FXUS66 KMTR 092245
AFDMTR
Area Forecast Discussion
National Weather Service San Francisco CA
345 PM PDT Tue Jun 9 2026
...New KEY MESSAGES...
.KEY MESSAGES...
Updated at 345 PM PDT Tue Jun 9 2026
- Warmer and dry weather expected Wednesday - Saturday
- Moderate risk of heat-related illnesses for interior locations on
Wednesday and Thursday
- Critical fire weather concerns for the interior North Bay and
the East Bay Mountains late Wednesday into Thursday morning.
- Elevated fire weather conditions for the Santa Clara Hills late
Wednesday into Thursday morning.
&&
.SHORT TERM...
Issued at 335 PM PDT Tue Jun 9 2026
(This evening through Wednesday)
The pattern change continues as a front worked its way through the
region earlier this morning. Behind it, drier air filled in clearing
the clouds and leading sunny skies and a warm afternoon. High
temperatures appear to be on track, with interior valley locations
making it into the upper 70s to mid 80s while coastal and some Bay
shoreline communities made it into the upper 50s to the mid 70s.
Dry air will continue to nestle in, which should keep skies clear
tonight. Low temperatures will generally be in the 50s for most
sites, though temps in the 60s will be possible for areas at or
above the thermal belt.
Tomorrow, Wednesday, the warming trend really kicks off. High
pressure builds to the west of us, while upper level troughing moves
east. Drier air and northerly winds will help usher in warmer air to
the region. Many interior locations, both for mountains and interior
valleys for the Bay Area and the Central Coast have a Moderate
threat for HeatRisk. What does that mean? This type of heat affects
those who are sensitive to heat, especially those without cooling
and hydration, and some health and industries. In terms of high
temperatures, they will vary from the mid 70s to the mid 80s around
the Bay Shoreline, the upper 80s to mid 90s for interior valleys and
mountains, and the low 60s to mid 70s for the coastal communities.
Wednesday night into Thursday morning, there will be some reprieve
from the heat, as valley locations and areas beneath the thermal
belt drop into upper 50s to low 60s. For those in the thermal
belt, overnight lows will be warmer and in span the low 60s to
upper 70s. This is also when the offshore flow / north to
northeast winds pick up, particularly across the interior North
Bay Mountains and the East Bay Hills. Peak wind gusts up to 45 mph
can be expected and ridge top wind gusts may exceed 60 mph. Winds
will be strongest overnight and then begin to ease around
sunrise. These hot, dry, and windy conditions combined with mixed
vegetation, such as drying or dead grass, will lead to near
critical to critical fire weather conditions. A Red Flag Warning
has been issued for these areas starting late Wednesday night and
continuing into Thursday morning.
&&
.LONG TERM...
Issued at 335 PM PDT Tue Jun 9 2026
(Wednesday night through next Monday)
The pattern holds on Thursday, which will lead to our warmest day of
the week. Many locations will experience Moderate HeatRisk across
the Bay Area and the interior Central Coast. High temperatures will
vary from the low 80s to the mid 90s around the Bay Shoreline, the
upper 80s to the low 100s for interior valleys and mountains, and
the low 60s to low 80s for the coastal communities. With that being
said, a Heat Advisory will go into effect on Thursday from 12pm-
11pm: the Bay Shoreline, North Bay Interior Mountains and Valleys,
and the Santa Clara Valley and Eastern Hills.
Starting on Friday, the NBM begins a gradual cool down across the
region. This will have to be something we watch closely as there
is no defining synoptic feature that changes the pattern. Meaning
we could see another day of warmer temperatures. Some models try
to bring a marine influence back into the region, but that may
struggle depending on the strength of the high. Opted to trend a
few degrees warmer on Friday, given the current model diagnosis
but should we see marine influence, the NBM may be on to
something. Saturday, an upper level shortwave tries to form over
the northern part of the state. This may bring another burst of
northerlies depending on the placement or usher in onshore flow.
Opted to generally keep the gradual decrease / moderation of
temperatures for the weekend and into early next week.
&&
.AVIATION...
(18Z TAFS)
Issued at 1133 AM PDT Tue Jun 9 2026
Lingering MVFR ceilings are making their way out of the region by
this afternoon. Widespread VFR conditions are also expected to
prevail by the afternoon through the TAF period. W to NW winds
increase to a moderate breeze (10-15kts) with a few terminals
experiencing ~20kt gusts. Winds begin to ease by sunset and continue
to diminish overnight.
Vicinity of SFO...VFR through the TAF period. High confidence that
westerly winds will increase by the early afternoon with some
embedded gusts above 20kts. Winds are expected to diminish overnight
and increase back to moderate breezes by Wednesday early afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...The remaining low-level clouds are
currently mixing out as onshore winds increase by the early
afternoon. NW winds are expected to begin to ease by sunset and
remain light overnight. Low confidence on an MVFR ceiling this
evening given how dry the atmosphere is (and will continue to be)
in this post-frontal environment. VFR all the way!
&&
.MARINE...
(Tonight through next Sunday)
Issued at 335 PM PDT Tue Jun 9 2026
Gusty northwest winds have spread across the waters resulting in
hazardous conditions for small craft. Gale force gusts will spread
across the northern waters overnight night into early Thursday.
Wind and seas begin to ease by Thursday evening and are expected
to stay light through the remainder of the forecast period.
&&
.FIRE WEATHER...
Issued at 1208 AM PDT Tue Jun 9 2026
Hot temperatures, gusty north winds, and low humidities across the
North Bay interior mountains into the Diablo Range will raise the
fire weather threats late on Wednesday into Thursday, with a
particular emphasis on the interior mountains of Napa County.
Although the strongest winds will remain within the Sacramento
Valley, gusts of 25 to 35 mph are expected to spread into Napa
County and the Diablo Range south through Santa Clara County, with
stronger gusts of 40-50 mph possible along the Vaca Mountains along
Napa County's eastern edge. Meanwhile, daytime humidity retention
will be very poor with relative humidity values as low as 10-15%,
while overnight recoveries are likewise poor as RH values top out at
20-30%. Thus, fuels are expected to dry rapidly, leading to the
elevated fire weather concerns. Also important to note that even
with the drizzle and light rain coming through the region, wetting
rains (rain totals above 0.1") are not expected, limiting any relief
that will be realized for the midweek period. Elsewhere across the
district, conditions remain hot and dry, but we're not expecting
winds to be as strong as they are across the interior North Bay.
We are continuing to monitor the potential for fire weather products
to be issued for the interior mountains of the North, East, and
South Bays for Wednesday and Thursday. At present, conditions are
right on the edge of critical fire weather criteria, but the
confidence isn't there at this point to pull the trigger on any
warnings. The day shift will reevaluate the fire weather forecast
for Wednesday and Thursday and in collaboration with neighboring
offices, will be in a better position to determine the extent of
necessary products. Regardless of whether any products are issued
across the interior, elevated to near critical fire weather
conditions are still forecast and care must be taken to avoid
starting a fire that could spread rapidly. Remember, one less
spark, one less wildfire.
DialH
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from noon to 11 PM PDT Thursday for CAZ503-504-506-
508-510-513>515.
Red Flag Warning from 11 PM Wednesday to 9 AM PDT Thursday for
CAZ504-515.
PZ...Small Craft Advisory until 9 PM PDT this evening for Mry Bay-Pt
Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 9 AM to 9 PM PDT Wednesday for Mry Bay.
Small Craft Advisory until 9 AM PDT Wednesday for Pt Arena to Pt
Reyes 0-10 nm.
Gale Warning from 9 AM Wednesday to 3 AM PDT Thursday for Pt
Arena to Pt Reyes 0-10 nm.
Small Craft Advisory until 9 PM PDT Wednesday for Pigeon Pt to
Pt Pinos 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 3 AM PDT Thursday for Pt Pinos to Pt
Piedras Blancas 0-10 nm.
Gale Warning from 9 PM this evening to 3 AM PDT Thursday for Pt
Arena to Pt Reyes 10-60 NM.
Small Craft Advisory until 3 PM PDT Thursday for Pigeon Pt to Pt
Pinos 10-60 NM.
&&
$$
SHORT TERM...KR
LONG TERM....KR
AVIATION...Navarrete
MARINE...Murdock
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Prepared by Boulder-Creek.com Weather at: Tue Jun 9 16:30:03 PDT 2026
From the National Weather Service
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