329
FXUS66 KMTR 071807
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1007 AM PST WED JAN 7 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 247 AM PST WED JAN 7 2026
- HIGH AND DRY PATTERN THROUGH THE WEEK WITH OFFSHORE FLOW AND
COLD OVERNIGHT CONDITIONS
- HAZARDOUS BEACH CONDITIONS AT ALL PACIFIC COAST BEACHES
THURSDAY AND FRIDAY AND AGAIN EARLY NEXT WEEK
SHORT TERM
ISSUED AT 247 AM PST WED JAN 7 2026
(TODAY AND TONIGHT)
FLOODING CONTINUES FOR AREAS NEAR AND DOWNSTREAM OF MARK WEST CREEK
NEAR MIRABEL HEIGHTS AS INDICATED BY GAUGES AND CAMERAS. A FLOOD
WARNING IS IN EFFECT UNTIL 8 AM - THIS WILL LIKELY BE REPLACED BY A
LONG DURATION FLOOD ADVISORY THEN AS THAT IS WHEN IT IS FORECAST TO
RECEDE INTO MINOR FLOOD STAGE. RESIDUAL TROUGHINESS WILL ALLOW FOR A
DYING COLD FRONT TO SKIRT THE REGION TODAY. HIGH CLOUDS FROM THIS
FEATURE WILL CONTINUE TO STREAM INTO THE REGION WHICH WILL HELP
LIMIT THE EXTENT OF FOG AND STRATUS THIS MORNING. SENSIBLE WEATHER
WISE, EXPECT NEAR NORMAL TEMPERATURES AND MORE GLOOMY CONDITIONS.
LONG TERM
ISSUED AT 247 AM PST WED JAN 7 2026
(THURSDAY THROUGH TUESDAY)
GLOBAL ENSEMBLE CLUSTERS ARE IN AGREEMENT OF SOME FORM OF LONGWAVE
UPPER-LEVEL RIDGING DOMINATING OUR LONG TERM FORECAST AND BEYOND.
THIS WILL YIELD FAIR DAYTIME CONDITIONS WITH COLD OVERNIGHT
CONDITIONS. AN EXTREME COLD WATCH HAS BEEN ISSUED FOR MOST OF THE
AREA FROM 1 AM FRIDAY TO 9 AM FRIDAY TO COVER THE THURSDAY NIGHT
PERIOD. IT'S A BIT OF A NUANCED FORECAST THOUGH AS IT ISN'T A COLD
AIR MASS BRINGING THIS ALONG. IN FACT, 850 MILLIBAR TEMPERATURES ARE
FORECAST TO WARM NEAR 7 DEGREES CELSIUS WHICH IS NEAR THE DAILY
MEAN. SOME METEOROLOGICAL RULE OF THUMB EQUATES THIS TO 45 DEGREES
AT 5,000 FEET. TO FIGURE OUT WHAT'S GOING ON, WE NEED TO ZOOM OUT.
IT IS WINTER WHICH MEANS NIGHTS ARE LONG AND THEREFORE THERE IS A
LOT OF TIME FOR RADIATIONAL COOLING TO OCCUR. AS THE EARTH COOLS, A
SHALLOW, STABLE LAYER DEVELOPS NEAR THE SURFACE, THIS IS KNOWN AS A
TEMPERATURE INVERSION. QUANTITATIVELY, THIS IS WHEN TEMPERATURE
INCREASES WITH HEIGHT, LIKE IN THIS CASE WHERE WE HAVE ~0 DEGREES
CELSIUS AT THE SURFACE AND ~7 DEGREES CELSIUS AT 5,000 FEET. YOU CAN
THINK OF IT AS A "COLD LID". WE ARE GOING TO PUT A PIN IN THIS FOR
NOW. AT THE SURFACE, HIGH PRESSURE WILL NOSE INTO THE
CALIFORNIA/OREGON BORDER BEFORE ULTIMATELY BUILDING INTO THE GREAT
BASIN. ALONG THE CALIFORNIA COAST, A COASTAL TROUGH WILL DEVELOP
WHICH WILL FACILITATE OFFSHORE FLOW. NORMALLY THIS WOULD BE A FIRE
WEATHER CONCERN, BUT WE ARE WAY PAST THAT. WE ARE GOING TO KEEP OUR
FIRE WEATHER THINKING CAPS ON THOUGH TO UNDERSTAND WHY IT IS GOING
TO BE COLD IN SOME SPOTS AND NOT OTHERS. CIRCLING BACK TO OUR "COLD
LID", OFFSHORE FLOW ALOFT WILL NOT BE STRONG OR TURBULENT ENOUGH TO
BREAK ITS SEAL. SOME LOCATIONS DOWNSLOPE OF/IN THE HIGHER TERRAIN
ARE NOT IN THE EXTREME COLD WATCH AS SUFFICIENT MIXING WILL KEEP
THEM RELATIVELY WARMER. THE COLDEST SPOTS WILL BE INTERIOR MONTEREY
AND SAN BENITO COUNTIES, WHERE BELOW FREEZING TEMPERATURES ARE
POSSIBLE. THE NORTH BAY COAST AND SAN FRANCISCO PENINSULA COAST WILL
BE MODERATED BY THE PACIFIC OCEAN AND DOWNSLOPE FLOW COMING OFF OF
THE ADJACENT TERRAIN. THE FRIDAY NIGHT PERIOD WILL BE COLD, BUT NOT
QUITE AS COLD AS THURSDAY NIGHT. OVERNIGHT TEMPERATURES WILL SLOWLY
RISE THROUGH THE WEEKEND TO BECOME ABOVE CRITERIA BY THE START OF
NEXT WEEK.
AVIATION
(18Z TAFS)
ISSUED AT 943 AM PST WED JAN 7 2026
VFR IS EXPECTED TO PREVAIL THROUGH THE FORECAST PERIOD FOR ALL
TERMINALS. THERE IS A SLIGHT CHANCE (PRIMARILY SOUTH BAY AND
MONTEREY BAY TERMINALS) FOR MVFR CIGS TO DEVELOP LATER TONIGHT
INTO EARLY THURSDAY MORNING, AS A RELATIVELY WEAK COLD FRONT
PUSHES THROUGH OUR AREA. WINDS WILL INCREASE ALONG AND BEHIND THE
FRONT BECOMING GUSTY AT TIMES FROM THE W/NW.
VICINITY OF SFO...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH
THE FORECAST PERIOD WITH GUSTY ONSHORE WINDS SETTLING IN THIS
EVENING AND PERSISTING THROUGH A MAJORITY OF THE REMAINING TAF
PERIOD AS A COLD FRONT PASSES SOUTH THROUGH OUR AREA.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR IS EXPECTED TO PREVAIL THROUGH A
MAJORITY OF THE TAF PERIOD WITH A CHANCE FOR MVFR CIGS LATE INTO
THE OVERNIGHT THROUGH MID-THURSDAY MORNING. WINDS WILL INCREASE
AND BECOME GUSTY LATER THIS EVENING AND CONTINUE THROUGH THE
OVERNIGHT AS A COLD FRONT PUSHES THROUGH OUR AREA.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 943 AM PST WED JAN 7 2026
NORTHERLY WINDS SETTLE IN BEHIND A SERIES OF WEAK FRONTS TODAY,
GRADUALLY INCREASING THROUGH THE AFTERNOON AND OVERNIGHT. ALONG
WITH THE INCREASING NORTHERLY WINDS WILL BE A BUILDING MODERATE
NORTHWEST SWELL ON THURSDAY, COMBINING O CREATE HAZARDOUS
CONDITIONS ON THE WATER THROUGH LATE THURSDAY NIGHT, WITH WINDS
EASING AND WAVE ENERGY DECREASING INTO THE WEEKEND.
MTR WATCHES/WARNINGS/ADVISORIES
CA...HIGH SURF ADVISORY FROM 1 AM THURSDAY TO 10 PM PST FRIDAY FOR
CAZ006-505-509-530.
EXTREME COLD WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY
MORNING FOR CAZ502-506-508-510-512>518-528>530.
BEACH HAZARDS STATEMENT FROM LATE TONIGHT THROUGH FRIDAY EVENING
FOR CAZ529.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM PST
THURSDAY FOR MRY BAY-PIGEON PT TO PT PINOS 0-10 NM-PT ARENA
TO PT REYES 0-10 NM-PT REYES TO PIGEON PT 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PST
THURSDAY FOR PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT
REYES 10-60 NM-PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...SARMENT
LONG TERM....SARMENT
AVIATION...JM
MARINE...JM
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO
FOLLOW US ON FACEBOOK, X, AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSBAYAREA
X.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page