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Area Forecast Discussion (AFD)

Issued by San Francisco Bay Area, CA (MTR)

FXUS66 KMTR 171733

Area Forecast Discussion
National Weather Service San Francisco Bay Area
933 AM PST Sun Feb 17 2019

.SYNOPSIS...Showers will be decreasing during the day and ending
by tonight. Snow is possible above 2000 feet. Clearing skies will
allow for cold minimum temperatures for the upcoming week. Dry 
weather is expected for Monday and Tuesday with a chance of 
showers returning by the middle of the week. Temperatures will 
remain below normal. 

&& of 9:10 AM PST Sunday...There was an uptick in 
shower activity this morning as an upper level low dropped 
southeast along the California interior. Rainfall amounts 
overnight were light ranging from about one-tenth to one-third of 
an inch. Freezing level on the morning OAK sounding was 3800 ft so
snow levels may be as low as 2000 ft in the North Bay where the 
airmass is a bit colder...and 3000 ft over the southern CWA. 

Radar shows showers have decreased across the SFO Bay Area as most
of the main shower activity has pushed to the southeast. 
Scattered showers will continue over the coastal waters through 
the day. Short-range models indicate a few showers developing over
the higher terrain from the East Bay Hills south this afternoon 
so a slight chance of showers remains in the forecast for the 
area. Shower activity should be over tonight and dry weather is 
expected for Monday and Tuesday. Skies will clear tonight as a dry
cool northerly flow settles over the area. Low temperatures 
tonight will cool into the upper 20s to lower 30s in the interior 
valleys. Urban areas will be in the mid to upper 30s with low 40s 
in San Francisco. On Monday night the airmass will warm a couple 
of degrees but the air will be drier so low temperatures will end
up being about the same as Sunday night. By Tuesday night the 
lows will be a couple of degrees higher. High temperatures will 
be in the 50s which is about 5 degrees below normal.

Current forecast looks good. No updates.

From previous discussion...The next chance of rain will arrive 
on Wednesday and Thursday as another upper trough approaches from 
the north. Models have trended the trough a little further east, 
with the result being scattered light showers over the region. 
Cool temperatures will continue with highs in the mid 50s, but 
lows will likely be a couple degrees milder. 

On Friday, the trough will move east and a weak ridge will move
overhead. Forecast confidence decreases over the weekend. Another
cold upper low will drop south from the Gulf of Alaska but will
slow as it encounters the ridge. Models disagree on how far south
the trough and precipitation reach by Sunday. Overall, below
normal temperatures look likely to continue through next weekend
with additional wet weather possible by early next week. 


.AVIATION...As of 9:33 AM PST Sunday...For 18Z TAFs. VFR 
conditions are forecast to prevail at most terminals over the next
24-30 hour period. The exception to this would be STS with some 
locally dense morning fog, and possibly LVK as well. Other than 
that, isolated rain showers this morning will decrease in coverage
through the day with some SCT or possibly BKN decks at/around 
3,500-5,000 ft AGL this afternoon with some cumulus/stratocumulus 
build-up. Onshore winds 10-20 kt with locally gusty conditions 
expected through the evening hours for most TAF sites.

Vicinity of KSFO...VFR conditions are forecast to prevail today.
SCT-BKN cumulus and stratocumulus decks will likely develop
between 3,500-5,000 ft for the late morning and afternoon hours.
Breezy west winds 15-20 kt with gusts near 30 kt this afternoon.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR with scattered showers this morning
dwindling in coverage as the day continues. SCT-BKN decks
3,500-5,000 ft AGL this afternoon with some cumulus and 
stratocumulus build-ups. Onshore winds this afternoon around 10-20

&& of 8:42 AM PST Sunday...Northwest winds are forecast
to prevail over the coastal waters for the next several days. The
northwest swell that arrived late Friday and Saturday will begin 
to decrease today. A second long period northwest swell train is 
set to arrive during the week and will bring with it more modest 
swell heights.


     .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...SF Bay
             SCA...Mry Bay




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