Walnut Heights, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

815
FXUS66 KMTR 261159
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
359 AM PST Thu Dec 26 2024

...New AVIATION, MARINE, BEACHES...

.SYNOPSIS...
Issued at 1238 AM PST Thu Dec 26 2024

The first in a series of rainmakers comes through the North Bay
through the morning, with more systems impacting the region through
the weekend. New northwest swell arrives today, driving dangerous
surf and beach conditions into the weekend.

&&

.SHORT TERM...
(Today and tonight)
Issued at 1238 AM PST Thu Dec 26 2024

Radar products show generally light rain setting up across the San
Mateo Peninsula, the fringe of a larger system centered in the
eastern Gulf of Alaska that is primarily impacting the Pacific
Northwest and northern California. Impacts are generally limited
to mainly beneficial rain over the North Bay, with rainfall totals
ranging from 0.1-0.3" in the valleys up to 0.5-0.75" in the
higher elevations. Elsewhere in the forecast region, the highest
rainfall totals are generally around 0.1", and this is for favored
locations in the coastal ranges, many inland regions should
remain dry into the afternoon. Otherwise, a second push of
northwest swell should arrive in the coastal waters today, leading
to a second round of dangerous surf and beach conditions (see the
BEACHES section for more information).

A more significant round of rain comes through later tonight into
Friday with a low pressure system expected to develop and travel a
little further south, heading into the Pacific Northwest. This will
result in a more southerly distribution of rainfall impacts for us,
and will bring higher rainfall totals to the Bay Area and Central
Coast. The North Bay remains the wettest region with 0.5-1" in the
valleys and up to 3" in the higher elevations, while 1-2" of rain is
expected along the Santa Cruz Mountains, 0.25-0.75" in the Bay Area
valleys, Monterey-Salinas region and the Big Sur Coast (locally up
to 1" in the Santa Lucias), and up to 0.1" in the interior Central
Coast valleys. The risk of flooding does increase with each passing
system, with soils getting ever more saturated (especially in the
North Bay), but confidence in flooding impacts is too low to issue
any products at this time. In addition, gusty winds are expected to
develop with this system. The coastline, the ridgetops, and the gaps
and passes could see gusts of 30-35 mph with this system, and 20-25
mph gusts are possible in the valleys. These gusts are not expected
to reach Wind Advisory criteria, but they could still create
hazards, such as objects being blown away and difficult driving for
high profile vehicles.

High temperatures reach the upper 50s to middle 60s in the lower
elevations and into the lower to middle 50s in the higher
elevations. Low temperatures remain quite chilly this morning with
the inland valleys reaching the low to mid 40s, near 50 at the
coast, before warming into Friday morning with readings in the upper
40s to middle 50s across the lower elevations.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 1238 AM PST Thu Dec 26 2024

A couple more rounds of rain are in store through Sunday, and with
the storm track migrating northward, the greatest impacts will once
again be focused on the North Bay. Cumulative rain totals from
Friday afternoon through Sunday evening are 0.5-1.5" across the
North bay, 0.25-0.5" near the coastal ranges down to Santa Cruz, up
to 0.25" in the inland East Bay and coastal Monterey County, and up
to 0.1" in the inland Central Coast.

Ensemble model guidance continues to show signals of potential
rainfall in the first days of the New Year. Cluster analysis reveals
a stronger signal for rain from the American GEFS and Canadian GEPS
models, while the European ENS model leans more towards a drier
solution. As of now, cluster analysis suggests that the chances for
any rainfall in the first days of the New Year lie around 40-50%.
We`ve kept the NBM forecast guidance for the later part of the 7-day
grids for now, as there`s not enough confidence as of yet to nudge
the precipitation totals higher.

&&

.AVIATION...
(12Z TAFS)
Issued at 342 AM PST Thu Dec 26 2024

The southern end of a PNW atmospheric river is bringing light
rain and IFR-MVFR ceilings to the regional terminals this morning.
These conditions will improve through the morning before a more
robust system moves through this evening through Friday morning.
Widespread MVFR conditions with light to moderate rainfall and
strong southerly winds will move from N to S through the night.

Vicinity of SFO...MVFR ceilings will lift to low VFR for the
majority of the daylight hours before returning overnight. There
is high confidence in MVFR ceilings, light to moderate rain and
strong southerly winds overnight. SFO is close to gusting to 35
knots, which would trigger an airport weather warning. We will
need to assess the nocturnal stability to determine if the winds
will mix down to the surface, but with moderate rain rates and a
dry slot around 900 mb, the momentum transfer will likely be
efficient.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...These terminals are far enough south to
reamin out of the overcast for the moment, but that will likely only
last for another few hours. The wind are rain overnight will be
less impactful here, although moderate southerly winds and IFR
ceilings are still possible early Friday morning.

&&

.MARINE...
(Today through Tuesday)
Issued at 342 AM PST Thu Dec 26 2024

Disturbed weather has returned to the coastal waters and buoys
are showing sea heights have starting to rebuild. Strong SW winds
and rough seas will persist through Saturday, before a cold front
flips the wind direction to NW on Sunday. Conditions will improve
next week as high pressure rebuilds over the area and the swell
abates.

&&

.BEACHES...
Issued at 342 AM PST Thu Dec 26 2024

A High Surf Advisory is in effect from 10 AM this morning through
4 PM Sunday. Large NW swell is arriving to the coastal waters and
will persist through the weekend. Satellite observations and wave
models continue to suggest the swell will be roughly 15 feet high
with a 15 second period. That translates to 20-30 foot breaking
waves, depending on the beach orientation and bathymetry (beach
slope). The waves now look to peak Friday and abate through the
day Saturday. If that trend holds, we may have to shorten the
advisory duration. While these waves are smaller than the
monsters we got on Monday, the coast is still dangerous.
Inexperienced swimmers should stay out of the water, wave watchers
should maintain a a safe distance, and no one should ever turn
their back on the ocean. Let`s get through this weekend without
another ocean fatality.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory from 10 AM this morning to 4 PM PST Sunday
     for CAZ006-505-509-529-530.

PZ...Small Craft Advisory from 9 PM this evening to 9 AM PST Friday
     for SF Bay N of Bay Bridge.

     Small Craft Advisory from 3 PM this afternoon to 9 PM PST Friday
     for Mry Bay.

     Small Craft Advisory until 9 PM PST Friday for Pigeon Pt to Pt
     Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm.

     Small Craft Advisory from 9 AM this morning to 9 PM PST Friday
     for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras
     Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

     Small Craft Advisory until 9 PM PST this evening for Pt Arena to
     Pt Reyes 10-60 NM.

     Gale Warning from 9 PM this evening to 3 AM PST Friday for Pt
     Arena to Pt Reyes 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Flynn
MARINE...Flynn

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