Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
438 am PDT Thursday Oct 23 2014
Synopsis...the weak tail end of an approaching Pacific weather
system will likely bring some light rainfall to the northernmost
portions of our district today...otherwise mild conditions are
expected. Friday looks to be mostly sunny and mild...but then a
somewhat wetter system will move in on Saturday and spread rain
chances across much of our area. After a few residual showers on
Sunday...dry conditions and seasonal temperatures are projected
into the first part of next week.
Discussion...as of 3:09 am PDT Thursday...mainly high clouds are
streaming across the northern two thirds of the County Warning Area at this
time...as the southern edge of a system now affecting the Pacific
northwest moves through. Latest radar imagery shows echoes are mainly
remaining north of Sonoma and Napa counties at this time and no
appreciable rainfall has yet been picked up by automated gauges.
Expect the rain line to sag into the North Bay today but not much
rainfall is expected with this weak system.
After this weak system moves to the east...a stronger system is
prognosticated to affect more of the district late Friday night and
Saturday with rain chances extending as far south as well into
Monterey County by midday Saturday. Rainfall amounts of up to one
inch are possible across portions of the North Bay...with much
less from the Bay area south. As the upper low center moves
across...enough instability and colder air aloft for a slight
chance of thunderstorms across portions of the North Bay Saturday
afternoon. Showers to taper off on Sunday then drier conditions
are expected into the early part of next week. There continues to
be large differences amongst the medium range models regarding
rain chances next week. Thus have left some slight chance probability of precipitation
across the north for Tuesday and Wednesday but dry elsewhere. Low
Aviation...as of 4:30 am PDT Thursday...satellite image suggests
areas of stratus along the coastal hills of the sfo extending into
sfo and Oak as well as the North Bay valleys. The high clouds will
allow for slower clearing of the stratus and therefore burnoff
time is not until 18-19z despite the patchy nature of the stratus.
Vicinity of ksfo...MVFR conditions through 18z.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...no stratus reported in the mry Bay
area this morning. Believe there may be an offshore drainage wind
that is keeping the coastal stratus out of the Bay. Feet Ord
profiler supports this. Therefore forecast has been changed to VFR
conditions for the day.
Marine...as of 3:05 am PDT Thursday...high pressure continues
off the Southern California coast while low pressure is off
Vancouver Island. This is bringing light winds to the area with
stronger winds in the southern waters. Southerly winds will
increase Friday night and Saturday as a low pressure system
deepens off the Oregon coast. High pressure will build off the
California coast Sunday and Monday after the low moves inland.
Public forecast: Sims
aviation/marine: west pi
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