Castro Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

530
FXUS66 KMTR 060901
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
201 AM PDT Tue Oct 6 2026

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 155 AM PDT Tue Oct 6 2026

 - Hazardous heat inland persist through Thursday, never leave
   children or pets in unattended vehicles!

 - Elevated fire weather conditions persist in the interior
   through Thursday

 - Coastal flooding concerns due to astronomical tides and
   thermal expansion through the weekend

 - Hazardous beach conditions along Pacific coastline later this
   week into the weekend due to long period swell

&&

.SHORT TERM...
Issued at 155 AM PDT Tue Oct 6 2026
(Today and tonight)

A shallow and compressed marine layer confined to the coast most of
Monday afternoon has made some slight progress inland over the
Russian River Valley, city of San Francisco and Monterey Bay into
the Salinas Valley into the overnight hours. The low
ceilings/patchy fog may limit visibility down to 1/2mi or less
overnight into early Tuesday morning. The ridging pattern over our
area will continue to be reinforced today and tonight in the wake
of the weak disturbance that shifted east yesterday. Moderate
HeatRisk continues to be the primary concern in the short term
forecast along with elevated fire weather conditions, especially
for higher elevation locations due to hot and dry conditions.

Follow these tips to avoid heat exhaustion and heatstroke:

* Stay hydrated and drink plenty of fluids.
* Wear lightweight, light-colored clothing.
* Reduce time spent outdoors or stay in the shade.
* Never leave people or pets unattended in vehicles.
* Use sunscreen if going to the coast or the pool.

&&

.LONG TERM...
Issued at 155 AM PDT Tue Oct 6 2026
(Wednesday through Monday)

Wednesday and Thursday will see similar temperatures as today,
however improved onshore flow developing during the day on Thursday
will mark the beginning of a return to more normal or slightly
below normal temperatures for Friday into the weekend. Another
weak upper level disturbance will develop offshore similar to this
past weekend, however its fate appears to be a merger with the
remnants of Rachel. While Rachel and that disturbance merge, a
more potent trough embedded in the Polar Jet will lift Rachel`s
remnants into the desert southwest while providing us with a
potential `inside slider`. Whether the energy associated with the
Polar Jet increases onshore flow (deterministic GFS) or an inside
slider (deterministic ECMWF), we`re going to see dry and gusty
winds develop over the weekend potentially increasing fire
weather concerns, with the inside slider scenario possibly leading
to another warm- up. The gusty winds over the East Bay may
approach wind advisory levels Saturday morning albeit at high
elevations. Unfortunately we continue to be dry through the
extended forecast.

&&

.AVIATION...
(06Z TAFS)
Issued at 947 PM PDT Mon Oct 5 2026

Stratus has settled in along the coastline and is trying to
intrude into the North Bay/Golden Gate Gap areas. Confidence
remains low that stratus will reach STS, SFO, or OAK but there
remains a slight chance. Night shift will need to keep an eye as
to if the Golden Gate Gap stratus intrusion is able to hold
together and if it starts to push towards SFO/OAK. Model guidance
is underdoing the amount of stratus along our coastline with HAF
and MRY reporting LIFR conditions as of 4Z. Fog will set in along
the coast overnight and impact HAF, MRY, and SNS. If stratus is
able to reach STS, OAK, or SFO it is likely that temporary
reductions in visibility/ceiling height to IFR-LIFR conditions
will occur. Conditions improve mid to late morning with model
guidance mixed as to when stratus will return tomorrow night.
Satellite shows a swath of dry air pushing north to south towards
our coastal waters which may impact our stratus chances for
tomorrow night. Winds remain diurnally breezy with moderate
onshore winds during the day and lighter, variable winds
overnight.

Vicinity of SFO...VFR with a low potential for IFR-LIFR conditions
overnight if the shallow marine layer/stratus deck is able to make
it into the San Francisco Bay. Confidence remains low that stratus
will make it to SFO but chances increase slightly (10-20%) between
12 to 18Z. Moderate onshore winds expected during the day with
winds decreasing overnight.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR conditions expected with fog to
develop tonight. Visibilities drop to 1/2SM with the potential for
dense (1/4SM) fog to develop. Moderate confidence that conditions
will improve by 18Z but significant improvement may occur as late
as 20Z. The caveat is the drier airmass moving in offshore,
visible on satellite imagery, which may result in stratus/fog
clearing slightly earlier than expected if the drier air makes it
closer to shore. Light onshore winds continue at MRY through the
day while moderate onshore winds return to SNS.

&&

.MARINE...
(Tonight through next Sunday)
Issued at 947 PM PDT Mon Oct 5 2026

A gentle to moderate northwesterly breeze continues through
midweek with locally fresh gusts over the northern outer waters.
Winds increase Friday into the weekend with near gale to gale
force gusts likely. Seas will build in response to increasing
winds and become rough. Additionally, southerly swell will impact
the coastal waters starting Tuesday night with long period
southerly swell increasing Friday into the weekend.

&&

.FIRE WEATHER...
Issued at 306 AM PDT Mon Oct 5 2026

Strong ridging aloft will lead to hot and dry conditions through
Thursday with elevated fire weather conditions across the higher
elevations. Poor to very poor overnight humidity recoveries will
continue across the thermal belts with pushes of offshore flow
each morning. Hazardous heat will continue through Thursday with
major to extreme risks of heat-related illnesses across most
mountain ranges. A pattern change later this week will bring
cooler conditions to the region.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 10 PM PDT Thursday for CAZ503-504-506-508-
     510-512>518.

     Coastal Flood Advisory until 1 PM PDT Thursday for CAZ506.

PZ...None.
&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JM
MARINE...JM

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