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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

                            
000
FXUS66 KMTR 200010
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
410 PM PST Tue Feb 19 2019

.SYNOPSIS...After a few days of dry weather, isolated to 
scattered rain/snow showers are forecast to return to the region 
Wednesday and persist into early Thursday morning. Snowfall will be 
likely in the region's highest elevations, especially across the 
Diablo Range, Sierra de Salinas and Santa Lucia Mountains. Dry 
conditions return late Thursday and continue into at least Friday 
before chances for rain return to northern California over the 
weekend. 

&&

.DISCUSSION...as of 02:03 PM PST Tuesday...Weather conditions 
today are very similar to those yesterday with temperatures 
generally in the 50s. While sky conditions are mainly clear over 
our region, an increase in cloud cover can be seen offshore and to
our north ahead of our next approaching storm system. 
Temperatures will be cold once again tonight, yet should be a few 
degrees warmer that previous days given the increase in cloud 
cover and moisture.

The latest thinking is that light rain showers will develop during 
the overnight hours near the coast and locally inland over East Bay 
Hills and Central Coast. The main mid/upper level system forecast to 
drop southward out of the Pacific Northwest and into 
California/Nevada will result in an increase in shower activity on 
Wednesday during the day. Snow levels are forecast to lower to 
between 2,500-3,000 feet a reinforcing shot of colder aid advects 
southward across the region. This will likely result in additional 
snowfall in the region's highest peaks, especially over the Diablo 
Range, Sierra de Salinas and Santa Lucia Mountains through early 
Thursday morning. Meanwhile, convective showers will impact lower 
elevations with the potential for brief moderate rainfall and small 
hail given the cold air mass aloft. Overall, rainfall amounts will 
be on the order of a few hundredths to a few tenths of an inch 
across the San Francisco Bay Area with locally higher amounts within 
heavier showers over the Central Coast. 

Showers will tapper off by Thursday morning as drier northwest flow 
returns in wake of the exiting system. Dry weather conditions will 
then develop region-wide by Thursday night and persist into Friday 
as a weak shortwave ridge develops aloft. The upcoming weekend looks 
to start off dry before another mid/upper level trough develops over 
the Pacific Northwest. This will bring increased chances for 
precipitation over Northern California and potentially down into the 
northern portions of our region. The storm door appears to remain 
open with a cool pattern in place, yet confidence in the details 
remain low at this time given model-to-model and run-to-run 
inconsistencies. With all this said, a widespread heavy rainfall 
event does not appear likely within the next 7-10 days. 

&&

.AVIATION...As of 4:10 PM PST Tuesday...Satellite image shows low
clouds offshore that are moving south for the moment. Dry 
northerly flow will keep VFR conditions through the night but as 
an upper level system drops down from the Pacific Northwest clouds
will increase on Tuesday. Moisture is limited so there is only a 
slight chance of showers. We expect cigs to remain in the VFR 
range but cannot rule out brief periods of MVFR associated with a 
heavy shower or from the clouds offshore. This system is an
upper-level system with no surface feature so winds will remain 
west to northwest. 

Vicinity of KSFO...VFR through tonight. Increasing clouds Tuesday
after 15Z with cigs down to 3500-4500 ft. West winds increasing to
15 kt gusting to 20 kt after 09Z. Winds increasing to 20 kt with
gusts 25-30 kt after 16Z. 

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals....VFR conditions through this evening. 
Increasing clouds around the bay after 10Z with cigs down to
3500-4500 ft. Scattered showers arond southern MRY Bay after 16Z
with winds increasing to 15 kt gusting 20-25 kt. 

&&

.MARINE...as of 03:50 PM PST Tuesday...Northerly winds will
steadily increase over the waters through the night as a system
drops south from the Pacific Northwest. A  series of northwest
swells will impact the region through the rest of the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...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...SF Bay from 3 AM
             SCA...Mry Bay from 3 AM

&&

$$

PUBLIC FORECAST: RGass
AVIATION: W Pi
MARINE: Rowe

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