Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 260313
Area Forecast Discussion
National Weather Service Seattle WA
815 PM PDT Tue Oct 25 2016
.SYNOPSIS...A weather system will bring rain to Western Washington
on Wednesday. The weather pattern will remain generally unsettled
and wet at times, except for Friday which should be dry.
.SHORT TERM...A weather system will bring another round of rain to
the area Wednesday and Wednesday night. A low pressure center
will move north through the offshore waters and give the coastal
waters southeasterly gales and some areas of breezy weather over
land. There will be a some areas of rain or showers Wednesday night
and Thursday as disorganized systems continue to move into the area.
Western Washington will see a break between weather systems Friday.
.LONG TERM...The long wave trough reloads off the U.S. west coast on
Saturday. Models show a series of lows lifting northward over the
area or just offshore just above every day through the middle of
next week. There is no skill in timing each of these systems so a
broad brush chance of rain is in the forecast. None of these systems
look particularly strong so mostly light rain or showers with
sunbreaks expected. Highs near average in the low 60s. Mercer
.HYDROLOGY...Around two inches of rain is likely for the Olympics on
Wednesday and that should not be enough for a risk of flooding on the
Skokomish river. Flooding is not expected on any rivers over the
next seven days.
.AVIATION...An upper trough between 130W and 140W will give
moderate to strong southwesterly flow aloft through Wednesday
night. A 992 mb surface low well off of the northern California
coast will lift northward about 250 nm offshore Wednesday
afternoon and Wednesday night. A warm front will spread up through
the area from the south late tonight and Wednesday morning,
followed by southerly flow late Wednesday afternoon and Wednesday
night. The air mass will be moist and stable.
Light rain will spread northward into the area about 10Z-12Z Wed
and will become moderate 14z-20Z as a warm front lifts north
across the area. Easterly pressure gradients at the lower levels
ahead of the incoming warm front will have the effect of holding
ceilings and visibilities in the VFR category through about 15Z,
then rainfall will overwhelm the offshore flow resulting in
conditions falling to MVFR and locally to IFR in reduced
visibility with moderate rainfall during the late morning and
early afternoon hours. Some low level wind shear is possible for a
couple of hours before the passage of the warm front as moderately
strong south flow aloft works down toward the surface. Conditions
will improve to VFR and low level wind shear will end as the warm
front lifts north of the area during the afternoon hours. Albrecht
KSEA...Mid- and high-level clouds will thicken overnight in
advance of a warm front that will move across the area early
Wednesday afternoon. Light rain will likely begin around 12Z with
rain becoming moderate at times from 16Z-21Z. Visibility will
likely drop to 2-4 sm at times 16Z-21Z with the moderate rainfall.
A period of low level wind shear with surface winds east 12G20KT
and 2000 ft winds south 30-35 KT can be expected 18Z-21Z. Surface
wind will switch to south 14G22KT with the front about 21Z and
conditions will improve to VFR. Albrecht
.MARINE...A 992 MB low center will track northward about 250 nm w
of the coastline Wednesday afternoon and night. A warm front will
lift north through the waters midday Wednesday and will be
followed by southerly flow Wednesday afternoon and Wednesday night.
The low will weaken as it moves onto northern Vancouver Island
late Wednesday night.
Over the coastal waters, small craft advisory conditions continue
this evening with hazardous 10-11 ft at 10 second period seas.
Winds will increase from the east ahead of an incoming warm front
later tonight. A small craft advisory has been hoisted for the
coastal waters tonight. Gale conditions will develop from the
south as the warm front passes will continue into Wednesday night
before slowly easing from the south.
An assortment of small craft advisories are in effect for east to
southeast winds in the Strait of Juan de Fuca and the Northern
Inland Waters on Wednesday. Small craft advisory conditions will
spread into Admiralty inlet and the northern portions of Puget
Sound and Hood Canal Wednesday afternoon or evening as the low and
associated warm front lifts to the north.
Light offshore flow will prevail on Thursday through Friday.
A weaker low will lift northward through the offshore waters
Friday night, possibly bringing small craft advisory conditions to
the coastal waters. Albrecht
PZ...Small Craft Advisory until 6 AM PDT 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.
Gale Warning from 6 AM Wednesday to 3 AM PDT Thursday 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 for rough bar until 5 AM PDT Wednesday for
Grays Harbor Bar.
Small Craft Advisory for rough bar from 2 PM Wednesday to 3 AM
PDT Thursday for Grays Harbor Bar.
Small Craft Advisory from 6 AM Wednesday to 3 AM PDT Thursday
for East Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 9 AM Wednesday to 3 AM PDT Thursday
for Northern Inland Waters Including The San Juan Islands.
Small Craft Advisory from 6 AM to 6 PM PDT Wednesday for Central
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 2 PM Wednesday to 3 AM PDT Thursday
for Admiralty Inlet.
Small Craft Advisory from 6 PM Wednesday to 3 AM PDT Thursday
for Puget Sound and Hood Canal.
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