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NWS Forecast Area Discussion - San Francisco Area

000
FXUS66 KMTR 220535
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
935 PM PST Fri Jan 21 2022

.SYNOPSIS...Strong and gusty offshore winds will continue over the
higher terrain of the Bay Area through Saturday. Winds ease by
midday Saturday followed by continued dry and mild weather Sunday
through most of next week. Increasing potential for NorCal to
return to a more unsettled, wet pattern by early February.

&&

.DISCUSSION...as of 08:54 PM PST Friday...Strong offshore winds
prevail over the region this evening, especially across the higher
terrain of the San Francisco Bay Area. As of this writing, Pine
Flat Rd (@ 3308 ft) in the Mayacamas Mountains is reporting a gust
of 70 mph and humidity value of 24%. Elsewhere, our typically
windy spots like Mt. Diablo and Mt. Umunhum in the Santa Cruz
Mountains are seeing gusts in excess of 50 mph as well. Given
this, a High Wind Warning remains in effect for the North Bay
Mountains while a Wind Advisory continues as well for the East Bay
Hills/Diablo Range and Santa Cruz Mountains through Saturday
morning. While a few wind gusts did mix down to the lower
elevations this afternoon, only saw reports of up to around 40 to
45 mph in isolated areas. Thus, cancelled the Wind Advisory for
the lower elevations early this evening as the strongest winds are
likely to remain confined to the higher peaks and ridges of the
Bay Area. Breezy offshore flow is also reported across the ridges
and peaks of the Central Coast, yet gusts are generally in the
25-35 mph range in the Santa Lucia, Gabilan and southern Diablo
ranges. Having said that, GOES-17 Satellite imagery is picking up
on what has become a vegetation fire along the Big Sur Coast. CHP
reports the fire is near Coast Rd and Palo Colorado Canyon Rd,
inland from the Bixby Creek Bridge.

All this said, the remainder of the forecast remains on track for
this evening. Other than lowering wind speeds and gusts in the lower
elevations and dropping the Wind Advisory, no additional updates are
anticipated at this time. Please see the previous forecast
discussion below for additional details.

&&

.PREV DISCUSSION...as of 01:44 PM PST Friday...Strong gusts
continue to impact higher terrain with gusts ranging 35 to 60 mph.
However, we`re starting to see some of those winds mix down into
the valleys. Napa Airport has had gusts ranging 30 to 39 mph in
the past hour and Livermore Airport has had gusts up to 33 mph in
the past couple of hours. Meanwhile, other valley sites in North
and East Bay are only seeing gusts around 15 to 20 mph.

The WMC to SFO offshore gradient has been increasing today. This
morning around 7 am, it was 6 mb, but has now increased to a
little over 9 mb. NAM and GFS continue to show that pressure
gradient increasing tonight into Saturday morning ranging 12 to
15 mb. The local WRF model shows that 925 mb winds (a good
estimate for wind gusts over higher terrain) will strengthen
further after 4pm, especially across North Bay, but also impacting
the East Bay and into San Francisco/Peninsula. This is when we may
see more coverage of Bay Area valleys experience winds mixing
down to the surface. During the overnight hours, winds in the East
Bay and SF/Peninsula should gradually diminish by the early
morning hours before sunrise, but stronger winds will persist
across North Bay through the morning and diminish Saturday
afternoon. Wind Advisory and Wind Warning products continue to
look on track.

The offshore winds are keeping some areas warmer than normal.
Current temps are running about 5 to 15 degrees warmer than 24
hours ago with many thermometers reading in the mid 60s to low
70s. This puts today`s forecast daytime highs about 5 to 13
degrees above normal. In addition to warmer temps, we`re also
seeing some drying occur. RH values are showing a noticeable drop
of 30 to 50% in the past 24 hours. Fortunately, the fuels are
still fairly moist from rains in December so there is limited fire
concern, but folks should still be cautious of anything that could
cause a spark as the winds pick up.

Once we get past this wind event, expect sunny and mild weather
for the rest of the weekend and we should also remain dry through
the rest of the month. As has been said in prior discussions, long
range models are coming into better agreement that we should see
more troughing over NorCal starting in early February which would
put us back into a wetter pattern.

&&

.AVIATION...as of 9:35 PM PST Friday...For the 06Z TAFs. VFR with
offshore winds. Low level wind shear through much of the forecast
period, best chances at night/morning with surface winds decoupling
from winds aloft.

Vicinity of KSFO...VFR. Mainly northeast wind through the period,
with low level wind shear tonight and Saturday morning.

KSFO Bridge Approach...Similar to KSFO.

Monterey Bay...VFR. Low level wind shear this evening, winds at the
surface and aloft easing overnight.

&&

.MARINE...as of 8:54 PM PST Friday...Gusty offshore winds will
continue tonight and Saturday morning then diminish during the day
Saturday. Moderate period west to northwest swell continues in
the near term, with a longer period west to northwest swell
arriving late Sunday into Monday morning.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...High Wind Warning...CAZ507
             Wind Advisory...CAZ511-512
             SCA...SF Bay
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm until 3 AM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
             SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 AM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM

&&

$$

PUBLIC FORECAST: RGass/Bingaman
AVIATION: Canepa
MARINE: Canepa

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