Small Craft Advisory 4, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
919 AM PST Sat Jan 6 2018

.SYNOPSIS...High pressure will build into the area today with most
of the shower activity this morning in a convergence zone over the
central Puget Sound area. The next system in this series will
reach the area on Sunday, shift north on Monday then move through
the area on Tuesday. Additional weather systems will affect the
area Wednesday and again Thursday into Friday.

&&

.SHORT TERM...A Puget Sound Convergence Zone will linger north of
Seattle most of the day today for some drizzle. Otherwise, it
will be a mostly dry day with a flat upper ridge over the area. A
frontal system will bring increasing rain on Sunday. The front
will hang up across the area Sunday night as an upper trough
digs offshore causing the flow aloft over Western Washington to
become more southerly. The digging trough will lift the front
northwest and push most of the precipitation west and north of the
area during the day Monday. The Cascades should pick up a decent
amount of snow from roughly 06Z tonight through 06Z Sunday night
with the bulk of the snow during the day on Sunday. Mount Baker
and Steven Pass will probably get advisory amounts and Paradise
might wind up with heavy snow. Snow levels will pop up during the
day which will complicate matters and could limit snow amounts a
bit. Schneider

.LONG TERM...Previous discussion...Extended models in pretty good
agreement with what is left of the very elongated front moving
inland Monday night into Tuesday morning. Upper level trough
moving through the area Tuesday night keeping a chance of showers
in the forecast. Another somewhat negatively tilted front reaching
the area on Wednesday followed by a more consolidated and much
wetter system Thursday into early Friday with an upper level ridge
building behind the front for the first part of next weekend.
Felton

&&

.AVIATION...A flat upper ridge axis will move across Western
Washington this afternoon and evening, bringing a relative lull in
precip. A warm front will spread rain and southeast surface winds
across the region on Sunday morning. Moderate northwest flow aloft
today will become westerly on Sunday. The air mass will be moist
and increasingly stable. Some scattering of lower clouds will take
place this PM as low-level wind takes an offshore component.

KSEA...Beyond the next hour, shower activity should be done for
the day at SEA, though showers will linger north of the terminal
until a PSCZ dissipates this afternoon. OVC013 at 17z will be very
slow to lift above 020 today. May take until 04z-06z this evening
for lowest clouds to actually scatter. Rain with the next warm
front will arrive around 12z-14z on Sunday morning. Cigs on Sunday
morning will commonly be in the 020-030 range. Haner

&&

.MARINE...Onshore flow will continue to ease today as high
pressure builds over the area. Small craft advisory winds in the
Strait of Juan de Fuca are in the process of easing and should
fall below 21 knots by early afternoon. A marginal Small Craft
Advisory for Hazardous Seas is also in effect for 10+ foot seas
over the coastal waters until the next routine issuance at 3 pm.

A warm front will spread across the offshore waters tonight and
Sunday morning, bringing an increase in southeast gradients
tonight with a peak on Sunday morning. Currently have 20 to 30 kt
in the forecast for the coastal waters and the eastern Strait for
SE wind, but this could very well turn out to be a gale which the
12z HiRes ARW model supports.

A weakening low center near Haida Gwaii will then pivot a
weakening cold front inland across Western Washington on Sunday
PM. This will cause weakening of the southeast gradients and
wind.

Weak onshore flow will prevail Tuesday, and a weak system will
move into the region on Wednesday. Haner

&&

.HYDROLOGY...There is a chance the Skokomish river in Mason
county could reach flood stage around Sunday night as a front
hangs up over the area. In additional, extended models show a
fairly wet system late next week. If the system stalls over the
area a little there could be some minor flooding again on the
Skokomish river. For the remainder of the rivers, flooding is not
expected in the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory for hazardous seas until 3 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 until 1 PM PST this afternoon for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

&&

www.weather.gov/seattle