High Wind in Washington, February 5, 2017

Area Forecast Discussion
National Weather Service Seattle WA
834 PM PST Sun Feb 5 2017

.SYNOPSIS...A frontal system is over the region tonight and some
areas in the lowlands are getting heavy wet snow. The Seattle area
has had rain so far except for wet snow falling on the hills. The
snow level will fall to near sea level Monday. Cold Fraser outflow
is giving windy conditions up around Bellingham. A cold upper trough
will move over the region Monday and Tuesday. A warm front will
arrive Wednesday night and Thursday.

&&

.SHORT TERM...Cold rain and wet snow are falling over much
of Western Washington this evening. Some places in Lewis and Thurston
county have had some areas with good accumulation. Temps have
ever so slowly and begrudgingly cooled closer to 32. Downtown Seattle
may not see any snow stick and most roadways around Puget Sound
should not get icy, but slushy roads on the hills and in the
outlying areas are a pretty good bet by daybreak. The radar
return is not impressive and the idea that heavy precip would drive
the snow level down depends on heavier precip, so that is working
against the forecast. What we do have working is the northerly
gradient--so even though it has warmed from -5c to -2.5c at 850mb
over Seattle, the rain has been very slowly turning over to
wet snow, at least on those hills and away from the water. Where it
is cold up north in the Fraser outflow, there is less precip. Areas
south of Seattle with a little elevation are doing pretty good and
getting some significant accumulation.

On Monday, through the morning and midday, areas that have missed out
on snow overnight may finally see some accumulation as cold air
aloft arrives--the UW wrfgfs shows some snow between Seattle and
Everett as some convergence sets up. That may seem like grasping at
straws with a forecast that, so far, is being thwarted by temps a
few degrees too warm, but it wont be the first time that many wake
up to a winter wonderland while others have missed out. What I do
like that favors snow is that the temp at 500mb will cool to around
-36c on the coast late tonight and that cold air aloft will spread
into the interior of Western Wahington by mid morning. So, as the
cold air aloft moves overhead, showers will fall as snow, even as
onshore flow develops--and heavy snow showers in a convergence zone
can make a wintry scene develop in just an hour.

Scattered showers will taper off Monday afternoon and night, with
the snow level still below 500 feet, and at sea level up in the
Fraser outflow--which will be giving out. Tuesday will be cool and
showery, with a low snow level but probably not at sea level as
temps aloft warm a notch. Then the air mass will warm signficiantly
midweek with a strong warm front due in Wed nite and Thu that will
drive the snow level well above the passes for a day.

.LONG TERM...The warm front mentioned above should move N of W WA by
early Thursday morning. The associated cold front should cross the
area by late Thursday morning. The associated upper level trough and
surface low is due on Friday. This should be a warmer wet period
with high temperatures reaching the upper 40s or lower 50s. This
will likely bring significant rain to the mountains. At this point
around 3 inches of rain may fall in the 30 hours from 18Z Wednesday
through 00Z Friday.

The GFS and ECMWF still show a somewhat strong upper level ridge
crossing over the area late Saturday through Sunday for a potential
dry period. Kam

&&

.AVIATION...Strong southwest flow aloft over Western Washington
this evening will ease gradually tonight and veer to westerly late
Monday. A frontal band extending from northwest Montana across
Washington and into the Oregon coastal waters will bring
widespread precipitation -- falling mainly as snow -- through this
evening. The front will move east and snow should generally
decrease late tonight and Monday.

Conditions at 8 pm were mainly IFR due to low visibility and
ceilings in light snow over the Puget Sound region and southwest
interior of Western Washington, with ceilings 030-050 at the coast
and in the north interior with lighter snow. In addition Fraser
outflow is resulting in northeast winds gusting to 35 kt in the
north interior. Low conditions should continue tonight and Monday
morning with marginal improvement Monday afternoon.

KSEA...North wind 8-14 kt tonight...probably switching to south to
southwest 6-12 kt Monday. Low IFR conditions will probably
continue tonight, with gradual and marginal improvement Monday as
precipitation decreases. A Puget Sound convergence zone could
develop between Seattle and Everett late tonight or Monday
morning. McDonnal

&&

.MARINE...High pressure over British Columbia and a weak trough
across Washington is producing northerly flow across Western
Washington this evening, with northeast Fraser outflow gales in
the northern inland waters. The Fraser outflow -- and the
northerly offshore flow in general -- will ease Monday, with
westerly winds developing over the southern coastal waters and
south to southwest flow into the Puget Sound region.

Weaker east to northeast flow will continue Tuesday and Wednesday. A
vigorous Pacific frontal system could move through the area
Wednesday night and Thursday. McDonnal

&&

.HYDROLOGY...No river flooding expected through Wednesday. A warm
wet Pacific frontal system will spread rain across the area late
Wednesday through Friday. At this point around 3 inches of rain may
fall in the 30 hours from 18Z Wednesday through 00Z Friday. S-SW
winds at 850 MB will reach 40-50 KT over the Olympics. Rivers will
rise and there may be some potential for one or more to reach flood
stage Thursday or Friday. Kam

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 4 PM PST Monday for Bellevue and
     Vicinity-Bremerton and Vicinity-Cascades of Pierce and
     Lewis Counties-East Puget Sound Lowlands-Eastern Strait of
     Juan de Fuca-Everett and Vicinity-Hood Canal Area-Lower
     Chehalis Valley Area-Seattle and Vicinity-Southwest
     Interior-Tacoma Area.

     Winter Weather Advisory until 4 PM PST Monday for Cascades of
     Snohomish and King Counties.

     Winter Weather Advisory until 4 PM PST Monday for Admiralty
     Inlet Area-Central Coast-North Coast-San Juan County-
     Western Skagit County-Western Strait of Juan De Fuca-
     Western Whatcom County.

     Wind Advisory until noon PST Monday for San Juan County-Western
     Whatcom County.

PZ...Small Craft Advisory until 3 PM PST Monday for Central U.S.
     Waters Strait Of Juan De Fuca-Coastal Waters From Cape
     Flattery To James Island 10 To 60 Nm-Coastal Waters From
     Cape Flattery To James Island Out 10 Nm-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from midnight tonight to noon PST Monday
     for Coastal Waters From James Island To Point Grenville Out
     10 Nm.

     Small Craft Advisory until noon PST Monday for East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Gale Warning until 9 AM PST Monday for Northern Inland Waters
     Including The San Juan Islands.

     Small Craft Advisory from 9 PM this evening to noon PST Monday
     for Admiralty Inlet-Puget Sound and Hood Canal.

&&

www.weather.gov/seattle

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
531 PM PST SUN FEB 05 2017

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

0530 PM     SNOW             4 SW ETHEL              46.49N 122.79W
02/05/2017  M1.0 INCH        LEWIS              WA   TRAINED SPOTTER

            STILL SNOWING.

&&

GRUB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
547 PM PST SUN FEB 05 2017

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

0547 PM     HEAVY SNOW       5 NNW GRAND MOUND       46.88N 123.04W
02/05/2017  M4.0 INCH        THURSTON           WA   TRAINED SPOTTER

            32 DEGREES. STILL SNOWING.

&&

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PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE SEATTLE WA
604 PM PST SUN FEB 05 2017

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

0445 PM     SNOW             1 S OLYMPIA             47.03N 122.89W
02/05/2017  M2.7 INCH        THURSTON           WA   COCORAHS

0430 PM     SNOW             4 ESE MONTESANO         46.99N 123.51W
02/05/2017  M1.0 INCH        GRAYS HARBOR       WA   COCORAHS

&&

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
604 PM PST SUN FEB 05 2017

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

0601 PM     SNOW             1 S OLYMPIA             47.03N 122.89W
02/05/2017  M2.7 INCH        THURSTON           WA   COCORAHS

0430 PM     SNOW             4 ESE MONTESANO         46.99N 123.51W
02/05/2017  M1.0 INCH        GRAYS HARBOR       WA   COCORAHS

&&

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
605 PM PST SUN FEB 05 2017

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

0250 PM     SNOW             6 SW OLYMPIA            46.98N 122.98W
02/05/2017  M1.0 INCH        THURSTON           WA   COCORAHS

&&

GRUB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
608 PM PST SUN FEB 05 2017

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

0607 PM     SNOW             SHELTON                 47.21N 123.11W
02/05/2017  M1.5 INCH        MASON              WA   PUBLIC

            ELEVATION 297 FEET. REPORT IS FROM SPOTTER.

&&

GRUB