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Castro Valley, California 7 Day Weather Forecast
Wx Forecast - Wx Discussion - Wx Aviation
NWS Forecast for Castro Valley CA
National Weather Service Forecast for: Castro Valley CA
Issued by: National Weather Service San Francisco Bay Area/Monterey, CA
Updated: 9:01 pm PDT Jul 3, 2025
 
Overnight

Overnight: Mostly cloudy, with a low around 54. Southwest wind around 9 mph.
Mostly Cloudy
Independence
Day
Independence Day: Mostly sunny, with a high near 68. West wind 8 to 13 mph, with gusts as high as 18 mph.
Mostly Sunny
Friday
Night
Friday Night: Partly cloudy, with a low around 52. West southwest wind 7 to 11 mph.
Partly Cloudy
Saturday

Saturday: Partly sunny, then gradually becoming sunny, with a high near 72. West wind 6 to 10 mph.
Becoming
Sunny
Saturday
Night
Saturday Night: Partly cloudy, with a low around 54. West southwest wind 6 to 10 mph.
Partly Cloudy
Sunday

Sunday: Mostly sunny, with a high near 74.
Mostly Sunny
Sunday
Night
Sunday Night: Partly cloudy, with a low around 54.
Partly Cloudy
Monday

Monday: Mostly sunny, with a high near 75.
Mostly Sunny
Monday
Night
Monday Night: Partly cloudy, with a low around 55.
Partly Cloudy
Lo 54 °F Hi 68 °F Lo 52 °F Hi 72 °F Lo 54 °F Hi 74 °F Lo 54 °F Hi 75 °F Lo 55 °F

 

Overnight
 
Mostly cloudy, with a low around 54. Southwest wind around 9 mph.
Independence Day
 
Mostly sunny, with a high near 68. West wind 8 to 13 mph, with gusts as high as 18 mph.
Friday Night
 
Partly cloudy, with a low around 52. West southwest wind 7 to 11 mph.
Saturday
 
Partly sunny, then gradually becoming sunny, with a high near 72. West wind 6 to 10 mph.
Saturday Night
 
Partly cloudy, with a low around 54. West southwest wind 6 to 10 mph.
Sunday
 
Mostly sunny, with a high near 74.
Sunday Night
 
Partly cloudy, with a low around 54.
Monday
 
Mostly sunny, with a high near 75.
Monday Night
 
Partly cloudy, with a low around 55.
Tuesday
 
Mostly sunny, with a high near 75.
Tuesday Night
 
Partly cloudy, with a low around 56.
Wednesday
 
Mostly sunny, with a high near 80.
Wednesday Night
 
Partly cloudy, with a low around 56.
Thursday
 
Mostly sunny, with a high near 83.

 

Forecast from NOAA-NWS for Castro Valley CA.

Weather Forecast Discussion
152
FXUS66 KMTR 040507
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1007 PM PDT Thu Jul 3 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 135 PM PDT Thu Jul 3 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.

&&

.UPDATE...
Issued at 904 PM PDT Thu Jul 3 2025

Taking a quick look at various observations this evening and
things look to be on tap. Stratus is forming along the San Mateo
and Monterey coasts and slowly while breezy onshore flow is being
observed, especially over the portions of the Diablo Range.

&&

.SHORT TERM...
Issued at 135 PM PDT Thu Jul 3 2025
(This evening through Friday)

The forecast is on track early this afternoon with onshore flow
continuing this afternoon. The SFO-SAC MSLP "gradient" continues
to increase as diabatic heating induces surface pressure falls
across the Central Valley. In addition, larger scale synoptic
scale forcing in the form of an upper trough continues to
encourage onshore flow. In response, areas across the East Bay,
the San Bruno Gap and Salinas Valley are experiencing wind gusts
averaging between 25 mph and 45 mph. Short term hi-res guidance
such as the 2km PG&E WRF along with our in house WRF indicate that
gusts as great as 55 mph are still within the realm possibility
this afternoon. We`ll continue to advertise an elevated to near-
critical fire weather threat across the area this afternoon as a
few sites have seen RH fall down to near or below 15%. The
isolated nature of these "dry" sites precludes a Red Flag Warning,
however, we`ll continue to advertise/promote fire safety via
partner discussions as well as via our web page and social media.

Winds will continue through the evening hours and the airmass
across some of the elevated regions of the East Bay will likely
not decouple. This will translate to winds remaining elevated.
The 12Z OAK RAOB showed the moist layer beneath the inversion (the
marine layer) was around 1200 ft AGL. Forecast cross-sections
show the marine layer compressing further to around 1000 ft AGL in
the wake of the aforementioned upper trough (slight shortwave
ridging). This will translate to overnight RH recovery below 50%
for the higher terrain across parts of the Santa Cruz Mountains,
the Diablo and Santa Lucia Ranges.

With the loss of the upper trough, onshore flow and an
approaching diffuse frontal boundary (albeit weakening) may loosen
up the surface gradient some on Friday. In fact the PG&E WRF, the
MTRWRF and higher-end NBM probabilities indicate reduced flow as
a whole during the afternoon hours. While the lack of upper
support may take the edge off of the wind, the Central Valley
will still warm up quickly. This should continue to drive an MSLP
difference and thus diurnal onshore breezes. There will remain an
enhancement of the wind field across gaps, passes, and valleys
with gusts still as great as 45 to 50 mph. Afternoon RH will
still dip down between 15 and 25 percent, and that`ll necessitate
another round of an elevated to near critical fire weather threat.
This will be particularly true, given the potential for
additional ignitions given the holiday weekend. Please be mindful
of your outdoor activities and obey any local burn/fire
restrictions.

&&

.LONG TERM...
Issued at 135 PM PDT Thu Jul 3 2025
(Friday night through next Wednesday)

Not to sound like a broken record, but please be mindful of your
outdoor activities and obey any local burn/fire restrictions on
Friday evening given the dry grasses and brush.

With winds offshore abating some, we`ll likely see upwelling of
colder Pacific Ocean waters setting the stage for the development
of a thick deck of marine layer stratus. The diurnal pressure
gradient should support advection of the marine stratus into the
coastal regions this weekend. The marine layer is forecast to
thicken some up to around 1500 ft this weekend which fits our
climatological pattern ("No Sky July"), particularly along the
coast. The Extreme Forecast Index (from the EFI) suggests that the
EPS mean forecast is cooler than the model climate along the
coast and this increases confidence in a marine layer intrusion.
NBM temperatures seem reasonable, but we may need to make some
alterations to MaxTs on Saturday and Sunday.

Next week will be characterize by a gradual warming trend. The
global guidance indicates that the progression of the ridge will
be impeded by a developing cutoff upper trough that spawning from
the zonal flow across the Pacific Northwest. Both the 12Z
GFS/ECMWF advertise this feature in addition to the 00Z Cluster
Analysis through at least the middle of next week. This translates
to predominantly onshore flow until the SW US ridge attempts to
build. When/how that happens yields a high degree of forecast
uncertainty. EFI also seemed a bit underwhelming (and quite
negative) for MaxT/MinT through next week, though this is likely
biased by the cooler conditions along the coast. Examining the
850mb temperatures with respect to the SPC Sounding Climatology at
Oakland and Vandenberg and forecast mean values would place them
roughly around the 75th percentile for both areas. The 850mb
temperature forecast exhibited a high degree of spread (especially
in the GFS ensemble), so there`s still an opportunity for things
to be warmer or colder than forecast. What does appear most
certain is that the warmest locations (perhaps with isolated
pockets of `Moderate` HeatRisk) across the Bay Area and Central
Coast Wednesday onward will be across the southern Salinas Valley,
as well as across interior sections of the North Bay, East Bay,
and South Bay. Stay tuned for details.

&&

.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 135 PM PDT Thu Jul 3 2025

An elevated to near critical fire weather threat will persist
this afternoon and again on Friday. 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.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM Friday 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 to 9 PM PDT Friday 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...Bain
LONG TERM....Bain
AVIATION...Murdock
MARINE...Murdock

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