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

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000
FXUS66 KMTR 052041
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
141 PM PDT THU MAY 5 2016

.SYNOPSIS...AN UPPER LEVEL LOW OFF OF THE CENTRAL COAST WILL
SHIFT INLAND OVER SOUTHERN CALIFORNIA AND RESULT IN ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS THROUGH SATURDAY. BY SUNDAY,
DRY WEATHER CONDITIONS ARE FORECAST TO RETURN AND PERSIST THROUGH
THE MIDDLE OF NEXT WEEK ALONG WITH A GRADUAL WARMING TREND.

&&

.DISCUSSION...AS OF 01:41 PM PDT THURSDAY...THE CENTER OF A
MID/UPPER LEVEL LOW IS CURRENTLY POSITIONED OFF OF THE CENTRAL
COAST THIS AFTERNOON. WITH THIS SYSTEM, MOISTURE CONTINUES TO
ADVECT OVER THE REGION WITH INCREASED INSTABILITY. AS A RESULT,
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS HAVE IMPACTED THE
NORTH AND EAST BAY REGIONS EARLY THIS MORNING AND CONTINUE OVER
THE NORTH BAY AT THIS HOUR. MEANWHILE, SHOWERS HAVE FINALLY
STARTED TO DEVELOP OVER THE CENTRAL COAST AND IS EXPECTED TO
INCREASE IN COVERAGE THROUGH THE AFTERNOON. ISOLATED TO SCATTERED
SHOWERS WILL PERSIST THROUGH THE EVENING AS THE MID/UPPER LEVEL
SYSTEM SLOWLY PUSHES INLAND OVER SOUTHERN CALIFORNIA THROUGH
TONIGHT. RAINFALL AMOUNTS WILL BE SPOTTY, YET CANNOT RULE OUT
BRIEF MODERATELY TO LOCALLY HEAVY RAINFALL WITH ANY SHOWERS THAT
MOVE OVER A REGION.

THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH
SATURDAY AS THE MID/UPPER LEVEL SYSTEM MOVES VERY LITTLE INLAND
THROUGH LATE WEEK. THE FORECAST MODELS DO INDICATE THE POTENTIAL FOR
A MORE ORGANIZED BAND OF PRECIPITATION WRAPPING AROUND THE UPPER
LEVEL LOW FRIDAY MORNING/AFTERNOON. HOWEVER, THE MODELS DIFFER ON
THE LOCATION OF THIS DEVELOPMENT. THUS, DO HAVE INCREASED CHANCES OF
PRECIPITATION REGION-WIDE ON FRIDAY AS A RESULT. WHILE THE THREAT
FOR THUNDERSTORMS DECREASES SLIGHTLY ON FRIDAY, THERE REMAINS A
SLIGHT CHANCE GIVEN THE COLDER, MORE UNSTABLE AIR MASS ALOFT. IN
ADDITION, TEMPERATURES WILL REMAIN ON THE COOL SIDE OF SEASONAL
AVERAGES GIVEN THE PROXIMITY OF THE UPPER LEVEL FEATURE.

SHOWER ACTIVITY WILL DIMINISH DURING THE DAY ON SATURDAY AS THE
UPPER LEVEL SYSTEM PUSHES INTO THE DESERT SOUTHWEST. BY SUNDAY, DRY
CONDITIONS ARE FORECAST TO RETURN TO THE ENTIRE REGION AS MID/UPPER
LEVEL HIGH PRESSURE BEGINS TO DEVELOP OVER THE EASTERN PACIFIC.
EARLY NEXT WEEK, THE RIDGE WILL BUILD AND SHIFT CLOSER TO THE WEST
COAST AND RESULT IN A GRADUAL WARMING TREND. AS A RESULT, EXPECT
TEMPERATURES TO REBOUND BACK TO NEAR OR SLIGHTLY ABOVE SEASONAL
AVERAGES BY THE MIDDLE OF NEXT WEEK WITH ONGOING DRY WEATHER
CONDITIONS.

&&

.AVIATION...AS OF 10:45 AM PDT THURSDAY...A SLOW MOVING UPPER LOW
WILL BE IN THE VICINITY OF THE REGION TODAY AND TOMORROW. CHAOTIC
SKIES VISIBLE ACROSS THE REGION WITH SEVERAL DIFFERENT CLOUD
DECKS RANGING FROM 1500-6000 FT BRINGING MIXED BAG OF VFR AND
MVFR CONDITIONS. UNSTABLE AIR MASS ASSOCIATED WITH THE CORE OF THE
UPPER LOW IS ALSO BRINGING HIT OR MISS RAIN SHOWERS ACROSS
PREDOMINATELY THE NORTH AND EAST BAY... WITH AN ISOLATED
THUNDERSTORM OR TWO POPPING UP PREDOMINATELY AROUND THE EAST BAY
AND NAPA COUNTY SO FAR THIS MORN. SIMILAR CONDITIONS WILL PERSIST
THROUGHOUT THE DAY... SO HAVE LEFT IN VCSH THROUGHOUT ALL TAFS.
WINDS GENERALLY 15 KT OR LESS BUT VCTS MAY BRING GUSTY ERRATIC
WINDS. INTERMITTENT MVFR/VFR CIGS EXPECTED THROUGH THE DAY BUT
WITH MARGINALLY RISING CIGS.

VICINITY OF KSFO...PREDOMINATELY VFR BUT OCCASIONAL MVFR POSSIBLE
WITH CIGS DROPPING INTO 2500-3000 FT RANGE THROUGH THE DAY. VCSH
THROUGHOUT THE DAY. ONSHORE WINDS GENERALLY 15 KT OR LESS.

SFO BRIDGE APPROACH...SIMILAR AS KSFO.

MONTEREY BAY TERMINALS... PREDOMINATELY VFR TODAY BECOMING MVFR TO
IFR OVERNIGHT. VCSH POSSIBLE THROUGHOUT THE DAY. ONSHORE WINDS
GENERALLY 10 KT OR LESS. UP VALLEY WINDS UP TO 15 KT FOR KSNS
EARLY TOMORROW.

&&

.MARINE...AS OF 10:38 AM PDT THURSDAY...AN UPPER LOW OVER THE AREA
WILL BRING MODERATE NORTHERLY WINDS TO THE OUTER WATERS NORTH OF
PT REYES AND LIGHT SOUTH WINDS ELSEWHERE. HAZARDOUS CONDITIONS
FROM SQUARED SEAS WILL BE ALSO BE POSSIBLE IN THE NORTHERN OUTER
WATERS. THIS STORM MAY PRODUCE SHOWERS AND A STRAY THUNDERSTORM
OVER THE COASTAL WATERS TODAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PT ARENA TO PIGEON PT 10-60 NM
             SCA...SF BAY UNTIL 9 PM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION: DRP
MARINE: DRP


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