280
FXUS66 KMTR 211137
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
437 AM PDT FRI AUG 21 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1017 PM PDT THU AUG 20 2026
- TEMPERATURES WILL BE CLOSE TO OR BELOW NORMAL INTO THE
BEGINNING OF NEXT WEEK
- WARM AND DRY CONDITIONS ABOVE 1000FT PERSIST INTO THE WEEKEND
SHORT TERM
ISSUED AT 1017 PM PDT THU AUG 20 2026
(FRIDAY AND FRIDAY NIGHT)
IMPROVED ONSHORE FLOW IN THE LOWER BOUNDARY LAYER ESPECIALLY FOR THE
NORTH BAY AND BAY AREA SHOULD RESULT IN MORE EXTENSIVE STRATUS
INTRUSION OVERNIGHT COINCIDING WITH OVERNIGHT LOWS CLOSER TO NORMAL
FOR THIS TIME OF YEAR. WARM AND DRY CONDITIONS WILL CONTINUE BOTH
OVERNIGHT AND THROUGH THE DAY ABOVE 1000FT INLAND AND NEAR THE
COAST, THIS INCLUDES IN VICINITY OF THE TIMBER FIRE WHERE RELATIVELY
LIGHT WINDS CONTINUE TO BE A MITIGATING FACTOR. SOME ELEVATED
CONVECTION EARLIER THURSDAY NIGHT HAS TAPERED OFF OR NOW IN THE
STEERING FLOW OF THE RIDGE. ANY MID/UPPER LEVEL MOISTURE ATTEMPTING
TO REACH THE CENTRAL COAST WOULD BE GREETED BY ANEMIC INSTABILITY
AND CONFLUENT FLOW ALOFT.
AS THE CLOSED PORTION OF THE UPPER LEVEL LOW RESPONSIBLE FOR THE
PERSISTENT TROUGHING RECENTLY WILL SLOWLY APPROACH THE OREGON COAST
LATER TONIGHT WITH A STEADY FETCH OF ONSHORE FLOW CONTINUING ACROSS
OUR AREA, WITH ONLY A MARGINAL INCREASE IN DEPTH OF THE MARINE LAYER
EXPECTED INTO EARLY SATURDAY MORNING.
LONG TERM
ISSUED AT 1017 PM PDT THU AUG 20 2026
(SATURDAY THROUGH NEXT THURSDAY)
THE PARENT LOW MENTIONED ABOVE MOVES ONSHORE INTO THE PACNWEST
DURING THE DAY SATURDAY WITH A WEAK TROUGHING PATTERN LINGERING
OFFSHORE AT OUR LATITUDE THROUGH AT LEAST THE WEEKEND. HOWEVER, THE
PERSISTENT RIDGING OVER THE DESERT SOUTHWEST WILL SHIFT EAST AS WELL
DURING THIS TIME , THUS WE'LL CONTINUE TO SEE THE COOLING TREND
THROUGH THE WEEKEND INTO THE BEGINNING OF NEXT WEEK. THERE'S A WEAK
SIGNAL FOR THE RIDGING TO THE EAST TO BUILD BACK TOWARD THE WEST
COAST BY THE MIDDLE OF NEXT WEEK, WHICH WOULD BRING WARMER
TEMPERATURES, BUT AT THAT POINT A POTENTIAL TROPICAL SYSTEM WELL TO
OUR SOUTHWEST MAY ADD NOISE TO THE NWP.
AVIATION
(12Z TAFS)
ISSUED AT 437 AM PDT FRI AUG 21 2026
CURRENTLY LIFR-VFR. FLIGHT CONDITIONS WILL CONTINUE TO DETERIORATE
THROUGH THE MORNING; HOWEVER, CURRENT FLIGHT CATEGORIES SHOULD
PREVAIL. WITH IFR STRATUS RETREATING TO THE COAST THIS AFTERNOON,
VFR IS EXPECTED FOR ALL TERMINALS EXCEPT HAF. RELATIVELY LOWER
CONFIDENCE IN THE RETURN OF STRATUS TONIGHT DUE TO AN INCREASE IN
WIND AND GUIDANCE/MODELS SHOWING CLEARING UPSTREAM THIS EVENING.
NONETHELESS, THE FORECAST LEANED ON PERSISTENCE AND THE RESILIENCE
OF THE MARINE LAYER. DIURNAL WINDS WILL PREVAIL.
VICINITY OF SFO...CURRENTLY IFR WITH SOUTHWESTERLY FLOW. HIGH
CONFIDENCE IN VFR BY THIS AFTERNOON. MODERATE CONFIDENCE ON
AN IFR CEILING RETURNING TONIGHT. DIURNAL WINDS WILL PREVAIL.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...CURRENTLY LIFR WITH NORTHWESTERLY FLOW AT
MRY AND LIFR WITH WESTERLY FLOW AT SNS. FOG HAS RECENTLY DEVELOPED
AT MRY; THEREFORE, THERE IS LOW TO MODERATE CONFIDENCE THAT IT'LL
REACH SNS AS THE WORST CONDITIONS ARE AT THE IMMEDIATE COAST. IFR
STRATUS WILL STICK CLOSE TO THE COAST THIS AFTERNOON WITH ANOTHER
RETURN TO LIFR CONDITIONS THIS EVENING. DIURNAL WINDS WILL
PREVAIL.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 437 AM PDT FRI AUG 21 2026
WIDESPREAD HAZARDOUS CONDITIONS ARE EXPECTED WITH THE DIURNAL SEA
BREEZE FRIDAY AND SATURDAY. MODERATE TO FRESH NORTHWESTERLY
BREEZES WILL PREVAIL WITH LOCALLY STRONG BREEZES ACROSS THE
COASTAL JET REGIONS OF POINT REYES AND POINT SUR. SLIGHT TO
MODERATE SEAS WILL PREVAIL.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PDT THIS
EVENING FOR MRY BAY-SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT SATURDAY FOR PT ARENA TO PT
REYES 0-10 NM-PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 3 AM PDT SATURDAY
FOR PIGEON PT TO PT PINOS 0-10 NM-PT REYES TO PIGEON PT 0-
10 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 AM PDT
SATURDAY FOR PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...JM
LONG TERM....JM
AVIATION...SARMENT
MARINE...SARMENT
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