NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 222151

Area Forecast Discussion
National Weather Service San Francisco Bay Area
151 PM PST Fri Feb 22 2019

.SYNOPSIS...Dry and seasonably cool conditions will prevail across
the region through Saturday. Although the next system may bring
some light rain to the region late Saturday or Sunday across the
North Bay, do not expect the heavier rain to shift south of the
Golden Gate before late Monday or Tuesday and across the rest of
the area before late Tuesday into Wednesday. Gradual warming
trend will develop as well.


.DISCUSSION...As of 1:50 PM PST Friday...Water vapor imagery
continues to show the upper level trough of low pressure over the
Desert Southwest pushing eastward as another trough continues to
dig south across the Pacific Northwest. As a result, a transitory
ridge is building over the region, and will remain in place
through Saturday, with some minor warming possible.

The primary concern and challenge for this forecast will be with
the next system, as the models seem to be trending slower and
farther north. At this point in time, the models are showing it
slowing digging south over the next 24 to 36 hours, but then
stalling. If this occurs, the moisture plume looks like it will be
focused somewhere between the Southern Oregon Coast and the
Mendocino Coast, with the heaviest rain staying north of our area
these days. Sonoma and Napa counties should be on the southern
fringe, and may see some light rain starting late Saturday, but
more likely some time Sunday or Sunday night. It really isn`t
until Monday afternoon or evening though that the stalled front
starts to shift southward. Even then, it still appears that the
North Bay will be the primary focus of the rain, with little if
any making it as far south as the San Mateo or Santa Cruz
coastline before Tuesday afternoon.

Therefore, think if these current trends hold, any rain that falls
this weekend across the North Bay will be light and beneficial,
with amounts mainly less than a quarter inch. However, once the
heavier rain develops between Monday and Tuesday, believe 2 to 4
inches of rain may be possible across the North Bay, with local
amounts upwards of 6 inches possible. Southern areas will be lucky
to see up to a half inch of rain, with areas in between in the 1
to 2 inch range.

The models show a break in the rain between Thursday and Friday as
another transitory ridge builds over the region. However, models
are hinting at another potentially potent rain producer for next
weekend.  Palmer


.AVIATION...As of 10:05 AM PST Friday...for 18Z TAFS...VFR
conditions through the period with light to moderate winds. A few
cu build up clouds are possible this afternoon, but impacts will
be minimal. High level clouds increase on Saturday.

Vicinity of KSFO...VFR.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR.

&& of 8:25 AM PST Friday...Breezy northerly winds will
persist through early this morning before diminishing. Moderate
northwest swell will continue into next week. Southerly winds will
develop later this weekend and into early next weekend.


     .Tngt...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM




Visit us at

Follow us on Facebook, Twitter, and YouTube at:

NWS MTR Office Area Forecast Discussion