Heavy Snow in Washington, December 8 to 9, 2016

Area Forecast Discussion
National Weather Service Seattle WA
1025 AM PST Thu Dec 8 2016

.SYNOPSIS...A front will reach the area this evening. With cold
air in place, the precipitation will be snow, then turning to
rain by daybreak for most areas. Cool and rainy weather will
persist for the remainder of Friday and through the weekend.
Dry colder weather is possible again next week for several days.

&&

.SHORT TERM...Wind advisories were added to a few areas that are
going to continue to be windy today in this strong offshore flow.
Clouds will increase today with flurries developing this afternoon
south of Olympia. The winter weather advisory for the lowlands
tonight looks good for 1-3" of snow except around Hood Canal where
3-6" is in the forecast. The Bremerton area might do pretty well,
and the east side near the Cascade foothills could be at the low
range. After a few hours of flurries this evening the snow that
accumulates will arrive with the front later in the evening, and
the UW WRFGFS suggests late evening to just after midnight could
be the heavier snow--so that could be ideal for not many people
on the road at night. The UW model shows very little precip around
Port Angles, with a little snow east and west of there, but I think
a 1-3" forecast is fine for that area along the Strait as Fraser
winds keep the flow more NEly and that could keep the downslope
effect at bay--maybe it will even stay a little upslope. Out around
Clallam Bay/Sekiu will probably do better than Port Angles, and at
the eastern end the Quimper Peninsula might do pretty well with
the easterlies--but Hood Canal and the eastern half of the Olympics
are the odds on favorite to have the most snow. The snow will turn
to rain or showers by daybreak Friday for most areas, but the
Fraser outflow might very well keep Bellingham in a mix of wintry
precip for the morning hours.

Saturday and Sunday look wet at times with a fairly low snow level
and the snow level should taper from around 2000 feet in the southern
Olympics to near the surface in the North Cascades, and then late in
the weekend the snow level will fall--probably Sunday night back
toward sea level, but the moisture again dries up about that time. 19

.LONG TERM...While there may be some scattered breaks in the rain
Sunday morning and early afternoon...a secondary upper level low
looks to swing through Western Washington bring another shot of
precip. Gradual drying on the slate for Monday and continuing into
Wednesday night. For next Wednesday and into next Thursday...models
are starting to hint at a system that looks very similar to the
current one examined in the Short Term discussion. Obviously...will
not bite on that solution just yet...more prudent to wait and see
how current mess will pan out.  SMR

&&

.AVIATION...Strong low-level offshore wind flow will maintain a
dry and stable air mass through much of today. A warm front will
start to spread northward through western Washington tonight.
Precip will spread up from the south, reaching Lewis and Grays
Harbor Counties around 23z-02z, then spreading north and
beginning in the Puget Sound Region from 02z-05z. Look for a few
hours of snowfall, then a transition to rain later tonight. An
upper level impulse will enhance rainfall around mid-day Friday.
However, a drying offshore component to the surface wind will help
to hold ceilings up in MVFR and VFR ranges.

KSEA...Gusty east winds through this evening, with gusts commonly
up near 25 knots. Wind direction will veer slightly during the
day, favoring a slight southerly component (100-120 degrees) by
this evening. Otherwise, the dry air mass is serving to slow the
timing of the arrival of light snow this evening. Onset most
likely to be around 03z-05z. Light snow should last for about 3-4
hours, then transition over to rain overnight. A trace to 3 inches
of snow accumulation, with 1-2 inches most likely. More rain
expected on Friday, but a drying easterly component to the surface
wind will hold cigs up in the 020-030 range. Haner

&&

.MARINE...Strong offshore flow will prevail for gale force winds
across the east wind prone waters through this evening. Expect a
warm or occluded front to move north across the area late tonight
through early Friday. This will cause the flow to become southerly
across much of the area. Onshore flow will prevail on Saturday.

&&

.HYDROLOGY...

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory from 4 PM this afternoon to 8 AM PST
     Friday for Admiralty Inlet Area-Bellevue and Vicinity-
     Bremerton and Vicinity-East Puget Sound Lowlands-Eastern
     Strait of Juan de Fuca-Everett and Vicinity-Lower Chehalis
     Valley Area-San Juan County-Seattle and Vicinity-Southwest
     Interior-Tacoma Area-Western Skagit County-Western Strait
     of Juan De Fuca.

     Winter Weather Advisory from 4 PM this afternoon to 3 AM PST
     Saturday for Cascades of Pierce and Lewis Counties-Cascades
     of Snohomish and King Counties-Cascades of Whatcom and
     Skagit Counties-Olympics.

     Winter Storm Warning from 4 PM this afternoon to 8 AM PST Friday
     for Hood Canal Area.

     Winter Weather Advisory from 4 PM this afternoon to noon PST
     Friday for Western Whatcom County.

     Wind Advisory until 8 PM PST this evening for Western Whatcom
     County.

     Wind Advisory until 10 PM PST this evening for East Puget Sound
     Lowlands.

     Wind Advisory until 4 PM PST this afternoon for Central Coast.

     Wind Advisory until 9 PM PST this evening for North Coast-
     Western Strait of Juan De Fuca.

PZ...Gale Warning until midnight PST tonight for Central U.S. Waters
     Strait Of Juan De Fuca-Coastal Waters From Cape Flattery To
     James Island Out 10 Nm-Coastal Waters From James Island To
     Point Grenville Out 10 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning until 3 AM PST Friday for Coastal Waters From Cape
     Flattery To James Island 10 To 60 Nm-Coastal Waters From
     James Island To Point Grenville 10 To 60 Nm-Coastal Waters
     From Point Grenville To Cape Shoalwater 10 To 60 Nm.

     Small Craft Advisory until 3 PM PST Friday for East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 10 PM PST this evening for Northern Inland
     Waters Including The San Juan Islands.

     Small Craft Advisory from 6 PM this evening to 6 PM PST Friday
     for Admiralty Inlet.

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