Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
433 am PDT Thursday Jul 31 2014
Synopsis...a drier middle to upper level southwest flow has reached
the area and will persist into the weekend. Temperatures should
remain very warm inland and cooler along the coast. Cooler air is
expected to spread inland later in the weekend and early next week
as the marine layer deepens.
Discussion...as of 3:03 am PDT Thursday...high clouds from the
former tropical system Hernan have exited the area and are now
over Nevada. Now satellite shows coastal stratus has spread into
inland areas. The marine layer depth is roughly the same as 24
hours ago...just over 1000 feet deep and the onshore surface
pressure gradient has increased with 3.0 mb between sfo and SAC.
Current temperatures and dew points are mostly similar to those
from yesterday at this time...although some stations are reporting
readings that are a few degrees cooler.
A broad upper level trough over the eastern Pacific will provide a
dry southwest flow aloft across the district through the remainder
of the week and into the weekend. Onshore flow is expected to
increase by late in the weekend which will allow for cooler air to
filter farther inland with near normal temperatures expected.
There could be a slight warm-up once again late next week as high
pressure aloft builds westward into California from the Desert
Aviation...as of 04:24 am PDT Thursday...another tricky aviation forecast
this morning...especially at ksfo. Marine layer is a tad deeper
than yesterday with slightly more stratus coverage...especially in
San Francisco Bay. Current trends show the Bay filling in with
koak and smb already reporting ceilings. Based on this will forecast
ceilings to fill in over ksfo. Elsewhere ceilings filled in this morning.
Conf is medium.
Vicinity of ksfo...latest satellite trends show clouds creeping
toward ksfo. That being said 12z taf will have a ceilings for a few
hours this morning at ksfo with clearing around 16z as a first
guess. VFR this afternoon.
Ksfo bridge approach...similar to ksfo...ceilings prevail at or below 1k feet.
Clearing may be a little later than ksfo with clearing closer to 17z.
Monterey Bay area terminals...LIFR to IFR ceilings linger through
17-18z. VFR this afternoon. Ceilings return tonight.
Marine...as of 04:24 am PDT Thursday...northerly flow will
increase over the coastal waters today as high pressure builds off
the West Coast. Winds will be strongest north of Point Reyes.
Gusty winds will also be possible in the San Francisco Bay this
afternoon and evening. The increased winds will produce steeper
wind waves and locally hazardous conditions. Northwest swell will
increase Friday and over the weekend.
... Arena to pt Reyes 0-10 nm from 3 PM
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm from 3 PM
Small Craft Advisory...sf Bay north of the Bay Bridge from 1 PM
Public forecast: Sims
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