Coastal Flood in Washington, November 15, 2020

Area Forecast Discussion
National Weather Service Seattle WA
940 AM PST Sun Nov 15 2020

.UPDATE...Scattered showers continue across much of the region
this morning in the westerly flow aloft. The strongest of these
will likely include a surge of winds, heavy rain, and small hail.
Isolated thunderstorms are possible as well, especially on the
coast as some of the heavier showers move onshore. Meanwhile,
portions of the central Puget Sound remain well shadowed by the
Olympics and will remain relatively dry. Forecast remains on track
otherwise; see the previous short/long term sections below for
more details.   Cullen

&&

.SYNOPSIS...Cool unstable air mass over the area today keeping
showers in the forecast. Warm front moving through Western
Washington Monday with the trailing cold front arriving Tuesday.
High winds are possible along the coast just ahead and with the
cold front. Upper level trough Wednesday and Thursday for more
showers. Weak upper level ridge could give the area a dry day
Saturday.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Warm front currently well
southwest of the area will move east today and then northward
tonight. Warm advection ahead of the front will get rid of most of
the shower activity across Western Washington this evening. Rain
out ahead of the front could get into Lewis and Grays Harbor
county by 12z Monday. For the remainder of the area drying trend
overnight. Lows will be in the 40s.

Warm front lifting up into the area Monday spreading rain from
south to north in the morning hours with rain over the entire area
in the afternoon. Snow levels rising to at least 6000 feet for
rain in all the mountain passes. Highs in the lower 50s.

Front moving north of the area Monday evening. Brief dry spell
overnight with the trailing cold front slowing down its' eastward
progress as it becomes more north south oriented. With Western
Washington in the warm sector lows will mild, in the mid to upper
40s.

Cold front moving into Western Washington late in the day Tuesday
with rain out ahead of the front spreading over the area in the
morning and early afternoon hours. Models hinting at a secondary
low developing along the front. Some model solutions have 925 mb
winds as high as 50-60 knots with the front along the coast. With
these two variables in play there is the possibility for high
winds (sustained winds 40 mph with gusts to 60 mph) along the
coast just ahead and with the front during the day. Highs in the
mid 50s.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Extended models in good
agreement with an upper level trough along the west coast
Wednesday and Thursday keeping showers in the forecast.
Operational models try and build a weak upper level ridge over the
area Friday into Saturday with showers decreasing into the
weekend. Ensemble solutions on both the GFS and ECMWF are much
weaker with this feature keeping plenty of showers in the area.
Model blend gives most of the area a dry day Saturday. Having the
potential of 9 straight days with measurable precipitation
leading into next weekend will lean more toward the drier
solutions for Saturday. Felton

&&

.AVIATION...A stalled upper level shortwave will allow for some
breezes to continue over W WA through the morning hours but will see
surface winds gradually diminish throughout the day. Winds aloft to
remain generally westerly. The aforementioned shortwave will allow
for a little bit of instability to persist today, resulting in some
scattered showers. These showers may be strong at times producing
heavy rain and small hail is not out of the question.

Cigs a mixed bag as most terminals west of the Sound are reporting
VFR conditions. along and east of the Sound, however, low clouds
resulting in MVFR to isolated IFR conditions. Should still see some
improvement in cigs, but may end up holding off until the late
morning/early afternoon. Widespread VFR conditions expected in the
afternoon and early evening before cigs lower once more down into
MVFR conditions as next front approaches.

KSEA...Low clouds and MVFR conditions this morning before some
improvement in cigs after 18Z and return to low end VFR conditions
by afternoon. VFR to persist until tonight around 06Z as cigs sink
again to MVFR ahead of next front. South to southwest wind 10-15
knots with gusts 20-25 knots this morning before becoming more
South to southeast late this afternoon with speeds 8-12 kt.

18/Butwin

&&

.MARINE...Conditions have taper off slightly for the time being,
Small Craft advisories in the Inland Waters as well as through the
Strait will be tapering off through the rest of the morning as
winds calm. The Small Craft throughout the coastal waters will
remain in place due seas being at 20-25 feet. These will decrease
slightly tonight and into Monday. The next weather system is
expected to move through Monday afternoon through Tuesday. This
system is expected to bring high winds to all area waters, as well
as combined seas up to 20 feet. currently there is a gale
advisory set for the coastal waters, we will be assessing if this
should be upgraded throughout the day. Regardless of the status of
the wind over the coastal waters, we are confident that
conditions in the Inland Waters will also be rough and gale force
winds are likely. If you plan on going out on the area waters in
the coming days, make sure you check for the most recent forecast.

Butwin

&&

.HYDROLOGY...Rivers rising Monday with locally heavy rain and
rising snow levels. Right now the warm front looks to move through
the area quick enough to keep almost all of the rivers in their
banks. With the Skokomish running high at the beginning of the
event it is likely the river will flood again Monday evening or
Tuesday morning. There is a lesser threat of flooding for the
remainder of the rivers flowing off the Olympics. Rivers will
begin receding Tuesday. No flooding expected Wednesday through
Saturday. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Surf Advisory until 7 PM PST this evening for Central Coast-
     North Coast.

PZ...Gale Watch from Monday morning through late Monday night 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-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 10 AM PST Monday 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-West Entrance U.S. Waters Strait Of
     Juan De Fuca.

     Small Craft Advisory until 7 PM PST this evening for Grays
     Harbor Bar.

     Small Craft Advisory until 10 AM PST this morning for Central
     U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters
     Including The San Juan Islands-Puget Sound and Hood Canal.

&&

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