Scientific Forecaster Discussion
fxus66 kmtr 271100
Area forecast discussion
National Weather Service San Francisco Bay area
400 am PDT Sat may 27 2017
Synopsis...dry with seasonable temperatures for much of the
Holiday weekend. The next trough and associated cooling trend
arrives Tuesday and Wednesday with long range trends indicating
dry and benign weather pattern.
Discussion...as of 4:00 am PDT Saturday...cloud coverage is much
more patchy this morning compared to 24 hours ago with profiler
data showing a weak inversion above 4000 feet. At this time clouds
are most numerous around sf Bay, Marin County and the Santa Clara
Valley. Clouds will likely continue to expand through sunrise but
given the patchy nature inland and cooling aloft expect skies to
turn mostly sunny much earlier today as high pressure builds. The
increased sunshine will lead to a noted warming trend today,
especially after such a cool Friday where most climate sites
stayed in the 60s or struggled to reach around 70 even inland. It
should be a nice start to the Holiday weekend with widspread 70s
away from the coast and even some lower 80s for the warmest inland
spots while the coast should see peaks of sunshine with beach
temps in the lower 60s.
High pressure will nose over the region on Sunday with 850 mb
temps this morning around 12 celsius approaching 18 celsius inland
on Sunday afternoon. This should lead to a pronounced warming
trend for inland areas with more widespread 80s.
In general weather should be nice for Memorial Day but increasing
onshore flow ahead of the next trough will likely bring some gusty
west winds to the beaches with increased marine clouds. Inland
areas should enjoy another sunny and seasonably warm afternoon on
Monday for those looking to enjoy outdoor activities.
A fairly well defined upper trough will approach Cape Mendocino by
early Tuesday morning and likely bring some coastal drizzle and
increased marine push of clouds for Tuesday morning. In addition
temperatures will trend cooler again with a synoptically cooler
airmass aloft. Surface pressure gradients will increase such that
breezy west winds are forecast both Tuesday and weds in what will
likely be a fairly cool end to the month.
ECMWF shows dry with high pressure for the start of June into the
first weekend of the month.
Aviation...as of 10:45 PM PDT Friday...low clouds cleared from
most terminals on Friday evening. But significant moisture remains
in the boundary layer and so it's likely that most terminals will
develop MVFR ceilings overnight, continuing through much of
Saturday morning. VFR expected at all terminals by midday
Saturday. Light southwest winds overnight will turn to the west
and northwest on Saturday afternoon and increase.
Vicinity of ksfo...VFR early in period with MVFR ceilings likely
to develop overnight...most likely around 09z although confidence
is low concerning timing. Clearing expected to take place by
17-18z Saturday morning with VFR conditions for the remainder of
the day. Light westerly winds overnight, increasing Saturday
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...VFR early in period with MVFR ceilings
likely to develop by 08z and continue until 19z Saturday. Light
Marine...as of 03:46 am PDT Saturday...light west winds through
the morning. Northwest winds will begin to increase later today
and through the Memorial Day weekend as high pressure builds
offshore. The swell train will be generally 5 foot or less
through the forecast period so wind waves will dominate the sea
... Pinos to pt Piedras Blancas 0-10 nm from 3 PM
Small Craft Advisory...mry Bay from 3 PM
Public forecast: rww
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