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

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000
FXUS66 KMTR 050523
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1023 PM PDT SAT JUL 4 2015

.SYNOPSIS...A PERSISTENT MARINE LAYER AND LIGHT ONSHORE FLOW WILL
RESULT IN WIDESPREAD NIGHT AND MORNING LOW CLOUDS...PATCHY FOG
AND POSSIBLE DRIZZLE IN COASTAL LOCATIONS THROUGH EARLY NEXT WEEK.
OTHERWISE...DRY WEATHER CONDITIONS WILL PERSIST WITH TEMPERATURES
GRADUALLY COOLING THROUGH THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...AS OF 8:55 PM PDT SATURDAY...AN UPPER LOW CURRENTLY
CENTERED OFFSHORE NEAR 33N/133W IS BEGINNING TO MOVE SLOWLY TO THE
ENE. TEMPERATURES WERE SLIGHTLY COOLER TODAY COMPARED TO
YESTERDAY AND A GRADUAL COOLING TREND IS EXPECTED TO CONTINUE
THROUGH THE MIDDLE OF NEXT WEEK AS THE UPPER LOW VERY SLOWLY
APPROACHES THE COAST. THE MARINE LAYER HAS RECENTLY DEEPENED PAST
2000 FEET AND WOULD EXPECT A RELATIVELY DEEP MARINE LAYER TO
PERSIST OVER THE NEXT SEVERAL DAYS. THIS WILL MEAN WIDESPREAD
NIGHT AND MORNING LOW CLOUDS AND PATCHY FOG...ALONG WITH LOCAL
LATE NIGHT/EARLY MORNING DRIZZLE IN COASTAL LOCATIONS.
TEMPERATURES BY EARLY NEXT WEEK ARE EXPECTED TO BE AT LEAST
SLIGHTLY BELOW NORMAL ACROSS OUR ENTIRE AREA.

MONSOON MOISTURE CONTINUES TO TRIGGER WIDESPREAD AFTERNOON AND
EVENING CONVECTION OVER THE SIERRA NEVADA AND MOUNTAINS OF FAR
NORTHERN CALIFORNIA. THAT MOISTURE/CONVECTION IS EXPECTED TO
REMAIN TO OUR EAST. HOWEVER...AS THE UPPER LOW OFFSHORE DRAWS
CLOSER AROUND THE MIDDLE OF NEXT WEEK...THE MEDIUM RANGE MODELS
SUGGEST AN INCREASE IN MOISTURE OVER THE EASTERN PART OF OUR
FORECAST AREA BETWEEN LATE WEDNESDAY AND FRIDAY. THERE IS NOT YET
ENOUGH FROM THE MODELS TO SUPPORT THE IDEA OF CONVECTION IN OUR
AREA LATER NEXT WEEK AS THE UPPER LOW APPROACHES...BUT THIS IS
SOMETHING TO KEEP AN EYE ON.

&&

.AVIATION...AS OF 10:07 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.

THE MARINE LAYER INCREASED IN DEPTH THIS EVENING AT THE FORT ORD
PROFILER...JUMPED UP TO ABOUT 2500 FEET...BUT HAS REMAINED STEADY
AT ABOUT 1500 FEET DEEP AT THE BODEGA BAY PROFILER. A VERY GRADUAL
COOLING BY APPROX 1-2 CELSIUS IS FORECAST AT THE 850 MB LEVEL FROM
TONIGHT THROUGH SUNDAY. THE LOWER TO MID LEVEL COOLING WILL NOT BE
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...LIGHTER WESTERLY WINDS TONIGHT. LEFT IN MVFR TO
IFR CIGS TRANSITION LATE TONIGHT...BUT CONFIDENCE IS LOW REGARDING
CEILING ARRIVAL. VFR IS FORECAST TO RETURN BY LATE SUNDAY MORNING.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...IFR CIGS WILL CONTINUE TONIGHT. STILL
THINKING THE MARINE LAYER WILL COMPRESS BUT NOT UNTIL MUCH LATER
TONIGHT AND/OR SUNDAY. VFR IS FORECAST TO RETURN BY LATE SUNDAY
MORNING.

&&

.MARINE...AS OF 8:19 PM PDT SATURDAY...LOW PRESSURE LOCATED 650
MILES SOUTHWEST OF BIG SUR WILL REMAIN NEARLY STATIONARY THROUGH
THE WEEKEND. HIGH PRESSURE WILL TEMPORARILY BUILD OVER NORTHERN
CALIFORNIA SUNDAY. GUSTY AFTERNOON AND EVENING WINDS WILL RETURN
TO SAN FRANCISCO BAY LATER IN THE DAY SUNDAY AND AGAIN MONDAY. A
LONG PERIOD SOUTHWESTERLY SWELL FROM THE SOUTHERN HEMISPHERE WILL
MOVE INTO THE AREA EARLY ON MONDAY.

&&

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

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION/MARINE: CANEPA

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