Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
452 am PDT Sat Apr 25 2015
Synopsis...a fast-moving cold front will spread light to
moderate rain across the area this morning. Precipitation is
expected to end by this afternoon. High pressure will produce
warm and dry conditions on Sunday and Monday. A cooling trend will
develop by the middle of next week as a dry upper trough develops
over northern California.
Discussion...as of 3:03 am PDT Saturday...a fast moving cold
front is currently moving across the area. Currently the main
area of precipitation is occurring from the San Francisco
peninsula up through the East Bay counties. It appears that rain
has ended across Sonoma and Napa counties...and light rain has
just started in Watsonville. So far rainfall totals in the North
Bay have ranged from around a tenth of an inch to over 3/4 of an
inch...and around a third of an inch so far in downtown San
Rainfall will continue to push south into the southern third of
the district by daybreak...then taper off as the system moves
south and east out of the County Warning Area by late morning or early afternoon.
Breezy conditions will persist through the afternoon...especially
near the coast...where sustained northwest winds of 10 to 20 miles per hour
with locally stronger gusts...will be likely.
High pressure is then prognosticated to rebuild over the eastern Pacific
for warming conditions Sunday and Monday across the area. Monday
is expected to be the warmest day of the week with highs expected
to range from the 60s to 80s. An upper level trough is then
forecast to move onshore for cooler weather on Wednesday through
the remainder of the week. Conditions will remain dry.
Aviation...as of 4:52 am PDT Saturday...kmux Doppler radar is
showing the trailing edge of the cold front moving into the South
Bay area...bringing an end to rain in the San Francisco and
Oakland area. Showers will continue in San Jose for a few more
hours with rain in the Monterey and Salinas area expected to
persist into the late morning hours. Breezy conditions are
expected behind the front persisting into the afternoon hours.
Vicinity of ksfo...IFR conditions with an occasional shower are
expected to improve to MVFR around 1500z. MVFR bkn025 anticipated
by 1800z and VFR by 2000z. Gusty westerly winds 20 knots gusting to
30 knots are anticipated to persist all day today into the evening
Confidence is moderate.
Sfo bridge approach...similar to ksfo.
Monterey Bay area terminals...light rain with MVFR conditions are
expected to prevail today with occasional IFR conditions possible
between 1200 and 1600z this morning. Showers are expected to end
by 1700z. Winds are expected to be gusty throughout the day today
reaching 10 to 15 knots with gusts to 20 knots possible.
Confidence is moderate.
Marine...as of 01:54 am PDT Saturday...a cold front is passing
over the coastal waters this morning bringing light rain showers
along for the ride. The front will exit the area this afternoon
with northwesterly winds increasing behind the front. Moderate
northerly winds are forecast to prevail through midweek as high
pressure builds over the eastern Pacific and the surface pressure
gradient strengthens. The strengthening winds will result in
deteriorating sea conditions.
... Arena to pt Reyes 10-60 nm from 5 PM
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm from 5 PM
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm from 7 PM
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm from 7 PM
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm from 5 PM
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm from 2 PM
Small Craft Advisory...sf Bay north of the Bay Bridge from 2 PM
Small Craft Advisory...sf Bay south of the Bay Bridge from 2 PM
Public forecast: Sims
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