Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 230614

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1014 PM PST Wed Nov 22 2017

.SYNOPSIS...Rain chances return to the North Bay on Thanksgiving,
but the rest of the region is expected to remain dry with
continued warmer than normal temperatures. Dry weather is expected
to return to all areas on Friday. High pressure will move east
during the weekend and rain chances will begin in the north by
late Saturday and spread across most of the rest of the region by


.DISCUSSION...As of 9:10 PM PST Wednesday...For the second
consecutive day record high temperatures were set across the
southern portion of our region. San Jose (76 degrees) and Salinas
(85) both set daily record highs today, and the Salinas Airport
(86) tied a record. In addition, four locations in Monterey County
and San Benito County reported highs of 90 today, including
Carmel Valley, Pinnacles National Park, King City, and Bradley.

A strong upper level ridge continues to dominate the southwestern
United States, while an upper trough remains offshore along 140W.
In between is a moist southwesterly flow that resulted in
considerable mid and high level clouds over our region this
afternoon, as well as local virga. These clouds persist across our
region this evening and will help hold temperatures up overnight.
Although moisture is plentiful, forcing is weak due to the
proximity of the upper ridge. Thus, rainfall remains well to our
north. A shortwave trough moving into the Pacific Northwest on
Thanksgiving may trigger a few light showers across the North Bay.
If rain does fall tomorrow, accumulations are not expected to
exceed a few hundredths. For most of our forecast area, expect a
dry day on Thanksgiving with variable amounts of clouds.
Temperatures are expected to cool slightly from today, but still
remain well above normal.

After brief rain chances in the north on Thanksgiving, dry
weather is expected in all areas from Thursday night through at
least Friday night. Recent models maintain dry weather through
most of Saturday as well. A forecast update earlier this evening
included a reduction in rain chances for Friday night and

By Saturday night the ridge is forecast to finally move to the
east, allowing the eastern Pacific trough to advance across
California by late in the weekend. Model consensus suggests rain
will begin in the North Bay by Saturday evening and then spread
south across most of the remainder of our forecast area by midday
Sunday. The frontal rain band is expected to be through our area
by late Sunday, but post-frontal shower activity may persist into
Monday morning. Rainfall with the weekend system is expected to be
mostly light to moderate in intensity, with both the GFS and
ECMWF forecasting rainfall amounts of a half inch or less across
our area. Winds will increase ahead of the incoming system on
Saturday and remain locally gusty into Saturday night. However,
winds are not expected to reach advisory levels.

Dry weather is forecast to return by late Monday and longer range
models predict little or no rainfall for the remainder of next


.AVIATION...As of 10:13 PM PST Wednesday...VFR conditions prevail
with exception KSTS reports LIFR in fog. An increase in mid level
and surface based instability into Thursday will lead to showers
developing over the northernmost area southward to approx a KSFO-
KOAK line. Locally reduced slantwise visibilities are possible
Thursday morning over the Bay Area unless vertical mixing with the
aforementioned instability arrives in the morning helping to
disperse particulate matter.

Vicinity of KSFO...VFR, a few showers are possible Thursday.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR. Fort Ord profiler shows an inversion
near 1,000 feet. A little more than moderate confidence VFR holds
tonight into Thursday as conditions locally are not favorable for
the development of stratus or fog.

&& of 9:20 PM PST Wednesday...Moist unstable flow from
the subtropics will bring showers to the northern coastal waters
and from the San Francisco Bay to the Delta later tonight and
Thursday. Showers return over the weekend as a cold front moves
southeast across the coastal waters and bays.


     .Tngt...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 3 AM




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