791
FXUS66 KMTR 211826
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1126 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
(18Z TAFS)
ISSUED AT 1125 AM PDT FRI AUG 21 2026
CURRENTLY HAVE A MIX OF IFR TO VFR CEILINGS DUE TO PATCHY STRATUS
ACROSS OUR REGION. VFR CONDITIONS ARE EXPECTED TO PREVAIL THIS
AFTERNOON INTO THE EARLY EVENING HOURS. HAF IS AN EXCEPTION AS THEY
MAY HAVE A COUPLE HOURS OF VFR SCATTERED CLOUD DECKS IN THE EARLY
AFTERNOON BEFORE SHIFTING BACK TO IFR CEILINGS. MODERATE TO FRESH
ONSHORE BREEZES AROUND 10 TO 15 KT EXPECTED THROUGH THE DAY AND EASE
OVERNIGHT. THE MARINE LAYER RETURNS THIS EVENING IMPACTING COASTAL
SITES FIRST BEFORE FILLING IN OVER INLAND TERMINALS. LOW TO MEDIUM
CONFIDENCE ON THE EXACT STRATUS ARRIVAL AS IT IS DEPENDENT ON WHERE
THE UPPER LEVEL LOW SETS UP DURING THE DAY. CURRENTLY, ALL TAF SITES
ARE EXPECTED TO DEVELOP IFR TO MVFR CEILINGS, WITH COASTAL SITES
HAVING A HIGH CHANCE OF DROPPING TO LIFR IN THE OVERNIGHT HOURS.
VICINITY OF SFO...STRATUS IS BEGINNING TO MIX OUT OF THE SF BAY AS
MODERATE ONSHORE BREEZES INCREASE. VFR THROUGH THE AFTERNOON WITH
OCCASIONAL GUSTS AROUND 20-25 KT POSSIBLE. WINDS REMAIN AROUND 10 KT
OVERNIGHT. MEDIUM CONFIDENCE ON THE TIMING OF IFR CEILINGS AS THEY
MAY ARRIVE AS EARLY AS SUNSET. THE MARINE STRATUS IS EXPECTED TO
LINGER UNTIL LATE SATURDAY MORNING.
SFO BRIDGE APPROACH...CEILINGS THAT DEVELOP MAY NOT BE AS LOW AS SFO
AND CLEAR BEFORE SFO DOES. OTHERWISE, SIMILAR TO SFO.
MONTEREY BAY TERMINALS...STRATUS IS RECEDING TO THE COASTLINE
RESULTING IN VFR CONDITIONS THROUGH THE AFTERNOON. ONSHORE WINDS
WILL BE DIURNALLY DRIVEN THIS TAF PERIOD. THE MARINE LAYER HOLDS ON
STRONG AS IT RETURNS WITH IFR CEILINGS THIS EVENING AROUND 6-7 PM
PDT. MEDIUM CONFIDENCE THAT CEILINGS WILL DROP TO LIFR OVERNIGHT
(OVC003-004), BUT THERE IS STILL UNCERTAINTY REGARDING THE EXACT
TIMING AND DURATION OF LIFR CONDITIONS. IF LIFR CEILINGS DEVELOP,
THEY ARE LIKELY TO IMPACT VISIBILITY AND LINGER AT THE TERMINALS
THROUGH MID SATURDAY MORNING.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 1125 AM PDT FRI AUG 21 2026
AN UPPER LEVEL LOW PRESSURE SYSTEM SITUATED OFF THE WEST COAST IS
RESULTING IN MODERATE TO FRESH NORTHWEST BREEZES ACROSS THE OUTER
WATERS. STRONG BREEZES WITH OCCASIONAL NEAR GALE FORCE GUSTS IN
THE COASTAL JET REGIONS OF POINT REYES AND POINT SUR IS EXPECTED.
WIDESPREAD HAZARDOUS CONDITIONS TO SMALL CRAFTS ACROSS THE COASTAL
AND BAY WATERS CONTINUE INTO SATURDAY WITH DIURNAL SEA BREEZES.
WIND DRIVEN SEAS REMAIN SLIGHT TO MODERATE THROUGH THE WEEKEND.
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 PIGEON PT TO PT
PINOS 0-10 NM-PT ARENA TO PT REYES 0-10 NM-PT PINOS TO PT
PIEDRAS BLANCAS 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...NAVARRETE
MARINE...NAVARRETE
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