Altadena, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

092
FXUS66 KMTR 041129
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
429 AM PDT Fri Apr 4 2025

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

.SYNOPSIS...
Issued at 206 AM PDT Fri Apr 4 2025

Early Spring warmth will dominate the forecast period with
hazardous beach conditions and light rain expected Sunday into
Monday.

&&

.SHORT TERM...
(Today and tonight)
Issued at 206 AM PDT Fri Apr 4 2025

Cold conditions are expected through the morning as clear and calm
conditions support radiational cooling. The only record in jeopardy
this morning is the Oakland Museum - the minimum temperature
forecast is 45 degrees with a previous record of 40 degrees in 1950.
A high-amplitude longwave ridge axis will push into the West from
the Eastern Pacific Ocean today. As a result, the sensible weather
will feel noticeably warmer as diurnal winds return and temperatures
clock in at or slightly above seasonal averages. Minor HeatRisk will
return to San Francisco, the San Francisco Bay Shoreline, the Santa
Clara Valley, and the Northern Salinas Valley.

NWS Minor HeatRisk:

- Heat of this type is tolerated by most; however there is a minor
  risk for extremely heat-sensitive groups to experience negative
  heat-related health effects.

- The risk is primarily for those who are extremely sensitive to heat,
  especially when outdoors without effective cooling and/or
  adequate hydration.

- Very common heat.

- For those at risk, actions that can be taken: increase
  hydration, reduce time spent outdoors or stay in the shade when
  the sun is strongest, and open windows at night and use fans to
  bring cooler air inside buildings.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 206 AM PDT Fri Apr 4 2025

The warming trend continues Saturday with minor HeatRisk impacting
the Interior Bay Area and Interior Central Coast. An upper-level low
in Alaska will begin to nudge the ridge eastward on Sunday. Its
impacts will be felt more in higher latitudes (North Bay) than lower
latitudes (Central Coast). Impacts that can be expected are a pause
in the warming trend, an increase in cloud cover and wind, and light
rain of a few hundredths for the Bay Area with up to 0.25" expected
in far northwestern Sonoma County. Zonal flow on Monday and Tuesday
will make for near identical days of uneventful weather. Another
longwave ridge of high pressure builds Wednesday into Thursday with
temperatures as much as 15 degrees above average expected. While
global ensemble clusters are in excellent agreement through
Thursday, it is worth noting that we are in the shoulder season and
models generally struggle during this time period, particularly with
magnitudes (in this case temperatures). Because of this, I would not
be surprised if the temperature forecast evolves to become warmer in
later forecast issuances.

&&

.AVIATION...
(12Z TAFS)
Issued at 418 AM PDT Fri Apr 4 2025

Aviation impacts this morning: patchy fog, sea spray/haze, patchy
stratus. Satellite fog product indicates some low level moisture
flow off the ocean and interacting with the terrain leading to
stratus development. Impacts will be for KMRY and KHAF with MVFR
to IFR cigs. Sea spray will occasionally bring KHAF to 4-6 miles
on vsby today. Additionally, KSTS will have some patchy fog
during the morning hours. VFR this afternoon and tonight. Overall
confidence is medium to high.

Vicinity of SFO...VFR. Did include a FEW group around 1k feet to
capture a few clouds forming/spilling over the terrain west of the
terminal.  Gusty onshore flow again this afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Shallow cigs mainly impacting KMRY
through the morning.  VFR this afternoon and tonight.

&&

.MARINE...
(Today through Wednesday)
Issued at 418 AM PDT Fri Apr 4 2025

Weakening high pressure off the West Coast will lead to decreasing
winds and seas over the coastal waters Friday. Light to moderate
northerly flow will then persist through Saturday. By Sunday, a
cold front will move through the region bringing light rain to
the northern coastal waters. Additionally, long period moderate
swell will return Sunday into Monday and will result in increased
shoaling near the coast, bays, and harbor entrances.

&&

.BEACHES...
Issued at 418 AM PDT Fri Apr 4 2025

Still looking at hazardous beach conditions this weekend. A
longer period swell is still on track to reach the coast early
Sunday morning. Forerunners of 18-20 sec arrive around or shortly
before sunrise. Periods are forecast to diminish through the day
Sunday and into Monday, but swell heights will gradually increase.
Therefore, initially sneaker waves will be the main threat before
switching to larger shore break and rip currents. A Beach hazard
statement will likely be needed to cover the threat. Beachgoers
should be mindful Sunday and Monday given potential hazards.
Beachgoers should stay off of jetties and rocks, keep pets on a
leash, wear a life jacket, and never turn your back on the ocean!

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...Sarment
LONG TERM....Sarment
AVIATION...MM
MARINE...MM

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