Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 241122
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
320 AM PST Fri Jan 24 2020

.SYNOPSIS...Active weather will continue over the next week as a
series of weather systems move across the area.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Current radar and satellite
clearly show negatively tilted front moving through W WA this
morning with rainfall tapering off over southwestern portions of the
CWA. As this front continues to lift northeastward...could start to
see some locations emerge with dry conditions. However...looking
westward on current IR satellite shows some clouds starting to
develop within the approaching upper level trough. As such...model
progs look to be on track with showers developing in the wake of
this passing front as this upper trough starts to push into the area
with ample low level moisture to work with. As this activity
transitions into showers...models remain consistent that overall
action will trend downward throughout the day. This will help in
getting current hydro situation to behave. For further details on
that...please refer to the Hydrology section below. Will see snow
levels gradually fall through the day but are expected to remain
above 4000 ft for most locations. Portions of the North Cascades
will fall between 3500-4000 ft and as such some snow accumulations
will be possible there...but none that would require any headlines
at this time.

Next frontal system looks to make it to the coast very late
tonight/very early Saturday morning bringing a quick shot of rain
that starts wrapping up by early afternoon. As has been the case
throughout this active period...the brief respites in the
squishiness are measured more in hours than days...and sure enough
by Saturday evening a surface low creeps up the coast from OR to
bring yet another batch of rain...but with the potential for some
winds this time as well. Models still waffling a bit on wind speeds
associated with this system...as previous model runs looked
stronger...but feel safe in saying probably breezy to locally windy
conditions for the usual wind favored locations such as the coast
and north interior. Unless some consistency starts to
emerge...pretty low confidence on if these winds will spread to
other portions of the CWA. This surface low pushes north of the area
by late Sunday morning. A narrow window of diminished shower
activity or even possibly dry conditions exists thereafter but
models disagree as to how long. The GFS does not bring in the next
front until Sunday evening and thus providing a quiet 6-9 hour
window while the ECMWF suggests that if there is any break...if one
were to blink they would miss it before the next front comes in
Sunday afternoon. More inclined to lean toward the ECMWF solution if
for no other reason than that a mere 6-9 hour break just seems
patronizing.  18

.LONG TERM /MONDAY THROUGH THURSDAY/...The aforementioned front
starts to dissipate by late Monday morning but deterministic models
paint two very different pictures of the next system. The GFS brings
the next front up from OR and lifts it into W WA Monday night and
brings the associated upper level low in hot on the heels of said
front...making for wet conditions persisting into Tuesday evening.
The ECMWF actually keeps the worst of the precip down in OR and
while the area still sees precip...it wraps up by Tuesday afternoon.
Given this initial discrepancy...while models fall a bit more in
line with the general pattern...a brief upper level ridge moving
quickly through the area shockingly followed by yet another frontal
system...the timing is off. Ultimately...probably better off just
saying that the extended looks to remain active with the current
essentially wet pattern persisting for the remainder of the forecast
period.  18

&&

.AVIATION...Southwest flow aloft will transition westerly on Friday
as an upper level trough moves through. A cold front will slide
eastward into this morning. The air mass is moist and stable. The
air mass will be unstable Friday afternoon. Steady rain in places
this morning will transition to showers by this morning. VFR for
most spots will be MVFR for most of the morning with low clouds. IFR
for PWT. VFR cigs for most by this afternoon. South winds 7 to 12
knots through this afternoon. A few gusts up to 19 knots this
morning.

KSEA...VFR cigs will transition to MVFR cigs for much of this
morning. VFR cigs this afternoon as lower clouds scatter. Scattered
showers by late this morning. Winds 7 to 12 knots with a few gusts
to 19 knots through this afternoon. JD

&&

.MARINE...Small Craft Advisory level winds for most waters through
today as a front moves through this morning. Winds will be elevated
for the coastal waters this evening into tonight for SCA winds. A
front will slide northward late tonight through Saturday for SCA
winds for most waters. Multiple weather systems through the weekend
for more marine headlines. A strong surface low may move through on
Sunday for possible gales across the coastal waters and northern
inland areas.

Minor tidal overflow possible for the Admiralty Inlet and San Juan
Islands through the morning. JD

&&

.HYDROLOGY...Hydrologically significant precipitation has largely
ended as steady rains have transitioned to showers. Snow levels have
also begun to fall and should come down to 4000-4500 feet today.

Three rivers are currently flooding - the Stillaguamish, the Satsop,
and the Skokomish. All three have recently crested and will be
gradually receding today but flooding will continue for awhile.

A few other rivers flowing off the Cascades, such as the Nooksack
and the Chehalis, are still rising and could reach flood stage later
today or tonight.

The weather pattern will remain wet into next week as a series of
weather systems cross the area. Rivers will continue to run high and
there is the possibility of additional river flooding some time
later next week.

Lastly, an elevated threat of landslides will continue today due to
the recent heavy rains and saturated soils. Schneider

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through this afternoon for Bellevue and Vicinity-
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish
     and King Counties-Cascades of Whatcom and Skagit Counties-
     Central Coast-East Puget Sound Lowlands-Everett and
     Vicinity-Lower Chehalis Valley Area-Olympics-Seattle and
     Vicinity-Southwest Interior-Tacoma Area-Western Skagit
     County-Western Whatcom County.

     Coastal Flood Advisory until 7 AM PST this morning for Admiralty
     Inlet Area-San Juan County.

PZ...Small Craft Advisory until 4 AM PST Saturday for Grays Harbor
     Bar.

     Small Craft Advisory until 11 AM PST Saturday 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 AM PST early this morning for East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from midnight tonight to 11 AM PST Saturday
     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 PM PST this afternoon for Admiralty
     Inlet-Northern Inland Waters Including The San Juan Islands-
     Puget Sound and Hood Canal.

     Small Craft Advisory until 6 PM PST this evening for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

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