893
FXUS66 KMTR 121043
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
343 AM PDT FRI SEP 12 2025
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 240 AM PDT THU SEP 12 2025
- DRIER AND SLIGHTLY WARMER WEATHER FRIDAY AND SATURDAY, MUCH
WARMER EARLY NEXT WEEK WITH MODERATE HEATRISK
SHORT TERM
ISSUED AT 311 AM PDT FRI SEP 12 2025
(TODAY AND TONIGHT)
MARINE LAYER IS TRYING TO MAKE A COMEBACK AS NOTED ON THE
OVERNIGHT SATELLITE FOG PRODUCT AND THE BODEGA BAY PROFILER. THE
DEPTH OF THE MARINE LAYER IS CLOSE TO 1500 FEET PER PROFILER,
WHICH IS CLOSE TO MOISTURE X-SECTIONS ON MODEL GUIDANCE. INLAND
CLOUDS WILL SLOWLY ROLL BACK TO THE COAST MID-LATE MORNING, BUT
NOT EXPECTING A FULL CLEARING AT THE COAST. CLOUDS WILL LINGER
FOR MOST OF THE DAY. THE LONGWAVE PATTERN IN THE WEST IS STILL
GRIPPED BY A POSITIVELY TILTED UPPER TROUGH AND EMBEDDED UPPER
LOW. THIS FEATURE CONTINUES TO WEAKEN AND MOVE EASTERLY INTO WHAT
WILL BE AN OPEN WAVE. WAITING IN THE UPPER LEVEL WINGS IS
SHORTWAVE RIDGING. TODAY WILL BE A TRANSITION DAY IN THE LONGWAVE
PATTERN FROM A TROUGH TO A RIDGE. DESPITE SOME COASTAL CLOUDS, DO
EXPECT AN UPTICK (5-10 DEGREES) IN TEMPERATURES TODAY WITH THE
APPROACHING RIDGE.
ONE OTHER ITEM OF NOTE WE'LL BE MONITOR THIS AFTERNOON WILL BE
WILDFIRE SMOKE. WHILE ONE WOULD THINK IT WOULD BE FROM THE GARNET
FIRE OVER ON THE SIERRA IT'S ACTUALLY FIRES BURNING IN WA. GIVEN
THE UPPER LEVEL PATTERN SOME UPPER LEVEL SMOKE WILL BE POSSIBLE.
MORE LIKE SOME UPPER LEVEL HAZE. NO SURFACE SMOKE IS EXPECTED.
A MORE DEFINED MARINE LAYER WILL RETURN TONIGHT WITH A SLIGHTLY
DEEPER PUSH. SOLID HUMIDITY RECOVERY IS EXPECTED OVERNIGHT, BUT
THE HIGHEST PEAKS ABOVE 3-4K FEET WILL BE MODERATE HUMIDITY
RECOVERY AND IN AN ACTIVE THERMAL BELT.
LONG TERM
ISSUED AT 331 AM PDT FRI SEP 12 2025
(SATURDAY THROUGH THURSDAY)
LOOKING PRETTY DRY FOR THE UPCOMING WEEKEND. PREVIOUS MODEL RUNS
BROUGHT A FEW SHOWERS TO NORTHERN AREAS ON SUNDAY, BUT THE 00Z
RUNS HAVE ALL BUT ERASED IT. IN FACT, THE UPCOMING WEEKEND IS
TRENDING WARMER AND DRIER THAN PREVIOUS FORECAST. THE SHORTWAVE
RIDGE WILL SLIDE THROUGH SATURDAY WITH SHORTWAVE TROUGH TO QUICKLY
FOLLOW ON SUNDAY. THE RIDGE WILL CONTINUE THE SUBTLE WARMING
TREND ON SATURDAY WITH HIGHS RANGING FROM THE 60S/70S COAST AND
70S TO NEAR 90 INLAND. TEMPERATURES MODERATE ON SUNDAY AS A TROUGH
PASSES TO THE NORTH. THE PASSING TROUGH HAS A BETTER SHOT AT
PRODUCING PRECIP NORTH OF THE BAY AREA.
TO JUMP START THE WORK WEEK WILL BE ANOTHER UPPER LEVEL RIDGE. THE
HIGHER 500MB HEIGHTS AND WARMER 850MB WILL REINVIGORATE THE
WARMING AND DRYING TREND. BY TUESDAY AND WEDNESDAY 850MB TEMPS
REACH THE LOW 20C RANGE. IF YOU DO THE OLD RULE OF THUMB FOR A
MIXED ATMOSPHERE AND ADD 10-15C YOU CAN GET SURFACE TEMPERATURES
OF 95-100 DEGREES. THOSE VALUES ARE CURRENTLY IN THE FORECAST FOR
FAR INTERIOR LOCATIONS. LINGERING ONSHORE FLOW AND MARINE
INFLUENCE WILL KEEP THE COAST AND BAYS COOLER AND IN THE 70S AND
80S. REGARDLESS, TEMPERATURES WILL BE SEVERAL DEGREES ABOVE
NORMAL. HEATRISK VALUES AWAY FROM THE COAST DO SURGE INTO THE
MODERATE CATEGORY WITH A FEW PIXELS OF MAJOR.
NEXT THURSDAY AND BEYOND GET PRETTY INTERESTING ON THE LONG RANGE
FORECAST. KIND OF FANTASY LAND AT THIS POINT, BUT THERE ARE SIGNS
WE'LL NEED TO WATCH FOR ANOTHER ROUND OF TROPICAL/MONSOONAL
MOISTURE SURGE. IT'S TOO EARLY FOR DETAILS, BUT LONGER RANGE
GLOBAL ENSEMBLES/CLUSTER SHOW TRANSPORT FLOW THAT WOULD BRING
DECAYING TROPICAL SYSTEM MOISTURE WITH A HINT OF MONSOONAL. GFS
MODEL FOR INSTANCE HANDLED THE EARLY SEPTEMBER LIGHTNING EVENT
BETTER THAN OTHERS. IT'S FANTASY LAND PICTURE FOR THE 19-20TH OF
SEPT SHOWS SHOWERS AND THUNDERSTORMS OVER CENTRAL CALIFORNIA. AT
THIS POINT, IT WORTH KEEPING AND EYE ON. TIMING WOULD BE BAD FROM
A FIRE WEATHER STAND POINT AS WARMER WEATHER DEVELOPS OVER THE
WEEKEND AND PEAKS EARLY NEXT WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 1003 PM PDT THU SEP 11 2025
LOW CLOUDS ARE FILLING THE BAYS AND ALONG THE COAST. IFR/MVFR
CIGS BECOME MOSTLY WIDESPREAD INTO THE NIGHT, WITH MOMENTS OF CIGS
EXPECTED FOR SJC, STS, AND LVK INTO FRIDAY MORNING, WHILE THE
REST OF THE TAF SITES SEE MORE CONSISTENT CIGS. CLOUD COVER WILL
BE SLOW TO ERODE ON FRIDAY, BUT NEARLY WIDESPREAD VFR IS EXPECTED
INT THE AFTERNOON. THE EXCEPTION, BEING HAF, WHICH SEES CIGS RISE
TO MVFR LEVELS, BUT DON'T CLEAR. FRIDAY AFTERNOON OFFERS ANOTHER
ROUND OF MODERATE TO BREEZY WINDS ARRIVE FRIDAY AFTERNOON AND LAST
INTO THAT EVENING. CLOUD COVER BUILDS AROUND THE MONTEREY BAY IN
THE LATE AFTERNOON AND AROUND THE SF BAY THAT EVENING.
VICINITY OF SFO...MVRF CIGS FILL OVER SFO INTO THE NIGHT AND STAY
IN PLACE THROUGH THE NIGHT AN INTO FRIDAY AFTERNOON. THESE CIGS
ERODE AS BREEZY WEST WINDS BUILD FRIDAY AFTERNOON, BUT CIGS RETURN
AS THE WINDS REDUCE INTO THAT NIGHT.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...MVFR CIGS ARE BUILDING AROUND THE THE BAY
AND WINDS ARE GETTING LIGHT. CIGS AT MRY AND SNS LOOK TO FALL TO
IFR LEVELS IN THE LATE NIGHT WITH WINDS BECOMING LIGHT AND
VARIABLE. CLOUD COVER ERODES INTO FRIDAY AFTERNOON AS MODERATE
WEST WIND BUILD. WINDS WEAKEN IN THE EARLY EVENING WITH CIGS
BUILDING.
MARINE
(TONIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 905 PM PDT THU SEP 11 2025
WINDS INCREASE ACROSS THE WATERS BECOMING BREEZY TO GUSTY FOR
FRIDAY. LOCALIZED STRONG GUSTS ARE POSSIBLE ACROSS THE NORTHERN
OUTER WATERS. MODERATE TO ROUGH SEAS DEVELOP FRIDAY AND PERSIST
INTO NEXT WEEK. CONDITIONS TEMPORARILY IMPROVE SATURDAY, AS WINDS
DECREASE AND SEAS EASE, BEFORE ANOTHER ROUND OF FRESH TO STRONG
NORTHWEST WINDS RETURNS SUNDAY INTO NEXT WEEK WITH THE STRONGEST
WINDS LOCATED ACROSS THE FAR NORTHERN OUTER WATERS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PDT THIS
EVENING FOR MRY BAY-PIGEON PT TO PT PINOS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 3 AM PDT SATURDAY
FOR PT ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT EARLY THIS MORNING FOR PT
PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 AM PDT
SATURDAY FOR PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT SATURDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...MURDOCK
MARINE...MURDOCK
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