Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 230409
AFDSEW

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

.SYNOPSIS...Lingering scattered showers tonight fizzling out by
Thursday morning with most inland locations looking at dry
conditions for much of the day. 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...It is actually shaping up to be a pretty nice evening
ranging from a fairly picturesque sunset to a kinda-sorta clear
radar screen. There are some scattered areas of activity...mainly
out on the Olympic peninsula and a weakening convergence zone set up
over the Snohomish-Skagit county line. Downward trends continue on
the radar...so would expect activity to completely fizzle out during
the overnight hours.

Thursday looks to start off dry for W WA...how long the dryness
lasts will depend on location as the next system starts to impact
the coast in the early afternoon while the remainder of the area
looks to get a pass until the early evening. There may even be some
prospect for a few peeks at the sun during the morning hours. Models
have remained pretty consistent that this next frontal system will
be slow to traverse the area with the main front ejecting by late
Friday morning. Post frontal showers will linger...albeit being more
scattered...in the late morning and early afternoon before the upper
level trough associated with the front pushes through...heightening
pops for the late afternoon and evening time frame. Activity
scatters out overnight Friday and early Saturday before another dry
period sets up. A dry period that...sadly...like the one for
Thursday...will be best measured in hours and not days.  SMR

.LONG TERM...From previous discussion...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...Westerly flow aloft over Western Washington this
evening will continue tonight, then back to southwest Thursday as
the next frontal system approaches the region from the west. At the
surface, strong onshore flow that followed today`s cold front will
ease this evening and turn weakly offshore late tonight. The air
mass will remain slightly unstable and moist, especially in the
lower to mid layers tonight and Thursday morning.

VFR conditions prevail across the forecast area this evening SCT025
BKN-SCT045 BKN100; scattered showers are producing local BKN025
OVC040, but these should decrease and mostly end by midnight. VFR
conditions should continue Thursday with ceilings mainly above 060.

KSEA...Southwest wind 12-18 kt gusting 26 kt, becoming south and
easing to 6-12 kt by midnight. KSEA will likely have VFR conditions
the rest of tonight and Thursday, with the ceiling 035-050 at times
tonight. McDonnal

&&

.MARINE...Strong onshore flow developed across Western Washington
late this afternoon followed the cold front that crossed the area
from the west. Onshore flow is easing rather quickly though, and the
gale warning for the westerlies in the central and eastern Strait of
Juan de Fuca will end with the 9 pm forecast issuance.

A vigorous Pacific frontal system will move into the offshore waters
Thursday and inland Thursday night. Gale force southerlies are
likely over the coastal waters, as well as the east entrance Strait
of Juan de Fuca and northern inland waters. A weak trough will
follow the front on friday, and weak high pressure will build over
the region Saturday. Another Pacific frontal system will move
through Sunday night. McDonnal

&&

.HYDROLOGY...From previous discussion...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.

     Small Craft Advisory until midnight PDT tonight for Admiralty
     Inlet-Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca-Puget Sound and
     Hood Canal.

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

&&

$$

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