Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
000
FXUS66 KSEW 190420
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
920 PM PDT Mon Oct 18 2021

.SYNOPSIS...Upper level ridge to the east with upper level trough
and frontal system well offshore. Dry day Tuesday with southerly
flow aloft and weak offshore flow pushing temperatures a little
above normal. The pattern will become more active Wednesday
onward - with a series of Pacific frontal systems expected to
affect the area - bringing widespread rain, breezy and possibly
windy conditions to parts of the area at times through the
remainder of the week and into the weekend.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...Satellite imagery shows
upper level ridge to the east and upper level trough and frontal
system well to the west of the area this evening. A few high
clouds out ahead of the front over the area this evening along
with some remaining stratus from earlier today.

A few clouds remaining over the area overnight and a dry day on
Tuesday as the front offshore slowly moves toward Western
Washington.

Front offshore splitting as it moves into Western Washington
Wednesday which will reduce the rainfall amounts especially over
the interior. Parent low associated with the front weakening as it
moves into inland up near Haida Gwaii. Breezy conditions
developing along the coast and the Northwest Interior.

Huge low bombing out well offshore Wednesday night into Thursday
with the associated front moving inland Thursday night. Parent
low, which some models have below 960 mb, remaining west of 130W
as it moves by west of the area. With the low that far to the west
not expecting impactful winds over Western Washington.

No changes in the forecast this evening. Felton

.LONG TERM /FRIDAY THROUGH MONDAY/...Previous discussion follows.
Showers and unsettled weather will continue Friday, followed by
the next system sometime late Friday into Saturday, again bringing
another round of widespread rain and possibly breezy to gusty
winds again to the area. Snow levels may drop to around 4500-5000
feet by late Sunday allowing for snow accumulations on the higher
mountain peaks.

&&

.AVIATION...Southerly flow aloft will increase tonight and
Tuesday as an upper trough well offshore slowly approaches. At
the surface, weak high pressure over the area tonight will give
way to gradually increasing easterly flow on Tuesday as an
offshore frontal system approaches. The air mass will be stable.
Areas of ceilings 3000-5000 feet over the central and south Sound
should continue to break up this evening. Otherwise, mostly clear
with high clouds at times into Tuesday.

KSEA...Ceilings around 5000 feet should scatter after midnight
tonight with just high clouds at times after that into Tuesday.
Light wind. Schneider

&&

.MARINE...Weak high pressure over the area will shift inland
tonight. A series of vigorous frontal systems will move through
the area every 24 to 36 hours Tuesday through Saturday. Each
system will bring small craft advisory strength southerly winds
to most waters. Gale force winds are possible for the Coastal
Waters with each system as well. A system on Wednesday could also
bring gales to the East Entrance Strait of Juan de Fuca and
Northern Inland Waters.

West to southwest swell will build to 10-13 feet over the Coastal
Waters and West Entrance Strait of Juan de Fuca Tuesday night and
remain elevated for most of the rest of the week. Schneider

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from midnight tonight to 2 PM PDT Tuesday
     for Coastal Waters From Cape Flattery To James Island 10 To
     60 Nm-Coastal Waters From James Island To Point Grenville
     10 To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.

     Gale Warning from 2 PM Tuesday to 11 AM PDT Wednesday for
     Coastal Waters From Cape Flattery To James Island 10 To 60
     Nm-Coastal Waters From James Island To Point Grenville 10
     To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.

     Small Craft Advisory from 5 AM Tuesday to 5 AM PDT Wednesday for
     Coastal Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville Out 10
     Nm-Coastal Waters From Point Grenville To Cape Shoalwater
     Out 10 Nm.

     Gale Watch from Wednesday morning through Wednesday afternoon
     for East Entrance U.S. Waters Strait Of Juan De Fuca-
     Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 5 AM to 5 PM PDT Tuesday for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

www.weather.gov/seattle


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.