157
FXUS66 KMTR 291621
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
821 AM PST WED JAN 29 2025
..NEW UPDATE, MARINE
SYNOPSIS
ISSUED AT 231 AM PST WED JAN 29 2025
HIGH PRESSURE WILL DOMINATE THE REGION LEADING TO CHILLY MORNINGS
AND MILD DAYS THROUGH THURSDAY. COASTAL FOG AND STRATUS THIS
MORNING AND LIKELY AGAIN TONIGHT AND INTO THURSDAY MORNING. A
PATTERN CHANGE HAPPENS FRIDAY, WITH WET WEATHER RETURNING FOR THE
WEEKEND. RAIN CHANCES ARE BEST FOR THE NORTH BAY AND DECREASE AS YOU
MOVE SOUTHWARDS.
UPDATE
ISSUED AT 821 AM PST WED JAN 29 2025
CLOUDY CONDITIONS PREVAIL OVER MUCH OF THE REGION THIS MORNING WITH
TEMPERATURES UNDER CLOUD COVER REMAINING INSULATED FROM THE COLD
TEMPERATURES. HOWEVER, A FEW SPOTS ACROSS THE REGION DID DIP INTO
THE MID 20S TO JUST BELOW FREEZING. THUS, WILL ALLOW THE
FROST/FREEZE PRODUCTS TO EXPIRE AT 9 AM. OTHERWISE, WILL BE
CHALLENGING FOR DAY TIME HIGH TEMPERATURES DEPENDING ON HOW QUICKLY
LOW CLOUDS DISSIPATE AND IF THEY DISSIPATE AT ALL. ALSO, FORECASTING
TEMPERATURES OVERNIGHT TONIGHT WILL BE A CHALLENGE AS CLOUDS ARE
EXPECTED TO RETURN TO INLAND VALLEYS. OTHERWISE, NO FORECAST UPDATES
ARE ANTICIPATED AT THIS TIME AS THE REMAINING FORECAST REMAINS ON
TRACK.
RGASS
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 231 AM PST WED JAN 29 2025
WATER VAPOR SATELLITE IMAGERY THIS MORNING SHOWS THE OMEGA BLOCK
OVER THE EASTERN PACIFIC, WITH HIGH PRESSURE SITTING OVER THE
REGION. LOOKING ACROSS OTHER CHANNELS, SUCH AS THE NIGHTTIME
MICROPHYSICS AND NIGHT FOG, WE CAN SEE STRATUS WORKING TROUGH THE
VALLEYS OF THE GREATER BAY AREA AND CENTRAL COAST. OBSERVATIONS SHOW
A FEW POCKETS OF FOG IN THE NORTH BAY, WHERE WINDS ARE EITHER CALM
OR LIGHT, WHILE OTHER AREAS REPORT LOW CLOUDS. STRATUS LOOKS TO HANG
AROUND THROUGH THE MORNING AND MAY STRUGGLE TO MIX OUT COMPLETELY
DURING THE AFTERNOON HOURS. THIS COULD HINDER TEMPERATURE GROWTH AND
KEEP TEMPERATURES COOLER THAN FORECAST. WITH THAT BEING SAID, HIGHS
TODAY ARE FORECAST TO BE IN THE LOW TO MID 50S AND GENERALLY IN THE
MID TO UPPER 50S FOR VALLEYS, PERHAPS LOW 60S. TEMPERATURES REMAIN
ON THE MIND FOR TONIGHT, WITH THE QUESTION BEING HOW LOW WILL THEY
GO? SHOULD THE MORE OPTIMISTIC FORECAST OCCUR FOR THE CLEARING OF
STRATUS, THE SALINAS VALLEY SHOULD CLEAR OUT AS WELL AS THE NORTH
BAY VALLEYS. UNFORTUNATELY, HI-RES GUIDANCE IS A BIT DIVIDED ON FAST
STRATUS RETURNS. CONFIDENCE IS LOWEST IN THE BAY AREA, WHERE AS THE
CENTRAL COAST SEEMS TO HAVE A LATER ONSET ESPECIALLY FOR THE
SOUTHERN SALINAS VALLEY. AT THIS TIME, OPTED TO NOT CHANGE THE MINT
FORECAST AND ALLOW THE THE FREEZE WATCH TO REMAIN IN PLACE FOR MUCH
OF THE REGION.
LONG TERM
(THURSDAY THROUGH TUESDAY)
ISSUED AT 231 AM PST WED JAN 29 2025
OMEGA BLOCKING LASTS THROUGH THURSDAY, BEFORE UPPER LEVEL RIDGING
BECOMES FLATTENED BUT AN UPPER LEVEL TROUGH MOVING INTO THE PACNW.
UPPER LEVEL FLOW OVER THE BAY AREA AND CENTRAL COAST SHOULD BE ZONAL
THROUGH THE WEEKEND. ENSEMBLE TABLES FOR THE GEFS, NAEFS, AND ENS
HAVE SHOWN AN INCREASE IN PWATS AND IVT OVER THE REGION FOR THE
WEEKEND. PWATS GENERALLY RANGE FROM 0.75-1.25" NOW, FAVORING MORE
MOISTURE OVERHEAD. GUIDANCE STILL FAVORS THE NORTH BAY FOR THE
WEEKEND, THOUGH THERE HAS BEEN A SLIGHT SHIFT SOUTHWARD GIVING THE
GREATER BAY AREA A BETTER SHOT WETTING RAIN. AS YOU MOVE SOUTH INTO
THE CENTRAL COAST CHANCES DECREASE. WE MAY CONTINUE TO SEE
FLUCTUATIONS IN TIMING AND AMOUNTS OVER THE NEXT FEW DAYS AS HI-RES
MODELS WILL START TO CAPTURE THIS EVENT.
NEXT WEEK, ZONAL FLOW MOVES SOUTH AS THE MID AND UPPER LEVEL LOW
DROPS SOUTHWARD. THIS WILL BRING MORE WIDESPREAD RAIN THE AREAS
SOUTH OF THE GOLDEN GATE AND ACROSS THE CENTRAL COAST. THERE REMAINS
A GREAT DEAL OF UNCERTAINTY BEYOND MONDAY, SO EXPECT THE FORECAST TO
CHANGE IN THE COMING DAYS AND AS WE GET CLOSER TO THE WEEKEND.
AVIATION
(12Z TAFS)
ISSUED AT 326 AM PST WED JAN 29 2025
WIDESPREAD MVFR STRATUS ACROSS THE BAY AREA AND CENTRAL COAST
THROUGH THE EARLY MORNING HOURS, WITH LIFR-IFR ACROSS THE NORTH
BAY VALLEYS. STRATUS BEGINS TO MIX OUT AROUND 18Z, WITH THE
INLAND TERMINALS CLEAR BY AROUND 20-22Z. COASTAL TERMINALS REMAIN
SOCKED IN THROUGH THE DAY. LIGHT ONSHORE FLOW WILL DEVELOP THIS
AFTERNOON, WITH MVFR-IFR STRATUS REDEVELOPING INLAND IN THE
EVENING HOURS.
VICINITY OF SFO... MVFR STRATUS CONTINUES INTO THE MORNING, WITH
MODERATE CONFIDENCE FOR SCATTERING OUT BY 22Z. LIGHTLY BREEZY WEST
FLOW THIS AFTERNOON, WITH STRATUS RETURNING TO THE TERMINAL IN THE
EVENING.
SFO BRIDGE APPROACH... SIMILAR TO SFO.
MONTEREY BAY TERMINALS... MVFR WITH OCCASIONAL IFR STRATUS THROUGH
THE MORNING. SKIES DO NOT CLEAR OUT ALL THE WAY BUT THE CEILINGS
SHOULD LIFT TO VFR IN THE AFTERNOON, WITH HIGHER CONFIDENCE IN SNS,
MODERATE CONFIDENCE IN MRY. LIGHT WEST-NORTHWEST FLOW WILL DEVELOP
IN THE AFTERNOON BEFORE STRATUS RETURNS IN THE EARLY EVENING
HOURS.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 821 AM PST WED JAN 29 2025
WINDS AND SEAS STAY LIGHT THROUGH FRIDAY. UNSETTLED WEATHER
RETURNS FRIDAY INTO NEXT WEEK AS AN UPPER LEVEL LOW BRINGS GUSTY
CONDITIONS TO THE NORTHERN WATERS AND WIDESPREAD RAIN OVER THE
WATERS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...FROST ADVISORY UNTIL 9 AM PST THIS MORNING FOR CAZ504-506-513-
528.
FREEZE WATCH FROM LATE TONIGHT THROUGH THURSDAY MORNING FOR
CAZ504-506-508-510-512>518-528>530.
FREEZE WARNING UNTIL 9 AM PST THIS MORNING FOR CAZ514-516>518.
PZ...NONE.
SHORT TERM...KR
LONG TERM....KR
AVIATION...DIALH
MARINE...MURDOCK
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