Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
353 am PST Sat Jan 31 2015
Synopsis...dry and mild conditions are expected to continue
through the middle of next week with rain chances confined to far
northern California. Temperatures will remain several degrees
above normal. There are indications that rain may move into the
area by the end of next week.
Discussion...as of 3:45 am PST Saturday...offshore surface flow
is resulting in mostly clear skies across the northern half of the
district with much less stratus over the coastal waters from about
the Monterey Bay northward. Inland...the only areas with fog
formation include the Salinas valley and around the Monterey
Bay...and just now extending into the Santa Clara Valley. So far
the the North Bay valleys are fog-free...but some patchy fog is
still possible to develop there even with the offshore flow.
Currently surface pressure gradients are offshore with 8.1 mb from
wmc to sfo and 4.3 from acv to sfo. The offshore gradients are
forecast to persist through today then switch to onshore on
Sunday. Currently northerly winds are strongest in the North Bay
hills where gusts in the 20s and 30s are occurring. Winds are
expected to taper off later today when the gradients begin to
relax. High temperatures are forecast to be in the middle 60s to middle
70s today...warmer than yesterday and above normal. Slightly
cooler temperatures are expected on Sunday as the surface flow returns to
The dry weather will continue through at least the middle of next
week as the upper level ridge remains anchored over the west. A
system prognosticated to affect the Pacific northwest early in the week
could bring some rain to the extreme northern part of the state
but our district is expected to remain dry. Medium range models
continue to bring rain chances far enough south to reach our
district by the end of next week. There continue to be differences
in model solutions regarding this potential rain...but indications
are looking more favorable to finally seeing at least some
rainfall across the area by next weekend.
Aviation...as of 3:53 am PST Saturday...the current infrared satellite
fog product is showing clear skies in the San Francisco Bay area
with stratus in Monterey Bay stretching south into the Salinas
valley. Local surface observation are showing light offshore flow at the
surface due to a thermal trough positioned over California. The
gentle offshore flow should be sufficient enough to maintain VFR
in the San Francisco Bay area this morning and will aid in the
morning burn off for the Monterey Bay area.
Vicinity of ksfo...VFR. Generally light winds this morning with
sea breeze reaching 5 to 10 knots this afternoon.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...IFR conditions are anticipated to
burn off by 1600z at kmry and 1730z at ksns. VFR is then
anticipated to prevail into the evening hours. The sea breeze will
reach 5 to 10 knots this afternoon.
Marine...as of 02:39 am PST Saturday...northerly winds will
decrease this morning as the surface pressure gradient weakens.
As the winds decrease the sea conditions will improve. Light winds
and relatively gentle seas are then expected through middle week.
Public forecast: Sims
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