939
FXUS66 KMTR 220503
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1003 PM PDT TUE JUL 21 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1219 PM PDT TUE JUL 21 2026
- HEAT ADVISORY IN EFFECT FOR INTERIOR CENTRAL COAST AND BAY
AREA THROUGH 9 PM PDT
- BREEZY ONSHORE WINDS RETURN FOR THE SECOND HALF OF THE WEEK
- TEMPERATURES WILL HOVER AROUND NORMAL THROUGH THE WEEK
SHORT TERM
ISSUED AT 1219 PM PDT TUE JUL 21 2026
(THIS EVENING THROUGH WEDNESDAY NIGHT)
HAVE WENT AHEAD AND ISSUED A HEAT ADVISORY THROUGH 9 PM THIS
EVENING FOR INTERIOR AREAS OF THE BAY AREA AND CENTRAL COAST.
TEMPERATURES OVERNIGHT AND INTO THIS MORNING DIDN'T COOL OFF AS
MUCH AS ORIGINALLY EXPECTED, THANKS TO THE MID/UPPER LEVEL CLOUD
COVER ACROSS THE REGION. THAT COMBINED WITH TEMPERATURES FORECAST
TO REACH THE 90S (POTENTIALLY EXCEEDING 100 DEG F IN THE WARMEST
INTERIOR SPOTS) ACROSS THE INTERIOR MADE FOR WIDESPREAD MODERATE
HEATRISK. TODAY IS FORECAST TO BE THE HOTTEST OF THE WEEK!
FOR TONIGHT, EXPECTING AN INCREASE IN LOW LEVEL STRATUS TO RETURN
TO THE COAST AND EXPAND INLAND INTO THE COASTAL ADJACENT VALLEYS.
THERE IS A GREATER THAN 50% PROBABILITY OF THIS OCCURING AS MID-
TO-HIGH LEVEL CLOUDS BEGIN TO SHIFT TO THE EAST AS REMNANT
MOISTURE FROM ELIDA GETS ABSORBED IN THE MEAN FLOW ALOFT. CANNOT
RULE OUT COASTAL DRIZZLE TONIGHT, DEPENDING ON IF THE SHALLOW
MARINE LAYER IS ABLE TO REDEVELOP. IT WILL FEEL MUGGY ONCE AGAIN
TONIGHT AS HUMIDITY REMAINS ELEVATED.
TOMORROW WILL FEATURE A SIGNIFICANT COOL DOWN THANKS TO AN
INCREASE IN ONSHORE WINDS AND STRONGER MARINE INFLUENCES.
TEMPERATURES ACROSS THE INTERIOR WILL WARM INTO THE MID 70S TO MID
80S WITH THE WARMEST INTERIOR SPOTS REACHING INTO THE LOWER 90S
ACROSS THE CENTRAL COAST. MEANWHILE, COOLER CONDITIONS WILL
PREVAIL NEAR THE COAST WITH DAY TIME HIGHS IN THE MID 60S TO MID
70S.
LONG TERM
ISSUED AT 1219 PM PDT TUE JUL 21 2026
(THURSDAY THROUGH NEXT MONDAY)
NOT MUCH CHANGE TO THE FORECAST BEYOND THE SHORT TERM. STILL
EXPECTING TROUGHING OFF OF THE PACIFIC NORTHWEST COAST AS HIGH
PRESSURE REMAINS OVER THE INTERIOR WEST THROUGH LATE WEEK. THIS WILL
GENERALLY KEEP CONDITIONS NEAR SEASONAL AVERAGES WITH NIGHT/MORNING
LOW CLOUDS WORKING THEIR WAY INLAND AND THEN RETREATING TO THE COAST
BY THE AFTERNOON. AS THE HIGH PRESSURE APPEARS TO SHIFT MORE TOWARD
THE FOUR CORNERS REGION, WE MAY SEE THE MARINE LAYER COMPRESS OVER
THE WEEKEND WITH A SLIGHT INLAND WARMING TREND.
AVIATION
(06Z TAFS)
ISSUED AT 959 PM PDT TUE JUL 21 2026
AFTER A HOT AND CLEAR DAY WITH WIDESPREAD VFR, MARINE LAYER STRATUS
APPEARS TO BE RETURNING WITH A VENGEANCE. STRATUS ASSOCIATED WITH AN
OFFSHORE SURFACE LOW HAS BEGUN SPILLING OVER THE COASTAL RANGES, AND
PUSHING THROUGH THE GAPS AND VALLEYS OF THE BAY AREA, MONTEREY BAY
AND THE SALINAS VALLEY. EXPECT MVFR CEILINGS WITH ONSET, AND LOW
CONFIDENCE OF TIMING OR EXTENT OF IFR/LIFR THROUGH THE OVERNIGHT
HOURS.
VICINITY OF SFO...STRATUS MAKING A STEADY PUSH THROUGH THE GOLDEN GATE AND
SPILLING OVER THE SAN FRANCISCO PENINSULA COASTAL RANGE. THE
PROGRESSION IS FASTER THAN PREVIOUS GUIDANCE INDICATED BUT STILL
DON'T EXPECT MVFR/IFR CEILINGS UNTIL AFTER MIDNIGHT. EXPECT BREEZY
ONSHORE WINDS AT TIMES OVERNIGHT INCREASING BY WEDNESDAY AFTERNOON.
MVFR/IFR CEILINGS ARE EXPECTED TO LIFT BY EARLY AFTERNOON.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...STRATUS ACCELERATED THROUGH MONTEREY BAY INTO THE
SALINAS VALLEY AFTER SUNSET AND HAS ALREADY SETTLED IN WITH A MVFR
CEILING AT KSNS. THE NORTHWEST ONSHORE FLOW CURRENTLY AT KMRY IS
HOLDING OFF THE EASTERLY PUSH OF STRATUS FOR THE MOMENT, HOWEVER THE
STRATUS SHOULD FILL IN SHORTLY OVER THE TERMINAL. EXPECT CLEARING
TO VFR BY EARLY AFTERNOON, UNTIL SUNSET WHEN STRATUS CEILINGS
RETURN.
MARINE
(TONIGHT THROUGH NEXT MONDAY)
ISSUED AT 959 PM PDT TUE JUL 21 2026
GUSTY SOUTHERLY WINDS OVER THE INNER COASTAL WATERS AND ACROSS
THE SAN FRANCISCO BAY TO THE DELTA WILL CONTINUE TONIGHT.
OTHERWISE WEST-NORTHWEST BREEZES TONIGHT WILL GRADUALLY INCREASE
THROUGH THE MORNING INTO WEDNESDAY AFTERNOON BECOME NORTHWEST
WITH FRESH TO MODERATE BREEZES CONTINUING INTO THE WEEKEND.
MODERATE SOUTHWESTERLY SWELL FROM TROPICAL CYCLONE ACTIVITY IN THE
EASTERN PACIFIC WILL BRING MIXED SEAS WITH POTENTIALLY HAZARDOUS
CONDITIONS THROUGH THE WEEKEND.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT WEDNESDAY FOR SF BAY N OF
BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 9 PM WEDNESDAY TO 9 PM PDT THURSDAY
FOR PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...RGASS
LONG TERM....RGASS
AVIATION...JM
MARINE...JM
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