Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
900 am PDT Thursday Oct 8 2015
Synopsis...western Washington is between weather systems today.
A front will move through the area Friday...followed by another
front with more rain and locally windy conditions Saturday. A third
front should move through the region on Monday. High pressure will
build over the area by the middle of next week.
Short term...a ridge will nose north over the area today and shift
east tonight. Clouds this morning should give way to some clearing
later today. A deep low will move north through the offshroe waters
tonight and while most of the rain will head up into British
Columbia...the trailing front will still give western Washington some rain at
times on Friday...rainfall will be generally light. Another
progressive frontal system will bring rain and locally breezy to
windy conditions Saturday. A look at the 12z NAM suggests that most
of the rain with that front will be east of I-5 by Saturday evening
but there is an area of rain that redevelops along the South Washington and
north Oregon coast as if a weak trailing wave on the front gets hung
up there Saturday night so the next break in the precipitation may hold off
Long term...a break between systems and a dry day is looking
increasingly likely on Sunday. For now we will stay with a mostly
cloudy and chance of light rain forecast...but it could be dry and
partly sunny. Another front will sag slowly southeast across the
area late Sunday night through Monday night. Dry weather is likely
Tuesday and Wednesday as an upper ridge builds.
Aviation...west to southwesterly flow aloft with a flat upper level
ridge over the Pacific northwest. LIFR ceilings and visibilities in a few
locations this morning...mainly over the south sound...and patchy
low clouds and fog over the remainder of the area. Low clouds and
fog will lift and clear through the late morning followed by come
clearing in the middle level deck this afternoon and evening.
The air mass will remain moist and stable.
Ksea...middle level clouds have helped limit the impact of low clouds
and fog this morning...still possible to get some reduced
visibilities over the next hour or so. Expect middle level clouds and
VFR conditions through the afternoon and evening. Winds will remain
Marine...nominal southerly winds 10 to 20 knots are expected over the
coastal waters today and light winds for the inland waters.
Remnants of huricane oho will move to the west of the coastal waters
late tonight...bringing gale force winds to the outer coastal waters
by Friday morning as well as large southwesterly swell for all of
the coastal zones late tonight and Friday. Swells in the 12 to 14
foot range are forecast for the coast. A frontal system moving
through the area on Friday will subsequently bring Small Craft
Advisory winds to the remainder of the coastal zones and over the
northern portion of the area. A second...stronger front will affect
the area Saturday for Small Craft Advisory winds over all area
waters as well as another round of large swell for the coastal
waters. Sunday will see a break followed by a third system will on
A marine weather statement has been issued for the large swell
expected to affect the coastal waters going into the Holiday
weekend. Persons going to the coast should use caution when
approaching the surf zone.
Washington...none. Pz...Gale Warning outer coastal waters.
Small Craft Advisory inner coastal waters...northern inland
waters...East Entrance to the Strait and Admiralty Inlet...and Grays
Harbor for rough bar conditions.
You can see an illustrated version of this discussion at