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FXUS66 KMTR [Monterey CA] 150536 AFDMTR ∨

FXUS66 KMTR 150536
AFDMTR [HEAD]

National Weather Service San Francisco California 9:36pm PST Sun Dec 14 2025 ∨

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
936 PM PST SUN DEC 14 2025 [HEAD]

New aviation. ∨

...NEW AVIATION... [DISC]

Key Messages… updated at 1:22pm PST Sun December 14 2025 ∨

.KEY MESSAGES...
UPDATED AT 122 PM PST SUN DEC 14 2025 [DISC]

- stratus persists over the North and East Bay valleys and the coastal regions ∨

 - STRATUS PERSISTS OVER THE NORTH AND EAST BAY VALLEYS AND THE
COASTAL REGIONS [DISC]

- generally beneficial rain beginning this week ∨

 - GENERALLY BENEFICIAL RAIN BEGINNING THIS WEEK [DISC]

- heavier rain and strong wind possible next week ∨

 - HEAVIER RAIN AND STRONG WIND POSSIBLE NEXT WEEK [DISC]

Update. Issued at 9:11pm PST Sun December 14 2025 ∨

.UPDATE...
ISSUED AT 911 PM PST SUN DEC 14 2025 [DISC]

Fog set in a bit earlier this evening and in particular for the valleys of Sonoma County. As a result, and perhaps you've already guessed this, another Dense Fog Advisory has been issued for the North Bay and East Bay valleys. This will run until 11am on Monday, which means foggy conditions can be expected for the morning commute. We will need to keep an eye on visibilities for the Santa Clara Valley as well as San Jose and Hollister have already started to drop. For those commuting Monday morning, be sure to check the forecast and current weather and traffic conditions before heading out and allow extra time for your commute. If driving, slow down, use your headlights (not your high beams), and leave plenty of distance ahead of you. ∨

FOG SET IN A BIT EARLIER THIS EVENING AND IN PARTICULAR FOR THE
VALLEYS OF SONOMA COUNTY. AS A RESULT, AND PERHAPS YOU`VE ALREADY
GUESSED THIS, ANOTHER DENSE FOG ADVISORY HAS BEEN ISSUED FOR THE
NORTH BAY AND EAST BAY VALLEYS. THIS WILL RUN UNTIL 11AM ON
MONDAY, WHICH MEANS FOGGY CONDITIONS CAN BE EXPECTED FOR THE
MORNING COMMUTE. WE WILL NEED TO KEEP AN EYE ON VISIBILITIES FOR
THE SANTA CLARA VALLEY AS WELL AS SAN JOSE AND HOLLISTER HAVE
ALREADY STARTED TO DROP. FOR THOSE COMMUTING MONDAY MORNING, BE
SURE TO CHECK THE FORECAST AND CURRENT WEATHER AND TRAFFIC
CONDITIONS BEFORE HEADING OUT AND ALLOW EXTRA TIME FOR YOUR
COMMUTE. IF DRIVING, SLOW DOWN, USE YOUR HEADLIGHTS (NOT YOUR HIGH
BEAMS), AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU. [DISC]

Short term. Issued at 1:22pm PST Sun December 14 2025 (this evening through Monday) ∨

.SHORT TERM...
ISSUED AT 122 PM PST SUN DEC 14 2025
(THIS EVENING THROUGH MONDAY) [DISC]

The interaction between tule fog [Radiation fog in the Central Valley of California. It forms during night and morning hours in late fall and winter months following the first significant rainfall.] outgrowth from the east, and coastal stratus development from the west, continues to feature as the main short-term forecast issue as a shortwave trough passes over the state. The Salinas Valley has mostly cleared out, and the Monterey-Salinas region has generally cleared out, with lingering coastal stratus observed near Pacific grove and the immediate coast between Point Lobos [between Monterey & Big Sur CA] and Point Sur [Big Sur CA]. The coastal plain of Santa Cruz County and the San Juan bautista-Hollister Valley region remain socked in, the former extending up the coast of San Mateo County, and the latter connected to the extensive inland stratus that persists across much of the Bay Area Valleys. If you look closely at the satellite loop you could make out patches of clearing on the fringes — the Cloverdale area in extreme northern Sonoma County, Lake Berryessa in northeastern Napa County, parts of Livermore, western sections of Alameda County, and the southwest corner of San Francisco. Overall, there is much more stratus coverage today than we saw this time yesterday. As a result, confidence in the clearing of the North Bay valleys, the northern and eastern sections of Contra Costa County, and even southeastern San Mateo peninsula and the Santa Clara Valley has decreased. For the moment, the high temperatures today are similar to those from the overnight forecast update, with highs in the lower to middle 50s in the Bay Area Valleys, into the middle to upper 40s in eastern Marin County and northern and eastern Contra Costa County, the upper 50s to lower 60s along the Pacific coast, and the middle 60s to the lower 70s in the Salinas Valley. There's a chance that the temperatures could still undershoot the official forecast this afternoon, which comes into play if the clearing out process continues to lag the model projections. ∨

THE INTERACTION BETWEEN TULE FOG OUTGROWTH FROM THE EAST, AND
COASTAL STRATUS DEVELOPMENT FROM THE WEST, CONTINUES TO FEATURE AS
THE MAIN SHORT-TERM FORECAST ISSUE AS A SHORTWAVE TROUGH PASSES OVER
THE STATE. THE SALINAS VALLEY HAS MOSTLY CLEARED OUT, AND THE
MONTEREY-SALINAS REGION HAS GENERALLY CLEARED OUT, WITH LINGERING
COASTAL STRATUS OBSERVED NEAR PACIFIC GROVE AND THE IMMEDIATE COAST
BETWEEN POINT LOBOS AND POINT SUR. THE COASTAL PLAIN OF SANTA CRUZ
COUNTY AND THE SAN JUAN BAUTISTA-HOLLISTER VALLEY REGION REMAIN
SOCKED IN, THE FORMER EXTENDING UP THE COAST OF SAN MATEO COUNTY,
AND THE LATTER CONNECTED TO THE EXTENSIVE INLAND STRATUS THAT
PERSISTS ACROSS MUCH OF THE BAY AREA VALLEYS. IF YOU LOOK CLOSELY AT
THE SATELLITE LOOP YOU COULD MAKE OUT PATCHES OF CLEARING ON THE
FRINGES -- THE CLOVERDALE AREA IN EXTREME NORTHERN SONOMA COUNTY,
LAKE BERRYESSA IN NORTHEASTERN NAPA COUNTY, PARTS OF LIVERMORE,
WESTERN SECTIONS OF ALAMEDA COUNTY, AND THE SOUTHWEST CORNER OF SAN
FRANCISCO. OVERALL, THERE IS MUCH MORE STRATUS COVERAGE TODAY THAN
WE SAW THIS TIME YESTERDAY. AS A RESULT, CONFIDENCE IN THE CLEARING
OF THE NORTH BAY VALLEYS, THE NORTHERN AND EASTERN SECTIONS OF
CONTRA COSTA COUNTY, AND EVEN SOUTHEASTERN SAN MATEO PENINSULA AND
THE SANTA CLARA VALLEY HAS DECREASED. FOR THE MOMENT, THE HIGH
TEMPERATURES TODAY ARE SIMILAR TO THOSE FROM THE OVERNIGHT FORECAST
UPDATE, WITH HIGHS IN THE LOWER TO MIDDLE 50S IN THE BAY AREA
VALLEYS, INTO THE MIDDLE TO UPPER 40S IN EASTERN MARIN COUNTY AND
NORTHERN AND EASTERN CONTRA COSTA COUNTY, THE UPPER 50S TO LOWER 60S
ALONG THE PACIFIC COAST, AND THE MIDDLE 60S TO THE LOWER 70S IN THE
SALINAS VALLEY. THERE`S A CHANCE THAT THE TEMPERATURES COULD STILL
UNDERSHOOT THE OFFICIAL FORECAST THIS AFTERNOON, WHICH COMES INTO
PLAY IF THE CLEARING OUT PROCESS CONTINUES TO LAG THE MODEL
PROJECTIONS. [DISC]

On Monday, conditions are expected to be broadly similar to today's with a similar evolution of the stratus deck, as ridging forms on the backside of the shortwave trough. This ridge is remarkably positively tilted, such that the flow pattern off the California coast is quite zonal. This is a clue to the forthcoming pattern change, and so are the high clouds that are expected to flow over the region, thus increasing the uncertainty over the forecast. Will the high clouds bring breezier flow aloft that could help us scour out the tule fog [Radiation fog in the Central Valley of California. It forms during night and morning hours in late fall and winter months following the first significant rainfall.], or will they inhibit solar heating on Monday afternoon and keep the stratus around through the day? For now, have leaned towards another day of slower clearing, and have tamped Monday's lows cooler than the deterministic NBM output gives. ∨

ON MONDAY, CONDITIONS ARE EXPECTED TO BE BROADLY SIMILAR TO TODAY`S
WITH A SIMILAR EVOLUTION OF THE STRATUS DECK, AS RIDGING FORMS ON
THE BACKSIDE OF THE SHORTWAVE TROUGH. THIS RIDGE IS REMARKABLY
POSITIVELY TILTED, SUCH THAT THE FLOW PATTERN OFF THE CALIFORNIA
COAST IS QUITE ZONAL. THIS IS A CLUE TO THE FORTHCOMING PATTERN
CHANGE, AND SO ARE THE HIGH CLOUDS THAT ARE EXPECTED TO FLOW OVER
THE REGION, THUS INCREASING THE UNCERTAINTY OVER THE FORECAST. WILL
THE HIGH CLOUDS BRING BREEZIER FLOW ALOFT THAT COULD HELP US SCOUR
OUT THE TULE FOG, OR WILL THEY INHIBIT SOLAR HEATING ON MONDAY
AFTERNOON AND KEEP THE STRATUS AROUND THROUGH THE DAY? FOR NOW, HAVE
LEANED TOWARDS ANOTHER DAY OF SLOWER CLEARING, AND HAVE TAMPED
MONDAY`S LOWS COOLER THAN THE DETERMINISTIC NBM OUTPUT GIVES. [DISC]

Long term. Issued at 1:22pm PST Sun December 14 2025 (Monday night through next Saturday) ∨

.LONG TERM...
ISSUED AT 122 PM PST SUN DEC 14 2025
(MONDAY NIGHT THROUGH NEXT SATURDAY) [DISC]

More zonal flow [Large-scale atmospheric flow in which the east-west component is dominant] will come to the region on Tuesday, allowing a pattern change which will gradually open the proverbial storm door and lead to wetter conditions through the balance of the 7-day outlook and beyond. The first of the systems will come through Tuesday into Wednesday, with generally beneficial rainfall across our region focused on the North Bay, where rain totals will lie around 0.5–0.75" for the Sonoma coastal ranges, the 0.3–0.5" for the mayacamas, and 0.1–0.25" for the valleys. South of the Golden Gate, rainfall totals remain generally less than 0.1", with a few hundredths of an inch being the absolute maximum total across the Central Coast. More substantial rain is expected late on Thursday into Friday and the upcoming weekend, with the current forecast showing two distinct pulses of rain, one on Thursday and Friday and another for the upcoming weekend, each with the potential for more significant rainfall totals than the forecast for the Tuesday–Wednesday system. Initial forecasts suggest that rain totals over one inch are possible for the North Bay mountains. Beyond the upcoming weekend, uncertainty becomes high to very high, but ensemble model cluster analysis suggests good agreement in a deep upper level trough setting up in the eastern Pacific, which could support an atmospheric river setup assuming that the moisture plume sets up in the right place. The latest CPC [Climate Prediction Center] outlooks suggest that the North Bay faces a high risk (over 60% probability) of heavy rain early next week, with the rest of the region seeing a moderate risk (40–60% probability) of heavy rain in addition to the entire Bay Area and the northern Central Coast seeing a moderate risk of strong winds in the 8–14 day period (December 22–28). ∨

MORE ZONAL FLOW WILL COME TO THE REGION ON TUESDAY, ALLOWING A
PATTERN CHANGE WHICH WILL GRADUALLY OPEN THE PROVERBIAL STORM DOOR
AND LEAD TO WETTER CONDITIONS THROUGH THE BALANCE OF THE 7-DAY
OUTLOOK AND BEYOND. THE FIRST OF THE SYSTEMS WILL COME THROUGH
TUESDAY INTO WEDNESDAY, WITH GENERALLY BENEFICIAL RAINFALL ACROSS
OUR REGION FOCUSED ON THE NORTH BAY, WHERE RAIN TOTALS WILL LIE
AROUND 0.5-0.75" FOR THE SONOMA COASTAL RANGES, THE 0.3-0.5" FOR THE
MAYACAMAS, AND 0.1-0.25" FOR THE VALLEYS. SOUTH OF THE GOLDEN GATE,
RAINFALL TOTALS REMAIN GENERALLY LESS THAN 0.1", WITH A FEW
HUNDREDTHS OF AN INCH BEING THE ABSOLUTE MAXIMUM TOTAL ACROSS THE
CENTRAL COAST. MORE SUBSTANTIAL RAIN IS EXPECTED LATE ON THURSDAY
INTO FRIDAY AND THE UPCOMING WEEKEND, WITH THE CURRENT FORECAST
SHOWING TWO DISTINCT PULSES OF RAIN, ONE ON THURSDAY AND FRIDAY AND
ANOTHER FOR THE UPCOMING WEEKEND, EACH WITH THE POTENTIAL FOR MORE
SIGNIFICANT RAINFALL TOTALS THAN THE FORECAST FOR THE TUESDAY-
WEDNESDAY SYSTEM. INITIAL FORECASTS SUGGEST THAT RAIN TOTALS OVER
ONE INCH ARE POSSIBLE FOR THE NORTH BAY MOUNTAINS. BEYOND THE
UPCOMING WEEKEND, UNCERTAINTY BECOMES HIGH TO VERY HIGH, BUT
ENSEMBLE MODEL CLUSTER ANALYSIS SUGGESTS GOOD AGREEMENT IN A DEEP
UPPER LEVEL TROUGH SETTING UP IN THE EASTERN PACIFIC, WHICH COULD
SUPPORT AN ATMOSPHERIC RIVER SETUP ASSUMING THAT THE MOISTURE PLUME
SETS UP IN THE RIGHT PLACE. THE LATEST CPC OUTLOOKS SUGGEST THAT THE
NORTH BAY FACES A HIGH RISK (OVER 60% PROBABILITY) OF HEAVY RAIN
EARLY NEXT WEEK, WITH THE REST OF THE REGION SEEING A MODERATE RISK
(40-60% PROBABILITY) OF HEAVY RAIN IN ADDITION TO THE ENTIRE BAY
AREA AND THE NORTHERN CENTRAL COAST SEEING A MODERATE RISK OF STRONG
WINDS IN THE 8-14 DAY PERIOD (DECEMBER 22-28). [DISC]

Aviation. (06Z [10pm PST] TAFs [Terminal Aerodrome Forecasts]) issued at 9:25pm PST Sun December 14 2025 ∨

.AVIATION...
(06Z TAFS)
ISSUED AT 925 PM PST SUN DEC 14 2025 [AVIA]

Patchy low clouds and fog are beginning to fill back in over the region. Low ceilings and locally dense fog is expected once again tonight. Models indicate ceilings will scatter out around 17Z [9am PST]-19Z [11am PST]. However high clouds drifting in over the region may help mix out the boundary layer a bit resulting in some earlier clearing Monday morning across area terminals. ∨

PATCHY LOW CLOUDS AND FOG ARE BEGINNING TO FILL BACK IN OVER THE
REGION. LOW CIGS AND LOCALLY DENSE FOG IS EXPECTED ONCE AGAIN
TONIGHT. MODELS INDICATE CIGS WILL SCATTER OUT AROUND 17Z-19Z.
HOWEVER HIGH CLOUDS DRIFTING IN OVER THE REGION MAY HELP MIX OUT
THE BOUNDARY LAYER A BIT RESULTING IN SOME EARLIER CLEARING MONDAY
MORNING ACROSS AREA TERMINALS. [AVI2]

Vicinity of SFO [San Francisco CA]… VFR [Visual Flight Rules] conditions prevail currently however areas of patchy low clouds are anticipated to fill back in over the Bay tonight. Confidence is low as to the extent of coverage impacting SFO [San Francisco CA] and OAK [Oakland CA]. Models indicate ceilings may stay out of SFO [San Francisco CA] and OAK [Oakland CA] however satellite imagery indicates rapid spread close to the terminals and will need to watch closely. ∨

VICINITY OF SFO...VFR CONDITIONS PREVAIL CURRENTLY HOWEVER AREAS
OF PATCHY LOW CLOUDS ARE ANTICIPATED TO FILL BACK IN OVER THE BAY
TONIGHT. CONFIDENCE IS LOW AS TO THE EXTENT OF COVERAGE IMPACTING
SFO AND OAK. MODELS INDICATE CIGS MAY STAY OUT OF SFO AND OAK
HOWEVER SATELLITE IMAGERY INDICATES RAPID SPREAD CLOSE TO
THE TERMINALS AND WILL NEED TO WATCH CLOSELY. [AVI2]

SFO [San Francisco CA] bridge approach… low clouds over the approach expected to fill in overnight with locally dense fog. ∨

SFO BRIDGE APPROACH...LOW CLOUDS OVER THE APPROACH EXPECTED TO
FILL IN OVERNIGHT WITH LOCALLY DENSE FOG. [AVI2]

Monterey Bay terminals… IFR [Instrument Flight Rules] ceilings will prevail through tonight with clearing anticipated after 17Z [9am PST] Monday morning. ∨

MONTEREY BAY TERMINALS...IFR CIGS WILL PREVAIL THROUGH TONIGHT
WITH CLEARING ANTICIPATED AFTER 17Z MONDAY MORNING. [AVI2]

Marine. (tonight through next Saturday) issued at 9:11pm PST Sun December 14 2025 ∨

.MARINE...
(TONIGHT THROUGH NEXT SATURDAY)
ISSUED AT 911 PM PST SUN DEC 14 2025 [AVIA]

Southerly flow will prevail north of Pigeon Point [Pescadero CA] ahead of an approaching frontal system. Light to moderate northwesterly flow will prevail across much of the coastal waters with the exception of areas north of Pigeon Point [Pescadero CA] that will turn increasing to the south ahead of an approaching frontal system. Slightly stronger winds are expected along the immediate coast south of Point Sur [Big Sur CA] through Monday as the first in a series of weak systems reaches the coastal waters. Rain chances increase this week. Light seas will gradually build becoming moderate to rough by mid week. ∨

SOUTHERLY FLOW WILL PREVAIL NORTH OF PIGEON POINT AHEAD OF AN
APPROACHING FRONTAL SYSTEM.   LIGHT TO MODERATE NORTHWESTERLY FLOW
WILL PREVAIL ACROSS MUCH OF  THE COASTAL WATERS WITH THE EXCEPTION
OF AREAS NORTH OF PIGEON  POINT THAT WILL TURN INCREASING TO THE
SOUTH AHEAD OF AN  APPROACHING FRONTAL SYSTEM. SLIGHTLY STRONGER
WINDS ARE EXPECTED ALONG THE IMMEDIATE COAST SOUTH OF POINT SUR
THROUGH MONDAY AS  THE FIRST IN A SERIES OF WEAK SYSTEMS REACHES
THE COASTAL WATERS.  RAIN CHANCES INCREASE THIS WEEK. LIGHT SEAS
WILL GRADUALLY BUILD  BECOMING MODERATE TO ROUGH BY MID WEEK. [AVI2]

MTR Watches/Warnings/Advisories

California: Dense Fog Advisory until 11am PST Monday for CAZ506–510. ∨

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...DENSE FOG ADVISORY UNTIL 11 AM PST MONDAY FOR CAZ506-510. [WARN]

Pacific Ocean: Small Craft Advisory from 3pm Monday to 9am PST Tuesday for Pt Pinos [Monterey CA] to Pt Piedras Blancas [San Simeon CA] 0–10 nm [11 miles]. ∨

PZ...SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO 9 AM PST TUESDAY FOR PT
PINOS TO PT PIEDRAS BLANCAS 0-10 NM. [WRN2]

Short term…dialh long term…dialh aviation…cloud-water lightning marine…cloud-water lightning ∨

SHORT TERM...DIALH
LONG TERM....DIALH
AVIATION...CW
MARINE...CW [WRN2]

VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

FOLLOW US ON FACEBOOK, X, AND YOUTUBE AT:
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X.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA [DISC]

Weather NWS glossary About NWS point forecasts Hourly Weather Graph Long-range forecast Radar Satellite Max Temps Graphical Forecast	Area Forecast Discussion FXUS66 KMTR [Monterey CA] 150536 AFDMTR ∨ FXUS66 KMTR 150536 AFDMTR [HEAD] National Weather Service San Francisco California 9:36pm PST Sun Dec 14 2025 ∨ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO CA 936 PM PST SUN DEC 14 2025 [HEAD] New aviation. ∨ ...NEW AVIATION... [DISC] Key Messages… updated at 1:22pm PST Sun December 14 2025 ∨ .KEY MESSAGES... UPDATED AT 122 PM PST SUN DEC 14 2025 [DISC] - stratus persists over the North and East Bay valleys and the coastal regions ∨ - STRATUS PERSISTS OVER THE NORTH AND EAST BAY VALLEYS AND THE COASTAL REGIONS [DISC] - generally beneficial rain beginning this week ∨ - GENERALLY BENEFICIAL RAIN BEGINNING THIS WEEK [DISC] - heavier rain and strong wind possible next week ∨ - HEAVIER RAIN AND STRONG WIND POSSIBLE NEXT WEEK [DISC] Update. Issued at 9:11pm PST Sun December 14 2025 ∨ .UPDATE... ISSUED AT 911 PM PST SUN DEC 14 2025 [DISC] Fog set in a bit earlier this evening and in particular for the valleys of Sonoma County. As a result, and perhaps you've already guessed this, another Dense Fog Advisory has been issued for the North Bay and East Bay valleys. This will run until 11am on Monday, which means foggy conditions can be expected for the morning commute. We will need to keep an eye on visibilities for the Santa Clara Valley as well as San Jose and Hollister have already started to drop. For those commuting Monday morning, be sure to check the forecast and current weather and traffic conditions before heading out and allow extra time for your commute. If driving, slow down, use your headlights (not your high beams), and leave plenty of distance ahead of you. ∨ FOG SET IN A BIT EARLIER THIS EVENING AND IN PARTICULAR FOR THE VALLEYS OF SONOMA COUNTY. AS A RESULT, AND PERHAPS YOU`VE ALREADY GUESSED THIS, ANOTHER DENSE FOG ADVISORY HAS BEEN ISSUED FOR THE NORTH BAY AND EAST BAY VALLEYS. THIS WILL RUN UNTIL 11AM ON MONDAY, WHICH MEANS FOGGY CONDITIONS CAN BE EXPECTED FOR THE MORNING COMMUTE. WE WILL NEED TO KEEP AN EYE ON VISIBILITIES FOR THE SANTA CLARA VALLEY AS WELL AS SAN JOSE AND HOLLISTER HAVE ALREADY STARTED TO DROP. FOR THOSE COMMUTING MONDAY MORNING, BE SURE TO CHECK THE FORECAST AND CURRENT WEATHER AND TRAFFIC CONDITIONS BEFORE HEADING OUT AND ALLOW EXTRA TIME FOR YOUR COMMUTE. IF DRIVING, SLOW DOWN, USE YOUR HEADLIGHTS (NOT YOUR HIGH BEAMS), AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU. [DISC] Short term. Issued at 1:22pm PST Sun December 14 2025 (this evening through Monday) ∨ .SHORT TERM... ISSUED AT 122 PM PST SUN DEC 14 2025 (THIS EVENING THROUGH MONDAY) [DISC] The interaction between tule fog [Radiation fog in the Central Valley of California. It forms during night and morning hours in late fall and winter months following the first significant rainfall.] outgrowth from the east, and coastal stratus development from the west, continues to feature as the main short-term forecast issue as a shortwave trough passes over the state. The Salinas Valley has mostly cleared out, and the Monterey-Salinas region has generally cleared out, with lingering coastal stratus observed near Pacific grove and the immediate coast between Point Lobos [between Monterey & Big Sur CA] and Point Sur [Big Sur CA]. The coastal plain of Santa Cruz County and the San Juan bautista-Hollister Valley region remain socked in, the former extending up the coast of San Mateo County, and the latter connected to the extensive inland stratus that persists across much of the Bay Area Valleys. If you look closely at the satellite loop you could make out patches of clearing on the fringes — the Cloverdale area in extreme northern Sonoma County, Lake Berryessa in northeastern Napa County, parts of Livermore, western sections of Alameda County, and the southwest corner of San Francisco. Overall, there is much more stratus coverage today than we saw this time yesterday. As a result, confidence in the clearing of the North Bay valleys, the northern and eastern sections of Contra Costa County, and even southeastern San Mateo peninsula and the Santa Clara Valley has decreased. For the moment, the high temperatures today are similar to those from the overnight forecast update, with highs in the lower to middle 50s in the Bay Area Valleys, into the middle to upper 40s in eastern Marin County and northern and eastern Contra Costa County, the upper 50s to lower 60s along the Pacific coast, and the middle 60s to the lower 70s in the Salinas Valley. There's a chance that the temperatures could still undershoot the official forecast this afternoon, which comes into play if the clearing out process continues to lag the model projections. ∨ THE INTERACTION BETWEEN TULE FOG OUTGROWTH FROM THE EAST, AND COASTAL STRATUS DEVELOPMENT FROM THE WEST, CONTINUES TO FEATURE AS THE MAIN SHORT-TERM FORECAST ISSUE AS A SHORTWAVE TROUGH PASSES OVER THE STATE. THE SALINAS VALLEY HAS MOSTLY CLEARED OUT, AND THE MONTEREY-SALINAS REGION HAS GENERALLY CLEARED OUT, WITH LINGERING COASTAL STRATUS OBSERVED NEAR PACIFIC GROVE AND THE IMMEDIATE COAST BETWEEN POINT LOBOS AND POINT SUR. THE COASTAL PLAIN OF SANTA CRUZ COUNTY AND THE SAN JUAN BAUTISTA-HOLLISTER VALLEY REGION REMAIN SOCKED IN, THE FORMER EXTENDING UP THE COAST OF SAN MATEO COUNTY, AND THE LATTER CONNECTED TO THE EXTENSIVE INLAND STRATUS THAT PERSISTS ACROSS MUCH OF THE BAY AREA VALLEYS. IF YOU LOOK CLOSELY AT THE SATELLITE LOOP YOU COULD MAKE OUT PATCHES OF CLEARING ON THE FRINGES -- THE CLOVERDALE AREA IN EXTREME NORTHERN SONOMA COUNTY, LAKE BERRYESSA IN NORTHEASTERN NAPA COUNTY, PARTS OF LIVERMORE, WESTERN SECTIONS OF ALAMEDA COUNTY, AND THE SOUTHWEST CORNER OF SAN FRANCISCO. OVERALL, THERE IS MUCH MORE STRATUS COVERAGE TODAY THAN WE SAW THIS TIME YESTERDAY. AS A RESULT, CONFIDENCE IN THE CLEARING OF THE NORTH BAY VALLEYS, THE NORTHERN AND EASTERN SECTIONS OF CONTRA COSTA COUNTY, AND EVEN SOUTHEASTERN SAN MATEO PENINSULA AND THE SANTA CLARA VALLEY HAS DECREASED. FOR THE MOMENT, THE HIGH TEMPERATURES TODAY ARE SIMILAR TO THOSE FROM THE OVERNIGHT FORECAST UPDATE, WITH HIGHS IN THE LOWER TO MIDDLE 50S IN THE BAY AREA VALLEYS, INTO THE MIDDLE TO UPPER 40S IN EASTERN MARIN COUNTY AND NORTHERN AND EASTERN CONTRA COSTA COUNTY, THE UPPER 50S TO LOWER 60S ALONG THE PACIFIC COAST, AND THE MIDDLE 60S TO THE LOWER 70S IN THE SALINAS VALLEY. THERE`S A CHANCE THAT THE TEMPERATURES COULD STILL UNDERSHOOT THE OFFICIAL FORECAST THIS AFTERNOON, WHICH COMES INTO PLAY IF THE CLEARING OUT PROCESS CONTINUES TO LAG THE MODEL PROJECTIONS. [DISC] On Monday, conditions are expected to be broadly similar to today's with a similar evolution of the stratus deck, as ridging forms on the backside of the shortwave trough. This ridge is remarkably positively tilted, such that the flow pattern off the California coast is quite zonal. This is a clue to the forthcoming pattern change, and so are the high clouds that are expected to flow over the region, thus increasing the uncertainty over the forecast. Will the high clouds bring breezier flow aloft that could help us scour out the tule fog [Radiation fog in the Central Valley of California. It forms during night and morning hours in late fall and winter months following the first significant rainfall.], or will they inhibit solar heating on Monday afternoon and keep the stratus around through the day? For now, have leaned towards another day of slower clearing, and have tamped Monday's lows cooler than the deterministic NBM output gives. ∨ ON MONDAY, CONDITIONS ARE EXPECTED TO BE BROADLY SIMILAR TO TODAY`S WITH A SIMILAR EVOLUTION OF THE STRATUS DECK, AS RIDGING FORMS ON THE BACKSIDE OF THE SHORTWAVE TROUGH. THIS RIDGE IS REMARKABLY POSITIVELY TILTED, SUCH THAT THE FLOW PATTERN OFF THE CALIFORNIA COAST IS QUITE ZONAL. THIS IS A CLUE TO THE FORTHCOMING PATTERN CHANGE, AND SO ARE THE HIGH CLOUDS THAT ARE EXPECTED TO FLOW OVER THE REGION, THUS INCREASING THE UNCERTAINTY OVER THE FORECAST. WILL THE HIGH CLOUDS BRING BREEZIER FLOW ALOFT THAT COULD HELP US SCOUR OUT THE TULE FOG, OR WILL THEY INHIBIT SOLAR HEATING ON MONDAY AFTERNOON AND KEEP THE STRATUS AROUND THROUGH THE DAY? FOR NOW, HAVE LEANED TOWARDS ANOTHER DAY OF SLOWER CLEARING, AND HAVE TAMPED MONDAY`S LOWS COOLER THAN THE DETERMINISTIC NBM OUTPUT GIVES. [DISC] Long term. Issued at 1:22pm PST Sun December 14 2025 (Monday night through next Saturday) ∨ .LONG TERM... ISSUED AT 122 PM PST SUN DEC 14 2025 (MONDAY NIGHT THROUGH NEXT SATURDAY) [DISC] More zonal flow [Large-scale atmospheric flow in which the east-west component is dominant] will come to the region on Tuesday, allowing a pattern change which will gradually open the proverbial storm door and lead to wetter conditions through the balance of the 7-day outlook and beyond. The first of the systems will come through Tuesday into Wednesday, with generally beneficial rainfall across our region focused on the North Bay, where rain totals will lie around 0.5–0.75" for the Sonoma coastal ranges, the 0.3–0.5" for the mayacamas, and 0.1–0.25" for the valleys. South of the Golden Gate, rainfall totals remain generally less than 0.1", with a few hundredths of an inch being the absolute maximum total across the Central Coast. More substantial rain is expected late on Thursday into Friday and the upcoming weekend, with the current forecast showing two distinct pulses of rain, one on Thursday and Friday and another for the upcoming weekend, each with the potential for more significant rainfall totals than the forecast for the Tuesday–Wednesday system. Initial forecasts suggest that rain totals over one inch are possible for the North Bay mountains. Beyond the upcoming weekend, uncertainty becomes high to very high, but ensemble model cluster analysis suggests good agreement in a deep upper level trough setting up in the eastern Pacific, which could support an atmospheric river setup assuming that the moisture plume sets up in the right place. The latest CPC [Climate Prediction Center] outlooks suggest that the North Bay faces a high risk (over 60% probability) of heavy rain early next week, with the rest of the region seeing a moderate risk (40–60% probability) of heavy rain in addition to the entire Bay Area and the northern Central Coast seeing a moderate risk of strong winds in the 8–14 day period (December 22–28). ∨ MORE ZONAL FLOW WILL COME TO THE REGION ON TUESDAY, ALLOWING A PATTERN CHANGE WHICH WILL GRADUALLY OPEN THE PROVERBIAL STORM DOOR AND LEAD TO WETTER CONDITIONS THROUGH THE BALANCE OF THE 7-DAY OUTLOOK AND BEYOND. THE FIRST OF THE SYSTEMS WILL COME THROUGH TUESDAY INTO WEDNESDAY, WITH GENERALLY BENEFICIAL RAINFALL ACROSS OUR REGION FOCUSED ON THE NORTH BAY, WHERE RAIN TOTALS WILL LIE AROUND 0.5-0.75" FOR THE SONOMA COASTAL RANGES, THE 0.3-0.5" FOR THE MAYACAMAS, AND 0.1-0.25" FOR THE VALLEYS. SOUTH OF THE GOLDEN GATE, RAINFALL TOTALS REMAIN GENERALLY LESS THAN 0.1", WITH A FEW HUNDREDTHS OF AN INCH BEING THE ABSOLUTE MAXIMUM TOTAL ACROSS THE CENTRAL COAST. MORE SUBSTANTIAL RAIN IS EXPECTED LATE ON THURSDAY INTO FRIDAY AND THE UPCOMING WEEKEND, WITH THE CURRENT FORECAST SHOWING TWO DISTINCT PULSES OF RAIN, ONE ON THURSDAY AND FRIDAY AND ANOTHER FOR THE UPCOMING WEEKEND, EACH WITH THE POTENTIAL FOR MORE SIGNIFICANT RAINFALL TOTALS THAN THE FORECAST FOR THE TUESDAY- WEDNESDAY SYSTEM. INITIAL FORECASTS SUGGEST THAT RAIN TOTALS OVER ONE INCH ARE POSSIBLE FOR THE NORTH BAY MOUNTAINS. BEYOND THE UPCOMING WEEKEND, UNCERTAINTY BECOMES HIGH TO VERY HIGH, BUT ENSEMBLE MODEL CLUSTER ANALYSIS SUGGESTS GOOD AGREEMENT IN A DEEP UPPER LEVEL TROUGH SETTING UP IN THE EASTERN PACIFIC, WHICH COULD SUPPORT AN ATMOSPHERIC RIVER SETUP ASSUMING THAT THE MOISTURE PLUME SETS UP IN THE RIGHT PLACE. THE LATEST CPC OUTLOOKS SUGGEST THAT THE NORTH BAY FACES A HIGH RISK (OVER 60% PROBABILITY) OF HEAVY RAIN EARLY NEXT WEEK, WITH THE REST OF THE REGION SEEING A MODERATE RISK (40-60% PROBABILITY) OF HEAVY RAIN IN ADDITION TO THE ENTIRE BAY AREA AND THE NORTHERN CENTRAL COAST SEEING A MODERATE RISK OF STRONG WINDS IN THE 8-14 DAY PERIOD (DECEMBER 22-28). [DISC] Aviation. (06Z [10pm PST] TAFs [Terminal Aerodrome Forecasts]) issued at 9:25pm PST Sun December 14 2025 ∨ .AVIATION... (06Z TAFS) ISSUED AT 925 PM PST SUN DEC 14 2025 [AVIA] Patchy low clouds and fog are beginning to fill back in over the region. Low ceilings and locally dense fog is expected once again tonight. Models indicate ceilings will scatter out around 17Z [9am PST]-19Z [11am PST]. However high clouds drifting in over the region may help mix out the boundary layer a bit resulting in some earlier clearing Monday morning across area terminals. ∨ PATCHY LOW CLOUDS AND FOG ARE BEGINNING TO FILL BACK IN OVER THE REGION. LOW CIGS AND LOCALLY DENSE FOG IS EXPECTED ONCE AGAIN TONIGHT. MODELS INDICATE CIGS WILL SCATTER OUT AROUND 17Z-19Z. HOWEVER HIGH CLOUDS DRIFTING IN OVER THE REGION MAY HELP MIX OUT THE BOUNDARY LAYER A BIT RESULTING IN SOME EARLIER CLEARING MONDAY MORNING ACROSS AREA TERMINALS. [AVI2] Vicinity of SFO [San Francisco CA]… VFR [Visual Flight Rules] conditions prevail currently however areas of patchy low clouds are anticipated to fill back in over the Bay tonight. Confidence is low as to the extent of coverage impacting SFO [San Francisco CA] and OAK [Oakland CA]. Models indicate ceilings may stay out of SFO [San Francisco CA] and OAK [Oakland CA] however satellite imagery indicates rapid spread close to the terminals and will need to watch closely. ∨ VICINITY OF SFO...VFR CONDITIONS PREVAIL CURRENTLY HOWEVER AREAS OF PATCHY LOW CLOUDS ARE ANTICIPATED TO FILL BACK IN OVER THE BAY TONIGHT. CONFIDENCE IS LOW AS TO THE EXTENT OF COVERAGE IMPACTING SFO AND OAK. MODELS INDICATE CIGS MAY STAY OUT OF SFO AND OAK HOWEVER SATELLITE IMAGERY INDICATES RAPID SPREAD CLOSE TO THE TERMINALS AND WILL NEED TO WATCH CLOSELY. [AVI2] SFO [San Francisco CA] bridge approach… low clouds over the approach expected to fill in overnight with locally dense fog. ∨ SFO BRIDGE APPROACH...LOW CLOUDS OVER THE APPROACH EXPECTED TO FILL IN OVERNIGHT WITH LOCALLY DENSE FOG. [AVI2] Monterey Bay terminals… IFR [Instrument Flight Rules] ceilings will prevail through tonight with clearing anticipated after 17Z [9am PST] Monday morning. ∨ MONTEREY BAY TERMINALS...IFR CIGS WILL PREVAIL THROUGH TONIGHT WITH CLEARING ANTICIPATED AFTER 17Z MONDAY MORNING. [AVI2] Marine. (tonight through next Saturday) issued at 9:11pm PST Sun December 14 2025 ∨ .MARINE... (TONIGHT THROUGH NEXT SATURDAY) ISSUED AT 911 PM PST SUN DEC 14 2025 [AVIA] Southerly flow will prevail north of Pigeon Point [Pescadero CA] ahead of an approaching frontal system. Light to moderate northwesterly flow will prevail across much of the coastal waters with the exception of areas north of Pigeon Point [Pescadero CA] that will turn increasing to the south ahead of an approaching frontal system. Slightly stronger winds are expected along the immediate coast south of Point Sur [Big Sur CA] through Monday as the first in a series of weak systems reaches the coastal waters. Rain chances increase this week. Light seas will gradually build becoming moderate to rough by mid week. ∨ SOUTHERLY FLOW WILL PREVAIL NORTH OF PIGEON POINT AHEAD OF AN APPROACHING FRONTAL SYSTEM. LIGHT TO MODERATE NORTHWESTERLY FLOW WILL PREVAIL ACROSS MUCH OF THE COASTAL WATERS WITH THE EXCEPTION OF AREAS NORTH OF PIGEON POINT THAT WILL TURN INCREASING TO THE SOUTH AHEAD OF AN APPROACHING FRONTAL SYSTEM. SLIGHTLY STRONGER WINDS ARE EXPECTED ALONG THE IMMEDIATE COAST SOUTH OF POINT SUR THROUGH MONDAY AS THE FIRST IN A SERIES OF WEAK SYSTEMS REACHES THE COASTAL WATERS. RAIN CHANCES INCREASE THIS WEEK. LIGHT SEAS WILL GRADUALLY BUILD BECOMING MODERATE TO ROUGH BY MID WEEK. [AVI2] MTR Watches/Warnings/Advisories California: Dense Fog Advisory until 11am PST Monday for CAZ506–510. ∨ .MTR WATCHES/WARNINGS/ADVISORIES... CA...DENSE FOG ADVISORY UNTIL 11 AM PST MONDAY FOR CAZ506-510. [WARN] Pacific Ocean: Small Craft Advisory from 3pm Monday to 9am PST Tuesday for Pt Pinos [Monterey CA] to Pt Piedras Blancas [San Simeon CA] 0–10 nm [11 miles]. ∨ PZ...SMALL CRAFT ADVISORY FROM 3 PM MONDAY TO 9 AM PST TUESDAY FOR PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM. [WRN2] Short term…dialh long term…dialh aviation…cloud-water lightning marine…cloud-water lightning ∨ SHORT TERM...DIALH LONG TERM....DIALH AVIATION...CW MARINE...CW [WRN2] VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK] Follow us on Facebook, x, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea ∨ FOLLOW US ON FACEBOOK, X, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA X.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA [DISC]	Point Forecast Half Moon Bay CA 14 Dec 11:35pm PST Tonight Partly cloudy, with a low around 44°. NNE wind around 8 mph. Monday Mostly sunny, with a high near 59°. NE wind 7 to 9 mph. Monday Night Increasing clouds, with a low around 50°. NNW wind 3 to 8 mph. Tuesday A 30% chance of rain, mainly after 4pm. Patchy fog before 10am. Otherwise, mostly cloudy, with a high near 63°. Calm wind becoming NW 5 to 8 mph in the morning. Tuesday Night Rain likely, mainly after 10pm. Patchy fog between 10pm and 1am. Otherwise, cloudy, with a low around 53°. West wind 3 to 7 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible. Wednesday Rain likely, mainly before 10am. Mostly cloudy, with a high near 61°. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible. Wednesday Night A 20% chance of rain. Mostly cloudy, with a low around 48°. Thursday A chance of rain, mainly after 10am. Patchy fog before 10am. Otherwise, partly sunny, with a high near 60°. Thursday Night A chance of rain. Mostly cloudy, with a low around 49°. Friday Rain, mainly after 10am. Mostly cloudy, with a high near 61°. Friday Night Rain. Cloudy, with a low around 51°. Saturday A chance of rain. Mostly cloudy, with a high near 60°. Saturday Night Rain likely. Cloudy, with a low around 49°. Sunday Rain likely. Cloudy, with a high near 60°. Tonight Partly cloudy, with a low around 44. North northeast wind around 8 mph. Monday Mostly sunny, with a high near 59. Northeast wind 7 to 9 mph. Monday Night Increasing clouds, with a low around 50. North northwest wind 3 to 8 mph. Tuesday A 30 percent chance of rain, mainly after 4pm. Patchy fog before 10am. Otherwise, mostly cloudy, with a high near 63. Calm wind becoming northwest 5 to 8 mph in the morning. Tuesday Night Rain likely, mainly after 10pm. Patchy fog between 10pm and 1am. Otherwise, cloudy, with a low around 53. West wind 3 to 7 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible. Wednesday Rain likely, mainly before 10am. Mostly cloudy, with a high near 61. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible. Wednesday Night A 20 percent chance of rain. Mostly cloudy, with a low around 48. Thursday A chance of rain, mainly after 10am. Patchy fog before 10am. Otherwise, partly sunny, with a high near 60. Thursday Night A chance of rain. Mostly cloudy, with a low around 49. Friday Rain, mainly after 10am. Mostly cloudy, with a high near 61. Friday Night Rain. Cloudy, with a low around 51. Saturday A chance of rain. Mostly cloudy, with a high near 60. Saturday Night Rain likely. Cloudy, with a low around 49. Sunday Rain likely. Cloudy, with a high near 60.
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