Small Craft Advisory 300, NWS Seattle, WA

Area Forecast Discussion...CORRECTED
National Weather Service Seattle WA
534 AM PST Mon Dec 19 2016

Corrected to include another key message.

.SYNOPSIS...A cold front will sweep across the area this morning
for locally heavy precipitation and gusty winds. Expect scattered
showers behind the front. Alas, another Pacific storm will bring
more rain and mountain snow to the area tonight along with
locally windy conditions. Look for showery conditions behind the
front on Tuesday. Generally dry conditions will prevail on
Wednesday under high pressure aloft.

&&

.SHORT TERM...
There was some wet snow falling over parts of the Hood Canal area,
Kitsap Peninsula, and southwest interior early this morning. The
snow should end by sunrise and quickly melt off due to strong warm
air advection. There was likely snow falling in the Cascade
valleys near sea level as well. The snow in these areas will
persist a little longer or until about midmorning or so before
changing over to rain.

Meanwhile, the cold front was about 60 miles offshore and will
sweep across the CWA by late this morning. Expect gusty winds
ahead of and with the front. Winds will quickly drop off behind
it. The mountains can look for the steady snowfall (locally heavy)
to taper off to mostly light showers by midday.

After a very brief break in the weather action, another Pacific
storm will bring more rain and mountain snow to the region
tonight. Much of the Cascades could receive another 6 to 10 inches
of snow tonight. Also, expect locally windy conditions to develop
tonight ahead of the cold front. There continued to be differences
in the models concerning the wind field, with the GFS solution
being the strongest. However, this model has trended weaker with
the speeds with its latest cycle. For this reason, have held off
on issuing any wind hazards for later tonight for parts of the
CWA. If the ECMWF is correct, only breezy conditions (at best) can
be anticipated.

Look for post-frontal showers in the wake of the front on Tuesday.
Much of the activity should be light, with the mountains
generally receiving less than six inches of snow. There is a
possibility of a convergence zone developing on Tuesday, and this
could lead to locally higher snowfall amounts in the Cascades near
the Snohomish/King County line.

High pressure aloft will move over the region Tuesday night for a
drying trend. Expect high pressure to prevail over the area on
Wednesday for generally dry conditions. The exception will be the
far northern part of the CWA, where there will be a chance of
precipitation.

Concerning coastal flooding or minor tidal overflow...High
astronomical tides were occurring in the inland waters of western
Washington this morning. While the tides are expected to remain
about 1 foot below where minor tidal overflow normally begins,
they will occur about the time that strong winds with a passing
front is giving waves up to 5 feet to the inland waters. Exposed
south and southwest facing shorelines in the inland waters may see
some seawalls being overtopped by sea water at times around the
morning high tide today. Another system will be passing western
Washington around the time of high tide Tuesday morning. Any areas
that see waves overtopping exposed sea walls this morning will
likely see a repeat performance around Tuesday morning's high
tide. Albrecht

Key Messages:

1. Areas of lowland snow this morning should end by sunrise, with
the snow quickly melting as warmer air invades the region.
2. Expect locally heavy snow in the Cascades this morning and,
again, tonight. Note: There is also an Avalanche Warning for the
backcountry in effect for the Cascades.
3. Locally windy conditions can be expected this morning and,
again, later tonight.
4. Minor coastal flooding is likely on the shorelines adjacent to
the Puget Sound/Hood Canal, Admiralty Inlet and northern inland
waters (Saratoga Passage northward) this morning due to high
astronomical tides.
5. Generally dry conditions are anticipated on Wednesday.

.LONG TERM...
Confidence in the details during this period was low due to
differences in the medium range solutions. It did appear that the
models agreed that it will become cold enough the end of this
week for the possibility of lowland snow. However, the models
disagreed as to whether there will be any precipitation or not.
For now, kept PoPs below climatology for the latter part of the
period. Temperatures are anticipated to fall below normal again at
the end of the period. Note: Climatologically, the probability of
Seattle seeing a white Christmas is five percent.

&&

.AVIATION...Westerly flow aloft. A strong front will move across
the area about 15Z. A warm front will approach the area from the
southwest late tonight.

Conditions are generally MVFR across the area due to ceilings and
precipitation. Precipitation began as mixed rain and snow at
several inland terminals, but precipitation has rapidly turned
over to all rain as south winds scoured out the cold air. Most
terminals will see wind 18015-22kt with gusts to 27-35kt until
frontal passage about 15Z. Winds will then rapidly shift to the
west or southwest and diminish.

Behind the front expect precipitation to end with the exception to
scattered showers on the west slopes of the Cascades. Ceilings will
remain MVFR through the afternoon hours.

A warm front will approach the area from the southwest early this
evening with MVFR to local IFR ceilings and light rain spreading
rapidly northeastward. The warm front will pass the area around
12Z Tuesday. Areas of LLWS are possible, especially around KBLI
and KHQM and from KBFI southward in the interior after 06Z-09Z
tonight and until the warm front passes. Albrecht

KSEA...Expect CIGS around FL025 through this evening. Light rain
will come to an end by 17Z, then will redevelop again around 03Z
this evening. From this point onward, all precipitation is
expected to be in the form of rain. South winds 15G28KT this
morning will ease to 5 to 8 kt by 20Z then will back to more
east or southeast 5-9 kt tonight. Southwest winds 35 kt will lower
to below 2000 ft AGL after 09Z tonight and until the warm front
passes, resulting in LLWS. Albrecht

&&

.MARINE...A strong frontal system moving through the coastal
waters early this morning will move into the Cascades late in the
morning. Gales are occurring over most of the waters early this
morning and will continue until the front passes. Gale warnings
are now in effect for all of the western Washington waters except
the Central Strait of Juan de Fuca.

Post frontal onshore flow Monday morning will give a brief period of
small craft advisory winds to the central portions of the strait
later this morning. Otherwise winds will rapidly diminish by
midday as we move into a lull between this morning's front and
the next system upstream.

A developing low well offshore will develop to about 995 mb early
Tuesday morning as it moves onto the northern tip of Vancouver
Island. The low will then move east across south central British
Columbia on Tuesday. The warm front associated with this low will
move northeast across the area tonight, then the cold front will
push rapidly inland Tuesday morning. While latest model solutions
are not quite as strong with the pressure gradients associated
with this system as they were earlier, they continue to show
rather large south to north pressure gradients Tuesday morning.
Gale force winds are possible over most of the waters on Tuesday,
and gale watches have been issued for all of the waters from late
tonight through Tuesday afternoon.

Wave models continue to show seas building to 22 to 27 feet to
the south of the low moving onshore to the north, and moving onto
the coast Tuesday and Tuesday night.

A weaker front will move across the waters Wednesday night or
early Thursday. Albrecht

&&

.HYDROLOGY...
River flooding is not expected the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Coastal Flood Advisory in effect until 11 AM this morning
	 for the shorelines adjacent to the Puget Sound/Hood Canal,
 	 Admiralty Inlet, and northern inland waters (Saratoga
	 Passage northward).

 	 Winter Weather Advisories are in effect for the Cascades.

	 Wind Advisory in effect until 10 AM this morning for the
	 coast and parts of the interior.

PZ...Gale Warning in effect until 9 AM this morning for all waters
	 except the central Strait of Juan de Fuca.

	 Small Craft Advisory in effect until 3 PM this afternoon for
	 the central Strait Of Juan De Fuca.

 	 Gale Watch in effect from late tonight through Tuesday
	 afternoon for all waters.

&&

www.weather.gov/seattle

An illustrated version of this forecast discussion can be seen at
www.weather.gov/seattle/gafd/latest_webafd.html

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
829 AM PST MON DEC 19 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0800 AM     SNOW             8 E CHEHALIS            46.65N 122.79W
12/19/2016  M1.7 INCH        LEWIS              WA   TRAINED SPOTTER

            1.7 INCHES OF SNOW. 32 DEGREES. LIGHT DRIZZLE AT TIME OF
            OBSERVATION.

&&