Union City, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

704
FXUS66 KMTR 180951
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
251 AM PDT Mon Aug 18 2025

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

.KEY MESSAGES...
Updated at 247 AM PDT Mon Aug 18 2025

 - Warming into the late week

 - Moderate heatrisk in the inland areas Thursday-Saturday

 - Slight cooling into the weekend, but still warm into the next
   work week

&&

.SHORT TERM...
Issued at 247 AM PDT Mon Aug 18 2025
(Today and tonight)


Cloud cover is less widespread than previous nights, with still some
focus around the SF Bay for lingering low clouds, but clear
conditions for areas south of Half Moon Bay. Cloud cover for areas
not along the coast looks to burn off fairly quickly today. That,
along with a slight decrease in onshore flow, allows for slightly
warmer conditions than yesterday for all but the immediate coast.
Highs in the far interior look to peak in the low 90s, while the
coast and areas slightly inland mostly stick to the 60s and 70s.

Winds will also begin to back off today. Aside from the regularly
breezy passes and valleys, most of the region will begin to see
lighter winds that will last into the long term portion of the
forecast.


&&

.LONG TERM...
Issued at 247 AM PDT Mon Aug 18 2025
(Tuesday through Sunday)

The marine layer is compressing and winds will weaken as our upper
level pattern continues to build into a ridge into the work week. As
this ridge of high pressure builds, the interior areas will really
see the warming trend while the immediate coast and adjacent valleys
see only slight warming as the marine layer is set to compress, but
not completely erode.

A quick note about the coast: The astronomical set up will give us a
bit more movement in the tides into the  mid week. The high tides
will be higher and the low tides will be lower. This will get high
tide levels close to coastal flooding criteria, but not crossing the
threshold for coastal flood advisories. It`s still worth noting
because people may be heading to the SF Bay shoreline to beat the
heat in the next few days.

Meteorologist  Sarment, tonight`s marine forecaster, provided some
additional info:
"Localized minor coastal flooding will likely occur in Bayside Marin
County through Sunday, August 24th as high tides will remain in
excess of 6.0 feet. Coastal locations that are directly located next
to Richardson Bay such as Sausalito, Tam Valley, Manzanita, the
Sausalito-Mill Valley Bike Path, and the Manzanita Park N Ride can
expect nuisance flooding where typically dry land gets wet. Impacts
are expected to be minor at most - remember, do not drive around
barricades or through water of unknown depth."


Getting back to the heat and the interior: models continue to show a
peaking/plateauing of the warming trend by Thursday and Friday.
Highs look to break into the 100s for the far interior. Some
isolated areas in the Santa Lucias could break into the 110s due to
limited overnight cooling with as heat gets trapped in the thermal
belt in that mountain range. Luckily, these temps will not be
widespread, but heatrisk does become moderate for areas away from
the coast with 90s to low 100s possible. The coast, however looks to
be protected by a fairly shallow, but still intact marine layer,
keeping highs in the 60s and low 70s.

The biggest question in the longer term forecast continues to be how
long the heat persists. Confidence is increasing at small
improvements to onshore flow into the weekend, offering slightly
cooler temperatures Saturday and cooler still for Sunday. However,
models still keep us adjacent to the Ridge. They also don`t look to
break the ridge nor push it east until the middle of the next work
week. This could call for temperatures to remain on the warm side
well into the next work week.

&&

.AVIATION...
(06Z TAFS)
Issued at 950 PM PDT Sun Aug 17 2025

Stratus lingers along the immediate coast from Point Reyes through
HAF and in areas of the interior East Bay, with clear conditions
everywhere else. Some further development is possible with moderate
confidence in stratus impacts early Monday morning in the North bay
valleys and Monterey Bay. Breezy onshore winds continue to diminish
through the evening with light and variable winds overnight. Stratus
retreats to the immediate coast on Monday morning with breezy
onshore flow resuming in the afternoon.

Vicinity of SFO... MVFR ceilings will soon develop and persist
overnight, before mixing out Monday morning with breezy west flow
resuming in the afternoon. Stratus is expected to return sometime
Monday night or early Tuesday morning, with moderate confidence on
stratus timing. A possible complicating factor, as hinted by high
resolution model data, is the possibility for the edge of the
stratus deck Monday night to set up over the terminal area.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR conditions continue for at least the
next several hours. Monterey Bay has remained mainly clear through
the evening so far, with updated model guidance casting doubt on any
stratus impacting the terminals. Thus, the prevailing ceiling at MRY
overnight has been converted to a TEMPO group and the existing
stratus TEMPO at SNS has been removed. Will monitor for potential
radiational stratus development overnight. Any stratus that does
form mixes out through Monday morning. Light and variable winds
continue overnight before breezy northwest flow resumes Monday
afternoon.

&&

.MARINE...
(Today through Saturday)
Issued at 247 AM PDT Mon Aug 18 2025

Moderate northwesterly breezes will prevail today with strong
gusts  along the coastal jet regions of Point Reyes and Point Sur
and  across the bays. Northwesterly breezes will increase Tuesday
to  become fresh to strong with widespread hazardous conditions
for  small craft across the inner waters and outer waters by
Wednesday.  Moderate seas will prevail through Wednesday, building
to become  rough for the outer waters by Thursday.

&&

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

     Small Craft Advisory until 3 AM PDT early this morning for Pt
     Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory from 3 PM this afternoon to 3 AM PDT
     Tuesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

&&

$$

SHORT TERM...Murdock
LONG TERM....Murdock
AVIATION...DialH
MARINE...Sarment

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