Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1054 PM PDT Thursday Aug 21 2014
Synopsis...night and morning low clouds and slightly below
normal afternoon high temperatures are forecast through the
weekend. Warmer temperatures are possible inland by the middle of
Discussion...as of 8:35 PM PDT Thursday...warming occurred across
most of the region today as a weak shortwave upper level ridge
developed across central California. Warming was most pronounced in the
north and East Bay valleys where highs today were as much as 10
to 15 degrees warmer than yesterday. Highs today were close to
late August norms in most areas.
By early evening the marine layer depth had decreased to about
1500 feet. This should mean somewhat less inland intrusion of low
clouds tonight compared to the past few nights. An upper trough
currently dropping southeast into the Pacific northwest is forecast to continue to
dig southeast and into the Great Basin by tomorrow evening. This trough
probably won't have much impact on our weather tonight...but by
tomorrow expect an increase in the depth of the marine layer along
with increased onshore flow by afternoon. This will likely result
in cooling in most areas tomorrow and an earlier inland push of
low clouds tomorrow evening. Temperatures will cool back below normal
The trough setting up over the Great Basin late tomorrow is
forecast to move east over the weekend. However...500 mb heights won't
increase over our area due to a continuation of weak shortwave
troughs dropping in from the northwest...maintaining cyclonic
flow aloft over California through the weekend. This will likely mean
continue slightly cooler than normal conditions right on through
the Sunday...especially for inland areas.
Warming should occur by the middle of next week as an upper ridge
builds over California. However...there remains uncertainty as to the
magnitude of that warming given that the models are having a
difficult time figuring out just how strong that ridge might be.
Aviation...as of 10:50 PM PDT Thursday...low clouds are filtering
back in through coastal gaps and canyons. Models have back off on
cloud cover over ksfo however do not think it will stay clear all
night. Still anticipating a late return over the sf Bay terminals.
Clearing is expected around 17z Friday morning across area
terminals. Light winds will persist through the night.
Moderate to high confidence.
Vicinity of ksfo...VFR conditions expected through late tonight...
possibly after 10z. Clearing anticipated around 17z Friday
morning. Moderate to high confidence.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...IFR ceilings expected through the night
with clearing anticipated around 17z Friday morning. Moderate to high
Marine...as of 10:33 PM PDT Thursday...light to moderate winds
will continue across the coastal waters through much of the
forecast period. Strongest winds expected over the northern outer
waters. A moderate period southerly swell generated by tropical
storms will move into the region and continue into early next
... Arena to pt Reyes 10-60 nm from 11 PM
Public forecast: dykema
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