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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 222340

Area Forecast Discussion
National Weather Service San Francisco Bay Area
440 PM PDT Fri Mar 22 2019

.SYNOPSIS...A frontal boundary will move from northwest to 
southeast across the region today resulting in widespread rainfall
through tonight. Mainly dry conditions develop over the weekend 
with unsettled weather likely to return during at least the first 
half of next week. 

&& of 01:35 PM PDT Friday...KMUX radar imagery
remains active and Bay Area automated rain gauges continue to tip
as a weak system moves through the region. Rainfall totals since 
this morning: 0.1-0.3" North Bay, 0.01-0.1" SF Bay and East Bay,
little to no rain south of Watsonville. Precipitation thus far 
has mainly been associated with warm advection and a passing warm 
front. Despite the slow start for rain, expect it to pick up in 
intensity as a cold front lurking offshore moves through later 
today. Latest HRRR/WRF model pick up on the cold front and produce
some heavier showers/rain with the fropa. Rain will initially be 
heaviest across the North Bay before slowly spread southward 
across the rest of the forecast area. The increased rain rates 
will likely impact portions of the evening commute. Steadier 
rainfall will transition to showers behind the front from N-S 
overnight and early Saturday morning. Only minor tweaks were made 
to previous rainfall totals. Rainfall amounts are forecast to 
range from 0.25-0.75" for most urban areas while the coastal 
ranges and North Bay Mountains/Hills could see upwards of 1.50" 
through Saturday. 

Winds will be breezy to gusty with the fropa and behind the front
with gusts of 30-40 mph in the higher peaks and immediate coast.

Gradual drying trend Saturday into Sunday before the next round of
The next round of rain is still on track to be Sunday night into
Monday. The 12Z model suite has trended slower with the onset of
rain Sunday night and the current forecast will reflect this. That
being said, expect rain to develop Sunday night and continue into
Monday morning. Impacts to the Monday morning commute seem likely.
A brief break Monday night into Tuesday with a few linger showers
possible. Yet another system is then slated for Tuesday night into
the middle of the week. Simply put, an active pattern remains
heading to the end of the month.  


.AVIATION...As of 4:30 PM PDT Friday...Light rain spreading over
the SFO Bay Area. The rain will spread into the MRY Bay Area 
after 03Z. Frontal system will be slow to move tonight so rain 
should last through Saturday morning. Models indicate frontal band
moves out of the area after 15Z with a few residual showers
through late morning. Rapid drying is indicated Saturday 
afternoon. Strongest winds will occur early evening with maximum
speeds 10-15 kt out of the south to southeast.  

Vicinity of KSFO...MVFR cigs with light rain and reduced vsbys to
3-5 miles. Conditions improve to VFR after 12Z. Southeast winds
10-15 kt becoming southerly tonight and westerly after 09Z. 

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Cigs lowering into the MVFR range after
03Z with light rain. Onshore winds to 10 kt becoming southeast
later tonight. 

&& of 04:22 PM PDT Friday...Moderate southerly winds
will continue today across the coastal waters as a frontal system
moves through. Expect winds to shift back out of the west to
northwest tonight and tomorrow behind the front. Winds will become
southerly again on Sunday before  increasing Sunday night ahead of
the next system. A moderate west  to northwest swell will continue
to build into tonight persisting  through tomorrow. This will
bring hazardous seas conditions over  the waters, particularly for
smaller vessels.


     .Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 PM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 9 PM
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Rough Bar Advisory for SF Bar




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