453
FXUS66 KMTR 041005
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
305 AM PDT Fri Jul 4 2025

...New SHORT TERM, LONG TERM, FIRE WEATHER...

.KEY MESSAGES...
Updated at 208 AM PDT Fri Jul 4 2025

 - Elevated fire weather concerns persist through Friday for the
   East Bay and Santa Cruz Mountains.

 - Northwest winds of 30 to 55 mph through Friday across gaps,
   passes, and some valleys.

 - Near normal temperatures with slightly below normal through the
   weekend with a gradual warming trend next week.

&&

.SHORT TERM...
Issued at 208 AM PDT Fri Jul 4 2025
(Today and tonight)

For the midshift and satellite features of note: still seeing
noticeable hot spots (10.3-3.9um band )associated with the Madre
fire to the south in SLO, a few lightning hold over fires up near
the OR/CA border, much less stratus covering the coastal waters,
some patchy stratus filling in along the coast, and stratus
covering Monterey Bay Region and Salinas Valley. Speaking of
stratus, the marine layer remains, but has compressed thanks to
rising 500mb heights as the shortwave trough from Thursday tracks
eastward. Other items of note on the mid are the winds. While
onshore flow pressure gradient has eased it still hovering near
4mb leading to gusts 40-50 mph across the East Bay passes.

For the Fourth of July holiday: as the night progresses expect
stratus to fill in more along the coast and locally inland. As
such, a cloudy start to the day for some areas. By the afternoon,
a few high clouds with pockets of low clouds along the immediate
coast. Temperatures will be pleasant for early July: 60s to mid
70s coast and 70s to low 90s inland or seasonably cool. Onshore
gradient will be slightly less today, but still greater than 4mb.
Therefore, breezy to gusty onshore will be possible once again.
Windiest locations will be inland gaps/pass with gusts
approaching or barely exceeding 50 mph. For evening activities:
pockets of coastal low clouds will begin to expand along the
coast. Coverage of low clouds overnight Friday will be similar to
Thursday.

It goes without saying, but be mindful with outdoor activities
today. Be one less spark. As noted below we still have one more
day of elevated fire weather concerns.


&&

.LONG TERM...
Issued at 255 AM PDT Fri Jul 4 2025
(Saturday through Thursday)

The longwave pattern over the weekend continues to advertise broad
upper level troughing initially before developing into another
cut-off low for Sunday/Monday. So what does this mean for
sensible weather? The patchy marine layer will become more
widespread and deeper. Additionally, breezy onshore flow will
remain, but not as strong as Thursday/Friday. Temperatures will
remain seasonably cool through Monday.

Late Monday into Tuesday the meandering upper low begins to lift
northward. Of greater importance will be the very robust area of
high pressure over the Four Corners building westward into CA.
The initial building of the high will be buffeted by the upper
low. The upper low finally lifts northeast and rides over the
ridge by Thursday. This will allow our region to feel the more
full influence of the robust high pressure. In the big picture, a
gradual warming trend will kick off Tuesday and peak across the
interior Central Coast on Thursday. Probabilities of exceeding
100 degrees will be highest for interior Monterey/San Benito at
70-80%. The coast will be spared again as onshore flow remains.
This upcoming round of heat will be similar to previous heat
events this year - large temperature spread from the coast to
interior. The hottest interior locations will also reach the
moderate HeatRisk category. As always with upper lows and an
evolution upper level pattern there is some uncertainty. This
longer range heat potential will be fine tuned over the coming
days.

&&

.AVIATION...
(06Z TAFS)
Issued at 1005 PM PDT Thu Jul 3 2025

IFR and MVFR CIGS are building along the coast along with mist and
drizzle and are affecting HAF as well as the Monterey Bay terminals.
Winds reduce across the region into the evening and CIGs look to
fall further into the night. Moments of low clouds also look to
affect OAK and the North Bay terminals later into Thursday morning.
Inland clearing begins in the mid morning with most TAF sites going
VFR before the midday. The exception will be HAF, which keeps CIGs
through the TAF period. Winds look to stay light to moderate through
the morning and increase into Thursday afternoon, with gusty winds
expected around the SF Bay. Expect winds to reduce into Thursday
evening but remain breezy around the SF BAY. CIGs begin to move
inland from the coast into the late evening, affecting the Monterey
Bay terminals and then OAK later that night.

Vicinity of SFO...VFR through the TAF period. Breezy to gusty winds
reduce into early night, becoming moderate. Breezy west winds return
into the late morning on Thursday with stronger winds and around 31
kt gusts expected in the mid afternoon and through much of the
evening. These winds reduce in the late evening but look to stay
breezy through that night.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR CIGs look to turn to LIFR later into
the night with some pockets of mist and drizzle in the area. Winds
become moderate into mid to late Friday morning CIGs erode over
the terminals, but expect cloud cover to linger over the Monterey
Bay itself. Cloud cover beings to push inland as winds reduce into
Friday evening with IFR CIGs filling over the terminals.

&&

.MARINE...
(Tonight through next Wednesday)
Issued at 555 PM PDT Thu Jul 3 2025

Fresh to strong northwesterly breezes and rough seas will continue
into Friday. Gale force gusts will be likely across northern
waters  and near Pt. Sur through Thursday night. Winds easing by
early next  week. A low-amplitude long period southerly swell will
persist  through Friday.

&&

.FIRE WEATHER...
Issued at 3 AM PDT Thu Jul 4 2025

Breezy onshore flow persist overnight with gusts 30-50 mph.
Thankfully, most areas are seeing some marine influence with
at least moderate humidity recovery. Winds may ease slightly
before sunrise. Onshore flow will ramp back up this afternoon as
the Central Valleys heats up. RH values will drop, but be tempered
by onshore flow keeping them from really bottoming out. That being
said, strong winds for inland gaps/passes and moderate RH will
lead to elevated or near critical fire weather concerns. Grasses
and finer fuels remain cured and available, and given the
potential for new ignitions due to the holiday weekend, an
increase in initial attack type activity should be expected by
local fire personnel. Less favorable burn conditions are
anticipated this weekend as the marine layer deepens and invades
parts of the area. However, far interior portions of the Bay Area
and Central Coast, as well as regions above 1500-2000 feet may
still remain within an airmass characterized by near-critical
humidity and winds where there may remain some potential for fire
spread/growth.

MM/Bain

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM this morning to 3 AM PDT Saturday
     for Pigeon Pt to Pt Pinos 0-10 nm-SF Bay N of Bay Bridge.

     Small Craft Advisory from 9 AM this morning to 9 PM PDT this
     evening for Mry Bay.

     Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt
     Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm.

     Gale Warning until 3 AM PDT Saturday for Pt Pinos to Pt Piedras
     Blancas 0-10 nm.

&&

$$

SHORT TERM...MM
LONG TERM....MM
AVIATION...Murdock
MARINE...Murdock

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