Winter Storm Warning 3, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
245 AM PST Tue Jan 22 2019

.SYNOPSIS...A pair of frontal systems will bring rain to the
lowlands, snow to the mountains, and breezy to windy conditions
today into Wednesday. A ridge of high pressure aloft will build over
the offshore waters Wednesday night and continue into the weekend
for generally dry conditions. A couple of weak weather systems may
clip the northern part of the region Thursday night and again Sunday
for a chance of showers.

&&

.SHORT TERM...A warm front is lifting north through the
offshore waters this morning with rain spreading onto the coast. The
rain will reach the Puget Sound area around daybreak. Rainfall looks
initially light across the area with the warm front, but will
intensify later this evening and tonight as the associated surface
trough and cold front approach the coast. Models give a fairly
significant (but short-lived) shot of QPF between 00Z and 06Z this
evening. While the snow levels will be rising tonight, much of this
QPF could amount to some substantial snowfall at places like Mount
Baker and Stevens Pass before the snow level takes a jump late
tonight. With this in mind, will be going with a Winter Storm
Warning for the Cascades from Whatcom County southward through King
County effective through late this evening and a Winter Weather
Advisory for the Cascades in Pierce and Lewis counties. In addition
to the precip, it be come windy along the coast this afternoon and
tonight and breezy to locally windy over the interior.

A cold front will push into the Cascades early Wednesday morning
with precipitation gradually diminishing from the west through the
day. An upper ridge will begin to the build over the offshore waters
Wednesday night for what should be a generally dry period from
Thursday into the weekend. Models do have a weak system clipping the
northern part of the forecast area Thursday night so a chance of
rain was added to the forecast from the Puget Sound northward.
Temperatures through the short term period will be near to a little
above average.   27

&&

.LONG TERM...The upper ridge offshore gains some amplitude Friday
and the axis shifts eastward over Western Washington on Saturday.
Looks like a pleasant start to the weekend with some sunshine after
areas of morning fog and daytime temperatures a little above
average. The GFS and Euro are in general agreement with retrograding
the upper ridge offshore late in the weekend and allowing another
system to clip the area from the northwest on Sunday. At this point,
it looks like nothing more than a low chance of showers for the
northern Cascades and remaining dry for the rest of the region. The
ridge then reasserts itself on Monday for more dry weather.   27

&&

.AVIATION...A warm front will spread rain to Western Washington
today with mainly VFR conditions expected. MVFR conditions are
likely tonight as the cold front moves S/SE through the region.
Rain will be moderate to heavy at times along the coast. The flow
aloft is westerly. Expect windy conditions tonight with S winds
gusting to 20-30kt. Showers will mainly impact the Cascades
Wednesday morning as this system exits. 33

KSEA...Mainly light rain at the terminal today then rain increasing
tonight with a cold front. South winds 10-20kt with gusts to 30kt
tonight, along with MVFR cigs. 33

&&

.MARINE...A frontal system will move through the waters late this
afternoon through this evening. This front will be followed by a
1007 mb low west of the northern tip of Vancouver Island that will
fill to around 1016 mb as it moves across the northern waters late
tonight into Wednesday morning. Gale warnings continue today for the
coastal waters, the east entrance to the strait, Admiralty Inlet,
and the northern inland waters. Small craft advisories are in effect
for the remaining waters. Small craft advisory conditions will
continue over all of the waters tonight with conditions gradually
improving on Wednesday.

High pressure over the waters Thursday through Saturday will give
generally light winds to the area.

Minor coastal flooding remains likely along the Pacific coastline in
Grays Harbor county around the high tide early Tuesday afternoon.
The astronomical high tide is expected to be within 0.25 feet of HAT
-the point where minor flooding begins- and tidal anomalies are
expected to be just large enough to result in some minor flooding
around the time of high tide there. A coastal flood advisory is in
effect for the shoreline of Grays Harbor County.

Extratropical storm surge guidance suggests that the inland waters
could see some minor tidal overflow around the morning high tide on
Wednesday. However, conditions are marginal enough that advisories
will be issued this afternoon if later solutions continue to show
the tides exceeding HAT. Albrecht

&&

.HYDROLOGY...The Skokomish river in Mason county will rise tonight
due to a period of heavy rain in the Olympics. This system will
push through relatively quick but may still see 2-3 inches of
rainfall in the basin, pushing the Skokomish river to around 16
feet (a half foot below minor flood stage). The river will recede
on Wednesday.

Otherwise, no river flooding concerns over the next 7 days. 33

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory from 7 AM this morning to midnight PST
     tonight for Cascades of Pierce and Lewis Counties.

     Winter Storm Warning from 7 AM this morning to midnight PST
     tonight for Cascades of Snohomish and King Counties-
     Cascades of Whatcom and Skagit Counties.

     Coastal Flood Advisory from noon today to 4 PM PST this
     afternoon for Central Coast.

PZ...Gale Warning until 2 PM PST this afternoon 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 for rough bar from noon today to 9 PM PST
     Wednesday for Grays Harbor Bar.

     Gale Warning until 4 PM PST this afternoon for Admiralty Inlet-
     East Entrance U.S. Waters Strait Of Juan De Fuca-Northern
     Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 4 AM PST Wednesday for Puget Sound
     and Hood Canal-West Entrance U.S. Waters Strait Of Juan De
     Fuca.

&&

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