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000
FXUS66 KSEW 200318
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
818 PM PDT Fri Apr 19 2024

.UPDATE...Clear skies continue this evening with upper ridging
across the area. Offshore winds continue to be locally breezy in
the Cascade Gaps where wind gusts of 20 to 30 MPH are likely into
Saturday. Otherwise, high clouds will slowly increase into
Saturday ahead of the next front.

&&

.SYNOPSIS...Ridging will maintain dry and warm conditions into
Saturday ahead of an approaching front that will bring in light
lowland rain, mountain snow, and breezy winds. Unsettled
conditions will continue through the remainder of the weekend.
Next week will start out drier and warmer ahead of more rainy
weather mid- week.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Dry conditions will prevail
today as a shortwave ridge continues to shift inland. Temperatures
across the lowlands are on track to peak near or slightly below
the 70 degree mark as offshore continues. Areas sheltered from the
easterly winds will once again see much cooler overnight lows in
the 30s, whereas more open areas will bottom out in the low to mid
40s. Temperatures will continue a warming trend into Saturday as
surface winds shift southerly in the warm sector ahead of an
incoming front, with ensembles showing a moderate (50% to 60%)
chance of surpassing 70 degrees across much of the lowlands.

A front will cross western Washington mid-day Saturday, bringing
in a band of precipitation and breezy southwest winds as the front
moves through. Post-frontal conditions will destabilize with
troughing maintaining shower activity through Sunday afternoon.
Snow levels will lower to around 2500-3000 ft by Sunday morning
with generally light rainfall amounts for the lowlands and 1 to 2
inches of snow accumulation through the Cascade passes over the
span of the weekend. The bulk of the moisture with this system
will be focused over the Northern Cascades, where the higher peaks
will see up to 6 to 8 inches of snow through Sunday. Some
mesoscale models also hint at convergence activity from Skagit
County northward, which would locally enhance snowfall amounts
over higher terrain, but confidence is low. Lingering shower
activity will be cut off later on Sunday as a positively tilted
trough swings a front across the Pacific Northwest. Cool air aloft
paired with onshore flow will make for a brisk day on Sunday,
with temperatures in the lowlands peaking in the mid 50s.

Decreasing cloud cover overnight Sunday into Monday morning paired
with light winds will allow temperatures to drop quickly.
Conditions will be conducive for areas of frost to develop
outside of the Puget Sound metro areas. High pressure will build
inland on Monday, allowing conditions to dry out and temperatures
to rebound back into the 60s.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Temperatures will warm into
Tuesday as high pressure continues to amplify into western
Washington. Models continue to show large model differences mid-
week and beyond, but ensembles maintain a return to near normal
conditions with a chance of light precipitation through the
remainder of the period.

Lindeman

&&

.AVIATION...Upper ridge axis will shift onshore overnight then
east of the Cascades on Saturday morning as a front approaches the
region. West to northwest flow aloft will become southwesterly after
18Z Saturday. High level moisture will gradually increase overnight
with ceilings lowering to MVFR along the immediate coast by Saturday
afternoon as precipitation spreads onshore. Low level easterly flow
will quickly flip onshore with the arrival of front. Gusty post-
frontal W/SW surface winds are expected across much of the area
Saturday afternoon and evening.


KSEA...Increasing high and mid level clouds late tonight into
Saturday morning. Areas of light precip are expected to reach the
terminal after 00Z, but ceilings likely remaining above MVFR
thresholds. E/NE surface winds will reverse to S/SW around 20Z on
Saturday and remain gusty well into Saturday evening. 27

&&

.MARINE...Broad high pressure situated across the Pacific Northwest,
with a weak thermal trough situated along the coastline. The next
frontal system is situated well offshore, sitting around 135 W as of
this afternoon. Winds are offshore/easterly across the coastal
waters today, with the breeziest winds through the Central Strait of
Juan de Fuca, reaching 15 to 20 kt. Winds should remain just below
Small Craft Advisory level going into tonight, so the advisory has
been dropped. Offshore flow will be enhanced through the gaps around
the Olympics tomorrow as the system approaches, thus a Small Craft
Advisory will begin early tomorrow morning for the coastal waters
north of Point Grenville, as well as the Central and West Entrance
to the Strait of Juan de Fuca. Winds will pickup in the coastal
waters north of Cape Shoalwater, as well as into the Eastern Strait
of Juan de Fuca and through Puget Sound Saturday afternoon as the
front moves through the coastal waters. Winds look to ease area-wide
late Saturday night into Sunday.

High pressure will return Sunday afternoon into the beginning of
next week, with a few pushes of westerly winds down the Strait of
Juan de Fuca which will likely require additional headlines.

Seas remain around 3 to 5 ft through tonight. Seas will rise to 8 to
12 ft Saturday afternoon into Sunday. Seas may be steep,
particularly through the outermost waters, over the weekend with the
dominant period being 9 seconds. Seas decreasing to 6 to 8 ft Sunday
and Monday then decreasing further into midweek.

LH

&&

.HYDROLOGY...No river flooding expected over the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 3 AM Saturday to 5 AM PDT Sunday for
     Central U.S. Waters Strait Of Juan De Fuca-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-West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM to 11 PM PDT Saturday for East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 2 PM to 11 PM PDT Saturday for Puget
     Sound and Hood Canal.

     Small Craft Advisory from 11 AM to 11 PM PDT Saturday for
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm.

&&

$$