Port Costa, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

999
FXUS66 KMTR 090400
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
900 PM PDT Tue Jul 8 2025

...New UPDATE, MARINE...

.KEY MESSAGES...
Updated at 1200 PM PDT Tue Jul 8 2025

 - A warming trend will bring minor to moderate HeatRisk for
   inland and higher elevations Thursday - Friday.

 - Localized elevated fire weather conditions starting Wednesday
   across the higher elevations.

&&

.UPDATE...
Issued at 900 PM PDT Tue Jul 8 2025

Overcast conditions are moving in faster than originally expected
with satellite showing stratus moving in along the coast and SF Bay
region. High temperatures were largely in the upper 70s to mid 80s
across the interior. Most sites were running at least a few degrees
below normal today. For example, San Jose only reached 77 degrees
today and Redwood City only reached 76 degrees with today`s normal
high for both cities being 81 degrees. If you`re not a fan of the
cooler than normal weather so far this month, you`re in luck as a
warming trend remains on track to begin tomorrow. Temperatures will
rise into the 80s to low 90s across the interior on Wednesday and
90s to low 100s in the warmest locations Thursday and Friday.

&&

.SHORT TERM...
Issued at 1200 PM PDT Tue Jul 8 2025
(This evening through Wednesday)

The marine layer is currently between 2,200 and 2,700 feet as weak low
pressure remains offshore. This system will gradually move inland
over the next 36 hours while weakening. Meanwhile, its previous
position offshore will be replaced by ridging from subtropical
high pressure in the Eastern Pacific. This pattern change will
cause the marine layer to compress while onshore NW winds
increase. All this means that temperatures will begin to increase
starting Wednesday. Highs are forecast to be around 5-10 degrees
warmer than today for inland areas. While becoming more shallow,
the marine layer will continue to keep coastal areas in the 60s.

&&

.LONG TERM...
Issued at 1200 PM PDT Tue Jul 8 2025
(Wednesday night through next Monday)

The warming trend will continue into Thursday as the synoptic high
pressure becomes more established offshore. For inland areas, this
will cause another 5-10 degree jump in temperatures from
Wednesday. Some interior and high elevation areas will experience
moderate HeatRisk from Thursday - Friday with afternoon
temperatures in the 90s. A very weak mid-level disturbance will
bring some relief over the weekend, but broadly speaking the
pattern looks fairly stable through at least early next week.
There will be a very broad area of high pressure across the Northeast
Pacific, with an embedded mesoscale high sitting over the Channel
Islands. While ensembles are confident that the persistent high
pressure will increase the 850 mb temperature to around 24C (90th
percentile) by Saturday, this pattern supports steady onshore
wind. With ocean temperatures cooler than normal (54F), the marine
layer should continue to keep coastal areas seasonably cool, even
while the Central Valley flirts with triple digit heat throughout
the long term forecast. There is some elevated fire weather
concerns above and inland of the marine layer`s influence. The RH
will drop below 30% at times, and afternoon wind gusts will reach up
to 30 mph. Fortunately with onshore winds, these conditions will
be diurnally driven with lighter winds and good humidity recovery
in the foothills expected each night.

&&

.AVIATION...
(00Z TAFS)
Issued at 640 PM PDT Tue Jul 8 2025

IFR and MVFR CIGS are building along the coast and have filled at
HAF. These CIGs are also beginning to filter into the Monterey Bay
and look to fill over those terminals into the early evening. Winds
reduce across the region into the evening and CIGs look to fall
further and become more widespread later into the night, becoming
widespread IFR CIGs into Wednesday with MRY and HAF falling to LIFR.
Inland clearing begins in the mid morning with most TAF sites going
VFR in the late morning and early afternoon. 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 late
Wednesday morning and afternoon. Expect winds to reduce into
Wednesday evening with CIGs slower to move inland that night.

Vicinity of SFO...VFR lasts into the late night. Winds reduce into
the evening and stay light through the night and much of the
morning. Expect MVFR CIGs to fill over the terminal into the late
night and erode into the late morning as moderate to breezy west
winds arrive. These winds reduce into late Wednesday evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR CIGs are building into the Monterey Bay
and look to fill over the terminals into the early night as winds
reduce.  MRY sees winds become very light into the night and CIGs
fall to LIFR with some pockets of mist and drizzle in the area.
Winds become moderate into mid to late Wednesday morning as CIGs
erode over the terminals.

&&

.MARINE...
(Tonight through next Monday)
Issued at 900 PM PDT Tue Jul 8 2025

Expect light to moderate winds with weak seas into Wednesday.
Winds will strengthen and turn more northerly by Wednesday
afternoon and continue strengthening, becoming fresh to strong on
Thursday and into the weekend. Significant wave heights will be
rough to very rough Thursday through Saturday for the outer
waters.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Wednesday to 3 AM PDT Thursday
     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 Pinos to Pt Piedras
     Blancas 0-10 nm.

&&

$$

SHORT TERM...Flynn
LONG TERM....Flynn
AVIATION...Murdock
MARINE...Murdock

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