Scientific Forecaster Discussion
fxus66 kmtr 182342
Area forecast discussion
National Weather Service San Francisco Bay area
442 PM PDT Fri Aug 18 2017
Synopsis...look for one more day of minor warming this afternoon
as a ridge of high pressure continues to build into our region.
Minor cooling can be expected over the weekend into next week as
an upper level low and shortwave trough move into our region.
Overnight clouds can be expected especially along the coast.
Discussion...as of 1:47 PM PDT Friday...this morning's low
clouds were quick to clear for most locations as we transition to
a mostly clear afternoon. A few areas along the Monterey Bay
shoreline and coastal areas from San Francisco northward still
have some lingering clouds. Synoptically-speaking, there is an
upper level ridge centered near 38n 135w that has gradually
strengthened over the past 24 hours. This strengthening is
expected to correspond with several degrees of warming at the
surface for inland areas. When all is set and done this Friday
afternoon, expect highs to reach the 60s and 70s along the coast
and 80s and 90s for the interior. This equates to temperatures
near middle August climatological normals along the coast, and
about 2 to 7 degrees above normal for the interior. Can't rule out
the chance that a few areas near Pinnacles National Park surpass
the century mark.
Over the weekend an upper level low will develop just off the
coast of Point Conception. This will allow for heights and
thickness values over central and northern California to
decrease. We'll see afternoon temperatures across the interior
trend downward several degrees per day through the weekend.
The main thought on many minds as we head into next week is the
cloud cover for Monday morning's solar eclipse. If conditions
permit, the partial solar eclipse can be viewed throughout
California. Right now, models are all in good agreement that the
upper level low will remain parked near Point Conception in
Southern California. For US along the central coast and north to
the San Francisco Bay area, this yields a few outcomes. For one,
the low can help mix out the marine layer, resulting in mostly
clear conditions. On the other hand, the upper low could help to
enhance the marine layer depth. We'll know a little bit more over
the weekend and will continue to monitor the marine layer's
response to the trough. Climatologically, the best locations in
the Bay area for clear skies on a mid/late August morning would be
interior areas of the East Bay away from the coast, as well as the
higher elevations in the Santa Cruz Mountains, North Bay
mountains, and Diablo Range. The eclipse of the sun will begin
shortly after 9:00 am PDT for the Bay area with peak obscuration
happening around 10:15 am PDT. Peak obscuration of the sun will
range from 71 percent in Monterey and up to 78 percent in Santa
Aviation...as of 4:45 PM PDT Friday...clouds are hugging most of the
coastline and with a nearly 3 mb west-to-east surface gradient
component, only a matter of time before it moves back to most
terminals. Guidance is running with a range of solutions however
generally went with middle of the Road start times that would
still be earlier than this morning. Cigs forecast to be in the IFR
to low-end MVFR categories. Moderate confidence.
Vicinity of ksfo...VFR with winds up to 20 knots currently. Look for
cigs in the IFR/MVFR category to return around 09z although
possibly earlier than that. Winds will diminish after 04z.
Sfo bridge approach...similar to ksfo although scattered deck could
impact approach as early as 07z.
Monterey Bay terminals...cigs down to 005 forecast to return
around 0#z at kmry and later at ksns. Will stay IFR all night with
a return to VFR around 17-18z. Moderate confidence.
Marine...as of 01:30 PM PDT Friday...expect increasing
northwesterly winds to continue through the weekend as high
pressure builds over the eastern Pacific. Locally steep wind waves
will also accompany the increasing winds.
... Arena to Pigeon pt 10-60 nm
Public forecast: Rowe
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