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

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000
FXUS66 KMTR 060543
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
1043 PM PDT THU MAY 5 2016

.SYNOPSIS...AN UPPER LEVEL LOW OFF OF THE CENTRAL CALIFORNIA COAST
WILL SHIFT INLAND OVER SOUTHERN CALIFORNIA ON FRIDAY AND RESULT
IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THROUGH FRIDAY
EVENING. SCATTERED SHOWERS WILL LIKELY LINGER INTO SATURDAY WITH
DRY WEATHER EXPECTED TO RETURN TO MOST AREAS BY SUNDAY. DRY
WEATHER IS THEN FORECAST THROUGH THE MIDDLE OF NEXT WEEK ALONG
WITH A GRADUAL WARMING TREND.

&&

.DISCUSSION...AS OF 9:10 PM PDT THURSDAY...SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS OCCURRED ACROSS PORTIONS OF OUR FORECAST
AREA TODAY. THIS CONVECTIVE PRECIPITATION WAS TRIGGERED BY AN
UPPER LOW THAT IS CURRENTLY CENTERED ABOUT 100 MILES SOUTHWEST OF
MONTEREY. THE MOST SIGNIFICANT RAINFALL TO OCCUR FROM TODAY`S
SHOWER ACTIVITY WAS AT PINNACLES NATIONAL PARK WHERE 0.33" WAS
RECORDED. IN OTHER LOCATIONS WHERE RAIN FELL TODAY...AMOUNTS WERE
MOSTLY LESS THAN A TENTH OF AN INCH.

A LINE OF INTENSE SHOWERS AND THUNDERSTORMS DEVELOPED JUST TO THE
EAST OF SANTA CLARA AND SAN BENITO COUNTIES LATE THIS AFTERNOON.
BUT THIS CONVECTIVE ACTIVITY EITHER WEAKENED CONSIDERABLY OR
DISSIPATED AS IT MOVED TO THE NORTHWEST TOWARDS THE SANTA CLARA
AND HOLLISTER VALLEYS THIS EVENING. NOW THAT THE SUN HAS SET ALL
ACTIVITY HAS DIMINISHED AND EXPECT ONLY ISOLATED SHOWERS
OVERNIGHT.

THE CUTOFF LOW IS FORECAST TO MOVE GRADUALLY TO THE
SOUTHEAST OVERNIGHT AND THEN TURN TO THE EAST AND INLAND OVER
SOUTHERN CA ON FRIDAY MORNING. MEANWHILE...A SHORTWAVE TROUGH
ROTATING AROUND THE LOW IS FORECAST TO MOVE ACROSS OUR AREA ON
FRIDAY MORNING AND EARLY FRIDAY AFTERNOON. THE MODELS ALL SHOW AN
ORGANIZED AREA OF PRECIP WITH THIS SHORTWAVE...TRACKING FROM
NORTHEAST TO SOUTHWEST ACROSS OUR AREA TOMORROW.
HOWEVER...PRECISELY WHERE THAT PRECIP WILL BE FOCUSED IS DIFFICULT
TO SAY GIVEN DIFFERING MODEL SOLUTIONS. THE 00Z NAM FORECASTS
THIS AREA OF PRECIP TO TRACK ACROSS THE CENTRAL SF BAY AREA FROM
MID MORNING TO EARLY AFTERNOON. THE 00Z GFS AND LATEST HRRR MODEL
BOTH INDICATE THIS PRECIP WILL BE FOCUSED ACROSS EASTERN ALAMEDA
AND SANTA CLARA COUNTIES AND SOUTH INTO SAN BENITO COUNTY. GIVEN
MODEL DIFFERENCES...BELIEVE IT`S BEST NOT TO TRY TO PINPOINT
AREAS OF HIGHEST PRECIP POTENTIAL AND INSTEAD CONTINUE TO
DISTRIBUTE CHANCE POPS ACROSS OUR FORECAST AREA RATHER UNIFORMLY.
THUNDERSTORMS ARE A POSSIBILITY ONCE AGAIN TOMORROW.
HOWEVER...BECAUSE THE SHORTWAVE TROUGH WILL HAVE ROTATED OUT OF
OUR AREA PRIOR TO THE BEST SURFACE HEATING IN THE
AFTERNOON...THUNDERSTORM POTENTIAL WILL BE SOMEWHAT DIMINISHED.

THE UPPER LOW IS FORECAST TO LIFT TO THE NORTHEAST AND INTO THE
SOUTHERN GREAT BASIN BY SATURDAY. THE MODELS AGREE THAT MOISTURE
WILL CONTINUE TO WRAP AROUND THE LOW AND ACROSS OUR AREA ON
SATURDAY AND THAT INSTABILITY WILL REMAIN SUFFICIENT FOR SCATTERED
SHOWERS TO CONTINUE. HOWEVER...THUNDERSTORM CHANCES WILL HAVE
FADED CONSIDERABLY BY THEN.

A FEW SHOWERS MAY LINGER INTO SUNDAY MORNING...BUT FOR THE MOST
PART SUNDAY LOOKS TO BE A DRY DAY WITH TEMPERATURES NEAR AVERAGE.

DRY WEATHER WILL THEN CONTINUE THROUGH THE MIDDLE PART OF NEXT
WEEK AS AN UPPER RIDGE BUILDS NEAR THE WEST COAST. THIS RIDGE WILL
ALSO MEAN A GRADUAL WARMING TREND FOR MUCH OF NEXT WEEK. LONGER
RANGE MODELS HINT AT THE POSSIBILITY OF ANOTHER CUTOFF LOW
IMPACTING OUR AREA BY THE FOLLOWING WEEKEND (MAY 14 AND 15).

&&

.AVIATION...AS OF 10:30 PM PDT THURSDAY...UPPER LEVEL LOW WEST OF
THE CENTRAL COAST MOVING TOWARDS SOUTHERN CALIFORNIA. ISOLATED
SHOWERS ARE CONFINED TO THE HILLS THIS EVENING WHILE PATCHY LOW
CLOUDS ARE ALONG THE COAST. MVFR EXPECTED TO SPREAD OVER THE MRY
BAY AREA THIS EVENING AND INTO THE SFO BAY AREA LATER TONIGHT.
AN UPPER LEVEL DISTURBANCE ROTATING AROUND THE LOW WILL BRING A
CHANCE OF SHOWERS TO THE AREA FRIDAY MORNING. THESE SHOWERS WILL
BE COMING FROM THE NORTHEAST. MVFR CIGS EXPECTED MOST OF THE DAY
FRIDAY. CANNOT RULE OUT AN ISOLATED THUNDERSTORM FRIDAY AFTERNOON.

VICINITY OF KSFO...MVFR CIGS AFTER 12Z CONTINUING THROUGH THE REST
OF THE DAY. SCATTERED SHOWERS AFTER 16Z. MAINLY LIGHT SOUTHWEST
WINDS.

SFO BRIDGE APPROACH...SIMILAR AS KSFO.

MONTEREY BAY TERMINALS...MVFR CIGS AFTER 08Z. A FEW SHOWERS
POSSIBLE AFTER 17Z.

&&

.MARINE...AS OF 10:30 PM PDT THURSDAY...LOW PRESSURE DEVELOPING
OVER NEVADA WILL MODERATE NORTHERLY WINDS TO THE OUTER WATERS
NORTH OF PT REYES AND LIGHT SOUTH WINDS ELSEWHERE THROUGH FRIDAY.
AN UPPER LEVEL LOW OFF THE CENTRAL CALIFORNIA COAST WILL MOVE INTO
SOUTHERN CALIFORNIA ON FRIDAY. THIS WILL BRING A SLIGHT CHANCE OF
THUNDERSTORMS TONIGHT AND FRIDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION: W PI
MARINE: DRP


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