Scientific Forecaster Discussion
fxus66 kmtr 162349
Area forecast discussion
National Weather Service San Francisco Bay area
449 PM PDT Wed Oct 16 2019
Synopsis...light rain will be possible across portions of the
region this evening into early Thursday morning as a weak cold
front sweeps through northern and central California. Cooler,
breezy conditions develop in wake of the frontal passage by
Thursday afternoon and will continue into Saturday. A warming and
drying trend is then forecast late in the weekend and into early
Discussion...as of 02:10 PM PDT Wednesday...only minor
adjustments were made to the forecast this afternoon. High clouds
ahead of an upper trough and cold front continue to spread through
the region. Temperatures so far today have been cooler under the
extensive cloud cover and a cooler air mass beginning to advect
into the region. The cold front will begin to move into the North
Bay this evening and push into the greater Bay area late in the
evening, continuing through the remainder of the forecast area
overnight. Showers will accompany the cold front but rainfall will
be scattered and light. The cold front will also weaken as it
moves through the forecast area, so the highest precipitation
totals will be across northern Sonoma County (up to 0.10) with a
hundredth or two elsewhere. Any rain which occurs create
temporary slick roads overnight, but otherwise impacts should be
minimal. Rainfall for most areas will end before sunrise Thursday,
with only a few isolated showers remaining in the hills of
Monterey County Thursday morning.
Cooler temperatures will continue through Thursday and winds will
increase behind the cold front. The strongest winds will be felt
along the coast and in the hills with gusts up to 25-35 mph with
isolated gusts to 40 mph. Valley locations can expect to see
gusts 15-25 mph Thursday afternoon. Winds will decrease after
sunset, but breezy winds will develop once again on Friday.
Temperatures will remain cool as northwesterly flow continues to
bring in cool air behind the departing trough. Coastal areas will
see highs in the 60s while inland areas only warm into the low
Another weak system will move through the region on Friday night
and Saturday. This will bring a chance of showers to the North Bay
on Saturday morning, with dry conditions elsewhere. Cool
temperatures will continue on Saturday.
A ridge of high pressure over the northern Pacific will then
begin to amplify on Sunday and shift towards the West Coast early
next week. A robust warming trend will develop as a result with
highs near the coast in the 70s to low 80s and inland temperatures
in the 80s early next week. Ensemble forecasts indicate this
pattern is likely to persist through much of the week as the ridge
remains centered just off of the West Coast. Periods of offshore
flow will likely develop next week, but the details remain
uncertain at this time.
Aviation...as of 4:45 PM PDT Tuesday...based on metars and
webcams low clouds have cleared out even from the coastal areas.
Models in general agreement bringing low level moisture back in at
around 06z so this is about the time lower cigs should return.
Some light rain within the low cigs getting as far south as the
sfo Bay area. Winds becoming southwest after 03z.
Vicinity of ksfo...MVFR cigs after 06z with bases around 1200-1500
feet. Light rain may accompany the low clouds. West winds 10-15
kt with a gradual turn to the southwest at around 10 kt after
Sfo bridge approach...similar to ksfo.
Monterey Bay terminals...low clouds have cleared from the mry Bay
area. Models Show Low level moisture returning by 05-06z which
should bring IFR cigs to mry and sns. Slight chance of showers
early in the morning.
Marine...as of 04:28 PM PDT Wednesday...light northwesterly winds
will persist over the coastal waters this afternoon. Winds will
then briefly turn southerly from north to south late this
afternoon and tonight as a weak cold front moves through the
waters bringing some light rain. Northwest winds will return and
gradually increase behind the front tomorrow. Expect locally
stronger winds along the Big Sur coast through much of the
weekend. A large northwest swell will arrive tomorrow and build
into Friday. These swells will create hazardous seas over the
waters tomorrow and Friday.
... Arena to pt Reyes 0-10 nm from 3 am
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm from 3 am
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm from 3 am
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm from 3 am
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Public forecast: St
aviation: west pi
Visit US at www.Weather.Gov/sanfrancisco