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

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000
FXUS66 KMTR 241751
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1051 AM PDT Mon Jul 24 2017

.SYNOPSIS...Cooler conditions can be expected Today and Tuesday
due to a deepening marine layer and increased onshore flow.
Warming is then expected during the second half of the week as an
upper ridge builds back across California. Aside from some
possible coastal drizzle/mist during the next few nights/early
mornings, no precipitation is expected through the forecast
period.

&&

.DISCUSSION...as of 08:41 AM PDT Monday...Based off of the Fort
Ord Profiler the marine layer rapidly deepened overnight and is
now around 2000 feet in depth. This is due to the mid/upper level
low and associated trough approaching the California coast this
morning with low clouds spreading well inland to many valley
locations. With this, mist has been reported throughout the
morning, especially near the coast. Will see these low clouds
burn-off through the morning over the valleys with the potential
for some coastal areas to stay under cloud cover a good portion of
the day. This marine push has also resulted in a decent cool down
region-wide with many locations showing temperatures a good few
to several degrees cooler than 24 hours ago. Overall, the ongoing
forecast remains on track and only made minor adjustments to the
sky cover based off of current satellite trends. Please see the
previous forecast discussion below for additional details.

&&

.PREV DISCUSSION...as of 3:00 AM PDT Monday...The marine layer
which has been under 1,000 for several days has deepened overnight
to over 1,5000 feet as a shortwave trough and upper level low
approaches the coast. At the same time the surface flow has
switched to more pronounced from the west. All of these factors
will lead to cooler conditions today for nearly all locations,
especially those that are away from the coast. Far inland towns
that were in the 90s to lower 100s on Sunday will drop 5 to 10
degrees today while closer to water only a few degrees of cooling
can be expected. Similar conditions can be expected on Tuesday.

The synoptic pattern will undergo a change for the second half of
the week as a ridge of high pressure rebuilds toward our region.
This will lead to warmer weather going into next weekend. Most
areas will return to values that we have had recently with very
warm readings likely for many inland spots.

Next week remains worth keeping an eye on with the ECMWF showing
the ridge strengthening to almost 600 DM at 500 MB. Latest GFS
has a slightly weaker ridge although still brings in impressive
values for the Western Conus. ECMWF ensemble members continue to
show a substantial spread next week, however members with the
highest temperature are well in the advisory level (case in point
San Jose in the lower 100s). Far from a done deal, but will
definitely need to be closely monitored. Current 6 to 10 and 8 to
14 day forecast from CPC favors warmer than normal conditions.

&&

.AVIATION...as of 10:51 AM PDT Monday...Clearing of stratus and fog
is accelerating while the marine layer depth continues to increase.
The marine layer is nearing 2,200 feet deep at the Bodega Bay and
Fort Ord profilers.

The 2.6 mb SMX-SFO and 2.9 mb SNS-SJC pressure gradients are a little
more robust than the NAM is forecasting thus ongoing southerly flow
may hold on a bit longer into this afternoon before the sea-breeze
circulation sets up. A deep, nearly vertically stacked closed low
west of the Bay Area will remain quasi-stationary through Tuesday,
possibly undergoing a little strengthening and amplification at the
mid-upper levels tonight and Tuesday.

Vicinity of KSFO...VFR through this evening. MVFR cig possibly
returning by 10z Tuesday. Light E-NE wind has developed, and it
may hang on til 21z time-frame before onshore wind returns, low
confidence.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR through this afternoon. Cigs probably
returning this evening though low confidence on timing at this time.

&&

.MARINE...as of 9:33 AM PDT Monday...A weak low pressure system
off the California coast will result in light to moderate southerly
flow along the coast. Northerly winds will return midweek as low
pressure moves inland and high pressure builds over the eastern
Pacific.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...SF Bay

&&

$$

PUBLIC FORECAST: RGass
AVIATION: Canepa
MARINE: Canepa/MM


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