Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 261144
Area Forecast Discussion
National Weather Service San Francisco Bay Area
444 AM PDT Wed Apr 26 2017
.SYNOPSIS...A weak system passes inland to the north dragging a cool
front southeastward through the Bay Area today. This will result
in light rain mainly from the Santa Cruz Mountains northward. A
warming and drying trend will then get underway beginning Thursday
and likely continuing into the upcoming weekend as high pressure
builds over the eastern Pacific. Breezy northerly winds are also
possible from Thursday into Friday, especially in the hills.
.DISCUSSION...as of 3:05 AM PDT Wednesday...A weak system will
pass through our region today which will trigger a few showers
especially over the northern half of our CWA. So far radar returns
have been next-to-nothing although those should pick up later this
morning especially in the North Bay. Last few runs of the HRRR
plus 06Z of the NAM have backed off on rainfall and have greatly
reduced rainfall from San Francisco southward. Still looks like we
could see similar amounts to what we saw yesterday with up to a
tenth for Napa/Sonoma/Marin counties with generally just a few
hundredths or less elsewhere. Highs will be mostly in the 60s
expects some lower 70s over parts of Monterey and San Benito
The synoptic pattern will undergo a substantial change starting on
Thursday as a ride of high pressure begins to build into the
Pacific. At the same time an upper level low will begin to drop
southward from Canada. This will lead to a much tighter pressure
gradient aloft while at the surface a ridge of high pressure will
start to build into our region. The combination of both factors
will help to produce gusty northerly winds especially over higher
elevation locations plus near the coast. 925 MB speeds off the
NAM have backed off compared to previous runs and now just have
speeds to 30 KT, so will not be issuing a wind advisory with this
package. Breezy conditions will continue into Friday.
The ridge off the coast will build into our region starting over
the weekend which will help to push inland highs into the mid 70s
to the mid 80s. At the coast enough of a coastal flow should be in
place to keep local beaches in the 60s.
Longer range guidance continues to indicate the ridge being the
dominate feature with the storm track well to our north.
Temperatures next week should average warmer than normal.
.AVIATION...as of 04:45 AM PDT Thursday...Widespread MVFR
expected through the day under moist northwest flow aloft. CIGS
may descend to IFR level through the early morning and then again
tonight as upstream moisture continues to advect inland. CIGS
should lift by a few to several hundred feet by midday through
the late afternoon. Thickest low level cloud decks will be in the
South Bay area, similar to yesterday, where advected moisture
pools under the NW flow. Winds will generally be light to breezy
today, with some occasional gusts in the 20-25kt range possible.
In addition, very light rain will accompany an air mass boundary
over the northern TAF sites this morning.
Vicinity of KSFO...MVFR cigs will prevail most of the day. West
winds generally 10-20kt with gusts up to 25kt possible. A passing
shower or two possible mid to late morning.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Becoming MVFR early this morning, then
borderline IFR/MVFR today. Light onshore winds, gusting to
15-20kt by this afternoon. IFR cigs tonight.
.MARINE...as of 04:35 AM PDT Wednesday...Predominately light to
moderate northwest winds today with stronger winds locally along
the Big Sur coast. Northwest winds increase tonight across the
coastal waters as high pressure builds offshore. Strong winds and
steep fresh swell will then persist through the remainder of the
.Tday...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...SF Bay from 3 PM
PUBLIC FORECAST: Bell
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, twitter, and youtube at: