212
FXUS66 KMTR 240339
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
839 PM PDT SUN AUG 23 2026
..NEW UPDATE, MARINE
KEY MESSAGES
UPDATED AT 1237 PM PDT SUN AUG 23 2026
- NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES PERSIST IN THE
MARINE LAYER THIS WEEK
- WARM AND DRY CONDITIONS CONTINUE ABOVE 1000 FEET
UPDATE
ISSUED AT 836 PM PDT SUN AUG 23 2026
STRATUS CLOUDS HAVE BEEN REPORTED ALONG THE COASTAL AREAS ALONG
WITH EXTENSIVE HIGH CLOUD COVER ACROSS THE REGION. SOME EXPANSION
OF THE LOW CLOUDS IS POSSIBLE THROUGH THE NIGHT INTO THE EARLY
HOURS OF MONDAY MORNING, WITH A COMPRESSED MARINE LAYER COMBINED
WITH IMPAIRED RADIATIONAL COOLING DUE TO THE HIGH CLOUDS RESULTING
IN LIMITED INLAND DEVELOPMENT TONIGHT. THE FORECAST REMAINS ON
TRACK.
DIALH
SHORT TERM
ISSUED AT 1237 PM PDT SUN AUG 23 2026
(THIS EVENING THROUGH MONDAY NIGHT)
NOT TOO MUCH CHANGE IN THE FORECAST TODAY AS THE BAY AREA AND
CENTRAL COAST REMAIN IN BETWEEN AN UPPER LEVEL TROUGH TO THE NORTH
AND A RIDGE OVER THE DESERT SOUTHWEST. RIDGING REMAINS MORE DOMINANT
THROUGH THIS EVENING BEFORE THE CENTER OF THE RIDGE SHIFTS EASTWARD
EARLY MONDAY AND TROUGHING BECOMES MORE DOMINANT OVER THE REGION.
HIGH TEMPERATURES ARE FORECAST TO PEAK IN THE UPPER 80S TO LOW 90S
ACROSS THE INTERIOR WITH FAR INTERIOR MONTEREY COUNTY REACHING THE
LOW 100S. COASTAL AREAS ARE BENEFITING FROM A SHALLOW (~1000 FOOT)
MARINE LAYER THAT BROUGHT PATCHY STRATUS AND DRIZZLE TO THE COAST
AND THE SF BAY SHORELINE. THIS WILL KEEP TEMPERATURES COOLER IN
COASTAL AREAS WITH HIGHS PEAKING IN THE 60S TO LOW 70S.
HEADING INTO MONDAY, THE CENTER OF THE UPPER LEVEL RIDGE WILL SHIFT
EASTWARD WITH TROUGHING BECOMING THE DOMINANT FEATURE OVER US. THE
RETURN OF TROUGHING WILL HELP THE MARINE LAYER TO (SLIGHTLY) DEEPEN
AND BRING IT FROM APPROXIMATELY 1000 FT TO 1200-1500 FT. A SLIGHTLY
DEEPER MARINE LAYER WILL ALLOW FOR A GREATER INLAND INTRUSION OF
STRATUS, BUT, STRATUS IS NOT LIKELY TO BE AS WIDESPREAD AS IT WAS
LAST WEEK. TEMPERATURES ARE EXPECTED TO DROP BY AROUND 5 DEGREES FOR
MOST INTERIOR LOCATIONS. THIS WILL SEE A RETURN OF HIGHS IN THE LOW
TO MID 80S WHILE THE HIGHER ELEVATIONS ABOVE THE MARINE LAYER WILL
STAY COMPARATIVELY WARMER IN THE UPPER 80S TO LOW 90S. COASTAL AREAS
WILL REMAIN IN THE 60S TO LOW 70S WITH ADDITIONAL PERIODS OF COASTAL
DRIZZLE LIKELY DURING THE EARLY MORNING HOURS. THE ONE QUESTIONABLE
PART OF THE FORECAST IS IF ANY THUNDERSTORMS WILL BE ABLE TO DEVELOP
ACROSS THE NORTH BAY INTERIOR MOUNTAINS (PARTICULARLY NAPA COUNTY)
EARLY MONDAY MORNING. THE EURO SUGGESTS THAT THERE WILL BE
SUFFICIENT MOISTURE, INSTABILITY, AND LIFT AS A WEAK SHORTWAVE
TROUGH MOVES IN TO CALIFORNIA FOR OROGRAPHICALLY DRIVEN
THUNDERSTORMS TO DEVELOP THERE EARLY MONDAY MORNING. NBM GUIDANCE
GIVES AROUND A 5% CHANCE OF THUNDERSTORMS DEVELOPING. ANY
PRECIPITATION THAT FALLS WOULD LIKELY BE VIRGA/EVAPORATE BEFORE
REACHING THE SURFACE GIVEN MODEL SKEW-T SOUNDINGS SHOWING A LARGE
DRY LAYER BETWEEN THE MID AND LOWER LEVELS OF THE ATMOSPHERE.
CONFIDENCE REMAINS LOW OVERALL IN STORM DEVELOPMENT, HOWEVER, AS
OTHER MODELS (GFS, NAM, HRRR, RRFS) DO NOT SUPPORT STORMS DEVELOPING
TOMORROW MORNING WITH THE EURO BEING AN OUTLIER.
LONG TERM
ISSUED AT 1237 PM PDT SUN AUG 23 2026
(TUESDAY THROUGH NEXT SATURDAY)
TROUGHING PREVAILS THROUGH TUESDAY WITH HIGH TEMPERATURES REMAINING
IN THE 60S TO 70S ALONG THE COAST, 80S ACROSS THE INTERIOR, UPPER
80S TO LOW 90S ACROSS THE HIGHER ELEVATIONS, AND UPPER 90S TO LOW
100S ACROSS THE INTERIOR CENTRAL COAST. STRATUS IS EXPECTED ALONG
THE COAST AND PORTIONS OF THE SF BAY SHORELINE BUT CONTINUES TO BE
LIMITED IN EXTENT. THE CENTER OF THE UPPER LEVEL RIDGE SHIFTS BACK
WESTWARDS WEDNESDAY TO THURSDAY WITH HIGH TEMPERATURES WARMING BY
AROUND 5 DEGREES ACROSS THE INTERIOR (LARGELY RETURNING TEMPERATURES
TO THE UPPER 80S TO 90S). FRIDAY INTO THE WEEKEND, TEMPERATURES COOL
BY A FEW DEGREES AS RIDGING WEAKENS AND TROUGHING
DEEPENS/STRENGTHENS OVER THE PACIFIC. TROUGHING LOOKS TO CONTINUE
INTO NEXT WEEK WITH A DEEP UPPER LEVEL LOW MOVING INTO THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA. IT WILL BE WORTH KEEPING AN EYE
ON THIS INCOMING TROUGH AND THE ARRIVAL OF ANY POTENTIAL TROPICAL
MOISTURE TOWARDS THE END OF THE FORECAST PERIOD. THE LATEST NHC
GUIDANCE SHOWS THREE ACTIVE AREAS OF TROPICAL INTEREST OFFSHORE OF
MEXICO WITH RECENTLY NAMED TS ISELLE IN THE VICNITY AS WELL.
GUIDANCE IS STARTING TO INDICATE SOME TROPICAL MOISTURE FROM THESE
SYSTEMS MAY BE BROUGHT NORTH AS THE TROUGH ARRIVES BUT IT IS UNCLEAR
HOW FAR NORTH THIS TROPICAL MOISTURE WILL GO. SOME MODELS KEEP IT
MORE OVER SOUTHERN CALIFORNIA WHILE OTHERS BRING IT UP INTO
MONTEREY/SAN BENITO COUNTIES. MODELS ARE ALREADY SHOWING AN INCREASE
IN SOUTHERLY SWELL ASSOCIATED WITH THE UPTICK IN TROPICAL ACTIVITY
ACROSS THE EASTERN PACIFIC THIS WEEKEND INTO EARLY NEXT WEEK.
AVIATION
(00Z TAFS)
ISSUED AT 439 PM PDT SUN AUG 23 2026
VFR CONTINUES EXCEPT FOR PATCHY COASTAL STRATUS AND FOG /MVFR-
IFR/. MID AND HIGH CLOUDS, INCLUDING WILDFIRE SMOKE OVER THE NORTH
CENTRAL COAST, ARE MOVING NORTHEASTWARD OVER THE FORECAST AREA.
COASTAL STRATUS AND FOG /MVFR-IFR-LIFR/ REDEVELOP TONIGHT AND
MONDAY MORNING. CONDITIONS IMPROVE TO MVFR-VFR ALONG THE COAST
LATE MONDAY MORNING AND AFTERNOON OTHERWISE VFR MONDAY.
VICINITY OF SFO...VFR PREVAILS UNTIL STRATUS /MVFR/ DEVELOPS 12Z
MONDAY. VFR RETURNS 18Z MONDAY. WEST WIND 5 TO 15 KNOTS WITH
OCCASIONAL AFTERNOON AND EVENING GUSTS NEAR 20 KNOTS.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR THEN STRATUS /IFR-LIFR/ MOVES INLAND
MID TO LATE EVENING TO MONDAY MORNING. CONDITIONS IMPROVE TO MVFR-
VFR LATE MONDAY MORNING AND AFTERNOON. WEST TO NORTHWEST WINDS 5
TO 15 KNOTS.
MARINE
(TONIGHT THROUGH NEXT SATURDAY)
ISSUED AT 836 PM PDT SUN AUG 23 2026
MODERATE NORTHWEST BREEZES GRADUALLY DIMINISH THIS EVENING AND
BECOME GENTLE BY TOMORROW. OCCASIONAL STRONG GUSTS ARE POSSIBLE
THIS EVENING, PARTICULARLY ACROSS THE NORTHERN OUTER WATERS AND
NEAR THE BIG SUR COAST. SLIGHT TO MODERATE WIND DRIVEN SEAS
PREVAIL INTO THE WORK WEEK.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT MONDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...CANEPA
MARINE...CANEPA
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