Gale Warning 68, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
906 AM PST Sat Nov 28 2020

.UPDATE...Radar this morning shows some lingering showers across
portions of the central Sound in a weak convergence zone. Expect
to see some showers linger through the late morning and into the early
afternoon hours, however expect to see an overall drying trend as
a brief, weak upper level ridge traverses the region. Otherwise,
satellite imagery still indicates some low clouds and fog across
portions of the Sound this morning, with areas of clearing across
the northern Olympic Peninsula and Pacific Coast as the front
continues to exit to the southeast. Made some minor adjustments to
the morning forecast to account for current trends. Otherwise,
the previous discussion follows, with updates made to the aviation
and marine sections. 14

&&

.SYNOPSIS...Rain and mountain snow tapers off today behind the
departing front. Expect generally dry conditions late tonight into
Sunday as weak ridging builds over Western Washington. A stronger
front follows Monday, with breezy winds and widespread precipitation
expected. An upper ridge will then move into the region and remain
through much of the week, resulting in mostly dry conditions through
much of the week.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...Last evening's front
continues to advance to the east and south of the region early this
morning, and it will be mostly clear of the forecast area by 4 AM.
Some lingering precipitation remains evident behind the front, both
in portions of the Strait of Juan de Fuca and in a weak convergence
zone stretching across northern Snohomish/southern Skagit counties.
Will need to continue to monitor trends, as some hint in the
guidance that light precip will linger in a convergence zone near
central Puget Sound through the morning. However, expect a drying
trend by afternoon (and sooner elsewhere) as heights begin to rise
under a weak upper ridge. Lower stratus remains across the region,
but satellite imagery does reveal some clearing upstream to the
northwest. Likely will have some lingering low stratus and/or fog
early this morning, depending on how much clearing does occur
behind the front.

Dry conditions will then continue through the first half of Sunday,
with increasing cloud cover and a return of precipitation later
Sunday. The leading warm front may bring some light rain to the
Olympic Peninsula by afternoon, but most of the moisture will remain
offshore until the evening. Ahead of this front, expect to see south
or southeast winds to increase across the region. Latest guidance
continues to suggest some potential for gusts into the 45-55 mph
range near the coast and from northern Whidbey Island north
through the San Juan Islands, including western portions of
Whatcom and Skagit counties; will continue to monitor the latest
trends, and wind advisories may be needed if this forecast remains
on track.

The front will push through the area late Sunday night into early
Monday, with another round of lowland rain and mountain snow. Snow
levels will rise a little bit through the day on Sunday, but the
induced offshore flow may help keep snow levels near the passes.
Expect snow levels to be in the 3000-4000 ft range early Monday as
most of the moisture moves through, with a few inches of snow at
Stevens Pass late Sunday night through Monday morning. Steadier
precipitation will taper off Monday morning, but a few showers may
continue into the afternoon as the upper trough moves across the
region. Cullen

.LONG TERM /TUESDAY THROUGH FRIDAY/...Tuesday will mark the return
of dry conditions across most of the region as an upper ridge is
likely to build over the Pacific Northwest. A weak front may
approach the coast around Thursday, but ensemble guidance continues
to suggest this system will split and leave the area mostly dry.
Some slight chances PoPs were maintained near the coast with at
least a handful of ensemble members indicating some light
precipitation is possible. However, this will likely be short-lived,
with another dry day expected Friday. Expect that some morning fog
or low stratus will develop across the lowlands in this pattern
under strengthening inversions. Temperatures look to remain rather
steady through the week and remaining near normal in the metro areas
(generally upper 40s/around 50 for highs and upper 30s for overnight
lows), though areas of fog or stratus that linger could hold daytime
temperatures a bit cooler than the current forecast.     Cullen

&&

.AVIATION...An upper ridge will cross the area today and tonight
with westerly flow aloft. At the surface, weak high pressure
will move over the area today then shift inland tonight. A weak
area of convergence over central Puget Sound this morning should
dissipate this afternoon.

The air mass will be stable. Widespread low clouds will slowly
lift later this morning and afternoon and then mostly scatter this
evening. Areas of low clouds and fog are likely again Monday
morning. Schneider

KSEA...Low clouds and fog should lift late this morning and
afternoon then scatter this evening. Some fog or low clouds are
possible again Monday morning. Light wind. Schneider

&&

.MARINE...Winds will continue to ease today as weak high
pressure moves over the area. West swell around 10 feet over the
Coastal Waters this morning will subside below 10 feet this
afternoon.

A vigorous frontal system will bring gale force southerly winds
to most waters Sunday night. A westerly gale is likely in the
Strait behind the front on Monday.

Onshore flow will rapidly ease Monday night as weak high pressure
moves over the area. Offshore flow will develop on Tuesday and
continue into Wednesday. Schneider

&&

.HYDROLOGY...No river flooding is expected during the next seven
days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from Sunday morning through Monday morning 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 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 from 1 AM to 10 AM PST Sunday 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 6 PM PST this evening for Grays
     Harbor Bar.

     Gale Watch from Sunday afternoon through late Sunday night for
     Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De
     Fuca-Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 10 AM to 4 PM PST Sunday for Admiralty
     Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca-
     Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 10 AM to 10 PM PST Sunday for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

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