391
FXUS66 KMTR 171149
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
449 AM PDT THU APR 17 2025
..NEW AVIATION
SYNOPSIS
ISSUED AT 313 AM PDT THU APR 17 2025
CLOUDY START TO THE DAY TODAY AS AN UPPER LEVEL DISTURBANCE MOVES
OUT. WARM UP ON THE WAY FOR THE WEEKEND. BREEZY OFFSHORE WINDS FOR
THE INTERIOR MOUNTAINS FRIDAY AND SATURDAY MORNINGS (LOW IMPACT).
QUIET PATTERN WITH TEMPERATURES AROUND SEASONAL NORMALS FROM THE
WEEKEND ONWARD.
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 313 AM PDT THU APR 17 2025
FAIR WEATHER TO ROUND OUT THIS WEEK AS WE SAY GOODBYE TO ANY RAIN
CHANCES THAT MAY HAVE ACCOMPANIED THE WEAK UPPER LOW WE'VE BEEN
DEALING WITH THESE PAST COUPLE OF DAYS. CLOUDY START TO THE MORNING
UNDER A BETTER-DEVELOPED MARINE LAYER. OUTSIDE OF SOME LINGERING
PATCHY CLOUDINESS THIS AFTERNOON, DON'T EXPECT TOO MUCH TO WRITE
HOME ABOUT WEATHER-WISE TODAY. PERHAPS SOME DRIZZLE AND PATCHY FOG
FOR COASTAL LOCATIONS AND HIGHER ELEVATION COASTAL RANGES, BUT
NOTHING WE AREN'T USED TO.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 313 AM PDT THU APR 17 2025
DECENT WARM UP ON THE WAY FRIDAY THROUGH THE WEEKEND AS THE UPPER
LOW MOVES OUT AND A RIDGING PATTERN BUILDS IN ACROSS THE WEST COAST.
WITH THE LOW MOVING OUT, WE DO HAVE A WINDOW OF AN OFFSHORE-ORIENTED
PRESSURE GRADIENT AS SURFACE HIGH PRESSURE BUILDS INLAND IN THE PNW.
THIS WILL PROMOTE A SHORT PERIOD OF OFFSHORE WINDS BOTH FRIDAY AND
SATURDAY MORNINGS, BUT IT LOOKS TO BE MOSTLY UNIMPACTFUL. THE
SURFACE PRESSURE GRADIENT ISN'T PARTICULARLY STRONG, AND WE'RE
REALLY LACKING THE UPPER LEVEL SUPPORT NEEDED FOR A STRONG,
PROLONGED OFFSHORE WIND. THERE IS A RELATIVE MAX IN THE 850MB FLOW
ACROSS THE NORTH BAY FRIDAY MORNING, MIGRATING OVER COASTAL MARIN
AND SF BY THE EVENING HOURS. I WOULD EXPECT AT LEAST SOME BREEZY NE
WINDS IN THE INTERIOR NORTH BAY FRIDAY MORNING. HOWEVER, BY THE
EVENING HOURS, THE PRESSURE GRADIENT TURNS MORE ONSHORE DURING PEAK
SURFACE HEATING, AND THE LAYER REMAINS INTACT. WITH THIS NEAR
CANCELING OUT OF THE PRESSURE GRADIENT AND STRONG STABILITY ABOVE
THE MARINE LAYER (WHICH SITS BELOW THE 850MB HEIGHT), I REALLY DON'T
EXPECT ANY OFFSHORE WIND TO BE OF ANY IMPACT TO AREAS OUTSIDE OF THE
INTERIOR HIGHER TERRAIN. EVEN WITH THIS OFFSHORE WIND FOR INLAND
AREAS, MOISTURE RECOVERY WILL BE IN GOOD SHAPE, AND BEING SHORT-
LIVED, AFTERNOON MINIMUM RH DOESN'T SEEM TO BE AN ISSUE EITHER.
THIS ALL SEEMS LIKE IT WILL BE JUST MORE OF A NUISANCE, REALLY.
FOR THE REST OF THE FORECAST PERIOD, QUIET WEATHER IN STORE WITH
AFTERNOON HIGHS RIGHT AROUND SEASONAL AVERAGES.
AVIATION
(12Z TAFS)
ISSUED AT 432 AM PDT THU APR 17 2025
MVFR CEILINGS WILL DOMINATE THROUGH THE MORNING DUE TO A WELL-
ESTABLISHED MARINE LAYER. CEILINGS WILL LIKELY LIFT AND SCATTER
OUT FOR A FEW HOURS THIS AFTERNOON BEFORE SIMILAR CONDITIONS
RETURN OVERNIGHT. CEILINGS MAY BE A BIT LOWER TONIGHT AS THE
MARINE LAYER BECOMES MORE SHALLOW UNDER HIGHER PRESSURE. WITH
HIGHER HUMIDITY, THERE IS A GOOD CHANCE FOR FOG EARLY FRIDAY
MORNING, BUT MOST GUIDANCE SUGGESTS IT WILL ONLY IMPACT THE
IMMEDIATE COAST (HAF) AND TYPICAL FOGGY SITES (STS).
VICINITY OF SFO...HIGH CONFIDENCE IN MVFR CEILINGS THROUGH THE
MORNING HOURS BEFORE SOME DIURNAL IMPROVEMENT STARTS TO
ARRIVE SOMETIME BETWEEN 23Z AND 01Z. VFR CONDITIONS WILL PERSIST
FOR ABOUT 6 HOURS BEFORE MVFR CEILINGS REDEVELOP THURSDAY NIGHT.
OTHERWISE GENTLE ONSHORE WIND WILL INCREASE TO A MODERATE BREEZE
THIS AFTERNOON.
SFO BRIDGE APPROACH... SIMILAR TO SFO.
MONTEREY BAY TERMINALS...THE GUIDANCE HAS TRENDED CLOUDIER OVER
THE WITH THE LATEST TAF UPDATE AND MVFR STRATUS IS NOW LIKELY
THROUGH THE PERIOD. THERE IS STILL A CHANCE FOR SOME IMPROVEMENT
FOR A FEW HOURS THIS AFTERNOON, BUT IF SO THE CEILINGS WILL VERY
LIKELY RETURN BEFORE THE SUN SETS.
MARINE
(TODAY THROUGH TUESDAY)
ISSUED AT 313 AM PDT THU APR 17 2025
THE GRADIENT BETWEEN HIGH PRESSURE IN THE EASTERN PACIFIC AND
LOWER PRESSURE OVER THE WESTERN US IS SUPPORTING A MODERATE TO
FRESH NORTHERLY BREEZE ACROSS THE OUTER COASTAL WATERS WITH LIGHT
AND VARIABLE WINDS CLOSER TO THE COAST. AS THE WINDS DIMINISH,
ROUGH SEAS WILL SUBSIDE THURSDAY NIGHT THROUGH FRIDAY BEFORE
ANOTHER STRONG BREEZE REBUILDS SEAS THIS WEEKEND WHICH WILL LIKELY
PERSIST INTO EARLY NEXT WEEK.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 PM PDT THIS AFTERNOON FOR PT ARENA
TO PT REYES 10-60 NM.
SMALL CRAFT ADVISORY FROM 9 PM FRIDAY TO 3 AM PDT SATURDAY FOR
PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...BEHRINGER
LONG TERM....BEHRINGER
AVIATION...FLYNN
MARINE...FLYNN
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