Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
FXUS66 KMTR 250555
Area Forecast Discussion
National Weather Service San Francisco Bay Area
1055 PM PDT Fri Mar 24 2017
.SYNOPSIS...Showers can be expected through this evening behind a
departing cold front, mainly from Monterey Bay southward. A break
in the rain is expected from Saturday through early Sunday. Rain
chances will return by Sunday afternoon and continue through
Sunday night. A few showers may linger into Monday morning.
Otherwise, dry and mild weather is expected from Monday through
the remainder of next week.
.DISCUSSION...As of 9:05 PM PDT Friday...Today`s cold front
generated respectable rainfall totals across the North Bay, down
the San Francisco Peninsula, across the Santa Cruz Mountains, and
locally into the East Bay. Elsewhere, rainfall amounts were rather
meager. By late afternoon the front had moved through most of our
forecast area and rainfall was quickly ending form northwest to
southeast. However, a wave that developed along the front offshore
this afternoon has since generated renewed light rainfall from
Monterey Bay southward. The 00Z NAM appears to have picked up on
this and is forecasting areas of light rain lingering across the
southern half of our forecast area through much of tonight. Rain
chances tonight have been updated to reflect these developments.
The forecast was also updated to add patchy fog overnight and into
Saturday morning as it appears the low levels will be moist and
relatively stable overnight.
A few showers may linger over the southern portion of our forecast
area into Saturday morning. Otherwise expect dry conditions on
Saturday along with gradual clearing and afternoon highs mostly
in the lower 60s.
Dry weather will persist into early Sunday. A relatively weak
weather system is then projected to sweep in from the west-
northwest and bring light rainfall to much of our forecast area
later on Sunday and through Sunday night. The NAM is somewhat
faster compared to the GFS And ECMWF in developing rain in the
North Bay by late Sunday morning, but the models generally agree
that the bulk of the rain with this system will occur during the
afternoon and evening hours of Sunday, and that the greatest rain
totals will occur in the North Bay. In any case, the Sunday system
is not expected to generate more than a half inch of rain, and
most locations south of the Golden Gate will likely pick up a
quarter of an inch or less. Winds are not expected to be a
significant factor with the Sunday system with forecast wind
gusts of perhaps 25 mph along the immediate coast during the late
afternoon and early evening hours.
A few showers may linger into Monday morning, but for the most
part Monday should be a dry day as an upper ridge begins to build
near the California coast. That ridge is then expected to be the
dominant weather feature through most of next week and into the
following weekend, likely producing several days of dry and mild
weather conditions. A weak system approaching the northern
California coast by Wednesday night may bring a temporary slight
chance of precipitation, but as of now those chances appear slim.
.AVIATION...As of 10:55 PM PDT Friday...Residual scattered showers
persist tonight especially over the north Central Coast. Local
IFR/LIFR/VLIFR tonight and Saturday morning as the surface to
lower levels remain quite moist. Drying in the mid-upper levels
tonight and Saturday support fog development especially if and
where lower clouds happen to partially clear.
A secondary slow moving and dry cool front slides SE across the Bay
Area Saturday evening. Preceding this front it`s a low confidence
cloud cover forecast though due to a lack of near surface inversions
if there is cloud cover best guess would be that primarily MVFR/VFR
will prevail. Post frontal drier air intrusion should help keep VFR
going Saturday night and Sunday morning.
Vicinity of KSFO...MVFR/VFR. Wind light onshore tonight. 15-20 knots
onshore winds developing Saturday from 21z to 04z Sunday.
SFO Bridge Approach...Same as KSFO.
Monterey Bay Terminals...Light southeast to south winds with showers
continuing most of tonight. MVFR/VFR except local IFR tonight.
.MARINE...as of 10:37 PM PDT Friday...Expect light northwest winds
tonight in the wake of a cool frontal boundary. Southerly winds are
forecast to return Sunday as the next system approaches. Fresh short
period swells will make for choppy conditions over the coastal waters
through the weekend.
PUBLIC FORECAST: Dykema
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