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NWS Forecast Area Discussion - San Francisco Area

444
FXUS66 KMTR 230557
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
957 PM PST Wed Jan 22 2020

.SYNOPSIS...Mainly dry weather conditions along with a gradual
warming trend is expected through Friday. A weak storm system moving
into Northern California will bring a chance of precipitation to
the region this upcoming weekend.

&&

.DISCUSSION...as of 9:10 PM PST Wednesday...Temperatures finished
off on average 3 to 6 degrees warmer across the board today with
some locations in the warmer inland areas seeing upward of 11
degrees of warming. Temperatures reached mid 50s to mid 60s under
the influence of a building trough despite patchy morning fog and
a slow clearing this morning.

Mostly clear skies persist across the region at this hour with a
few high clouds streaming across the sky. Lingering low level
moisture and light winds will once again lead to patchy low
clouds and fog overnight. Satellite imagery depicts low clouds
already developing along the Big Sur coast as well as advecting
into the eastern portions of Alameda, Santa Clara, and San Benito
counties from the Central Valley.

From previous discussion...Mainly dry weather conditions will
persist through late week with a gradual warming trend region-
wide. Will likely see more widespread 60s during the afternoon
hours by Thursday, Friday and potentially Saturday as high
pressure builds over the region. Cannot even rule out a few of the
warmer interior locations of the Central Coast approaching 70s
deg F late this week. The only chance of precipitation late in the
week will be over northern Sonoma County late Thursday into
Friday when a system passes inland to the north. Regardless,
widespread precipitation is not likely.

The next chance of widespread rainfall is forecast for this upcoming
weekend when a mid/upper level trough pushes into the Pacific
Northwest. This will drag a frontal boundary into the North Bay
sometime around Friday night before moving southward through the
weekend. While this system looks to bring some precipitation to much
of the region, widespread heavy rainfall is unlikely. Additionally,
impacts from this system will be minimal with mostly beneficial
rainfall. Temperatures will also cool late in the weekend into early
next week in response to the upper level trough. Precipitation
chances diminish early next week for much of the region as weak
ridging builds back into place. However, unsettled conditions are
likely to persist over northern California through at least the
first half of next week as systems push inland. This may allow for
some light rainfall over the North Bay, but again widespread impacts
are unlikely.

&&

.AVIATION...as of 09:55 PM PST Wednesday...For 06z TAFs. Skies
are mostly clear with a few high clouds passing overhead this
evening. Near surface moisture remains elevated and patchy low
cloud and fog development will be a concern tonight through
Thursday morning. Fog is most likely across the North Bay
overnight. Have maintained mention of low clouds and reduced vis
across the Bay Area terminals in the tafs but confidence remains
low. High clouds will increase and thicken late tonight. Any fog
which forms tonight will clear by Thursday afternoon, with VFR
during the afternoon hours. Winds will generally be light through
the period.

Vicinity of KSFO...VFR expected through 12z with passing high
clouds. Low clouds and patchy fog may develop after 12z, however
exact timing and coverage remain lower confidence. Patchy haze and
reduced vis will be possible through 21z Thursday, otherwise VFR
Thursday afternoon and evening. Winds will be light through the
period. A weak boundary late in the period will bring increased
low-level moisture and low clouds late Thursday night.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Comms issues continue with Salinas ASOS
and FAA lines. VFR expected late this evening with patchy low
clouds and fog returning early Thursday morning. Exact timing and
coverage remain lower confidence. Light offshore winds through
Thursday morning with onshore winds Thursday afternoon.

&&

.MARINE...as of 8:57 PM PST Wednesday...Seas will continue to
decrease overnight into Thursday with light winds over the waters.
Generally light winds will persist Friday and Saturday with high
pressure over the region. However a long period northwest swell
will pass through the waters Friday and Saturday. The next storm
approaches later Saturday into Sunday with increasing southerly
winds followed by another large northwest swell behind the front
Sunday into Monday.
&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...None.

$$

PUBLIC FORECAST: CW
AVIATION: ST
MARINE: ST

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NWS MTR Office Area Forecast Discussion

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