Strong Wind in California, May 11, 2018

Area Forecast Discussion
National Weather Service San Francisco Bay Area
904 PM PDT Fri May 11 2018

.SYNOPSIS...Offshore winds develop over the region today with
warmer temperatures expected in the interior. Winds will be
strongest in the North Bay and East Bay Hills/Mountains tonight
into early Saturday morning. A cooling trend will return region-
wide on Sunday as onshore winds spread inland. Seasonably cool
conditions are then expected into next week.

&&

.DISCUSSION...as of 9:03 PM PDT Friday...Mostly clear conditions
dominated the skies across the San Francisco Bay Area and central
California coast this afternoon and evening. Temperatures this
afternoon generally maxed out in the 70s and 80s for locations
away from the Pacific Coast, and the middle 60s to near 70 for
coastal communities. The Sonoma County Airport just north of Santa
Rosa maxed out at 85 degrees, making it the warmest day of the
month and tied for the warmest day of the calendar year so far
(the other 85 degree reading at the Sonoma County Airport was on
March 29). Napa Airport topped out at 84 degrees, making today the
warmest day of the calendar year so far.

These warm temperatures are a result of the downsloping north to
northeast winds that developed over the North Bay earlier this
afternoon, and are expected to persist into the overnight hours.
A Wind Advisory is in effect for the North Bay Mountains and East
Bay Hills through 5 am PDT Saturday as these moderate to locally
strong winds continue. These dry winds will allow for moderate to
locally poor overnight relative humidity recoveries. No major
updates planned for the short-term; for additional details, please
refer to the previous discussion section.

&&

.PREV DISCUSSION...as of 01:39 PM PDT Friday...Sunny skies and warmer
temperatures thanks to developing offshore flow Friday afternoon.
Latest 24 hour trends indicates many locations around the Bay Area
are running several degrees warmer than Thursday afternoon. Max
temps today will top out in the 80s for North, East and South Bay.
Slightly cooler temperatures near the coast and Bay Shoreline.
Breezy conditions also continue across the North Mts and East Bay
Hills.

The most active portion of the seven day forecast will occur over
the next 24-36 hours with offshore flow followed by a southerly
surge. High pressure will continue to build across the Great Basin
strengthening offshore flow (N to NE winds) across the Bay Area.
The SFO-WMC pressure gradient is already trending in that
direction and the SFO-ACV gradient is a whopping 8+mb. Latest
model guidance continues to advertise pretty stout winds at 925mb
(~2,500ft) with 35-45 kts Friday night/early Saturday. Therefore,
Wind Advisory remains in effect for the North Mountains and East
Bay Hills. Gusts 50-60 mph seems plausible over the higher
peaks/ridges. The offshore will also lead to another night of
thinning stratus. Low clouds/fog will once again be confined to
portions of Monterey Bay and the Big Sur Coast. The combination of
gusty N to NE winds and lowering relative humidity overnight will
lead to increased fire weather concerns. It's still early in the
season and fine fuels have not completely dried out yet, but it is
still something to be mindful of.

Winds are forecast to gradually subside Saturday morning into
Saturday afternoon. For several days models have been developing a
strong southerly surge coming up the Big Sur Coast as offshore
flow weakens. Current forecast will keep this thinking going.
Temperatures on the immediate coast and the north end of Monterey
Bay could end up being cooler Saturday depending on development of
the surge. Interior areas and locations north of the surge will be
mild and several degrees above normal.

Not much change for the extended forecast. Night and morning low
clouds/fog will be common as an upper lows drifts westward over
the region. Seasonably cool, but dry weather is expected for much
of next week.

&&

.AVIATION...As of 4:45 PM PDT Friday...Strong northerly gradient
this afternoon has pushed the stratus well south of the MRY Bay
Area. Flow is expected to turn more northeast tonight which will
keep clear VFR conditions. Main concern is the winds. North to
northeast winds 30-40 kt above 1000 feet will create LLWS over the
North Bay and SFO Bay Area after 02-03Z and continuing through
12Z. Greatest chance for LLWS will be the North and East Bay which
are closest to the hills.

Models indicate a southerly surge developing Saturday which could
impact the MRY Bay Area terminals early Saturday night.

Vicinity of KSFO...VFR. Breezy northwest winds gusting 28-30 kt
through 03Z. LLWS for lighter winds at the surface and NE winds
30-40 kt above 1000 feet after 03Z.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR.

&&

.MARINE...as of 8:34 PM PDT Friday...A 1033 mb high is centered
650 miles west of Crescent City. A 1002 mb thermal trough is over
the California interior. This is causing strong northwest winds
with near gale force winds over the northern and outer waters.
Winds will decrease Saturday as the systems weaken. A southerly
flow is expected to develop along the Big sur coast Saturday and
will spread north Saturday night. Patchy dense fog is possible
ahead of the southerly flow. Light winds are then expected for
&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...Wind Advisory...CAZ507-511
             SCA...Pt Arena to Pt Reyes 0-10 nm until 9 AM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm until 9 AM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 AM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 9 AM
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             GLW...Pt Arena to Pigeon Pt 10-60 nm until 3 AM
             SCA...SF Bay until 3 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 PM
             SCA...Mry Bay from 6 AM until 4 PM

&&

PUBLIC FORECAST: Rowe/MM
AVIATION: W Pi
MARINE: W Pi

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