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

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FXUS66 KMTR 252233
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
233 PM PST Sat Feb 25 2017

.SYNOPSIS...Two weather systems dropping southward down the West
Coast will result in chances for showers across portions of the
region today through early Monday. However, widespread rainfall is
not expected with either system. Dry weather conditions are
favored from Tuesday through the remainder of the upcoming
workweek as high pressure builds over the region. Along with the
dry weather, temperatures will be on a gradual warming trend
through late week.

&&

.DISCUSSION...as of 12:46 PM PST Saturday...Mix of high and low
level clouds across the region as a mid/upper level low continues
to rotate offshore, west of the northern California coast. At
this time, just about all precipitation associated with this
system remains offshore with dry conditions inland. The latest
forecast models continue to indicate development of showers inland
late this afternoon across portions of the region as the
mid/upper level system begins to take a southeastward jog toward
the coast. Do expect to see an increase in showers later this
afternoon and evening as some deeper moisture gets advected inland
on the southern end of the system toward the Central Coast. While
widespread, heavy rainfall is not forecast with this system, do
expect a quick 0.10"-0.25" of precipitation within heavier showers
that move across any given area. Precipitation chances then
diminish late in the night into early Sunday morning as the
mid/upper level system shifts inland across southern California.
With snow levels forecast to range between 3,000 and 3,500 feet,
do expect some snow accumulations along the higher peaks of the
Big Sur coast late today into tonight.

Another round of showers will be possible by late Sunday morning
(North Bay) into Sunday night as another mid/upper level short-
wave drops southward across the region. This system too is not
forecast to result in widespread rainfall, yet many areas can
expect a few passing showers as the system moves across the
region. Each of the aforementioned systems will advect a renewed
cooler air mass across the region and result in continued cool day
time temperatures with chilly overnight/morning temperatures as
many inland areas drop into the 30s. Cannot rule out a few
lingering showers into Monday as the trough axis remains stretched
along much of the West Coast.

Building high pressure is then forecast over the eastern Pacific
from Tuesday through much of the remainder of the week. This will
result in dry weather conditions region-wide with a gradual
warming trend, especially for daytime temperatures. By the latter
half of the week, do expect widespread 60s to return to the region
with some of the warmer inland portions of the Central Coast
seeing maximum temperatures in the lower 70s. Generally clear
skies will allow for cool overnight conditions to persist as well.

The forecast model do differ slightly late in the forecast period
with a least a break down of the dominate ridge aloft. The GFS
keeps a weak ridge in place however and maintains dry weather
conditions into next week while the ECMWF has shown signs of a
more westerly flow and potential for at least light precipitation.
However, there is no strong signal at this point for a major
shift in the dry weather pattern. Will continue to monitor in the
coming days.

&&

.AVIATION...As of 9:55 AM PST Saturday...For 18z Tafs. Light
showers this morning have dissipated, but more showers are
possible this afternoon through tonight as an offshore disturbance
moves down the coast. Overall, today is expected to be a VFR day
with cigs coming down slightly as the disturbance passes late in
the day and overnight. If showers develop a stronger than
forecast, the forecast will need to be adjusted to reflect a more
robust cloud layer in the lower levels. VFR is expected to return
overnight into Sunday. STS may encounter some dense morning fog
due to residual moisture and radiational cooling. Moderate
confidence forecast.

Vicinity of KSFO...VFR through much of the day. A passing
disturbance may drop cigs for a short time in isolated showers,
but conditions will return to VFR once passed. Timing for any
shower would be between 23Z and about 2-4Z. Moderate confidence
forecast due to uncertainty in development of showers over SFO.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR today. Showers are looking like a
likely bet at MRY this evening and tonight as a disturbance slides
southward along the coast. SNS is expected to be on the periphery
of the shower band, making for a tough precip forecast. Behind the
showers, conditions will revert to VFR. Winds will generally be
light to moderate today. Moderate confidence forecast for SNS due
to showers potential. High confidence forecast for MRY due to
proximity to the coast and the passing disturbance.

&&

.MARINE...as of 02:23 PM PST Saturday...Low pressure sliding down
the california coast today will bring moderate to fresh southerly
winds for the outer waters with resultant seas. this will exit
quickly tonight. another system will clip the area sunday night
with moderate to fresh northerly conditions. monday onward
conditions look to remain moderate to fresh with possible near
gale conditions by late in the week. no significant swell trains
are expected through the week.

&&

.BEACHES...A Beach Hazard Statement was issued for the threat of
Sneaker Waves on Sunday. A long period swell arriving Sunday
morning, along with fair weather and light morning winds, will
bring a moderate risk of Sneaker Waves to North Bay and Bay Area
coastal beaches. Arrival of the long period swell will coincide
with a rapidly rising tide on Sunday morning, pushing more energy
up the beach. West and Northwest facing and steep sloped beaches
will be at greatest risk. The threat is expected to abate in the
afternoon as the tide drops, onshore winds develop, and long
period waves transition to shorter periods. BFG

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm until 9 PM

&&

$$

PUBLIC FORECAST: RGass
AVIATION: BFG
MARINE: BFG


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