Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 230422
Area Forecast Discussion
National Weather Service Seattle WA
922 PM PDT Sat Oct 22 2016
.SYNOPSIS...A weak front will move through Western Washington
tonight and Sunday for areas of light rain, mainly at the coast.
A series of relatively weak fronts will also bring rain at times
next week. Precipitation should be generally light, except for a
stronger system on Wednesday that will bring wetter and blustery
.SHORT TERM...A relatively weak front is moving into Western
Washington this evening, with a little rain starting to fall along
the coast within the last hour or so. Higher clouds -- mainly
above 10,000 ft -- cover the interior of Western Washington. The 8
pm temperatures were in the upper 40s and 50s.
The support for this frontal system is swinging northeastward off
the coast of British Columbia, so the portion of the front
affecting our forecast area will weaken further as it moves slowly
inland tonight and Sunday morning. The Western Washington interior
lowlands and the Cascades will generally receive less than a tenth
inch of precipitation, and some areas will probably remain dry.
The coast and the Olympics will only receive up to a third inch or
so. There will likely be mid and high level moisture over the area
through Sunday afternoon, so not much in the way of sun breaks is
Southerly flow aloft will continue over the region Sunday night
and Monday ahead of a deep, vertically-stacked low well offshore.
Another weakening frontal band associated with the low will move
through the area mainly on Monday. Another rather disorganized
front will move through late Monday night and Tuesday, as the low
tracks almost due north toward Haida Gwaii. The bottom line for
the forecast is that Western Washington will get some rain at
times Sunday night through Tuesday night, but it won`t amount to
much. Up to an inch total could fall at the coast and in the
Olympics, with around a quarter inch over the interior lowlands
and in the Cascades. The snow level will remain around 6000 ft.
.LONG TERM...Here is the long term section from the afternoon
forecast discussion -- Models are in pretty good agreement showing a warm
front moving up from the southwest and through Western Washington
on Wednesday. It looks like a good soaker. There will also be a
surface low around 990 mb passing offshore and into Vancouver
Island. This should keeps things breezy to windy coast and north
interior although models differ on how close the low will get
which would affect how much wind occurs.
Models begin to diverge Thursday and there is little agreement
after that other than the general idea of additional frontal
systems keeping things wet at times. Schneider
.AVIATION...An upper trough will persist around 130W-140W
through Monday with moderate S-SW flow aloft over Western
Washington. A weakening will reach the coast in the early
morning hours on Sunday and dissipate over the interior in the
morning. Low level easterly flow will keep ceilings aoa 4000
feet through Sunday morning with the exception of some brief
ceilings in the 2000-3000 foot range along the coast. Ceilings
will rise again Sunday afternoon.
KSEA...A drying easterly component to the low-level flow will keep
VFR cigs through Sunday. The dying front will bring some light
showers the terminal in the 10z-14z time frame. Even with the
showers ceilings will remain aoa 4000 feet. Light wind becoming
light southeasterly Sunday morning. Felton
.MARINE...A strengthening 998 mb low will move due north along
130W tonight, on its way to Haida Gwaii on Sunday morning. A
trailing front will slowly move onshore early Sunday morning and
then dissipate over the inland waters later Sunday morning.
Dissipation of the front will lead to a lull in the wind on Sunday
afternoon. An even stronger 970 mb low will slowly move northward
near 130W and west of Washington on Monday afternoon and Monday
night, bringing gales to the coastal waters. Yet another strong
low center will move northward along 130W on Wednesday.Felton/Haner
PZ...Small Craft Advisory until 5 AM PDT Sunday 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-West Entrance U.S. Waters Strait Of
Juan De Fuca.
Small Craft Advisory from midnight tonight to 3 PM PDT Sunday
for East Entrance U.S. Waters Strait Of Juan De Fuca-
Northern Inland Waters Including The San Juan Islands.
You can see an illustrated version of this discussion at