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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 201130

Area Forecast Discussion
National Weather Service San Francisco Bay Area
430 AM PDT Mon May 20 2019

.SYNOPSIS...Dry weather conditions are expected through much of the 
day ahead of another storm system set to arrive tonight. Look for 
light rain to develop late this evening over the North Bay and then 
across the remainder of the region overnight. Showers will linger 
into Tuesday before the return of dry conditions Tuesday night into 
Wednesday. Cool and unsettled conditions are likely through the
remainder of the week, yet widspread rainfall appears less likely.

&& of 02:55 AM PDT Monday...Isolated showers linger
off of the Central Coast early this morning as the core of a cold
mid/upper level low shifts eastward away from the region. 
Expecting a drying trend to continue region-wide through much of 
the day with temperatures warming only into the 60s for most 
locations this afternoon. A mix of sun and clouds can also be 
expected through the afternoon ahead of the next approaching 
weather system. 

Another mid/upper level storm system is forecast to push inland over 
the Pacific Northwest today with the tail end of a frontal boundary 
dropping across the San Francisco Bay Area late this evening and 
through the Central Coast tonight. Light rain will first develop 
over the North Bay this evening before spreading southward/inland 
during the overnight hours. Rainfall will generally range from a few 
hundredths of an inch to around one-quarter inch through the night. 
In wake of the frontal passage, lingering showers will persist into 
Tuesday as the core of the mid/upper level trough drops southward 
over the West Coast. The post frontal showers will be mostly 
isolated to scattered in nature with the potential for brief 
moderate to locally heavy rainfall. Overall, this system will be 
weaker and produce less rainfall than the system that moved across 
the region this past weekend. 

Drier weather is forecast to develop Wednesday and likely to persist 
into late week. However, a broad upper trough remains over the 
western portion of the country keeping temperatures below seasonal 
averages. The best chance for precipitation looks to stay over the 
interior portion of the state. Chances for precipitation may return 
late in the week and into the upcoming weekend as weak disturbances 
round the base of the retrograding trough. Thus, look for cool and 
unsettled conditions to persist through the end of the month. 

&& of 04:30 AM PDT Monday...For 12z tafs. Showers have
mainly ended across the region. Ample low level moisture remains
in place leaving patchy MVFR cigs and fog in the North Bay. Cigs
should become more widely scattered by late this morning. An 
upper low will bring increasing clouds and westerly winds to the 
area tonight along with some scattered showers. Winds may be gusty
tomorrow morning.

Vicinity of KSFO...Patchy cigs around the Bay Area between
2000-4000 ft AGL. Cigs may occasionally become BKN this morning
before scattering out by the afternoon. West to southwest winds
through the period becoming gusty tomorrow morning. Cigs will
lower as showers approach this evening.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Showers have mainly ended with patchy
VFR/MVFR cigs 2500-5000 ft through mid morning. Cigs will
redevelop early this evening as showers approach.

&& of 02:55 AM PDT Monday...Generally light west to 
northwest winds will persist over the coastal waters through 
tonight before increasing on Tuesday. Winds will then remain 
elevated through late this week. Large swells generated by the 
last storm system will continue to create hazardous conditions, 
particularly for smaller vessels. West to northwest swell will 
briefly decrease later today and tonight before building again 
Tuesday and Wednesday.


     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Rough Bar Advisory for SF Bar until 4 PM
             SCA...Mry Bay from 1 PM




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