014
FXUS66 KMTR 171122
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
422 AM PDT THU SEP 17 2026
..NEW AVIATION, MARINE, FIRE WEATHER
KEY MESSAGES
UPDATED AT 1211 AM PDT THU SEP 17 2026
- COOLER TEMPERATURES THROUGH THURSDAY
- WARMING TREND FRIDAY INTO THE WEEKEND
SHORT TERM
ISSUED AT 1211 AM PDT THU SEP 17 2026
(TODAY AND TONIGHT)
SATELLITE IMAGERY ONCE AGAIN SHOWS STRATUS HUGGING PORTIONS OF
THE COAST AND BEGINNING TO MOVE INLAND. AS NOTED IN THE EVENING
UPDATE, THIS ISN'T A CLASSIC MARINE LAYER. IT HAS A MORE STRATO-CU
VIBE DUE TO THE PROXIMITY OF COLD UPPER LEVEL LOW NEAR PT ARENA.
DO EXPECT STRATUS TO EVENTUALLY FILL IN ALONG A MAJORITY OF THE
COAST BY SUNRISE. THE LOWER HEIGHTS ALOFT HAVE ALSO ALLOWED THE
CLOUD DECK TO DEEPEN 2500-3000 FT PER PROFILERS AND ACARS
SOUNDING. GIVEN THE NEARBY LOW,ONSHORE FLOW, AND DEEP LAYER
DRIZZLE REMAINS IN THE FORECAST AS WELL.
OUTSIDE OF DRIZZLE CHANCES - SIMILAR TO YESTERDAY THE MAIN
WEATHER HIGHLIGHTS FOR TODAY WILL BE BELOW NORMAL TEMPERATURES AND
GUSTY ONSHORE FLOW. GENERALLY SPEAKING - MAX TEMPS TODAY WILL BE A
FEW WARMER THAN YESTERDAY, BUT STILL BELOW SEASONAL AVERAGES.
HIGHS WILL TOP OUT IN THE 60S TO NEAR 70 ALONG THE COAST AND 70S
TO MID 80S INTERIOR. ONSHORE GRADIENTS AREN'T OVERLY IMPRESSIVE
OVERNIGHT, BUT STILL SEEING SOME GUSTS 30-45 MPH FOR THE DELTA AND
E BAY HILLS. THESE GUSTY CONDITIONS WILL LINGERING THROUGH THE
EARLY MORNING HOURS BEFORE EASING THROUGH THE AFTERNOON/EVENING
HOURS.
THURSDAY NIGHT: THE UPPER LOW BEGINS TO LOSE ITS GRIP ON THE BAY
AREA AS IT SLOWLY MOVES TO THE NORTHEAST. BEHIND THE DEPARTING
LOW SHORTWAVE RIDGING BUILDS. A MORE CLASSIC MARINE LAYER WILL
DEVELOP WITH SOLID STRATUS ALONG THE COAST AND INLAND VALLEYS.
CANNOT RULE OUT SOME PATCHY DRIZZLE.
LONG TERM
ISSUED AT 107 AM PDT THU SEP 17 2026
(FRIDAY THROUGH WEDNESDAY)
FRIDAY WILL BE A TRANSITION DAY AS THE UPPER LOW FULLY EXITS TO
THE NORTHEAST AND SHORTWAVE RIDGING BUILDS OVERHEAD. ONCE THE
MORNING MARINE LAYER ROLLS BACK TO THE COAST A MARKED WARMING
TREND WILL DEVELOP TO KICK OFF THE WEEKEND. 5-10 DEGREES OF
WARMING ARE EXPECTED. THE WARMING TREND WILL CONTINUE THROUGH
SATURDAY WITH TEMPERATURES REACHING ABOVE NORMAL BY SATURDAY. A
FEW LOW 90S WILL RETURN SATURDAY AFTERNOON ACROSS THE INTERIOR
CENTRAL COAST. TEMPERATURES WILL ALSO GET A BOOST ON SATURDAY
WITH A FEW BURSTS OF OFFSHORE FLOW. NOTHING OVERLY STRONG, BUT A
SWITCH NONETHELESS. OFFSHORE WINDS WILL BE MOST REALIZED OVER THE
HIGHER TERRAIN OF THE N AND E BAY. THE WARM UP WILL BE SHORT-LIVED
AS THE RIDGE GETS REPLACED BY YET ANOTHER UPPER LOW MOVING IN FROM
THE WEST ON SUNDAY. MARINE LAYER WILL LIKELY DEEPEN AND
TEMPERATURES COOL 5-10 DEGREES.
MONDAY AND BEYOND IS STILL ON THE LOWER END OF CONFIDENCE.
TONIGHT'S 00Z MODEL SUITE IS STARTING TO SHOW A ROLLER COASTER OF
TEMPS NEXT WEEK. A SLIGHT WARMING UP AND THEN A SLIGHT COOL DOWN.
UNCERTAINTY ON THE SHOULDER SEASONS IS ACTUALLY PRETTY COMMON.
CLUSTER ANALYSIS DOESN'T PROVIDE A LOT OF ADDITIONAL CLARITY
EXCEPT THAT MODELS ARE SPLIT. NOT EXPECTING RAIN PER SE THE
UNCERTAINTY IS AROUND TEMPERATURES.
AVIATION
(12Z TAFS)
ISSUED AT 421 AM PDT THU SEP 17 2026
A PATCHWORK OF VFR TO IFR CONDITIONS PREVAILS OVER THE REGION WITH
STRATOCUMULUS PERSISTING OVER THE BAY AREA AND PARTS OF THE CENTRAL
COAST THROUGH THE PRE-DAWN HOURS. THE CLOUD DECK SHOULD RETREAT BACK
TO THE COASTAL REGIONS THROUGH THE LATE MORNING AND AFTERNOON HOURS,
WITH A GENTLE TO MODERATE ONSHORE BREEZE DEVELOPING IN THE
AFTERNOON. THIS EVENING AND OVERNIGHT, THE MARINE LAYER WILL BEGIN
TO COMPRESS, WHICH SHOULD RESULT IN LOWER CEILINGS ALTHOUGH
CONFIDENCE IN CEILING HEIGHTS AND TIMING IS MODERATE AT BEST.
VICINITY OF SFO... LOW-END VFR TO HIGH-END MVFR CLOUDS CONTINUE
THROUGH THE LATE MORNING HOURS, WITH A MODERATE WEST BREEZE
DEVELOPING IN THE AFTERNOON. THE CLOUDS SHOULD RETURN IN THE EVENING
TO OVERNIGHT HOURS, WITH MODERATE CONFIDENCE IN TIMING AND CEILINGS
HEIGHT.
SFO BRIDGE APPROACH... SIMILAR TO SFO.
MONTEREY BAY TERMINALS... THE SOUTHERN MONTEREY BAY REGION HAS
GENERALLY REMAINED CLEARER THAN AREAS TO THE NORTH BUT THE LATEST
SATELLITE IMAGERY SHOWS THE CLOUD DECK MOVING INTO THE REGION WITH
MVFR CEILINGS EXPECTED TO DEVELOP IMMINENTLY. CLOUDS WILL RETREAT
BACK TO THE IMMEDIATE COAST THROUGH THE LATE MORNING HOURS WITH A
GENTLE WEST-NORTHWEST WIND DEVELOPING IN THE AFTERNOON. WINDS WILL
BECOME LIGHT OVERNIGHT WITH INDICATIONS THAT MVFR CLOUDS WILL
RETURN, ALTHOUGH CONFIDENCE IN TIMING IS MODERATE.
MARINE
(TODAY THROUGH TUESDAY)
ISSUED AT 421 AM PDT THU SEP 17 2026
GENTLE TO MODERATE BREEZES CONTINUE ACROSS THE WATERS THROUGH
FRIDAY, WHEN HAZARDOUS CONDITIONS FOR SMALL CRAFT RETURN AND
PERSIST INTO THE WEEKEND DUE TO FRESH TO STRONG NORTHWESTERLY
BREEZES. SLIGHT TO MODERATE SEAS WILL PREVAIL THROUGH SUNDAY.
FIRE WEATHER
ISSUED AT 421 AM PDT THU SEP 17 2026
THE COOLEST CONDITIONS AND DEEPEST MARINE LAYER ARE EXPECTED THROUGH
THE DAY TODAY AS THE UPPER LEVEL LOW STALLS OVER NORTHERN
CALIFORNIA. CURRENT OBSERVATIONS SUGGEST A MARINE LAYER DEPTH OF
OVER 3000 FEET, ALLOWING FOR MOIST CONDITIONS TO REACH VERY HIGH
INTO THE HIGHER ELEVATIONS. AS THE LOW MOVES AWAY ON FRIDAY, THE
MARINE LAYER WILL COMPRESS, TEMPERATURES WILL RISE, AND RELATIVE
HUMIDITIES IN THE HIGHER ELEVATIONS WILL START TO DECREASE. SOME
OFFSHORE FLOW IS POSSIBLE ON SATURDAY MORNING, BUT IT IS NOT
EXPECTED TO BE VERY STRONG AND THE BULK OF THE OFFSHORE INFLUENCE
WILL BE FELT ON THE HIGHER TERRAIN OF THE NORTH AND EAST BAY.
DIALH
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM FRIDAY TO 3 AM PDT SATURDAY FOR
MRY BAY-PIGEON PT TO PT PINOS 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PDT FRIDAY FOR PT PINOS
TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...MM
LONG TERM....PALMER
AVIATION...DIALH
MARINE...DIALH
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