Napa, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

253
FXUS66 KMTR 232037
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1237 PM PST Sat Nov 23 2024

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

.SYNOPSIS...
Issued at 1144 AM PST Sat Nov 23 2024

Scattered showers will continue through Sunday before a cold
front brings heavier precipitation to the Central Coast Monday
through Tuesday.

&&

.SHORT TERM...
(This afternoon through Sunday)
Issued at 1144 AM PST Sat Nov 23 2024

The cold front has moved into southern California, leaving behind
a much drier, colder airmass. The precipitable water has dropped
from 1.08" to 0.64" and the 850 mb temp has dropped from 7.35C to
4.35C from 12Z yesterday to 12Z today. The short term convection
forecast is a bit of a mixed bag. As the sun peaks through and
allows the surface to warm, instability will rise. On the other
had, overall forcing is waning as a short wave trough moves toward
the Sierra. With mid-level lapse rates below 5 C/km and a
freezing level around 7,600 ft, any convection that forms will be
weak and shallow. Thunderstorms are very unlikely this afternoon.
Minor flooding impacts are still possible, but will require steady
training showers, as we saw over the East Bay in the late
morning.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 1144 AM PST Sat Nov 23 2024

A weaker trough will quickly move through Sunday, keeping light
rain chances in the forecast and bringing a brief pulse of
stronger southerly winds. Beyond Sunday, there is a lot of
uncertainty regarding the precipitation this week. A weak low
pressure system is likely to form just offshore somewhere between
Monterey Bay and San Francisco Bay. This low will generate a cold
front and SE winds will draw in moisture and moderate rain to the
warm sector. Where exactly this boundary sets up will have a
great influence on where the heaviest rain ends up. Our current
forecast keeps the heaviest rain over the Central Coast, but
that`s far from a guarantee. The ECMWF ensemble members show
anywhere from 0.25" to 2.0" at SFO, for example. Coastal mountains
may see up to 3 or 4 inches, but it`s unclear if that will be the
Santa Cruz mountains or the Santa Lucias. Regardless of where
exactly this system sets up, it will move south and allow
northerly flow to return by late Tuesday or Wednesday. The dry
weather should hold through Thanksgiving as a ridge begins to
build over the Eastern Pacific.

&&

.AVIATION...
(18Z TAFS)
Issued at 1008 AM PST Sat Nov 23 2024

Scattered lower and mid-level cloud cover continues to affect the
region with some lingering light showers. As these showers pass,
expect moderate west winds building for much of the area. Expect
stronger gusts along the coast and at SFO in the mid afternoon with
these elevated winds lasting into the night before reducing. Low
cloud cover also reduces through the afternoon, with VFR expected
through the remainder of the TAF period. South and south east winds
affect some of the terminals overnight and into Sunday morning ahead
of a weak rain band entering the area late Sunday morning and
lasting through that afternoon.

Vicinity of SFO...VFR through the TAF period. Showers are exiting
the area with scattered to broken mid- level clouds lingering
through the night. Light southerly winds become more moderate and
westerly into the afternoon. These winds reduce overnight. Expect
additional rain chances and breezy southerly winds into late Sunday
morning. These winds and rains exit later that afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through the TAF period. Expect moderate
west winds to build this afternoon and last into the night. Winds
become light into the night with some passing showers. Expect
moderate southeast winds to build early sunday morning.

&&

.MARINE...
(Today through Thursday)
Issued at 1008 AM PST Sat Nov 23 2024

Winds continue to decrease with only lingering scattered showers
moving through the waters. Wave heights will also continue to
decrease a well. Seas and winds rebuild late tonight into early
next week as another storm approaches the region. Winds will
initially be strongest north of Point Reyes.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM to 3 PM PST Sunday for Pt Arena
     to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

&&

$$

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

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