Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
836 am PDT Friday Aug 28 2015
Synopsis...slight cooling is expected today as the upper ridge
over California weakens. A Pacific weather system will bring a
chance of light rain to the northern portion of our district late
tonight and Saturday morning. Much cooler weather will develop by
the weekend. Dry and seasonably cool weather is expected next
Discussion...as of 8:35 am PDT Friday...warm start to the day
today with many locations already in the upper 60s to upper 70s
thanks in large part to a surface flow from the north-northwest. Forecast
still calling for a return to more onshore flow later today in part
due to an approaching trough/cold front. This will drop highs as
much as 20 degrees over the weekend compared to values we hit
yesterday. Latest guidance in continues to show light rain mainly
for the North Bay tonight into Saturday.
Current forecast looks to be on track. No major changes expected.
Previous discussion...warm conditions persist across the
district this morning with 2 am temperatures as many as 5 degrees
warmer than 24 hours ago...ranging from the middle 60s to the middle
70s. Dew point temperatures are running a little warmer as well
and are generally in the 50s. Satellite imagery shows no stratus
or fog around the area...only some high clouds spreading across
the northern part of the state. Slightly cooler weather is
anticipated today as the upper level ridge is forecast to weaken
as an upper trough approaches the West Coast. Highs today are
expected to range from the middle 70s at the ocean to the 80s and 90s
inland...with warmest inland areas again topping the century mark.
The approaching upper level trough...and its associated cold
front...are prognosticated to slowly approach the coast from the west.
Precipitation from this system is forecast to remain well north of
our area...however models do continue to bring light rain chances
as far south as the San Francisco Bay area late Friday night
through Saturday morning...although the latest run of the nam12
does bring very light precipitation to the Monterey Bay. The system is
forecast to move through quickly with rain chances...such as they
are...ending by afternoon. Cooler weather will be the main benefit
from this system for our area as the marine layer deepens and
onshore flow increases. Cooler conditions will persist through
the weekend and right on through next week as a long-wave upper
trough remains anchored near the West Coast.
Aviation...as of 4:37 PM PDT Friday....VFR conditions will
continue through this evening with increasing high clouds through
the period. Light onshore flow.
Vicinity of ksfo...VFR. Light to moderate winds. Strongest wind
expected during the afternoon.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR. Light winds.
Marine...as of 08:29 am PDT Friday...light westerly winds and
seas are expected across the coastal waters. A long period swell
has begun to move into the area. A more energetic westerly swell
will impact the region this weekend.
Public forecast: Bell/Sims
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