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

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FXUS66 KMTR 241124

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

.SYNOPSIS...Cooler conditions can be expected 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 during the next few nights/early mornings, no
precipitation is expected through the forecast period.

&& 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 location s--
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.

&& of 04:19 AM PDT Monday...Increased onshore flow has
led to a deeper marine layer. Southerly flow along the coast has
also allowed clouds to fill into the N Bay. Expecting VFR this
afternoon. Clouds push inland again tonight.

Vicinity of KSFO...Cigs impacting east side of Bay, but SFO should
be in a hole. Will watch closely, but conf is low on cigs
impacting SFO. Gusty winds this afternoon. Better chance for cigs
tonight at SFO.

SFO Bridge Approach...Cigs at or below 1k through 1630-1700Z.

Monterey Bay Terminals...IFR cigs clearing after 17Z. VFR this

&& of 04:23 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.


     .Tday...SCA...SF Bay




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