Hercules, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

008
FXUS66 KMTR 061247
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
447 AM PST Fri Feb 6 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 115 AM PST Fri Feb 6 2026

 - Hazardous beach conditions from swells through Saturday
   evening at Pacific Coast beaches.

 - 20 to 40% chance of rain in the North Bay Sunday night.

 - Better chances for rain middle of next week.

&&

.SHORT TERM...
Issued at 115 AM PST Fri Feb 6 2026
(Today through Saturday)

Recent KMUX imagery shows scattered returns moving northward over
the Central Coast this morning. This is in response to mid level
moisture moving northward along a passing upper level low that
will travel southeastward over the ocean down the Central Coast
today. No measurable precipitation is expected, but given that
KMUX is getting some echos between 20-30 dBz, went ahead and threw
in mention of isolated sprinkles down the Big Sur coast for this
morning. Regardless, the vast majority of the area will remain
dry, with only an increase in cloud cover today. However, that
increased cloud cover will help minimize any valley fog this
morning. Temperatures are expected to still climb just slightly
above seasonal norms today, but with the increased cloud cover and
cooler air moving in with the low, it should feel a little cooler
compared to recently.

Weak ridging is expected to return tonight and into Saturday.
This should help clear some of the skies out tonight which may
allow for radiational fog development in valley locations.
Otherwise, the cooler airmass should provide similar temperatures
on Saturday with highs in the 60s and upper 50s/low 60s along the
coastline.

&&

.LONG TERM...
Issued at 115 AM PST Fri Feb 6 2026
(Saturday Night through Thursday)

The pattern begins to shift on Sunday. While the weak ridge will
remain in place over Central California during the day on Sunday,
a longwave trough in the northeast Pacific will begin to make it
slow movement southward down the British Columbia coastline. This
wave will eventually send a couple of shorter waves that can
provide additional chances for rain through the middle of next
week.

The first weak short wave is expected to eject away from this
parent wave and move over the Pacific northwest Sunday evening.
With the majority of ensemble members continuing to highlight the
higher QPF in the Pacific northwest, blended PoPs were adjusted
down for Sunday evening to confine the highest chances (20 to 40
percent) to the North Bay. This left just a 15 to 20 percent
chance that light rain makes it to the city of San Francisco with
a less than 15 percent chance it makes it to the South Bay (and
even then it probably would not reach the South Bay until around
or after midnight). Regardless, the amount of rain is expected to
be only a couple hundredths in the North Bay and less to the
south.

Models are projecting a more stout shortwave trough to descend
down the coastline Tuesday through Wednesday. Cluster analysis is
highlighting that models are still struggling with the depth and
track of the upper level trough. However, with increased moisture
and better forcing, it looks like a better chance for rain across
the forecast area. Higher coastal elevations could see over a
quarter of an inch of rain, but inland areas could be impacted by
the rain shadow and see much less. Lastly, a cooler air mass aloft
will accompany this trough, allowing for temperatures next week
to return to more seasonable norms.

Once that trough passes there could be a break in the precip
toward the end of next week. However, models are keeping an active
pattern aloft which may bring another rainy system to the area
next weekend. It is still a little too early for the details, but
something to certainly keep an eye on.

&&

.AVIATION...
(12Z TAFS)
Issued at 447 AM PST Fri Feb 6 2026

A combination of high and mid level clouds, a few sprinkles,
virga aloft with a 500 mb trough to our west-southwest, including
likely isolated very weak negative (downward directed) instability
due to evaporative cooling of showers in dry sub-cloud air resulting
in weak disruptive winds reaching land and/or sea surface e.g. KMRY
had a sudden, temporary southwest wind to 15 mph at midnight - are
all adding up to greatly limiting fog patches. All of the described
is also limiting and potentially mixing out much if not all stratus
clouds over our coastal waters. METAR observations heavily lean VFR
though there this the occasional IFR reported e.g. at KHAF and KLVK.
Hazy to haze conditions in the Bay Area are reducing surface
visibility, including slant range visibility mainly at sunrise and
sunset.

Conditions today favor VFR over the forecast area with exception of
MVFR surface visibilities at times in the Bay Area due to haze.
Another potential component in the mix today is the potential of
a southerly wind reversal reaching the north Central Coast,
however the NAM, HRRR model output show e.g. the SMX-SFO pressure
gradient weakens by late morning and afternoon, detrimental to a
southerly wind reversal (advection of stratus). Elsewhere today
with the departure of the high and mid clouds, there`ll be a greater
amount of incoming solar radiation and diurnal mixing including
over the coastal waters where stratus will likely mix out under
these conditions. Also, sea surface temps are running 3-4F above
Feb normal and coastal buoy data so far show little if any evidence
of cooler air temps relative to sea surface temps which is unfavorable
for stratus/fog development. The NAM does however show a shallow,
cooler air mass arriving tonight into the Bay Area, this coupled
to nocturnal radiative cooling will increase the probability of
stratus /MVFR-IFR/ arriving on onshore winds tonight and Saturday
morning. In the world of stratus and fog prediction, tonight and
tomorrow is a long time from now, a lot as in this case depends
on the level of mixing today as to how well the stratus holds
together before any benefit from cool air advection and/or radiative
cooling post sunset tonight. Currently the 12z TAFs are a low to
moderate confidence forecast with MVFR-IFR ceilings generally
introduced for tonight and Saturday morning.

Vicinity of SFO...Near high confidence VFR today into the evening,
then there is an increasing probability of stratus /MVFR/ arriving
beginning 11z Saturday with the ceiling potentially continuing
through 18z Saturday before mixing out. Northwest wind 5 to 10
knots today becoming westerly near 5 knots tonight and light and
variable Saturday morning.

SFO Bridge Approach...Slant range visibility potentially lower at
sunrise and sunset due to hazy conditions. These conditions may
improve during the afternoon depending if a westerly wind can
strengthen and bring in a fresher sea breeze, the cooler air also
deepening and weakening the marine layer. Otherwise similar to
SFO.

Vicinity of SJC and OAK...Here too, the slant range visibility
may be potentially lower at sunrise and sunset due to hazy
conditions. If SFO Bridge Approach sees improvement then here too
there may be improvement during the afternoon. Generally low to
moderate confidence on stratus /MVFR/ arriving tonight and
Saturday morning.

Monterey Bay Terminals...Near high confidence VFR today into the
early to mid evening before stratus /MVFR-IFR/ arrives here. It
does not look favorable for a southerly wind reversal (and stratus
advection) today based on what was described above, however of
course the caveat is need to monitor SMX-SFO, SBA-SFO pressure
gradients, winds and satellite closely during the day. With the
onset of nocturnal cooling and near surface cool air advection,
stratus development has a better chance to arrive here; the 12z
TAFs advertise timing of IFR by midnight tonight. Light southeast
winds shift to onshore 5 to 10 knots in the afternoon then light
and variable tonight and early Saturday.

&&

.MARINE...
(Today through Wednesday)
Issued at 247 AM PST Fri Feb 6 2026

A shallow cool air mass drifting over the coastal waters will
result in light to gentle northwest winds today in to Saturday.
Hazardous seas over the coastal waters today continues tonight
and early Saturday morning before seas diminish. A cold front
moves southeastward over the coastal waters and bays Sunday night
resulting in an increase in northwesterly winds Monday and
Tuesday.

&&

.BEACHES...
Issued at 247 AM PST Fri Feb 6 2026

A High Surf Advisory will be in effect beginning 4 AM PST today
at all Pacific Coast beaches, the High Surf Advisory continues
through 9 PM Saturday. Westerly swell will bring an increased risk
for sneaker waves and strong rip currents with breaking waves 17 to
22 feet.

Remember to stay off of jetties, piers, rocks, and other waterside
infrastructure, remain out of the water, and never turn your back
on the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 4 AM PST early this morning for
     CAZ006-505-509-529-530.

     High Surf Advisory until 9 PM PST Saturday for CAZ006-505-509-
     529-530.

PZ...Small Craft Advisory until 3 AM PST Saturday for Mry Bay-Pigeon
     Pt to Pt Pinos 0-10 nm-Pt Arena to Pt Reyes 0-10 nm-Pt
     Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-
     10 nm.

     Small Craft Advisory until 9 PM PST this evening for Pt Reyes to
     Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 AM PST Saturday for Pigeon Pt to Pt
     Pinos 10-60 NM.

&&

$$

SHORT TERM...DK
LONG TERM....DK
AVIATION...Canepa
MARINE...Canepa

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