPING & DRYING DIRECTION/. BANKED ON SW WIND DIRECTION TO
PULL KMRY BACK TO SCT010 01Z-04Z BUT THIS DOES NOT LOOK LIKE IT`LL
BE THE CASE. WILL MONITOR A BIT MORE BEFORE AMENDING. OTHERWISE
IFR CIGS FORECAST FOR TONIGHT AS THE MARINE LAYER IS EXPECTED TO
COMPRESS GRADUALLY LATE TONIGHT THROUGH SUNDAY MORNING. VFR IS
FORECAST TO RETURN BY LATE SUNDAY MORNING.

&&

.MARINE...AS OF 10:32 AM PDT SATURDAY...A WEAK LOW PRESSURE WILL
LINGER OVER THE COASTAL WATERS THROUGH MIDWEEK RESULTING IN LIGHT
WINDS AND SEAS THROUGH THE PERIOD.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...SF BAY UNTIL 9 PM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION: CANEPA
MARINE: DRP


VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO

FOLLOW US ON FACEBOOK AND TWITTER AT:
WWW.FACEBOOK.COM/NWSBAYAREA
WWW.TWITTER.COM/NWSBAYAREA


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.