Scientific Forecaster Discussion
fxus66 kmtr 201229
Area forecast discussion
National Weather Service San Francisco Bay area
529 am PDT Fri Oct 20 2017
Synopsis...showers to decrease and move out of the area this
morning. Cooler temperatures and brisk onshore winds will persist
today. Dry weather is then expected through the remainder of the
forecast period. A warming trend will begin during the weekend
and continue into next week. Temperatures are forecast to be well
above average through most of next week.
Discussion...as of 3:05 am PDT Friday...the early-season storm
was slow to arrive in our area yesterday, but once it did, it
moved through quickly. Rain began in the North Bay last evening,
and spread into the San Francisco Bay area right after 11 PM with
the frontal system moving quickly to the south and east. Brief
heavy rain reached the weather office in Monterey after 1:30 am,
with winds shifting to the west and briefly gusting to over 30
mph. Latest radar scans show the main rain band has now moved
south of San Jose with rainfall having ended across most of the
San Francisco Bay area. Rainfall totals have ranged from under a
tenth of an inch to over three quarters of an inch, with the
highest amounts falling in the North Bay. The largest amount seen
was Middle Peak RAWS site in Marin County which topped out at
Showers will continue to taper off, with some rain still expected
across the southern portions of Monterey and San Benito counties
through mid morning. Breezy conditions to persist through the day
with strong onshore winds in the 15 to 25 mph range, with higher
gusts possible. High temps today will be on the cool side - 50s
and 60s most areas.
A warming trend will begin during the weekend as an upper level
ridge builds over the state. Much warmer temperatures are then
forecast early in the work week as the upper ridge strengthens
along the West Coast and light offshore flow develops. On Monday
and Tuesday expect widespread high temperatures in the 80s to
around 90, with these warm temperatures developing not only
inland, but in coastal areas as well. Slight cooling is projected
late in the week as the ridge begins to weaken.
Aviation...as of 5:10 am PDT Friday...for 12z tafs. Colder and
drier air filter in on the backside of the frontal boundary has
resulted in mostly clear skies with only patches of low clouds
this morning. Temporary cigs possible between now and sunrise with
rapid clearing expected this morning. Winds anticipated to veer
increasingly to the west with speeds increasing this afternoon to
around 10-15 kt with gusts around 20-25 kt.
Overall forecast confidence: moderate to high
Vicinity of ksfo....MVFR cigs will scatter out relatively fast
this morning as a drier airmass settles into the region. VFR
conditions expected through the remainder of the forecast period.
West winds will gradually increase to around 15 kt this afternoon
with gust to around 25 kt possible.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...VFR conditions anticipated to persist
through the remainder of the forecast period. Light winds will
veer increasingly to the west with speeds increasing this
afternoon to around 10-15 kt with gusts around 20 kt possible.
Fire weather...as of 3:05 am PDT Friday...rainfall which moved
across the district overnight brought wetting rains to many
locations. Highest rainfall amounts were in the North Bay
mountains, but many locations at lower elevations received around
a quarter of an inch. Rainfall should end in most areas by mid
morning. Today will be a cool day with brisk northwest winds.
A warming trend will get underway during the weekend as a high
pressure ridge begins to build over California. This ridge will
strengthen into early next week and result in warm and dry
conditions districtwide from Monday through Wednesday. Will need
to be wary of possible gusty offshore winds in the hills beginning
late in the weekend and continuing into Monday night.
Marine...as of 2:37 am PDT Friday...moderate northwesterly winds
will persist in the wake of a cold front that is passing through
the coastal waters tonight. A long period northwesterly swell
will accompany this system creating hazardous seas for mariners
operating small crafts. Mariners are urged to use extreme caution
if out at sea as hazardous seas are forecast to persist over the
next few days.
... Surf advisory...caz006-505-509-529-530
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
Small Craft Advisory...mry Bay
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...rough bar advisory for sf bar
Public forecast: Sims
fire weather: Sims
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