Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1103 am PDT Wednesday Aug 27 2014
Synopsis...aside from a bit of additional warming inland...not
a great deal of change is expected in our weather conditions
through the end of the week as an upper level ridge of high
pressure remains parked over California. Thus...seasonally
typical weather conditions are expected to prevail through the
end of the forecast period.
Discussion...as of 08:44 am PDT Wednesday...made a few minor
changes to the short-term forecast this morning to reflect
current trends...mainly hourly temperatures and sky cover based
off the latest satellite imagery. Looking a bit ahead...no major
changes anticipated for the afternoon package with ridge of high
pressure dominating the weather pattern along the West Coast this
Previous discussion...as of 3:30 am PDT Wednesday...clear skies
continue to prevail across most of the district...aside from some
areas of stratus north of the Golden Gate along the coast and
locally into the coastal valleys. Temperatures are on the mild
side around the bays for this time of day...generally ranging from
the middle 50s to the lower 60s. This reflects continuation of the
unusually warm sea surface temperatures of our coastal
waters...presently 63 degree at both the Bodega Bay and San Francisco
buoys...and 65 degree at the ones offshore from Half Moon Bay and
Monterey Bay...or about 8 degree above climatological norms.
Consistent with latest satellite imagery and model output...have
backed off significantly on stratus coverage this morning...now
expecting no more than some patches near the coast at least from
about the Golden Gate southward. Consistent with this...latest
profiler data from Bodega Bay and Fort Ord show significant recent
shallowing of the marine layer...with its depth now down to around
In the shorter term...persistence of the upper level ridge of
high pressure in conjunction with the reduction in the marine
layer and a continuing modest upward trend in model-output 850 mb
temperatures is expected to result in some additional warming of
afternoon temperatures today and Thursday...especially away from the
coast and bays. And then little change as we head into Friday. Do
expect the marine stratus to redevelop tonight...and similarly
Thursday and Friday nights...but to only extend locally inland
around the bays.
Then Friday night and Saturday...the tail end of an upper level
trough moving into the Pacific northwest will approach our
district. Although details in this regard vary widely...basic
model consensus is that it will pick up some high level moisture
from the then well offshore remnants of Hurricane Marie and carry
it through our district. However...pretty high confidence that
this will result in no more impact for US than some middle and high
level cloudiness as the weekend starts.
Otherwise...not much change from our present weather conditions
is expected through the extended forecast period...aside from
some modulations in the marine layer and coastal stratus.
Temperatures through the weekend and into the first part of next
week look to continue near to a bit above seasonal norms.
Aviation...as of 11:00 am PDT Wednesday...outside of a patch of
clouds over coastal Sonoma VFR for the rest of the day (including at
the terminals). Decided to bring back MVFR late tonight for most
spots based off the WRF which initialized well. Winds should be
fairly light (generally under 12 kt) be a non-issue today. High
confidence through 00z.
Vicinity of ksfo...VFR today. Onshore winds to around 15 knots. MVFR
ceilings possible late so added a tempo for 11z to 15z. High confidence
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...VFR through this afternoon. MVFR
with stratus likely late evening after 06z. High confidence
Marine...as of 08:44 am PDT Wednesday...southerly swell from
Hurricane Marie will gradually subside through the end of the
week. Mostly light northwest winds will continue over the coastal
waters through Thursday. Winds increase Friday into the weekend.
Southwest swell moves into the waters over the weekend with lower
Public forecast: rgass
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