Monte Rio, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

036
FXUS66 KMTR 151629
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
829 AM PST Mon Dec 15 2025

...New UPDATE...

.KEY MESSAGES...
Updated at 343 AM PST Mon Dec 15 2025

 - Dense fog will continue to impact bayshore, coastal, and valley
   locations through the morning

 - Wet weather returns late today and persists through the week
   and likely into next week

&&

.UPDATE...
Issued at 822 AM PST Mon Dec 15 2025

Near term weather impacts are all about fog. Current
observations, webcams, and satellite imagery indicate dense fog
across inland valleys, West Delta, and bays. As a result, a Dense
Fog Advisory was issued earlier this morning. The advisory is
slated to expire at 11 AM, which seems reasonable at this time
given light winds and high cirrus filtering over the Bay Area.

No updates at this time, but will monitor how the fog lingerings
through the morning.

Afternoon forecast update will focus on rain chances the next
24-48hr and a more notable pattern change in the 7-10 day
timeframe. see below for those pattern changes...

&&

.SHORT TERM...
Issued at 343 AM PST Mon Dec 15 2025
(Today and tonight)

Today will start off foggy once again for bayshore, coastal, and
valley locations. Low visibility could make driving conditions
hazardous. If driving, slow down, use your low-beam headlights, and
leave plenty of distance ahead of you. If commuting, allow extra
drive time to reach your destination safely.

A change is on the way though! In fact it can be seen in the form of
high clouds streaming in from the west. These high clouds are
associated with a storm force low off the coast of the
Oregon/Washington border that is headed to British Columbia. The
accompanying cold front will lose steam as it approaches the area,
all but becoming stationary. While rainfall is possible as early as
tonight, it will more than likely have to wait until tomorrow. This
is when some form of upper-level support (longwave trough) skirts
the region. The aforementioned feature will act to sweep through
what is left of the first cold front by bringing a gale force low
and its attendant cold front along with it. Rainfall will be light
and beneficial, generally remaining confined north of the Golden
Gate with the Central Coast remaining dry outside of maybe some
coastal/higher terrain drizzle. Probably of more interest is that
this pattern change will finally put at least a temporary end to the
gloomy days as the atmosphere becomes too turbulent to support
radiation fog.

&&

.LONG TERM...
Issued at 343 AM PST Mon Dec 15 2025
(Tuesday through Sunday)

Some lingering rain showers are possible Wednesday and Thursday, but
generally speaking it will be dry. The next system arrives Friday as
a surface low pressure system enters into Northern California. The
attendant cold front will become a stationary front Saturday into
Sunday. This will be the thing to watch as stationary fronts offer
an area of convergence and are a conveyor belt of moisture. Still,
as of now, everything this week seems beneficial, especially coming
off of a notable dry spell for November/December. When all is said
and done, the official rainfall total forecast for the week (Monday
through Sunday) has 2.50"-4.00" for the higher terrain of the North
Bay, 1.25"-2.50" for North Bay Interior Valleys, 0.50"-1.25" for the
East Bay, South Bay, San Francisco Peninsula, and Central Coast, and
0.50" or less for the Interior Central Coast.

The Climate Prediction Center continues to highlight a moderate risk
for precipitation Monday, December 22nd through Friday, December
26th, moderate risk for high winds Monday, December 22nd through
Sunday, December 28th, and a high risk for precipitation for the
North Bay Monday, December 22nd through Thursday, December 25th. All
of the rainfall that we receive this preceding week will
undoubtedly play a role in potential impacts next week.

&&

.AVIATION...
(12Z TAFS)
Issued at 441 AM PST Mon Dec 15 2025

Fog and dense fog coverage continues to increase. Conditions are
near ideal for fog development as well as the transport of fog on
light offshore winds. The Central Valley`s tule fog and low
stratus ceilings continue to extend westward across the low lying
areas of the Bay Area. Fog and dense fog are also developing over
the north Central Coast. Lower to mid level stability is strengthening
with 500 mb ridging, this will reinforce the stable cap over the
fog, dense fog and low stratus ceilings. Cirrus clouds are also
inbound from the west which may slow diurnal warming and mixing
today, which is already feeble because of the low December sun
angle. The 12z TAFs are pessimistic and lean heavily near
persistence; extent of LIFR-IFR on the surface observations at
this hour is greatly elevated, increasing the probability of aviation
travel issues through morning and much of the day. On the public
and marine side, dense fog advisories are in effect until 11 am
today for essentially all low lying areas including across the
bays. With WMC-SFO 4.0 mb and SAC-SFO 1.5 mb offshore pressure
gradients, this pattern of cold air channeling into the Bay Area
remains strongly anchored in. Clearing will be slow going today,
fog and low stratus return tonight and Tuesday morning.

Vicinity of SFO...A cold channel of air, including low stratus
and fog /LIFR-IFR/ formation continues to extend from the Central
Valley into the Bay Area, including cold continental air reaching
the immediate coastline e.g. KHAF this morning. In the SFO approach
zone to SJC surface visibilities are low, visibility down to 1/2
to 1/4 mile in fog and ceilings ~ 200 feet. Improvement in
conditions will take time, the 12z TAF advertises MVFR-VFR by 22z
today. IFR returns 04z tonight with IFR continuing to Tuesday
morning. With cold air, fog and low stratus wobbling around the
Bay during the morning, this may result in sharply decreasing
runway visual ranges at any time.

SFO Bridge Approach...Conditions are poor visibility and low
stratus ceiling this morning. In the SFO approach zone to SJC
surface visibilities are low, visibility down to 1/2 to 1/4 mile
in fog and ceilings ~ 200 feet. Cold air conducive to fog, dense
fog and low stratus is an extension from the Central Valley, all
remaining well entrenched to the South Bay and Santa Clara Valley.
Improvement in conditions will take time, the best probability of
MVFR-VFR will be in the mid to late afternoon. IFR returns tonight
and Tuesday morning.

Monterey Bay Terminals...Low stratus ceiling, fog and dense fog
continue to form under favorable long December night-time cooling
hours. Cold air drainage winds may help somewhat earlier mix out
times here on the north Central Coast this morning, however recent
satellite imagery and surface observations show a fair amount of
LIFR-IFR. 12z TAFs for KMRY and KSNS indicate VFR returning by
late morning, a low to moderate confidence forecast. The highest
probability of VFR is during the afternoon, then stratus and fog
/IFR/ returns tonight and Tuesday morning.

&&

.MARINE...
(Today through Saturday)
Issued at 343 AM PST Mon Dec 15 2025

Southerly flow will prevail north of Pigeon Point ahead of an
approaching frontal system.   Conditions are ideal for dense fog
across the bays and clearing  may be slow today from the San
Francisco Bay to the West Delta.  Mainly light winds will prevail
across the coastal waters except  northwesterly winds becoming
gusty across the southern coastal  waters today to Tuesday. Winds
will become gusty with increasing  rain chances over the northern
waters mid-week. Light seas will  gradually build becoming
moderate to rough by mid week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Dense Fog Advisory until 11 AM PST this morning for CAZ506-508-
     510-513-516-528>530.

PZ...Dense Fog Advisory until 11 AM PST this morning for Mry Bay-SF
     Bay N of Bay Bridge.

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

&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...Canepa
MARINE...Canepa

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