Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
908 am PDT Sat Jul 4 2015
Synopsis...outside of some coastal drizzle during the early
morning hours...dry weather is forecast through next week. A
stronger marine influence will return through the weekend with
temperatures near or slightly below seasonal averages through at
least early next week.
Discussion...as of 09:00 am PDT Saturday...the stratus that
spread well inland overnight continues to slowly burn-off over
inland areas this morning. In addition...patchy coastal drizzle
appears to be diminishing at this hour. Temperatures are
generally in the upper 50s to middle 60s region-wide and will begin
to rapidly warm under mostly sunny conditions...especially inland
away from the marine influence. Coastal areas will likely warm
into the upper 60s to middle 70s while inland spots warm into the 80s
and 90s this afternoon. Low clouds will likely make a return by
early this afternoon and spread inland overnight. The ongoing
forecast remains on track and no updates are needed at this time.
Previous discussion...as of 3:00 am PDT Saturday...temperatures are
currently running close to 24 hours ago with clouds along the
coast and come adjacent valleys. With the marine layer around
1500 feet and deepening plus the surface flow directly from the
west should see clouds continue to advance inland until sunrise.
In addition...models also show possible patchy drizzle especially
along the coast. Highs today will on average be 3 to 5 degrees
cooler than yesterday thanks to the deepening marine layer and
stronger onshore flow. Highs will be in the 60s to lower 70s at
the coast with upper 70s to upper 80s for most inland spots.
Clouds will return to the coast and adjacent valley spots over the
evening which will impact some fireworks viewing locations.
Temperatures will continue to slightly cool for next week as an upper
level low will slowly drift from the west toward our area. This
will help to deepen the marine layer and with the flow at the
surface forecast to favor onshore/westerly we should see round
after round of nighttime clouds at the coast plus adjacent valley
spots along with possible drizzle. Longer range guidance through
the middle of the month keeps showers and any heat waves well out
of our area.
Aviation...as of 4:30 am PDT Saturday...marine layer has been
deepening since late Friday afternoon and is currently 2000 feet
deep at Fort Ord. Stratus has filled on over the sfo Bay area.
The deepening of the marine layer combined with a east-west
onshore gradient supports a slightly later clearing today.
Sfo may clear first at 1730-1800z with the approach clearing by
Vicinity of ksfo...IFR ceilings through 1730-1800z.
Light west winds increasing to about 18 knots by 21z.
Ksfo bridge approach...IFR ceilings clearing after 18z becoming VFR
Monterey Bay area terminals...IFR/LIFR ceilings through 19z.
Marine...as of 09:00 am PDT Saturday...a weak low pressure will
linger over the coastal waters through midweek resulting in light
winds and seas through the period.
... Bay from 3 PM
Public forecast: rgass
aviation: west pi
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