Forecast Discussion for SEW NWS Office
000
FXUS66 KSEW 281717
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
917 AM PST Tue Jan 28 2020

.SYNOPSIS...Showers will taper off later today. A front will move
through Western Washington on Wednesday and another will arrive
Thursday evening. Wet weather will continue into the end of the
week. A cooler drier air mass will arrive by early next week.


&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Showers will diminish and
sunbreaks will increase through the afternoon. Tonight will be a
break between systems. The next front will arrive Wednesday, and
then another pause will occur Wednesday night into Thursday
morning. A warm front will arrive Thursday afternoon or evening
and that will be the initial front in a rather wet pattern for the
end of the week into the weekend.

.LONG TERM /FRIDAY THROUGH MONDAY/...Friday and Saturday will be
rather wet across much of Western Washington as guidance indicates
a possible atmospheric river scenario aimed towards the Pac NW.
Although there is some uncertainty as to the exact placement with
this system, with at least some models suggesting the heaviest
amounts fall north of W WA, ensembles do highlight fairly
impressive 5-Day QPF rainfall anomalies for the area. Rain and
rather high snow levels, 6000-7000 feet Friday and Saturday, would
suggest flooding potential across the area into the weekend.
Guidance indicates the front slides south late Saturday into
Sunday, ushering in a cooler weather pattern, at least for Sunday
and Monday. Snow levels are expected to lower considerably Sunday
into Monday and forecasts will need to be monitored to identify
the degree to which there is any precipitation around, especially
on Sunday with the front. Otherwise, temperatures in the mid 50s
Friday and Saturday will cool to the mid 40s early next week. JD

&&

.AVIATION...Southwesterly flow aloft early becoming light as upper
level trough moves through the area. Northwesterly flow aloft behind
the trough this afternoon and evening becoming westerly on Wednesday
as next system approaches the area.

Ceilings in the 1000-2000 foot range with isolated ceilings below
1000 feet and visibility 3-5 in fog from about Seattle northward.
South of seattle mostly clear skies with local ceilings below 1000
feet and visibility 1-3sm in fog. Ceilings becoming 4000-5000 feet
all areas 15z-18z with light rain. Local visibility 3-5sm in the
rain. Scattered to broken layer around 4000 feet later this
afternoon into the evening hours.

KSEA...Periods of -SHRA to continue through the morning with
ceilings generally running around 2000 feet. Ceilings expected to
lift to near 4000 feet later this afternoon and into the overnight
hours. Ceilings are expected to lower back down to 3500-4500 feet
Wednesday morning with the onset of the next round of rain.
Prevailing south southeasterly winds 5 to 10 knots. Felton/Pullin

&&

.MARINE...A frontal system will move through the region
today followed by another system on Wednesday. Conditions will calm
briefly Wednesday night before the next series of systems late
Thursday into the weekend.

Small craft advisories up for the coastal waters and West Entrance
of the Strait of Juan de Fuca through Wednesday. For the coastal
waters a combination of wind and seas. For the West Entrance seas
remaining near 10 feet through Wednesday. Small craft advisory
southeast winds possible for the Northern Inland waters including
Admiralty inlet tonight. Additional systems reaching the area into
Friday with small craft advisory winds over the most of the
waters with each front. Felton/Pullin

&&

.HYDROLOGY...With the exception of the Skokomish river, flooding
is not expected through Thursday. The Skokomish will remain above
flood stage through the week. A possible atmospheric river
scenario could set up beginning later Thursday and continue into
Saturday. This event has the potential to create another round of
flooding on area rivers.

&&

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 4 PM PST this afternoon for
     Cascades of Pierce and Lewis Counties.

     Winter Weather Advisory until 10 AM PST this morning for
     Cascades of Snohomish and King Counties-Cascades of Whatcom
     and Skagit Counties-Olympics.

PZ...Small Craft Advisory until 6 PM PST Wednesday 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-Grays Harbor Bar-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

&&

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NWS SEW Office Area Forecast Discussion