Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
825 am PDT Tuesday Sep 2 2014
Synopsis...the area will see a cooling trend beginning
today as a low pressure trough approaches the coast. Dry
conditions will persist through the period.
Discussion...as of 8:20 am PDT Tuesday...some cooling for today
compared to yesterday as the marine layer has increased to over
1500 feet with a stronger onshore surface gradient compared to
yesterday. Forecast calls for sunny conditions for almost all
locations by afternoon although will keep a close eye on that if
the burn-off doesn't go as planned. Highs will generally be in the
middle 60s to middle 70s at the coast with upper 70s to around 90 well
inland. This will average out to a 5 to 10 degree drop for inland
locations with a small change expected near the water.
Looks very quiet through the forecast period with a longwave trough
advance to our area and then becoming fairly stationary at least
through the weekend. Outside of some coastal drizzle, no
precipitation is expected.
Previous discussion...with a marine layer depth of around 1200
feet...the satellite infrared fog product imagery is showing coastal
stratus extending from Point Reyes south...and pushing into the
Salinas valley. Expect cooler temperatures today across the
district as an upper level trough approaches the coast. This
trough is prognosticated to remain over the eastern Pacific resulting in
continued cooling through about middle to late in the week. Night and
morning coastal low clouds are expected as well as possible
drizzle right at the immediate coast during the early morning
hours. High temperatures are expected to remain around or slightly
below normal through the latter part of the week and into next
weekend as onshore flow persists.
Aviation...as of 4:30 am PDT Tuesday...the north-S gradient has
weakened. Stratus is increasing along the coast and is starting
to spread into the North Bay and the Golden Gate. Ceilings will spread
over the East Bay this morning. Believe ceilings will stop short of
getting into sfo but a patch of stratus may get into part of the
Vicinity of ksfo...VFR with ceilings staying south and east of the Airport.
However with the ceilings spreading in the East Bay we cannot rule out
stratus briefly getting in from 13z-16z.
Ksfo bridge approach...patchy stratus may affect the approach
Monterey Bay area terminals...IFR ceilings through 18z.
Marine...as of 5:00 am PDT Tuesday...high pressure continues off
the Pacific northwest coast. A thermal trough will shift to the
coast resulting in decreasing winds over the area except for the
outer waters north of Point Reyes.
... Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm until 3 PM
Small Craft Advisory...sf Bay north of the Bay Bridge from 1 PM
Public forecast: Bell/Sims
aviation/marine: west pi
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