NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 151204

Area Forecast Discussion
National Weather Service San Francisco Bay Area
504 AM PDT Wed Aug 15 2018

.SYNOPSIS...Temperatures will remain near to slightly below
seasonal averages today with widespread night/morning low clouds.
High pressure will build toward the West Coast by late week and
result in a gradual warming trend, especially over the interior.

&& of 3:59 AM PDT Wednesday...The marine layer is
nearly 2,000 feet deep this morning, areal coverage of low clouds
is nearly the same as it was over the Bay Area early yesterday
morning. From the Santa Cruz Mountains southward along the north
Central Coast however, low cloud coverage is much more sparse with
patchy clouds having developed mainly over the coastal terrain
based on recent GOES-16 night-time microphysics satellite imagery.
The 00z Aug 15th WRF boundary layer humidity forecasts did not
catch this stationary interruption of low clouds to immediate
drying over the waters; air temperatures are a little milder than
SSTs at the buoys located here thus this may be one reason why low
cloud (or fog) generation is not quite as ideal unless until it
becomes replaced by somewhat cooler air. There`s no appreciable
interruption of near surface based water vapor to the northwest
per WRF/NAM model output. With night-time cooling it`s remarkable
that neither Monterey nor Watsonville for example have low clouds
while it has been cloudy as far inland as Livermore since 9:30 pm
last evening.

Today`s temperatures, like yesterday, should once again run at
or a few degrees cooler than mid August normals coast to inland.
The low clouds may again hang on longer along the San Francisco
Bay shoreline today. With an increase in the depth of the marine
layer fog coverage is much less prevalent as compared to low cloud
coverage this morning.

High pressure redevelops over California later this week and into
the weekend, a warming and drying trend is forecast to return over
the weekend.

&& of 5:00 AM PDT Wednesday...Stratus covers the SFO
Bay Area but microclimates have kept stratus patchy in the MRY
Bay Area. MRY has been VFR most of the night. Expecting stratus to
fill in the MRY Bay Area this morning with clearing late morning.
Deep marine layer around 2000 feet will result in another late
burnoff for SFO and the approach. Latest forecast keeps MVFR cigs
at SFO through 20Z.

Latest HRRR vertically integrated smoke model suggests onshore
flow will blow most of the smoke out of the district today with
some smoke returning tonight.

Vicinity of KSFO...MVFR cigs through 20Z. Low confidence. West
winds gusting to 25 kt after 22Z.

SFO Bridge Approach...MVFR cigs through 21Z.

Monterey Bay Terminals...Stratus has been forming and then
dissipating repeatedly around the Monterey Bay area. This makes
for a low confidence forecast. Stratus expected to fill in towards
dawn with IFR cigs through 17-18Z but then again a few holes in
the clouds could keep MRY or SNS VFR.

&& of 04:48 AM PDT Wednesday...A 1026 mb high centered
1000 miles west of Cape Blanco will shift slightly east through
Thursday. Winds will remain light to moderate except for locally
gusty winds over outer Monterey Bay and along the Big Sur Coast. A
long=period southerly swell will  arrive along the coast this


     .Tday...SCA...Mry Bay from 3 PM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...SF Bay from 2 PM




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NWS MTR Office Area Forecast Discussion