Sonoma, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

107
FXUS66 KMTR 092034
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
134 PM PDT Wed Apr 9 2025

...New SYNOPSIS, SHORT TERM, LONG TERM...

.SYNOPSIS...
Issued at 122 PM PDT Wed Apr 9 2025

Warm and dry conditions continue through the forecast period.

&&

.SHORT TERM...
(This evening through Thursday)
Issued at 122 PM PDT Wed Apr 9 2025

The region will feel the maximum effects of the longwave ridge today
as the axis is overhead. I opted to abandon the NBM/NBM50 strategy
that was used and discussed yesterday and instead just roll with the
deterministic NBM, here`s why. For starters and most importantly,
the National Weather Service is impacts based. Our messaging of
minor HeatRisk does not change whether the maximum temperature is 76
degrees or 79 degrees. A look under the hood of the deterministic
NBM versus the probabilistic NBM reveals that the former allows for
a quicker response to changing weather patterns while the latter
runs warm leading into warm seasons and cold leading into cold
seasons. Being in the shoulder season of Spring between Winter and
Summer, it is likely that the probabilistic NBM is running warm.
The HREF depicts that it is likely (60%-80%) that low clouds will
return to coastal and valley locations overnight. Being under an
area of high pressure and thus subsidence, this promotes a
compressed/shallow marine layer which will result in both lower
ceilings and visibilities, but it also means that it won`t be deep
enough to penetrate too far inland.

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...
(Thursday night through next Tuesday)
Issued at 122 PM PDT Wed Apr 9 2025

Thursday begins the cooldown as heights begin to ever so slightly
fall as an upper-level shortwave trough in the Pacific Northwest
nudges the ridge to the east. A surface low in British Columbia and
its attendant weak, dry cold front will sweep through the region
on Friday bringing with it an increase in northerly winds,
particularly over the marine zones. There`s even the chance for
Oakland Museum (OAMC1) to challenge the daily minimum temperature
forecast Saturday morning, the forecast is 48 degrees with the
previous record of 45 degrees set in 2001. There`s good agreement
in the clusters through Saturday, but that`s where it ends. By
Sunday, it is likely (83%) that a shortwave trough will undercut
the shortwave ridge resulting in split flow over the region. The
lack of confidence comes from the location and amplitude of these
features. This compounds in the following days as the progression
of the longwave pattern becomes uncertain. Nonetheless, there`s
still no rainfall or widespread impacts aside from minor HeatRisk expected
through the forecast period.

&&

.AVIATION...
(18Z TAFS)
Issued at 1025 AM PDT Wed Apr 9 2025

VFR all terminals this morning and this afternoon. Offshore flow
and a much drier airmass allowed for clear skies. This will change
later today and tonight as onshore flow returns with a shallow
marine layer bringing cigs and some patchy fog. Fog most likely
for KSTS and KAPC with prob of 40-60%. Note KHAF has AMD not Sked
due to lack of obs. Overall confidence is medium to high.

Vicinity of SFO...VFR. Light NE this morning then breezy NW this
afternoon/evening. Cigs will fill in through the GG this
evening/early tonight then OAK and finally in SFO. Impacts will
linger through 17-18Z Thursday.

SFO Bridge Approach...Similar to SFO through this evening. Cigs
will likely impact N, NE, E side of approach zone on Thursday. S
end near the bridge may see occasional breaks.

Monterey Bay Terminals...VFR through this evening. Shallow cigs
move in close to 06Z and lingering through Thursday morning

&&

.MARINE...
(Today through Monday)
Issued at 1025 AM PDT Wed Apr 9 2025

Light to moderate northerly winds will persist over the region as
high pressure remains offshore. Winds will be locally stronger for
areas south of Point Sur. Expect a gradual improvement of the sea
state as swell heights subside through midweek. Winds increase
late this week and a larger swell will rebuild this weekend.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Thursday for Pt Pinos
     to Pt Piedras Blancas 0-10 nm.

&&

$$

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

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