764
FXUS66 KMTR 231204
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
404 AM PST FRI JAN 23 2026
..NEW SHORT TERM, LONG TERM, MARINE
KEY MESSAGES
UPDATED AT 401 AM PST FRI JAN 23 2026
- MORNING FOG ACROSS SOME BAY AREA VALLEYS AND AROUND MONTEREY
- GUSTY OFFSHORE WINDS ACROSS HIGHER TERRAIN OF THE NORTH BAY
SATURDAY
- POTENTIAL WEAK TO MODERATE STORM SYSTEM IN THE MIDDLE OF THE
NEXT WORK WEEK
SHORT TERM
ISSUED AT 401 AM PST FRI JAN 23 2026
(TODAY AND TONIGHT)
REDUCING PRESSURE HAS BROUGHT A STRONGER RETURN OF THE MARINE LAYER
TONIGHT. THIS ALONG WITH A REDUCTION OF HIGH CLOUDS, SOME MOISTURE
FROM THE CENTRAL VALLEY, AND A SLIGHT FEED OF MOISTURE FROM THE
SOUTH HAS ALLOWED FOR A GOOD SPREAD OF STRATUS AND DEVELOPING
POCKETS OF FOG. TEMPERATURES HAVE SLOWED THEIR COOLING AND ARE
ALMOST PLATEAUING FOR THE AREAS AFFECTED BY THE MARINE LAYER.
HIGH-RESOLUTION SHORT TERM MODELS SHOW THAT THESE CLOUDS AND POCKETS
OF FOG WILL BE SLOW TO ERODE. THE NEXT DEVELOPING RIDGE WILL BEGIN
TO PUSH WEAK NORTHERLY FLOW INTO THE NORTH BAY BY THE THE LATE
MORNING. THE SLIGHTLY DRIER AIR WILL HELP TO CLEAR THE NORTH BAY,
WHILE CLOUD COVER FARTHER TO THE SOUTH LINGERS INTO THE AFTERNOON.
HIGH TEMPERATURES WILL BE SLIGHTLY COOLER THAN PREVIOUS DAYS BECAUSE
OF THE PROLONGED CLOUD COVER, BUT ONLY BY A FEW DEGREES.
THE APPROACHING RIDGE WILL COMPRESS THE MARINE LAYER AND REDUCE THE
ADDITIONAL FEEDS OF MOISTURE TONIGHT, LEADING LESS LOW CLOUD COVER
AND FOG ACROSS THE AREA. HOWEVER THE MORE FOG-PRONED VALLEYS (SONOMA
CO, SALINAS VALLEY ECT) WILL STILL HAVE GOOD CHANCES FOR FOG
RETURNING TONIGHT.
LONG TERM
ISSUED AT 401 AM PST FRI JAN 23 2026
(SATURDAY THROUGH THURSDAY)
THE EASTERN PORTION OF THE DEVELOPING RIDGE WILL CONTINUE TO BUILD
INTO THE REGION INTO EARLY SATURDAY, CALLING FOR STRONGER NORTHERLY
TO NORTHEASTERLY (OFFSHORE) FLOW. THE CHANGE IN WINDS WILL LEAD TO
WIDESPREAD DRYING INTO SATURDAY, AND A MIXING OUT OF THE MARINE
LAYER. MORNING CLOUDS AND FOG WILL BE MUCH QUICKER TO ERODE ACROSS
THE REGION AND THAT EARLIER CLEARING ALONG WITH THE GENERALLY DRIER
AIRFLOW WILL CAUSE SLIGHTLY WARMER TEMPS FOR SATURDAY.
HIGHER ELEVATIONS LOOK TO SEE BREEZIER AND GUSTIER WINDS AS THE
OFFSHORE FLOW INCREASES INTO SATURDAY MORNING AND THROUGH THE DAY.
EXTRA ADJUSTMENTS WERE ADDED TO THE OVERNIGHT FORECAST PACKAGE TO
BETTER CAPTURE THE FLOW AND SPEED CHANGES, ESPECIALLY IN THE HIGHER
PEAKS OF THE NORTH BAY. LOCALIZED GUSTS AROUND 50 MPH WILL BE
POSSIBLE ON SOME OF THE PEAKS, BUT LUCKILY IT WON'T BE WIDESPREAD.
HUMIDITIES IN THESE ELEVATIONS WILL SUFFER FROM THESE INCREASED AND
DRIER WINDS, LEADING TO SOME FIRE WEATHER CONCERNS WITH A FEW AREAS
FALLING BELOW 20% HUMIDITY. WINDS LOOK TO REDUCE INTO THAT NIGHT,
BUT HUMIDITIES WILL STRUGGLE TO RECOVER ON THE HIGHER PEAKS. LOW
CLOUD COVER AND FOG WILL STRUGGLE TO FORM SUNDAY MORNING BECAUSE OF
THE DRY FLOW, BUT HIGH CLOUDS ENTER THE AREA INTO THAT AFTERNOON,
LEADING TO COOLER HIGH TEMPS.
THE RIDGE LOOKS TO FLATTEN INTO SUNDAY EVENING, WITH A ZONAL
JETSTREAM PATTERN TAKING ITS PLACE, AND OFFERING MORE ONSHORE FLOW.
HOWEVER THE JETSTREAM LOOKS TO SNAP BACK TO A QUICK RIDGE INTO THE
NEXT WORK WEEK. THIS MEANS TEMPERATURES WILL AND SOME BOUNCES UP AND
DOWN BY A FEW DEGREES, AND LOW CLOUD FORMATION WILL BE SPOTTY.
DESPITE THE QUICK RIDGE DEVELOPMENT, HIGH CLOUDS LOOK TO MOVE
THROUGH THE REGION AS A TROUGH DEVELOPS TO THE WEST. THE TROUGH
FORMATION IS WELL-ARGEED UPON BETWEEN THE LONGER TERM MODELS, BUT
THE TRAJECTORY IS A MATTER OF DEBATE. MORE MODELS POINT TO A COLD
FRONT, AND MAYBE A WEAK LOW PUSHING THROUGH THE AREA, BRINGING GOOD
CHANCES FOR WIDESPREAD MODERATE RAINS BY THE MID WEEK. HOWEVER, THE
GFS AND ITS ENSEMBLE MEMBERS SEEM KEEN ON THIS TROUGH GETTING PUSHED
UP AGAINST THE RIDGE AHEAD OF IT, AND PLACING ALL THE MOISTURE WELL
TO THE NORTH. THE GFS OUTPUT LOOKS A BIT LESS FIRM THAN OTHER MODELS
AND THE NATIONAL BLEND, BUT IS SOMETHING TO KEEP IN MIND AS THE
LONGER TERM MODELS UPDATE. FOR NOW, THE OFFICIAL FORECAST PLACES
RAIN CHANCES IN THE MIDDLE OF THE NEXT WORK WEEK ALONG THE INITIAL
FRONT WITH ADDITIONAL CHANCES POSSIBLE BEYOND THE FORECAST PERIOD.
AVIATION
(06Z TAFS)
ISSUED AT 939 PM PST THU JAN 22 2026
FOG AND/OR LOW CEILINGS ARE EXPECTED AT ALL TERMINALS TONIGHT.
THE COMBINATION OF ENHANCED RADIATIONAL COOLING OF THE SURFACE
UNDER CLEAR SKIES, MARINE LAYER ADVECTION FROM THE WEST AND TULE
FOG ADVECTION FROM THE EAST CREATE A VERY FAVORABLE ENVIRONMENT
FOR AVIATION IMPACTS THROUGH THE MORNING HOURS. SKIES WILL CLEAR
IN THE MID TO LATE MORNING.
VICINITY OF SFO...THE MARINE LAYER IS FORMING, AND IS EXPECTED TO
ADVECT OVER THE PENINSULA WITH A DEPTH OF AROUND 1,000 FEET. THAT'S
DEEP ENOUGH TO GET OVER SAN BRUNO MOUNTAIN AND IMPACT THE TERMINAL,
BUT MAY BE TOO DEEP FOR DENSE FOG TO FORM AT THE SURFACE. THE MOST
LIKELY OUTCOME IS IMC CONDITIONS DUE TO CEILINGS, WITH POSSIBLE
VISIBILITY DROPS IF THE WIND DIES DOWN.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...CEILINGS HAVE ALREADY BEGUN TO FORM AT
MRY, WITH AN EARLY BASE OF 1,000 FEET. THESE WILL SURELY LOWER
AND EXPAND TO SNS THROUGH THE LATE NIGHT AND EARLY MORNING HOURS.
DESPITE THE MODERATE DRAINAGE FLOW AT SNS, MODELS ARE BULLISH ON
FOG IMPACTS AT THE TERMINAL.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 401 AM PST FRI JAN 23 2026
STRONG NORTHERLY BREEZES WILL PREVAIL TODAY WITH NEAR GALE FORCE
GUSTS IN THE NORTHWEST WATERS. SEAS WILL BUILD TO 8-12 FEET ACROSS
EXPOSED WATERS TODAY THROUGH EARLY SATURDAY. CONDITIONS WILL
IMPROVE THIS WEEKEND WITH A GENTLE BREEZE AND MODERATE SEAS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PST SATURDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...MURDOCK
LONG TERM....MURDOCK
AVIATION...FLYNN
MARINE...CANEPA
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