Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 302340
Area Forecast Discussion
National Weather Service San Francisco Bay Area
440 PM PDT Sun Apr 30 2017
.SYNOPSIS...Warmer weather is forecast from Monday through
Wednesday as offshore flow develops and high pressure strengthens
over California. Widespread 80s are expected by Tuesday and
Wednesday, with some lower to mid 90s in the warmest inland areas.
A cooling trend is then forecast Thursday and Friday as the upper
ridge over California is replaced by a trough. Rain showers are
possible next weekend when an upper low approaches our region.
.DISCUSSION...As of 2:00 PM PDT Sunday...Sunny skies with
most temperatures running close to values from yesterday. A bit
of a surprise that some areas are actually a touch cooler compared
to Saturday. Was interesting to watch 5 minutes GOES16 data today
which picked up on a small pocket of clouds rotating and then
dissipating over Monterey Bay.
Synoptically a ridge of high pressure will build into our region
over the next several days while offshore flow at the surface
remains in place. In addition, 925 MB temperatures that are
generally 17 to 20C right now will increase to 21 to 24C by the
middle of the week. This will lead to warmer conditions with
widespread upper 80s to lower 90s for both Tuesday and Wednesday.
Near the coast the offshore flow should be strong enough to
minimize the impact of sea breezes. Highs will most be in the 70s
with a few lower 80s possible. Outside of a few pockets over the
East Bay Hills plus near Los Altos, health impacts are expected to
The moderate pressure gradient will lead to locally breezy
conditions for the overnight hours the next two nights, in
particular late tonight in Monday as 925 MB speeds are expected to
possibly top 40 KT for a brief period going from the East Bay
Hills to the Santa Cruz Mountains. Due to the very short duration,
a wind advisory was not issued. Urban spots will mostly see
speeds under 15 MPH.
The ridge will head off to the east as a longwave trough near the
coast starting Thursday night. An associated low will dive down
to either near our coast (ECMWF) by the weekend or into southern
Nevada (GFS both operational and ensemble mean). For now kept the
low end PoPs going in the forecast from the previous shift. Either
solution will bring cooler conditions and drop most spots back
into the 60s.
.AVIATION...As of 4:40 PM PDT Sunday for 00z TAFs. VFR conditions
expected to prevail at all terminals with the exception for
Monterey Bay terminals which may be impacted by stratus early
Monday. Breezy west to northwest winds will subside within a few
hours after sunset, and increase again by Monday afternoon.
Vicinity of KSFO...VFR. West to northwest winds at 15 to 25 kt
this afternoon and early evening will continue for another few
hours through sunset and then begin to subside. Might see a few
low clouds early Monday, but at this time not thinking any
impactful stratus for the terminal. Breezy west to northwest winds
will return by Monday afternoon.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR conditions through the evening hours.
Another chance for low clouds on Monday morning for both KMRY and
KSNS, bringing ceilings to MVFR/IFR levels. Expect VRF conditions
to return by midday with onshore winds 10 to 15 kt.
.MARINE...as of 04:38 PM PDT Sunday...High pressure will continue
to generate strong northwest winds across the coastal waters
through most of the forecast period. Winds may subside slightly
by Thursday. In addition...the strong winds will also continue to
cause very rough seas due to fresh swells with short periods.
.Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
PUBLIC FORECAST: Bell
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, twitter, and youtube at: