Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 222238
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
338 PM PDT Wed Mar 22 2017

.SYNOPSIS...Showers will taper tonight, then Thursday morning is
likely to be dry. The next system will approach the area Thursday
with rain beginning along the coast in the afternoon. The slow
moving front will not move completely through the area until Friday.
Post frontal showers will diminish Saturday with more weather systems
arriving late Sunday and again Wednesday.

&&

.SHORT TERM...The upper trough appears to be just inland from the
coast, where radar shows a pretty good band of showers holding
together. This band of showers will move through the Puget Sound
area late this afternoon. Showers will diminish in the evening, with
only the mountains, coast, and perhaps a convergence zone north of
Seattle retaining any shower activity. The breezy conditions around
the area this afternoon will also taper overnight.

High pressure will briefly build over the region tonight. This will
keep most of the forecast area dry later tonight and Thursday
morning, with inland areas probably remaining dry into Thursday
afternoon. Rain will develop on the coast in the afternoon, and
clouds will increase everywhere. Temperatures will be a few degrees
higher than today.

Rain will spread over the entire area Thursday night as a cold front
approaches the coast. Frontal passage will not occur until the
morning hours on Friday as a digging upper level trough behind the
front slows the eastward progress of the system. There will be
plenty of shower activity behind the front Friday afternoon. Lows
Thursday night will be in the 40s with highs on Friday only a few
degrees warmer than the lows, in the upper 40s to mid 50s.

High pressure will again build briefly over the area on Saturday,
with likely pops Friday evening diminishing to low chance pops by
Saturday afternoon. Saturday will be a few degrees cooler. Burke

.LONG TERM...The euro and GFS are in broad agreement. The next
system arrives from the southwest Sunday afternoon and evening.
Monday will be showery. Tuesday will be mostly dry. Another system
arrives around Wednesday. The best chance for rain will be on the
coast and in the mountains. High temperatures will probably be
within a few degrees of normal. Burke

&&

.AVIATION...An upper trough will zip across southwest B.C. early
this evening. An upper ridge will briefly build into Western
Washington on Thu morning with a decrease in showers and clearing
low clouds. Then an offshore trough late Thursday will start to
draw a warm front northward through the region, with a return of
thickening clouds and rain on Thu PM. Moderate west flow aloft
tonight, becoming strong southwest flow aloft late Thursday. Moist
and somewhat unstable air mass through Thursday morning, becoming
more stable on Thursday afternoon and evening.

KSEA...Broken clouds expected for much of this evening in the
030-040 range. Expect some passing showers through 6 pm, then
showers tapering off. Cigs may fall briefly into the 020-030
range overnight. Then a drying easterly component to the low-
level flow will develop early Thu morning, which will help clouds
below 050 to scatter out for late Thu morning and Thu afternoon.
Warm front will arrive on Thu evening with thickening clouds and
some rain. Haner

&&

.MARINE...Surface trough and cold front about to exit east of
Puget Sound. Westerly gales expected through the Strait this
evening. A warm front will spread up from the south late Thu,
which will bring a round of southeasterly gales to the coastal
waters, the eastern half of the Strait, and the northern inland
waters on Thu PM. Winds easing Friday. Surface high pressure
centered over Western Washington on Saturday will lead to light
winds.  Haner


&&

.HYDROLOGY...The White River at R Street near Auburn is forecast to
remain near flood stage through Thursday evening, primarily due to
releases from Mud Mountain Dam. Elsewhere, river flooding is not
expected for the next 7 days.

With more rain on the way, the landslide threat will increase on
Friday with the elevated threat continuing into the weekend. Burke

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 10 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.

     Gale Warning from 10 AM to 11 PM 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.

     Gale Watch from Thursday evening through late Thursday night 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.

     Gale Warning until 9 PM PDT this evening for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
     Juan De Fuca.

     Small Craft Advisory until 6 PM PDT Thursday for Admiralty Inlet-
     Northern Inland Waters Including The San Juan Islands-West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 9 AM PDT Thursday for Puget Sound and
     Hood Canal.

&&

$$

www.weather.gov/seattle

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