Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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063
FXUS66 KSEW 211655
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
855 AM PST Sat Jan 21 2017

.SYNOPSIS...A couple upper lows will bring showers at times
through the weekend. High pressure aloft will result in mainly dry
weather next week.

&&

.SHORT TERM...An upper low off the Washington coast will create
showers at times today through late Saturday. Another upper low
will replace the first one and bring in a weak frontal system for
a period of steadier precipitation on Sunday. Expect seasonable
temperatures during this time.

On Monday the second upper low will begin to move southward to
Northern California and an upper ridge will begin to build in for
drier weather. The GFS time-height diagram is showing plentiful low
level moisture next week during the ridging, indicating that foggy
conditions could develop. Have left fog out of the forecast for
now since there is still uncertainty this far out. JSmith

.LONG TERM...The drier upper ridge pattern will continue through
much of next week. Out past Thursday, the model solutions diverge
on whether the ridge will continue or there will be a return to
cloudy and showery conditions. The GFS has a drier solution while
the ECMWF indicates a chance for showers, especially in the
northern and western parts of the CWA. JSmith

&&

.AVIATION...An upper level trough will lift NE through Western WA
today for showers across the area. The air mass is moist and
slightly unstable. Showers will diminish tonight as the trough
exits north. Surface flow is E/SE with VFR conditions expected. 33

KSEA...VFR with E/SE surface flow. Showers in the vicinity this
morning, increasing in coverage 00-06Z. 33

&&

.MARINE...A surface trough will lift NE through Western Washington
today. A 960-965 mb surface low will track along 130W late
Saturday night with an occluded front moving inland on Sunday.
This front may produce gale force winds over the Coastal Waters.
The flow over Western WA will turn offshore early next week as the
surface low weakens and drifts south offshore. 33

&&

.HYDROLOGY...River flooding is not expected for the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Surf Advisory until 6 PM PST this evening for Central Coast-
     North Coast.

PZ...Gale Watch from late tonight through Sunday afternoon 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.

     Small Craft Advisory until 2 AM PST 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.

     Small Craft Advisory for rough bar until 4 PM PST Sunday for
     Grays Harbor Bar.

     Small Craft Advisory until 7 PM PST Sunday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca-Northern Inland Waters Including The
     San Juan Islands.

     Small Craft Advisory until 6 PM PST Sunday for West Entrance
     U.S. Waters Strait Of Juan De Fuca.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html



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