Gale Warning 101, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
330 AM PST Sat Nov 26 2016

.SYNOPSIS...Low pressure will continue to move northeastward over
Western Washington this morning...with rain and mountain snow
accompanying it as it does so. The low will weaken as it moves
allowing for precipitation to taper off to showers this afternoon
and evening. Generally dry conditions are expected tonight and
Sunday morning before a front will bring showers and possibly heavy
mountain snow Sunday night into early Monday. The active weather
pattern will then continue through much of next week.

&&

.SHORT TERM...A combination of radar and satellite imagery shows
that front is really not in any hurry to traverse the area. Surface
low visible on IR west of the southern OR coast is right about where
06Z models put it...which would put the surface low expected to
impact Western Washington just off to the west of the Olympic
peninsula. This low looks to weaken throughout the day...but given
the slow nature of the front and the upper level low that will swing
through the area behind it this afternoon...expecting wet conditions
this morning and this afternoon. Activity looks to start tapering
off from west to east mainly this evening before a weak ridge pushes
in for Sunday morning. An exception here looks to fall on Snohomish
county where there looks to be the makings of a convergence zone
late tonight. The break provided by this minor ridge will be
incredibly short...as next system starts to move into the area by
Sunday afternoon bringing rain and mountain snow once again. This
system does look to lower snow levels to right around 2500 feet or
so...which would allow for snowfall in the mountain passes. Current
model data suggests...however...that highest amounts are progged to
the south in PQR's CWA. As such...will not do anything in the way of
headlines for this system just yet but will advise day shift to
monitor. Main thrust of precip with this system will be
Sunday...although some showers may stick around into Monday
afternoon.

Speaking of headlines...inherited batch look good to continue...no
tweaks needed.  SMR

.LONG TERM...What follows must be conveyed in hushed tones...lest
the feature be frightened off or jinxed...but models do suggest an
upper level ridge over the area starting late Monday. The length of
its stay is up for dispute...as always...with the GFS being
optimistic and keeping things dry from Monday night through
Wednesday morning. Will not discuss the ECMWF until it embraces a
more positive attitude toward life. Like all good things though...an
upper level trough will bring an end to this dryness with more rain
by Wednesday afternoon before activity tapers off late Thursday
morning or early Thursday afternoon...with the possibility of
another prolonged break in precip starting Thursday night. SMR

&&

.AVIATION...An upper trough and surface low pressure system will
move through Western Washington this morning. The air is moist and
stable but will become somewhat unstable behind the system on
Saturday as the rain turns to scattered showers.

KSEA...Rain at times turning to scattered showers today as a trough
moves through. A southerly breeze will develop around daybreak as
pres gradients turn sly.

&&

.MARINE...There is one main area of falling pressure centered on the
north WA coast at 2am. For now small craft advisories are up for the
coastal waters and entrances to the strait as a low pressure area
develops and then moves through Western WA this morning. A front
will arrive Sunday afternoon or evening with gales possible.
Another front will arrive Tuesday night or Wednesday with gales
again possible.

&&

.HYDROLOGY...From previous discussion...The heavy rainfall that
occurred across southwest and west-central Washington Wednesday
through Thursday night produced flooding on the Skokomish River in
Mason County, Skookumchuck River in Thurston County and the Chehalis
River around Grand Mound. A flood watch continues for Lewis,
Thurston, and Grays Harbor counties. It is possible that the lower
reaches of the Chehalis could go above flood stage Saturday.

Models show another 12 hours of moderate to heavy rainfall
tonight into Saturday morning as a low pressure system moves
onshore on the central Washington coast and moves towards the
North Washington Cascades. The additional rainfall will have the
effect of slowing the recession of the rivers with the exception
of the Chehalis.

Elsewhere river flooding is not expected in the next 7 days.

Rainfall from recent events has left area soils saturated. USGS
soil wetness indices suggest landslides are possible in favored
locations. Rainfall tonight into Saturday morning will enhance
the landslide threat through Saturday. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through Saturday afternoon for Cascades of Pierce
     and Lewis Counties-Central Coast-Lower Chehalis Valley Area-
     Southwest Interior.

     Winter Weather Advisory until noon PST Saturday for Cascades of
     Pierce and Lewis Counties-Cascades of Snohomish and King
     Counties.

     Winter Storm Warning until noon PST Saturday for Cascades of
     Whatcom and Skagit Counties-Olympics.

PZ...Small craft advisories coastal waters...entrances to the Strait
     of Juan de Fuca...Grays Harbor Bar.

&&

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SEATTLE WA
744 AM PST SAT NOV 26 2016

WAZ001-503-504-506-507-509>517-555-556-558-559-567>569-271300-
SAN JUAN COUNTY-WESTERN WHATCOM COUNTY-SOUTHWEST INTERIOR-
WESTERN SKAGIT COUNTY-EVERETT AND VICINITY-TACOMA AREA-
ADMIRALTY INLET AREA-HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-
OLYMPICS-EASTERN STRAIT OF JUAN DE FUCA-
WESTERN STRAIT OF JUAN DE FUCA-NORTH COAST-CENTRAL COAST-
EAST PUGET SOUND LOWLANDS-BELLEVUE AND VICINITY-SEATTLE AND VICINITY-
BREMERTON AND VICINITY-CASCADES OF WHATCOM AND SKAGIT COUNTIES-
CASCADES OF SNOHOMISH AND KING COUNTIES-
CASCADES OF PIERCE AND LEWIS COUNTIES-
744 AM PST SAT NOV 26 2016

...HEAVY RAINFALL SINCE WEDNESDAY IS LEADING TO AN INCREASED
THREAT OF LANDSLIDES IN WESTERN WASHINGTON...

HEAVY RAINFALL...MOSTLY IN THE .50 TO 2 INCH RANGE HAS BEEN
OBSERVED ACROSS MUCH OF WESTERN WASHINGTON SINCE FRIDAY. THE
HEAVY RAINFALL ADDS TO ALREADY SATURATED SOIL FROM RAINFALL OVER
THE PAST SEVERAL WEEKS. THE RECENT RAINFALL HAS PUT EXTRA PRESSURE
ON SOIL INSTABILITY...LEADING TO AN INCREASED THREAT OF
LANDSLIDES.

FOR MORE INFORMATION ABOUT CURRENT CONDITIONS...VISIT
WWW.WEATHER.GOV/SEATTLE...SELECT HYDROLOGY...AND THEN SCROLL DOWN
FOR THE LINKS TO THE LANDSLIDE INFORMATION PAGES.

TO REPORT LANDSLIDES TO THE STATE FOR TABULATION...GO TO THE
WASHINGTON STATE LANDSLIDE RISK WEB PAGE AND THE LINK FOR
REPORTING.

WWW.WEATHER.GOV/SEATTLE
MERCER