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

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000
FXUS66 KMTR 080407
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
907 PM PDT TUE JUL 7 2015

.SYNOPSIS...SEASONALLY COOL TEMPERATURES ARE EXPECTED FOR MUCH OF
THE FORECAST AREA THROUGH THE WEEKEND...AS A LOW PRESSURE SYSTEM
SLIDES ACROSS CENTRAL AND NORTHERN CALIFORNIA. THIS LOW WILL ALSO
PROMOTE THE POSSIBILITY OF SHOWERS AND ISOLATED THUNDERSTORMS ON
WEDNESDAY AND THURSDAY.

&&

.DISCUSSION...AS OF 9:07 PM PDT TUESDAY...TODAY WAS A BEAUTIFUL
DAY AROUND THE AREA WITH PARTLY TO MOSTLY SUNNY SKIES FOR MOST AND
AFTERNOON HIGH TEMPERATURES IN THE LOW TO MID 70S ALONG THE COAST
AND LOW TO MID 80S INLAND. THE CURRENT SATELLITE WATER VAPOUR
IMAGE IS SHOWING A LOW PRESSURE SYSTEM POSITIONED JUST OFF SHORE
THIS EVENING...PROVIDING GENTLE ONSHORE FLOW WHICH WILL MODERATE
OVERNIGHT TEMPERATURES AND MOST LIKELY PUSH SOME MARINE CLOUDS
INTO LOW LYING AREAS ALONG THE COAST AND POSSIBLY THE INLAND
VALLEYS.

THE 1200Z ECMWF AND 0000Z GFS40 HAVE INITIALIZED WELL WITH THE
CURRENT SYNOPTIC WEATHER PATTERN AND REMAIN IN GOOD AGREEMENT
THROUGH THE FORECAST PERIOD. THE PREVIOUSLY MENTIONED LOW PRESSURE
SYSTEM WILL BE THE MAIN WEATHER PLAYER OVER THE NEXT FEW DAYS AS
IT SLOWLY SLIDES EAST ACROSS THE FORECAST AREA. AS THE LOW MOVES
INLAND WEDNESDAY EXPECT INCREASING CLOUDINESS...SEASONALLY COOL
BUT COMFORTABLE TEMPERATURES AND EVEN A POSSIBILITY OF SHOWERS AND
ISOLATED THUNDERSTORMS THROUGH THURSDAY EVENING.

THE LOW WILL EXIT THE AREA BY FRIDAY BRINGING AN END TO THE THREAT
OF SHOWERS AND THUNDERSTORMS FOR OUR AREA. HOWEVER...AS THE LOW
LEAVES THE AREA A TROUGH OF LOW PRESSURE PUSHES TOWARDS THE
PACIFIC NORTHWEST WHICH WILL REINFORCE SEASONALLY COOL TEMPERATURES
AROUND THE FORECAST AREA THROUGH THE WEEKEND. THE CURRENT FORECAST
PACKAGE SEEMS REASONABLE SO NO FURTHER UPDATES ARE NEEDED AT THIS
TIME.

&&

.AVIATION...AS OF 6:07 PM PDT TUESDAY...THE MARINE LAYER HAS
LIFTED AND GREATLY WEAKENED BY LOWER-MID LEVEL COOLING. WARMER
THAN AVERAGE SEA SURFACE TEMPS FOR EARLY JULY MAY ALSO BE
CONTRIBUTING TO MORE SURFACE TO LOWER LEVEL BUOYANCY...LEADING TO
A FURTHER WEAKENING OF THE MARINE LAYER. ADDITIONAL DEEPER LAYERED
COOLING IS FORECAST TONIGHT AND WEDNESDAY AS THE EPAC LOW DRIFTS
ESE REACHING THE MONTEREY BAY AREA WEDNESDAY AFTERNOON. ALL IN ALL
THE REDEVELOPMENT TIMING OF THE STRATUS AND FOG TONIGHT MAY BE
SIMILAR TO LAST EVENING...POSSIBLY EVEN A LITTLE LATER.

BACKTRACKING A LITTLE...THERE WAS A WEAK NEARLY STATIONARY OCCLUDED
FRONT SITUATED OVER THE COASTAL WATER THE LAST COUPLE DAYS...BUT
IT HAS SINCE COMPLETELY DIMINISHED. THE LACK OF A BOUNDARY AND
ASSOCIATED GENTLE LIFT MAY ALSO TEND TO CAUSE A SLOWER REDEVELOPMENT
OF THE STRATUS AND FOG TONIGHT...AND MAY ALSO OFFSET THE ABILITY FOR
PATCHY DRIZZLE TO FORM. W-NW WINDS WILL SHIFT THE HIGHEST HUMIDITY
SE LATE TONIGHT AND WEDNESDAY.

VICINITY OF KSFO...VFR. A FEW WESTERLY WIND GUSTS TO 20-22 KNOTS
ARE EXPECTED TIL 04Z. LOW CONFIDENCE MVFR CIGS 06Z-18Z. VFR IS
EXPECTED TO RETURN BY MID-LATE WEDNESDAY MORNING.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...A FEW FRAGMENTS OF LOW CLOUDS ARE
BEGINNING TO REDEVELOP ALONG THE BAY SHORELINE. TEMPO IFR
INDICATED 05Z-08Z WITH IFR PREVAILING OVERNIGHT. VFR IS FORECAST
TO RETURN BY LATE WEDNESDAY MORNING.

&&

.MARINE...AS OF 10:38 AM PDT TUESDAY...LIGHT TO MODERATE WINDS
WILL PERSIST ALONG THE CENTRAL COAST AS A WEAK LOW PRESSURE SYSTEM
REMAINS OVER THE EASTERN PACIFIC. WINDS WILL BE GUSTY EACH
AFTERNOON IN BOTH BAYS WITH DECENT ONSHORE FLOW. THE LOW PRESSURE
SYSTEM WILL MOVE ACROSS THE COASTAL WATERS THURSDAY BRINGING A
SLIGHT CHANCE OF THUNDERSTORMS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
 .TNGT...NONE

&&

$$

PUBLIC FORECAST: LARRY
AVIATION: CANEPA
MARINE: MM


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