Heavy Rain in Washington, February 9, 2017

Area Forecast Discussion
National Weather Service Seattle WA
847 PM PST Wed Feb 8 2017

.SYNOPSIS...A strong warm front will lift northward through Western
Washington tonight. A cold front and low pressure will move east
across the region Thursday through Friday. An upper ridge of high
pressure will build into the Pacific Northwest for the weekend
with dry weather likely through early next week. Weak fronts will
near the area by the middle of next week.

&&

.SHORT TERM...Warm air aloft has now overspread all of Western
Washington, and is also moving into the Fraser Valley from
Bellingham northeastward to the Canadian Border. The freezing
level at Forks late this afternoon was a whopping 8700 feet.
Precipitation has changed from snow or mixed precipitation to
mostly all rain this evening. There does remain a couple of
pockets of snow or mixed precipitation on the northern Olympic
Peninsula and near the Canadian Border where the cold air has yet
to scour out. All rain is expected everywhere in the lowlands by 9
PM.

In Western Whatcom County, temperatures remain below freezing
with northeasterly winds. The Bellingham-Williams Lake pressure
gradient is at -13 mb. Cold air at the lowest levels will scour
out first in Bellingham proper and around the airport, but will
take some time, likely until morning, to scour out from about
Lynden north and eastward. A Winter Storm Warning remains in
effect for Western Whatcom County until 4 AM PST Thursday and may
need to be extended a few hours. In the mountains, snow levels
will rise to 5000 feet around Mt Baker and 7000 feet at Mt Rainier
overnight. Low level easterly gradients will keep precipitation in
the form of freezing rain until morning once precipitation turns
over. The Winter storm warning in the mountains continues until 6
AM Thursday and may need to be extended a bit later tonight if
conditions don't warm as much as currently expected.

The lowlands will see heavy rain at times tonight into Thursday
morning behind the warm front and ahead of Thursdays cold front.
The frontal system is primed with an impressive plume of tropical
moisture that extends SSW to 20N 145W and is being advected
northeastward in 50-65 kt SSW winds at 5000 feet. Fortunately, the
frontal system is progressive in nature. See the hydrology section
below for impacts of the heavy rain on rivers.

Flow aloft will interact with the terrain later tonight into
Thursday which will result in windy conditions developing across
the region. At this time, winds are expected to remain below wind
advisory criteria.

A weakening 997 mb low will move east across the area on Friday
giving showers and windy conditions to the area.

Coastal Flood advisories are in effect for the shores of all of
the inland waters and for the coastal zones due to a combination
of high astronomical tides and low pressure around the high tides.
High tides will be late tonight or Thursday morning in the interior
and late in the morning through midday Thursday along the coast.

Will cancel the winter weather advisory for the San Juan Islands
and for the Strait of Juan de Fuca zones and will update the zones
for headlines and to refine the first period wording there.
Albrecht

.LONG TERM...From the previous long term discussion: A period of
dry weather is likely with an upper level ridge building over the
region over the weekend...and persisting into early the next work
week. The chance for rain will increase by the middle of next week
as the ridge fades and systems approach the area.

&&

.AVIATION...Strong, moist southwesterly flow will continue across Western
Washington tonight with a warm front over the region. The air mass
is moist and stable with mainly MVFR to IFR ceilings. N/NE Fraser
river outflow continues for mixed precipitation in western Whatcom
county. Freezing rain or snow will continue through 09-12z at KBLI
then change over to rain. Strong onshore flow will follow on
Thursday for more showers. 33

KSEA...Light to mod rain continuing tonight with MVFR to IFR
cigs. N/NE winds veering to to S/SE 09-12Z. Expect more showers
through Thursday. 33

&&

.MARINE...A strong warm front will bring gales to the Coastal Waters and
West Entrance tonight. Strong onshore flow will follow on
Thursday. A 990 mb surface low will shift inland Friday morning for
another round of gales over the Coastal Waters. There will be
another strong surge of onshore flow Friday afternoon as the low
moves farther inland and weakens. High pressure will bring a
period of lighter winds on Saturday. The flow will turn offshore
again on Sunday and continue through early next week. 33

&&

.HYDROLOGY...Total precipitation amounts of 3 to 5 inches are
expected in the Olympics and southern portions of the Washington
Cascades tonight into Thursday as snow levels rise to 6500 feet.
Snow levels will lower late Thursday. The rainfall will produce
rises on area rivers, and leftover lowland snow will melt. The
snow melt will only contribute a small amount to the runoff.

The rivers that are most likely to flood are the Skokomish in
Mason County and the lower White River along the King-Pierce
county line. Other rivers in southwestern Washington may reach
flood stage. A flood watch is in effect from King County southward
in the interior (including Mason County) and for Grays Harbor
County.

From Saturday onward, flooding is not expected on area rivers.
Albrecht

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch from 7 AM PST Thursday through Friday evening
     for King...Pierce...Thurston...Lewis...Mason...and Grays
     Harbor counties.

     Coastal Flood Advisory from 1 AM to 9 AM PST Thursday for
     Admiralty Inlet Area-Bremerton and Vicinity-Everett and
     Vicinity-Hood Canal Area-San Juan County-Seattle and
     Vicinity-Southwest Interior-Tacoma Area-Western Skagit
     County-Western Whatcom County.

     Winter Storm Warning until 6 AM PST Thursday for Cascades of
     Pierce and Lewis Counties-Cascades of Snohomish and King
     Counties-Cascades of Whatcom and Skagit Counties.

     Winter Storm Warning until 4 AM PST Thursday for Western Whatcom
     County.

     Flood Watch from Friday evening through Saturday evening for
     Central Coast.

     Coastal Flood Advisory from 8 AM to 1 PM PST Thursday for
     Central Coast-North Coast.

     Flood Watch from 7 AM PST Thursday through Saturday evening for
     Lower Chehalis Valley Area.

PZ...Gale Warning until 6 AM PST Friday for Coastal Waters From Cape
     Flattery To James Island 10 To 60 Nm-Coastal Waters From
     Cape Flattery To James Island Out 10 Nm-Coastal Waters From
     James Island To Point Grenville 10 To 60 Nm-Coastal Waters
     From James Island To Point Grenville Out 10 Nm-Coastal
     Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater Out
     10 Nm.

     Small Craft Advisory until 4 AM PST Friday for Admiralty Inlet-
     East Entrance U.S. Waters Strait Of Juan De Fuca-Northern
     Inland Waters Including The San Juan Islands.

     Gale Warning until 4 AM PST Thursday for West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from midnight tonight to midnight PST
     Thursday night for Central U.S. Waters Strait Of Juan De
     Fuca.

     Gale Warning until midnight PST tonight for Central U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory from 10 AM Thursday to 4 AM PST Friday for
     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
709 PM PST WED FEB 08 2017

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

0638 PM     HEAVY SNOW       7 WSW PORT ANGELES      48.12N 123.60W
02/08/2017  M5.5 INCH        CLALLAM            WA   TRAINED SPOTTER

            5.5 INCHES OF HEAVY AND WET SNOW TODAY. NOW DRIZZLING.

&&

ALBRECHT