319
FXUS66 KMTR 200954
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
254 AM PDT SUN JUL 20 2025
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 133 PM PDT SAT JUL 19 2025
- COOLING TREND BEGINS MONDAY WITH A WIDESPREAD RETURN TO BELOW
NORMAL TEMPERATURES.
- LOCALIZED ELEVATED FIRE WEATHER THREAT FOR THE EAST BAY HILLS
SUNDAY AND MONDAY DUE TO DRY CONDITIONS AND GUSTY WINDS.
- GUSTY WINDS RETURN LATE SUNDAY AND CONTINUE THROUGH MONDAY
ALONG THE COAST, THE HIGHER TERRAIN, AND MOUNTAIN GAPS/PASSES.
SHORT TERM
ISSUED AT 217 AM PDT SUN JUL 20 2025
(TODAY AND TONIGHT)
THE FORECAST FOR THE MOST PART IS STARTING TO SOUND LIKE A BROKEN
RECORD: MORNING STRATUS LAYER CLEARING TO THE COAST BY THE
AFTERNOON WITH SEASONABLY COOL TEMPERATURES. WHILE THE OVERALL
WEATHER PICTURE IS THE SAME THERE ARE SOME DETAILS THAT DIFFER:
HIGH TEMPS, MARINE LAYER DEPTH, AND WINDS. THE UPPER LEVEL RIDGE
THAT BROUGHT SOME INLAND WARMTH SATURDAY HAS WEAKENED AND IS BEING
REPLACED BY AN UPPER LEVEL TROUGH/LOWER 500MB HEIGHTS. THE
OVERNIGHT SATELLITE FOG PRODUCT SHOWS THE MARINE LAYER HAS BETTER
COVERAGE THAN 24 HOURS DUE TO THE BUILDING UPPER LEVEL TROUGH.
HAVE ADDED SOME COASTAL DRIZZLE/PATCHY FOG TO THE FORECAST GIVEN
THE CURRENT MARINE LAYER SET UP. THE UPPER LEVEL TROUGH WILL ALSO
HELP TO KNOCK INLAND TEMPERATURES DOWN A FEW DEGREES. THE BIGGEST
WEATHER CHANGE FOR TODAY WILL BE THE WINDS. FOR SEVERAL DAYS NOW
WE'VE BEEN MENTIONING INCREASING WINDS LATE SUNDAY INTO MONDAY.
LATEST GUIDANCE CONTINUES TO ADVERTISE A SOLID PUSH OF WINDS. IN
FACT, ONSHORE GRADIENTS (SFO-SAC) ARE PROJECTED TO BE 4 TO 5 MB
LATER THIS AFTERNOON AND EVENING YIELDING SOME ROBUST WINDS FOR
THE EAST BAY GAPS/PASSES AND WEST DELTA REGION. BORDERLINE FOR A
WIND ADVISORY, BUT GUSTS IN THE 30-40 MPH WITH A FEW ISOLATED UP
TO 50 MPH WILL BE POSSIBLE. IT WILL BE WINDY ALONG THE COAST,
HIGHER TERRAIN, AND FAVORED VALLEYS, BUT NOT AS STRONG AS THE EAST
BAY.
IT GOES WITH OUT SAYING, BUT THE UPTICK IN WINDS WILL CREATE
INCREASED FIRE WEATHER CONCERNS FOR THE EAST BAY. WHILE WINDS
INCREASE HUMIDITY VALUES ARE LOWERING TO THE 25-40% RANGE. WHILE
NOT CRITICAL RH THE WIND WILL OVERRIDE IT. ERC CHART VALUES TAKE
A DIP TODAY THE MORE WIND BASED INDEX OF THE BURN INDEX REACHES IN
THE 90TH PERCENTILE. SO THAT MEANS, FLASHIER FUELS AND MORE
FLAMMABLE LIVE FUELS COULD CARRY FIRE. SPEAKING OF FIRE WEATHER
CONCERNS A CLASSIC NOCTURNAL DRYING EVENT IS TAKING PLACE OVER
THE SANTA LUCIA RANGE. AS STRATUS ROLLED THROUGH THE SALINAS
VALLEY RAPID DRYING OCCURRED ABOVE IT WITH A SENSOR ON CHEWS
RIDGE DIPPING INTO THE SINGLE DIGIT RH.
SUNDAY NIGHT INTO MONDAY: SOLID ONSHORE FLOW REMAINS WITH BREEZY
CONDITIONS LINGERING IN THE EAST BAY. THE MARINE LAYER WILL
DEEPEN WITH MORE COASTAL DRIZZLE.
LONG TERM
ISSUED AT 254 AM PDT SUN JUL 20 2025
(MONDAY THROUGH SATURDAY)
TO KICK OFF ANOTHER WORK WEEK MORE OF THE SAME - NIGHT/MORNING
CLOUDS WITH AFTERNOON INLAND SUNSHINE. ONSHORE WINDS EASE
SLIGHTLY EARLY MONDAY BEFORE RAMPING BACK UP MONDAY
AFTERNOON/EVENING FAVORING THE INLAND GAPS/PASSES.
THEREAFTER PRETTY BENIGN WEATHER CONTINUES INTO NEXT WEEKEND.
MARINE LAYER IS LOCKED IN WITH COOLER THE SEASONAL TEMPERATURES
THANKS TO AN ANOMALOUSLY LOW UPPER LEVEL TROUGH OVERHEAD. SOME
LONGER RANGE GUIDANCE EVEN DEEPENS THE TROUGH AND HAS AN A CUT-
OFF LOW FORM OVER THE REGION BY THURSDAY. SIMPLY PUT, IF YOU'RE
ENJOYING THE COOLER WEATHER WITH SOME AFTERNOON SUNSHINE YOU'LL
ENJOY THE LONG TERM FORECAST.
AVIATION
(06Z TAFS)
ISSUED AT 958 PM PDT SAT JUL 19 2025
IFR-LIFR STRATUS IS DEVELOPING FROM THE COAST INTO THE SONOMA COUNTY
VALLEYS, THE EAST BAY, THE MONTEREY BAY REGION, AND THE SALINAS
VALLEY. BREEZY NORTHWESTERLY FLOW CONTINUES TO DIMINISH WITH WINDS
BECOMING LIGHT OVERNIGHT. STRATUS WILL CONTINUE TO DEVELOP THROUGH
THE NIGHT, WITH MODERATE CONFIDENCE FOR STRATUS AT LVK AND SJC,
BEFORE RETREATING TO THE IMMEDIATE COAST LATE SUNDAY MORNING.
GREATEST CHANCES FOR LIFR STRATUS LIE AT THE IMMEDIATE COAST, THE
NORTH BAY VALLEYS, AND THE MONTEREY BAY REGION. BREEZY ONSHORE FLOW
RESUMES SUNDAY AFTERNOON, DIMINISHING IN THE LATE EVENING. SOME
STRATUS WILL RETURN SUNDAY EVENING BUT MORE TERMINALS WILL SEE THE
CLOUDS DEVELOP AFTER THE END OF THE TAF PERIOD.
VICINITY OF SFO... VFR CONTINUES FOR NOW WITH THE STRATUS DECK TO
THE IMMEDIATE NORTH OF THE TERMINAL AREA. MODERATE CONFIDENCE THAT
THE STRATUS WILL DEVELOP OVER THE TERMINAL TONIGHT, WITH THE
GREATEST PROBABILITIES AFTER 9Z. STRATUS SHOULD MIX OUT THROUGH
SUNDAY MORNING WITH BREEZY NORTHWEST WINDS RESUMING IN THE AFTERNOON
AND EVENING. STRATUS SHOULD RETURN TO THE TERMINAL LAST SUNDAY NIGHT
THROUGH MONDAY MORNING.
SFO BRIDGE APPROACH... POTENTIAL FOR STRATUS IMPACTS TO ARRIVE AN
HOUR OR TWO LATER THAN THE TERMINAL. OTHERWISE SIMILAR TO SFO.
MONTEREY BAY TERMINALS... LIFR CEILINGS WITH LIGHT WINDS THROUGH THE
NIGHT. CLEARING SHOULD OCCUR SUNDAY MORNING WITH LOW TO MODERATE
CONFIDENCE IN CLEARING TIME AT MRY. LIGHT WINDS OVERNIGHT WITH
BREEZY NORTHWEST FLOW RESUMING SUNDAY AFTERNOON.
MARINE
(TONIGHT THROUGH NEXT FRIDAY)
ISSUED AT 841 PM PDT SAT JUL 19 2025
LIGHT TO MODERATE NORTHWEST BREEZES WILL INCREASE TO MODERATE TO
FRESH BREEZES THROUGH SUNDAY, BEFORE WINDS DIMINISH AGAIN ON
MONDAY. GUSTY WINDS, POTENTIALLY HAZARDOUS TO SMALL CRAFT, ALSO
DEVELOP EACH AFTERNOON AND EVENING THROUGH THE GOLDEN GATE, INTO
THE DELTA, AND THE FAVORED COASTAL JETS OFF OF PIGEON POINT AND
THE BIG SUR COASTLINES. SLIGHT TO MODERATE SEAS PERSIST THROUGH
THE REMAINDER OF THE FORECAST PERIOD.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 9 PM PDT MONDAY
FOR SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PDT MONDAY FOR MRY BAY-
PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT PIEDRAS
BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 9 AM PDT MONDAY
FOR PT ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT EARLY THIS MORNING FOR PT
PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 AM PDT MONDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...DIALH
MARINE...DIALH
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