Scientific Forecaster Discussion
fxus66 kmtr 251741
Area forecast discussion
National Weather Service San Francisco Bay area
1041 am PDT Tue Jul 25 2017
Synopsis...look for similar conditions today compared to
yesterday. Temperatures will begin to warm later in the week as a
ridge of high pressure rebuilds into our region.
Discussion...as of 08:43 am PDT Tuesday...the marine layer
continued to deepen over the past 24 hours and is now around 2500
feet based off of The Fort Ord profiler. This resulted in
widespread low clouds along the coast and locally inland into the
Sonoma Valley, Salinas valley and into the San Francisco Bay area.
With that said, the city of San Francisco and far inland East Bay
locations as well as the Napa Valley remain under mostly clear
skies at this hour. Given the depth of the marine layer, the cloud
deck generally remains above 1000 feet with no reports of fog or
coastal drizzle/mist. Thus, have removed mention of fog and
drizzle from the forecast. Lastly, temperatures this morning did
not cool as much as previously forecast (2-4 degrees warmer)
likely as a result of the solid cloud deck impacting the region.
Look for afternoon temperatures today to be similar to those
yesterday with low clouds retreating to the coast through the
Previous discussion...as of 3:00 am PDT Tuesday...overnight the marine
layer has continued to deepen and is now over 2,500 feet. With a
weak onshore flow at the surface clouds should continue to
increase into the morning hours. Similar to yesterday, clouds will
burn-off back to the coast by the afternoon with highs in the
upper 70s to the upper 80s for most inland spots while 60s will
again be common at coastal spots.
Starting tomorrow the upper level low centered overhead will begin
to dissipate and progress off to the northeast as a ridge of high
pressure rebuilds into our region. This will lead to temperatures
warming into the weekend. Although the increases will vary from
location to location, by Thursday places away from the coast will
mostly be 7 to 12 degrees warmer than today while coastal areas
will see only minor temperature increases.
Longer range guidance indicates that the ridge will remain in
place and likely strengthen going into next week. Previous runs
had indicated 500 mb heights possibly at 600 dm, however newer
guidance has backed off a bit. Regardless, looks like very warm
weather can be expected later this week through at least the
middle of next week. No chance of rain or showers through the
Aviation...as of 10:40 am PDT Tuesday...for 18z tafs. Currently
VFR with the last of the stratus retreating out to Monterey Bay.
VFR conditions should prevail this afternoon before clouds return
Vicinity of ksfo...VFR. VFR will prevail this afternoon before
cigs begin to return late tonight. Conditions for tomorrow looking
similar to what we saw this morning.
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...expecting VFR conditions at kmry shortly
as the stratus retreats out to the coast. VFR should remain this
afternoon before the stratus returns tonight.
Marine...as of 08:43 am PDT Tuesday...expect a southerly flow
today along the immediate coast due to a weak area of low pressure
off the California coast. West and northwesterly winds will
return tomorrow as high pressure builds over the eastern Pacific.
Several tropical disturbances will bring a longer period southerly
swell to the region later this week as they continue to move
westward from Mexico.
... Bay from 12 PM
Public forecast: rgass/Bell
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