Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
544 PM PDT sun Aug 30 2015
Synopsis...generally dry weather conditions will persist across the
region through the upcoming work week. Daytime temperatures near
the coast will continue to be near normal...while inland areas
will be slightly below seasonal averages.
Discussion...as of 01:46 PM PDT Sunday...mostly sunny conditions
prevail across the region this afternoon with temperatures
generally in the 70s to lower 80s in the warmer inland areas.
While low level clouds are patchy at best over the coastal
waters...do expect an increase in coverage near the coast
overnight tonight as boundary layer moisture is forecast to
rebound. Otherwise...a middle/upper level long-wave trough is
forecast to persist over much of the West Coast through the first
half of the week. This will result in near seasonal temperatures
and generally dry weather conditions. However...have added a
mention of coastal drizzle Tuesday morning and Wednesday morning
as the marine layer compresses and a series of weak short-wave
disturbances move across the region.
The aforementioned disturbances will help to reinforce the broad
trough along the West Coast and advect a slightly cooler air mass
down across the region by midweek. This will bring inland
temperatures back down a few degrees to below seasonal averages.
Meanwhile...limited moisture aloft will generally maintain dry
weather conditions region-wide (aside from the potential for
coastal drizzle Tuesday and Wednesday mornings).
Previous runs of the medium range models suggested a warming
trend late in the week into the weekend as the upper level trough
shifts inland. However...both the latest GFS and European model (ecmwf) models show
this pattern shift to occur later (late into next weekend). With
this...will show temperatures warming a few degrees from those on
Wednesday/Thursday by late in the week and into the upcoming
weekend. Also...should see a decrease in coastal stratus late in
the week as the trough axis shifts inland a bit and drier air
advects into the boundary later.
Aviation...as of 5:27 PM PDT Sunday...a fairly vigorous surface
trough is presently sliding south over the forecast area. A west-east
oriented brightness discontinuity can be seen in the vicinity of the
trough on the visible imagery loop in addition to patchy coastal
stratus clouds developing in the area of greatest surface convergence
in front of the trough. The trough will continue to slide south over
the area this evening per the GFS model. In its wake a drier air mass
will settle in tending to slow the redevelopment of stratus and fog
Vicinity of ksfo...VFR. Westerly wind gusts to 30 knots until 04z.
Ksfo bridge approach...VFR.
Monterey Bay area terminals...VFR. Gusty westerly winds will gradually
settle this evening.
Beaches...as of 11:10 am PDT Sunday...buoy reports this morning
are showing a mix of local wind waves and long period westerly
swell. Although this is not the ideal scenario for rip current
development can't rule out some stronger rip currents flaring up
from time to time today. West northwesterly winds are expected to
increase this afternoon which should further disrupt rip current
Marine...as of 09:02 am PDT Sunday...the surface pressure
gradient is expected to strengthen along the coast
today...promoting increasing northwesterly winds. These
strengthening winds will result in deteriorating sea conditions.
... Bay until 8 PM
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm until 8 PM
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm from 8 PM
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm from 8 PM
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm from 8 PM
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm from 8 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...sf Bay until 9 PM
Public forecast: rgass
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