847
FXUS66 KMTR 301734
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1034 AM PDT WED SEP 30 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1231 AM PDT WED SEP 30 2026
- ELEVATED FIRE WEATHER CONDITIONS ACROSS THE HIGHER TERRAIN
THROUGH THURSDAY
- AREAS OF MODERATE HEATRISK ACROSS THE INTERIOR THROUGH TUESDAY
- MINOR COASTAL FLOODING FOR BAYSHORE LOCATIONS ALONG THE SAN FRANCISCO,
SAN PABLO, AND MONTEREY BAYS MONDAY THROUGH THURSDAY
SHORT TERM
ISSUED AT 1231 AM PDT WED SEP 30 2026
(WEDNESDAY THROUGH THURSDAY)
WITH RIDGING NOSING IN FROM THE EASTERN PACIFIC OCEAN AND A LOW
ACROSS THE DESERT SOUTHWEST, THE UPPER-LEVEL PATTERN WILL SUPPORT
NORTHERLY/OFFSHORE FLOW THROUGH THURSDAY. NORTHERLY/OFFSHORE WINDS
WILL BE STRONGEST DURING THE OVERNIGHT PERIODS AND IN THE HIGHER
TERRAIN. MT. ST. HELENA GUSTED TO 48 MPH TUESDAY MORNING WITH GUSTS
OF 25-35 MPH ELSEWHERE, SIMILAR CONDITIONS CAN BE EXPECTED DURING
THE OVERNIGHT PERIODS THROUGH THURSDAY MORNING. THE COMBINATION OF
DRY AND WINDY CONDITIONS WILL RESULT IN ELEVATED FIRE WEATHER
CONDITIONS ACROSS THE HIGHER TERRAIN THROUGH THURSDAY. TEMPERATURES
WILL BE 5 TO 10 DEGREES ABOVE NORMAL WITH THE MARINE LAYER
STRUGGLING TO FORM. IF IT IS ABLE TO FORM, IT WILL BE COMPRESSED
AROUND 500 FEET AND REMAIN CONFINED TO THE COAST. MINOR COASTAL
FLOODING FOR BAYSHORE LOCATIONS ALONG THE SAN FRANCISCO, SAN PABLO,
AND MONTEREY BAYS WILL CONTINUE DURING THE HIGHEST HIGH TIDES
THROUGH THURSDAY.
LONG TERM
ISSUED AT 1231 AM PDT WED SEP 30 2026
(FRIDAY THROUGH TUESDAY)
GLOBAL ENSEMBLE CLUSTERS ARE IN AGREEMENT THAT ANOMALOUSLY HIGH
HEIGHTS WILL BE ACROSS OUR AREA THROUGH TUESDAY. 500 MB HEIGHTS AND
850 MB TEMPERATURES ARE FORECAST TO BE NEAR THE 90TH PERCENTILE FOR
THE FIRST WEEK OF OCTOBER, WHICH IS 588 DECAMETERS AND 21 DEGREES
CELSIUS, RESPECTIVELY. SATURDAY WILL LIKELY BE THE PEAK OF THE HEAT
AS UPPER-LEVEL LONGWAVE RIDGING DRIFTS IN FROM THE EASTERN PACIFIC
OCEAN. NONETHELESS, TEMPERATURES WILL BE 10 TO 15 DEGREES ABOVE
NORMAL WITH MODERATE HEATRISK AWAY FROM THE IMMEDIATE COAST THROUGH
TUESDAY. THE MARINE LAYER WILL LIKELY STILL STRUGGLE TO FORM; IF
IT'S ABLE TO FORM, IT WILL BE COMPRESSED AROUND 500 FEET AND REMAIN
CONFINED TO THE COAST.
AVIATION
(18Z TAFS)
ISSUED AT 1025 AM PDT WED SEP 30 2026
DEVELOPING MARINE LAYER IS BATTLING BUILDING HIGH PRESSURE OVER
THE REGION. AS SUCH, THE INVERSION HEIGHT IS COMPRESSED LEADING TO
LOW CIGS ALONG THE COAST. THAT BEING SAID, EXPECTING VFR THROUGH
EARLY THIS EVENING. CIGS RETURN EARLY FOR MRY/SNS AND LATER FOR N
BAY AND IN SF BAY. MODERATE CONF FOR FOG DEVELOPMENT TONIGHT GIVEN
THE SHALLOW NATURE OF THE MARINE LAYER.
VICINITY OF SFO...VRF THROUGH THIS EVENING. CIGS SLOWLY REDEVELOP
INSIDE SF BAY IMPACTING OAK AND SFO 07-09Z TIMEFRAME. LOWER CIGS
LINGER INTO THE AM RUSH FOR THURSDAY.
SFO BRIDGE APPROACH...LESS CHC FOR LATE NIGHT CIGS, BUT STILL
EXPECTING SOME AROUND THE APPROACH ZONE.
MONTEREY BAY TERMINALS...VFR THROUGH THIS AFTERNOON, BUT CIGS
LURKING OUTSIDE OF MRY BAY WILL RETURN EARLY THIS EVENING. HIGH
CONF ON FOG IMPACTS BY THURSDAY MORNING.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 1025 AM PDT WED SEP 30 2026
NORTHERLY WINDS WILL CONTINUE TO EASE THROUGH THE DAY, BUT STILL
HAZARDOUS WITH MODERATE TO STRONG BREEZES. STRONGEST WINDS ARE
OVER THE OUTER WATERS NORTH OF POINT REYES. CONDITIONS WILL
IMPROVE LATER THIS WEEK AND WEEKEND AS NORTHWESTERLY BREEZES
DIMINISH TO BECOME GENTLE TO MODERATE. ROUGH TO VERY ROUGH SEAS
TODAY WILL SUBSIDE TO MODERATE BY FRIDAY.
FIRE WEATHER
ISSUED AT 502 AM PDT WED SEP 30 2026
A HIGH PRESSURE SYSTEM WILL MOVE IN FROM THE WEST AND COMPRESS THE
MARINE LAYER TO APPROXIMATELY 500 FEET. HOT AND DRY CONDITIONS
WILL PREVAIL THROUGH LATE WEEK AND WEEKEND. EXPECT POOR OVERNIGHT
HUMIDITY RECOVERIES, WITH OVERNIGHT RELATIVE HUMIDITIES AS LOW AS
20-30% ABOVE THE MARINE LAYER.
MTR WATCHES/WARNINGS/ADVISORIES
CA...COASTAL FLOOD ADVISORY UNTIL 5 PM PDT THURSDAY FOR CAZ006-506-
508-529-530.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY FOR PIGEON PT TO PT
PINOS 10-60 NM-PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...SARMENT
LONG TERM....SARMENT
AVIATION...MM
MARINE...MM
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