Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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FXUS66 KMTR 231717
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1017 AM PDT Mon Oct 23 2017

.SYNOPSIS...Rapid warming trend will occur today with record or
near record highs this afternoon and then again Tuesday afternoon.
Long October nights will allow for sufficient night time cooling
to avoid any heat headlines. Offshore flow may weaken slightly by
midweek but temperatures look to remain above normal through the
end of the week and perhaps even into the weekend. Long range
models keep dry weather in place through Halloween.

&&

.DISCUSSION...as of 08:54 AM PDT Monday...Locally strong and
gusty winds persist in the peaks around the Bay Area this morning
where Mt. Diablo reported a gust of 70 MPH. However, these strong
winds appear to be localized and confined to the highest
elevations across the region. Meanwhile, winds near the surface
and in urban areas are generally light and variable this morning
with temperatures ranging from the upper 40s to upper 60s. Given
the developing offshore flow, temperatures are running a few to as
much as 23 degrees warmer (at Livermore Airport) compared to 24
hours ago. With this said, the forecast remains on track for
temperatures to warm to around 15-20 deg F above seasonal averages
this afternoon and again on Tuesday. The ongoing forecast remains
on track this morning and no major updates are needed at this
time. Please see previous forecast discussion below for additional
details.

&&

.PREV DISCUSSION...as of 2:50 AM PDT Monday...Skies are completely
clear across the Bay Area early this morning as offshore flow gets
firmly established. Northerly gradient down the coast is now 6 mb
with 8 mb offshore from the Nevada deserts towards the coast.
This has kicked up some winds in the hills with Mt Diablo gusting
to around 59 mph out of the north. The 00z Oakland sounding last
night showed the subsidence inversion around 3000 feet and it
appears that the strongest winds are staying at this level or
higher. The Rose Peak RAWS just above 3000 feet gusted to 43 mph
last hour. The Hawkeye RAWS, which we often monitor closely during
offshore/fire weather events has had temperatures warm into the
mid 70s with humidity down to 35% so far tonight as dry northeast
winds start to kick into place. So the stage is set for a sunny
and warm late Oct day. Record highs for today are generally in the
upper 80s to mid 90s so a few records may fall today into
Tuesday. Right now Tuesday looks like it may be the hottest day
but offshore winds may be slightly weaker, reducing adiabatic
compression, however an overall warmer airmass may negate that
impact. Either way expect sunny and warm to hot afternoons the
next few days. As always we are concerned about our more heat
sensitive populations such as the elderly, young and homeless
populations. The long October nights and dry airmass will allow
for sufficient overnight cooling with lows generally in the 50s
for populated areas. Hilly locations where the winds wont subside
will stay closer to 70 at night.

Any midweek cooling looks minor as dry east winds stay in place.
We may not have to worry about record highs Weds-Thursday but
there should still be plenty of highs in the 80s.

Latest long range ecmwf brings some stronger onshore flow by late
next weekend or early next week but temps should still be on the
warm side of normal with no rain in the forecast through the end
of the month.

&&

.AVIATION...as of 10:17 AM PDT Monday for 18Z TAFs...VFR
conditions are expected to prevail at TAF sites through the
forecast period. Winds are forecast to remain fairly light at most
sites. Forecast confidence is high.

Vicinity of KSFO...VFR conditions expected to prevail. Generally
light winds expected with speeds up to around 10 kt this
afternoon.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR conditions expected to prevail.
Locally breezy southeast winds will continue for another few
hours in the parts of the Salinas Valley, and will decrease in
the afternoon.

&&

.FIRE WEATHER...as of 2:50 AM PDT Monday...Light to moderate
offshore wind event seems to be unfolding about as expected.
Humidity values staying moist through 3 am with just a few of the
north bay hill sites showing signs of drying. More rapid drying
will occur through the afternoon with poor humidity recovery
forecast tonight. The strongest winds are currently remaining over
the highest hills and not see much evidence or trend for mixing
those down early this morning. None the less we still have warm,
dry and breezy conditions on tap today. Probability of new
ignitions will remain high the next few afternoons with near
record warmth and drying of the fine fuels. At this time just plan
to run generic headlines in the fire weather forecast to raise
awareness without issuing any specific watches or warnings.

&&

.MARINE...as of 08:54 AM PDT Monday...Northwest winds will
continue to gradually diminish through the day. Additionally, the
northwest swell will decrease through the middle of the week, but
then increase again late week as another long-period swell
arrives.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm

&&

$$

PUBLIC FORECAST: RGass/RWW
AVIATION: Rowe
MARINE: Rowe
FIRE WEATHER: RWW

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