163
FXUS66 KMTR 192326
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
426 PM PDT TUE MAY 19 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 138 PM PDT TUE MAY 19 2026
- DIURNALLY DRIVEN WINDS EXPECTED THIS WEEK, WITH ONSHORE WINDS
DURING THE AFTERNOON AND EARLY EVENING.
- ABOVE NORMAL TEMPERATURES CONTINUE THROUGH MIDWEEK WITH
SEASONAL TEMPERATURES RETURNING LATE WEEK
SHORT TERM
ISSUED AT 138 PM PDT TUE MAY 19 2026
(THIS EVENING THROUGH WEDNESDAY)
WINDS HAVE EASED ACROSS THE REGION WITH MOST SITES CURRENTLY
REPORTING LIGHT OFFSHORE WINDS UNDER 10 MPH. BREEZY, ONSHORE
AFTERNOON WINDS ARE LIKELY ALONG THE COAST AND WITHIN MOUNTAIN
GAPS/PASSES. NOT TOO MUCH CHANGE TO THE OVERALL SYNOPTIC PATTERN,
BROAD UPPER LEVEL TROUGHING CONTINUES OVER THE WESTERN UNITED
STATES WITH AN AREA OF RIDGING AND SURFACE HIGH PRESSURE TO OUR
WEST OVER THE PACIFIC. THE CENTER OF THE UPPER LEVEL TROUGH
CONTINUES TO PROGRESS EASTWARD WITH THE SURFACE PRESSURE GRADIENT
BECOMING MORE RELAXED, ALLOWING WIND SPEEDS TO DIMINISH OVERALL.
THE MARINE LAYER CONTINUES TO BE MIXED OUT THANKS TO HIGH PRESSURE
OFFSHORE WHICH IS ALLOWING WARMER TEMPERATURES TO SPREAD ACROSS
THE REGION. HIGH TEMPERATURES WILL BE SEASONABLY WARM TODAY AND
AGAIN TOMORROW WITH INTERIOR HIGHS IN THE 80S TO POSSIBLY THE LOW
90S AND COASTAL HIGHS IN THE 60S TO 70S. CRITICALLY DRY CONDITIONS
CONTINUE ACROSS THE INTERIOR WITH THE MAJORITY OF STATIONS
REPORTING RH VALUES IN THE 10S TO 20S. NOT MUCH RELIEF FROM DRIER
CONDITIONS HAS BEEN OBSERVED OVERNIGHT WITH MOST SITES ONLY SEEING
OVERNIGHT HUMIDITY RECOVERIES TO AROUND 20-30%. THIS SAME PATTERN
IS EXPECTED TO CONTINUE AGAIN ON WEDNESDAY WITH NO REAL RELIEF
UNTIL THE MARINE LAYER REDEVELOPS LATE WEEK INTO THE WEEKEND. FIRE
WEATHER CONCERNS THUS REMAIN ELEVATED GIVEN THE CRITICALLY DRY
CONDITIONS ACROSS THE INTERIOR. IF YOU ARE PARTICIPATING IN ANY
OUTDOOR ACTIVITIES INVOLVING SPARKS OR FLAME, EXERCISE CAUTION AND
BE AWARE THAT FINE FUELS ARE VERY FLAMMABLE AT THIS TIME.
LONG TERM
ISSUED AT 138 PM PDT TUE MAY 19 2026
(WEDNESDAY NIGHT THROUGH NEXT MONDAY)
THE GENERAL PATTERN REMAINS THE SAME THROUGH THURSDAY WITH HIGH
TEMPERATURES IN THE 80S TO LOW 90S ACROSS THE INTERIOR, 60S TO 70S
ALONG THE COAST, DIURNALLY BREEZY WINDS, AND CRITICALLY DRY
DAYTIME CONDITIONS ACROSS THE INTERIOR. A GRADUAL PATTERN CHANGE
WILL BEGIN THURSDAY INTO FRIDAY, BECOMING MORE NOTICEABLE OVER THE
WEEKEND, AS HIGH PRESSURE WEAKENS, SHIFTING WEST, AND BROAD
TROUGHING DOMINATES THE WEST COAST. WINDS WILL GENERALLY SHIFT
ONSHORE AGAIN BY FRIDAY WITH A SHALLOW MARINE LAYER REDEVELOPING.
HIGH TEMPERATURES WILL GENERALLY DROP INTO THE 70S ACROSS THE
INTERIOR AND 70S TO MID 80S ACROSS THE INTERIOR CENTRAL COAST
WHILE COASTAL HIGHS STAY IN THE 50S TO 60S. AS THE MARINE LAYER
REDEVELOPS, WE WILL SEE IMPROVING HUMIDITY VALUES ACROSS THE
INTERIOR WHICH WILL REDUCE OUR OVERALL FIRE WEATHER CONCERNS.
INITIALLY THE MARINE LAYER WILL BE AROUND 500 FT THURSDAY INTO
FRIDAY BUT IS EXPECTED TO DEEPEN TO AROUND 1000 FT BY THE WEEKEND.
DIURNALLY BREEZY AFTERNOON/EVENING WINDS CONTINUE WITH BREEZIER
WINDS ALONG THE COAST AND IN MOUNTAIN GAPS/PASSES.
THE INITIAL NBM FORECAST SHOWS TEMPERATURES WARMING BACK INTO THE
80S BY EARLY NEXT WEEK. THE CAVEAT TO THIS IS THAT MODELS ARE SPLIT
BETWEEN UPPER LEVEL RIDGING AND UPPER LEVEL TROUGHING DEVELOPING
OVER THE WEST COAST TOWARDS THE END OF MAY. IF RIDGING IS ABLE TO
DEVELOP, WARMER TEMPERATURES ARE LIKELY TO ROUND OUT THE MONTH BUT
IF TROUGHING IS ABLE TO DEVELOP THEN SLIGHTLY COOLER TEMPERATURES
ARE MORE LIKELY. IN THE TROUGHING SCENARIO, THERE IS THE POSSIBILITY
OF SOME LIGHT RAIN BUT THE MORE LIKELY SETUP IS A DEEP MARINE LAYER
AND COASTAL DRIZZLE.
AVIATION
(00Z TAFS)
ISSUED AT 421 PM PDT TUE MAY 19 2026
CURRENTLY VFR AT ALL TERMINALS. MODERATE TO HIGH CONFIDENCE IN VFR
AND DIURNAL WINDS PREVAILING THROUGH THE TAF PERIOD. WINDS MAY
BECOME CALM AND/OR LIGHT AND VARIABLE OVERNIGHT. LOW TO MODERATE
(UP TO 40%) CHANCE OF SUB-VFR CONDITIONS DEVELOPING AT TERMINALS
TONIGHT WITH THE BEST CHANCES BETWEEN 12Z AND 16Z. COASTAL
TERMINALS WILL BE AT GREATEST RISK WITH RISK DECREASING FOR
BAYSHORE AND INTERIOR TERMINALS, RESPECTIVELY. TO EVEN GET THERE,
IT WILL HAVE TO EITHER BE ADVECTED OR DEW POINTS NEED TO INCREASE,
A LOT. THE QUESTION WILL BE IF THIS CAN HAPPEN BEFORE SUNRISE. IF
IT CAN'T, THE PROBABILITY OF OCCURRENCE BECOMES EVEN LESS.
VICINITY OF SFO...CURRENTLY VFR WITH WESTERLY FLOW. MODERATE TO HIGH
CONFIDENCE IN VFR AND DIURNAL WINDS PREVAILING THROUGH THE TAF
PERIOD. LOW PROBABILITY FOR SUB-VFR CONDITIONS TO DEVELOP AT THE
TERMINAL WITH THE COMPRESSED (LIFR-IFR) MARINE LAYER UNABLE TO
PENETRATE THROUGH THE SAN BRUNO GAP. REASONABLE WORST CASE SCENARIO
IS STRATUS SNEAKS THROUGH THE GOLDEN GATE GAP AND BRINGS FEW/SCT TO
THE NORTH SIDE OF THE TERMINAL.
SFO BRIDGE APPROACH...THE SAN MATEO BRIDGE APPROACH HAS A LOWER
PROBABILITY OF SUB-VFR CONDITIONS.
MONTEREY BAY TERMINALS...CURRENTLY VFR WITH NORTHWESTERLY FLOW AT
BOTH TERMINALS. MODERATE TO HIGH CONFIDENCE IN VFR AND DIURNAL WINDS
PREVAILING THROUGH THE TAF PERIOD. IF A CEILING WERE TO DEVELOP, IT
WILL LIKELY BE ON THE CUSP OF IFR/LIFR AND TAKE PLACE IN THE 12Z-16Z
TIME RANGE. FOG IS LESS LIKELY, BUT SOME OF THE MOST PESSIMISTIC
GUIDANCE HAS IT.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 421 PM PDT TUE MAY 19 2026
THE NORTHERN OUTER WATERS WILL CONTINUE TO SEE FRESH NORTHERLY
BREEZES WITH HAZARDOUS CONDITIONS THROUGH THURSDAY MORNING. THE
NORTHERLY BREEZES WILL ALSO COMBINE WITH AN INCREASING NORTHWEST
SWELL THROUGH THURSDAY MORNING WITH SEAS UP TO 12FT.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 PM PDT THURSDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...SARMENT
MARINE...JM
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