Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 212111
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
211 PM PDT Tue Aug 21 2018

.SYNOPSIS...After a period of cooling, a slight warming trend will
begin tomorrow as the upper trough influencing our current weather
exits to the northeast. This will allow temperatures to rebound to
near seasonal averages by late this week. Coastal clouds are
still expected to persist and penetrate inland each night.

&&

.DISCUSSION...as of 02:11 PM PDT Tuesday...Stratus has mainly
dissipated across the region with some lingering clouds around the
San Francisco Bay and northward. Satellite imagery also shows
smoke drifting across the North Bay from various wildfires. Thanks
to persistent cloud cover and an upper trough stretching across
northern California, temperatures this afternoon are around 5 to
10 degrees cooler than this time yesterday. Expect another round
of overnight and morning low clouds as the marine layer is
forecast to remain above 1500 ft.

The upper low over Idaho and associated trough that brought us
cooler weather will move to the northeast tomorrow, allowing the
ridge of high pressure over the desert southwest to strengthen.
This will kick off a warming trend through the rest of the week
and into the coming weekend. A broad upper trough over British
Columbia and an upper low well to the west of California will
prevent the aforementioned ridge from strengthening enough to
cause any significant warming. Most locations will remain near
seasonal normals through the week. This translates to afternoon
high temperatures in the 60s to low 70s along the coast and 80s to
90s inland. Overnight and morning low clouds are expected to
continue as well.

Looking into the medium range, CPC outlooks continue to show near
normal temperatures over California. This morning`s 8-14 day
outlook even shows below normal temperatures for much of the west
coast.


&&

.AVIATION...as of 10:50 AM PDT Tuesday...A very deep marine
settled into the coastal valleys overnight, bringing widespread
IFR-MVFR cigs to the terminals. While the marine layer is
gradually eroding from the top and bottom, it is very likely
several areas will remain under at least MVFR cigs thru the day.
This is a result of a deep upstream feed pushing onshore as well
as the arrival of a broad smoke plume from Canada/PACNW. This
smoke plume is filled with tiny particulates that will act as
condensation nuclei, increasing the likelihood of clouds over the
area. In addition, this smoke will cause the skies to become hazy
and reduce visbys, especially slant wise, thru the next day or
so. Winds generally light onshore to locally breezy through
coastal gaps.

Vicinity of KSFO...Moderate confidence of all day stratus event,
with lowering cigs after 03Z. Breezy onshore winds up to around
16kt by the afternoon. Smoke may reduced slant range and
horizontal vsbys over area terminals this week.

SFO Bridge Approach...Moderate to poor slant range visibility for
the period. Otherwise similar to KSFO.

Monterey Bay Terminals...Moderate confidence of all day stratus
event, with lowering cigs after 02Z. Smoke may reduced slant
range and horizontal vsbys over area terminals this week.

&&

.MARINE...as of 08:53 AM PDT Tuesday...A weak pressure gradient
across the region will maintain generally light west to
northwesterly winds over the coastal waters through much of the
week. Winds will increase over the northern waters late in the
week and into the weekend. Light mixed swell.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...None.

$$

PUBLIC FORECAST: AS
AVIATION: DRP
MARINE: DRP

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