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

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000
FXUS66 KMTR 291030
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
330 AM PDT SUN MAR 29 2015

.SYNOPSIS...MUCH ABOVE NORMAL TEMPERATURES WILL CONTINUE TODAY WITH
RECORD HIGH TEMPERATURES POSSIBLE. A COOLING TREND IS THEN
FORECAST FROM MONDAY THROUGH WEDNESDAY. DRY WEATHER IS EXPECTED TO
PERSIST THROUGH THE FORECAST PERIOD.

&&

.DISCUSSION...AS OF 3:30 AM PDT SUNDAY...CONDITIONS EARLY THIS
MORNING AND SIMILAR TO WHAT THEY WERE 24 HOURS AGO. A STRONG
NORTH-SOUTH SURFACE PRESSURE GRADIENT CONTINUES TO MAINTAIN BRISK
NORTHERLY FLOW OVER THE COASTAL WATERS...WHICH IS KEEPING THE
BOUNDARY LAYER RELATIVELY WELL-MIXED AND FREE OF COASTAL STRATUS.
SURFACE DEWPOINTS ARE GENERALLY RUNNING A FEW DEGREES BELOW WHAT
THEY WERE 24 HOURS AGO...SO IT`S UNLIKELY THERE WILL BE MUCH IN
THE WAY OF COASTAL LOW CLOUD DEVELOPMENT PRIOR TO SUNRISE.
THUS...TODAY SHOULD BE A DAY MUCH LIKE YESTERDAY WITH LOTS OF
SUNSHINE (EXCEPT FOR OCCASIONAL THIN HIGH CLOUDS) AND WARM
TEMPERATURES. EXPECT AFTERNOON HIGHS IN THE MID TO UPPER 60S ALONG
THE IMMEDIATE COAST...WITH 70S TO LOWER 80S ELSEWHERE EXCEPT MID
TO UPPER 80S IN THE WARMEST INLAND VALLEYS. SOME WARM SPOTS LIKE
PINNACLES NATIONAL PARK MAY REACH 90. RECORD HIGH TEMPERATURES ARE
POSSIBLE TODAY.

TODAY WILL BE THE WARMEST DAY OF THE WEEK. AN UPPER TROUGH OVER
THE EASTERN PACIFIC WILL APPROACH THE WEST COAST ON MONDAY. THIS
APPROACHING TROUGH WILL TRIGGER AN INCREASE IN ONSHORE FLOW AND
TEMPERATURES WILL BEGIN TO TREND DOWNWARD ON MONDAY...ALTHOUGH
STILL PROBABLY REMAIN ABOVE NORMAL IN MOST PLACES. THE MODELS
INCREASE LOW LEVEL MOISTURE BY MONDAY EVENING AND WE SHOULD SEE
DEVELOPMENT OF LOW CLOUDS ALONG THE COAST. PRECIPITATION WITH
THIS TROUGH IS FORECAST TO REMAIN WELL TO OUR NORTH.
HOWEVER...STRENGTHENING ONSHORE FLOW ON MONDAY NIGHT COMBINED WITH
INCREASED LOW LEVEL MOISTURE MAY RESULT IN PATCHY DRIZZLE IN
COASTAL AREAS AND ON THE WEST SLOPES OF THE COASTAL HILLS FROM
MONDAY NIGHT INTO TUESDAY MORNING. TEMPERATURES WILL DROP BACK
DOWN TO AROUND NORMAL ON TUESDAY AND LOCALLY BLUSTERY CONDITIONS
ARE EXPECTED NEAR THE COAST AND IN THE HILLS WITH BRISK WEST TO
NORTHWEST WINDS.

A REINFORCING SHOT OF COOL AIR WILL ARRIVE WITH ANOTHER SHORTWAVE
TROUGH ON WEDNESDAY. BUT AT THE SAME TIME SURFACE HIGH PRESSURE
WILL BE BUILDING TO OUR NORTH WHICH WILL INHIBIT ONSHORE FLOW TO
SOME EXTENT AND HALT THE COOLING TREND. SLIGHT WARMING IS THEN
EXPECTED LATE IN THE WEEK AS WEAK UPPER LEVEL RIDGING DEVELOPS.
DRY WEATHER WILL PERSIST THROUGH AT LEAST FRIDAY...AND PROBABLY
INTO SATURDAY AS WELL.

A COLD UPPER TROUGH IN THE GULF OF ALASKA IS FORECAST TO DROP TO
THE SE LATE IN THE WEEK AND POSSIBLY GENERATE PRECIP IN OUR AREA
BY SATURDAY NIGHT AND SUNDAY. BUT THE MEDIUM RANGE MODELS ARE
HAVING A DIFFICULT TIME FORECASTING A CONSISTENT TRAJECTORY FOR
THIS SYSTEM...ALTERNATING BETWEEN A SOLUTION THAT DIGS THE TROUGH
SOUTH ALONG THE COAST (WET) OR ONE THAT SWEEPS IT INLAND TO OUR
NORTH (DRY).

&&

.AVIATION...AS OF 9:30 PM PDT SATURDAY...A DRY NORTHERLY WIND FLOW
WILL TEND TO KEEP VFR GOING AREA-WIDE FOR THE PERIOD. THE ACV-SFO
GRADIENT IS NEAR 8 MB AND THE UKI-STS GRADIENT IS 3 MB. STS REPORTS
A NORTH WIND AT 10 KNOTS. THE NORTH WIND AT STS COULD BECOME A LITTLE
GUSTY AT TIMES OVERNIGHT BUT ALSO WEIGHTED IN THE FORECAST IS THE
TENDENCY FOR THE SURFACE WINDS TO DE-COUPLE UNDER NIGHT-TIME COOLING.
THE 00Z NAM MODEL APPEARS TO BE UNDER-FORECASTING TONIGHT`S NORTHERLY
GRADIENTS BY APPROX 1-3 MB...WHICH MAY CARRY OVER INTO SUNDAY.
ALSO...7-8 MB OF OFFSHORE GRAD FROM WMC-SFO APPEARS VERY LIKELY LATE
TONIGHT AND EARLY SUNDAY MORNING LIKELY HELPING TO FURTHER DIMINISH
THE ONSHORE WINDS. IN SUMMARY IT LOOKS LIKE A HIGH CONFIDENCE VFR
FORECAST FOR THE PERIOD THE ONLY EXCEPTION IS THAT THERE MAY BE A
FEW SMALL PATCHES OF LOW CLOUDS AND/OR FOG OVER THE SOUTHERN MONTEREY
BAY AREA BRIEFLY VERY LATE TONIGHT AND/OR EARLY SUNDAY MORNING.

VICINITY OF KSFO...VFR. RECENT OBS INDICATE WESTERLY WIND GUSTS
STILL REACHING TO 20 KNOTS. SURFACE WINDS SHOULD TEND TO SETTLE
SLOWLY OVERNIGHT...A LITTLE SLOWER THAN PREVIOUSLY FORECASTED.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...SO FAR SO GOOD VFR CONTINUES TO HOLD
THIS EVENING...BUT AS DISCUSSED THERE MAY BE A FEW SMALL PATCHES
OF LOW CLOUDS AND/OR FOG VERY LATE TONIGHT AND/OR EARLY SUN MORNING.
24 HOUR TRENDS INDICATE DECENT DRYING OF THE AIR MASS THIS AREA
INCLUSIVE SO THE TAFS MAINTAIN OPTIMISTIC WITH VFR FOR THE OVERNIGHT
HOURS AND SUNDAY.

&&

.MARINE...AS OF 8:48 PM PDT SATURDAY...STRONG AND GUSTY NW WINDS WILL
CONTINUE OVER THE COASTAL WATERS THIS WEEKEND AND NEXT WEEK. HIGH
PRESSURE WILL REMAIN PARKED OVER THE EASTERN PACIFIC THROUGH THE
PERIOD. THE STRONG WINDS WILL PRODUCE FRESH AND SHORT PERIOD SEAS.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PIGEON PT TO PT PINOS 0-10 NM AFTER 3 PM
             SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT REYES TO PIGEON PT 0-10 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...PT ARENA TO PT REYES 10-60 NM
             SCA...PT REYES TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PINOS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM

&&

$$

PUBLIC FORECAST: DYKEMA
AVIATION/MARINE: CANEPA

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