Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
254 PM PST Thursday Feb 26 2015
Synopsis...a storm system will then bring showers and cooler
temperatures to the area tomorrow through the weekend. Another
weak system will bring additional shower chances to the area on
Discussion...as of 3:00 PM PST Thursday...thanks to an offshore
flow plus warming in the column indicated off the koak sounding
this morning...temperatures are running 4 to 9 degrees ahead of yesterday
in most spots. In fact...some North Bay locations have moved back
into the lower 70s and could even set a record or two. Satellite
shows mostly clear skies over land with clouds confined to the northwest
waters. Clouds are expected to be on the increase as a general northwest
flow brings clouds to the north down to our area.
A cold upper level low near the British Columbia coastline will dive southward
and be near the sf Bay area Saturday afternoon. As the system
approaches showers will be on the increase beginning Friday
afternoon over the North Bay and then spreading to the south
Friday evening and night. At the same time winds will pick up with
gusty northwest winds expected especially along the coast and coastal
ranges. As the low nears...instability will be on the increase
along with more favorable convective parameters with the main
focus of attention over the southern third of the County Warning Area. Rainfall
amounts are forecast to generally be light especially around sf
Bay where most places will pick up less than a tenth. Amounts will
likely be higher along coastal Santa Cruz and Monterey County
ranges where over half an inch can be expected.
In addition to the rain...some of the cells will have small hail
while elevations over 4000 feet could see light snow. Thunder and
lighting are also possible Saturday afternoon especially for
Monterey...Santa Cruz...and San Benito counties. The low will
continue to dive to the south Sunday leading to an end of showers
for almost all spots. Could still see a few showers pop up over
interior Monterey County late Sunday.
A second system from the north will then dive down to our area on
Monday with a few more showers expected. Rainfall amounts from
this this weaker system will generally be less than a tenth of an
Ridge of high pressure will build back into our area by the middle
of next week leading to dry conditions with above normal
temperatures into next weekend.
Aviation...as of 9:44 am PST Thursday...for 18z tafs. Strong
northerly gradient of 7 mb down the coast is keeping the area free
of low clouds...just some passing high clouds with gusty northwest winds at
the terminals this afternoon. Some evidence that incoming system
will bring some late night ceilings as moisture and onshore flow
returns but ceilings late tonight into Friday morning should be patchy
in nature with gusty winds aloft.
Vicinity of ksfo...VFR with mostly clear skies today into tonight.
Gusty west winds this afternoon and evening for ksfo with gusts to
28 knots forecast.
Confidence is moderate to high.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...low ceilings have mixed out of Salinas
valley and Monterey Bay region. Look for VFR with clear skies this
afternoon and evening with gusty northwest winds down the Salinas valley.
Confidence is moderate to high.
Marine...as of 3:00 PM PST Thursday...gusty northerly winds will
continue overnight into Friday as a weather system moves across
the northern waters. Some showers will be possible as well but the
main impact will be strong winds and rough seas. Shower chances
will linger into Saturday before winds finally subside as the
weather system moves inland. Lighter winds return Sunday but large
seas will continue through the weekend.
... Pt to pt pinos 0-10 nm
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm
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...pt pinos to pt Piedras Blancas 0-10 nm
Public forecast: Bell
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