Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
427 am PDT Monday Jul 25 2016
Synopsis...not much change in the weather today. However, a shift
in the wind will bring smoke to the Monterey area. A warm up
remains on track beginning Tuesday as high pressure strengthens
over the area, with cooling once again in the forecast this coming
weekend as a weak low pressure disturbance moves into the Pacific
Discussion...as of 3:12 am PDT Monday...currently the satellite
fog product is showing plenty of low clouds along the coast as
well as in the inland valleys. Also evident on the fog product is
the heat signature of the soberanes fire. The current satellite
water vapour image is showing an area of high pressure positioned
over the eastern Pacific and moisture rotating into and around the
Desert Southwest as The Four Corners high begins to set up.
The 0000z European model (ecmwf) and gfs20 have initialized well with the current
synoptic weather pattern and remain in good agreement through the
end of the week. Both models indicate a weak trough of low
pressure passing over the area today which has helped the marine
layer to deepen slightly this morning. Temperatures are expected
to warm up Tuesday, especially inland and over higher terrain, as
The Four Corners high builds and 850mb temperatures warm up. The
warmer temperatures look to stick around through at least Thursday
before cooling slightly for the weekend. Confidence on the weekend
cooling is on the low side since model agreement isn't the best
for the weekend.
In the near term, and local scale our high resolution WRF model is
showing that surface and 925mb (2500 foot elevation) winds become
southerly today along the Big Sur coast. Although winds are not
expected to be very strong the wind shift may be enough to push
the smoke north into the Monterey and Carmel area. Therefore have
expanded the smoke coverage in this morning's forecast package.
Fire weather...as of 3:15 am PDT Monday...a weak upper level
trough of low pressure has helped to deepen the marine layer
slightly to about 1500 feet. This has helped low elevation relative humidity
recoveries to improve greatly over those observed 24 hours ago.
Relative humidity recoveries at and above 2500 feet remain not
great. As mentioned in the main afd winds are expected to become
south southwesterly today along the Big Sur coast which may shift
the smoke plume towards the north.
Aviation...as of 4:21 am PDT Monday...widespread clouds along the
coast and locally inland with a marine layer depth near 1600 ft
this morning. The compressed marine layer has also led to some
patchy fog...mainly around Monterey Bay. Given the somewhat
shallow/thin marine layer burn off will be mid to late morning.
VFR this afternoon but IFR cigs return tonight. Overall conf is
medium to high.
Vicinity of ksfo...tricky forecast inside sf Bay as clouds pushed
through the Golden Gate and East Bay. Latest hi-res models show
some patchy cigs impacting sfo late this morning. Conf is marginal
so decided to include a tempo for some nearby cigs occasionally
moving over sfo. VFR this afternoon with gusty winds.
Sfo bridge approach...better chance of cigs around 1k feet.
Lingering cigs through 16-17z. VFR this afternoon.
Monterey Bay terminals...LIFR to IFR conditions through this
morning with mostly VFR this afternoon. Flow turns southerly later
today and smoke from the soberanes may impact mry and sns so fu
has been added to tafs.
Marine...as of 03:08 am PDT Monday...moderate to gusty northerly
winds will prevail over the coastal waters as high pressure
remains off the West Coast. The strong winds will be mainly over
the outer waters north of Pigeon Point. Winds will gradually
decrease Tuesday...but remain gusty north of Point Reyes.
... Arena to Pigeon pt 10-60 nm
Small Craft Advisory...pt Arena to pt Reyes 0-10 nm until 9 am
Small Craft Advisory...sf Bay
Public forecast: Larry
fire weather: Larry
Visit US at www.Weather.Gov/sanfrancisco
Follow US on facebook and twitter at: