Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 160358
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
858 PM PDT Wed Mar 15 2017

.SYNOPSIS...Strong west or southwest flow aloft with embedded
disturbances will keep the weather pattern over the region wet and
unsettled the rest of this week. There will probably be a brief dry
period with some sunshine Friday morning before steady, locally
heavy rain arrives later in the day. Anticipate the potential for
locally windy conditions on Saturday.

&&

.SHORT TERM...
There were scattered showers over the CWA at this time, more
numerous over the mountains and coast. Not much change is expected
overnight under weak cyclonic flow aloft. Meanwhile, winds picked up
over a number of places during the late afternoon through early
evening. Expect the winds to diminish overnight.

A weak front will keep rain likely on the coast Thursday and
Thursday night while inland areas dry out a bit. Highs will be in
the lower 50s on Thursday.

Friday will begin fairly dry but by afternoon rain ahead of a front
will spread over most of the area. Models continued to bring a deep
low toward the coast Friday night, then fill it as it moves inland
Saturday. Model tracks have diverged in recent runs with the GFS
bringing the low inland near Hoquiam and the ECMWF bringing it into
Vancouver Island. Regardless, Friday night and Saturday look wet
and at least breezy. Highs Friday will be near 50 but will rebound
into the mid 50s on Saturday. 05/Burke

.LONG TERM from the previous discussion...
A drying trend will begin Saturday night and continue Sunday.
Surface high pressure will build over southern British Columbia and
flow will turn more offshore Monday. Heights will not rise much so
temperatures will be on the cool side, with daytime highs in the low
50s and overnight lows dipping into the 30s. There could be some
mountain showers on Sunday but otherwise the two days look
completely dry. On Tuesday a weak system will arrive from the south
and another one will follow on Wednesday. Chance POPs cover these
systems. Highs will remain in the low 50s. Burke

&&

.AVIATION...A frontal system will move inland tonight with
southwest flow aloft. Westerly flow aloft will prevail on Thursday
with weak high pressure at the surface over Western Washington.
The air mass is moist and stable.

Low clouds should decrease tonight behind a front as somewhat
drier air moves into the area but some low clouds will probably
linger. There should mostly just be mid and high clouds across the
area on Thursday in between weather systems.

KSEA...Low clouds should lift and scatter tonight. A Puget Sound
Convergence Zone might complicate matters however. It looks like
mid level clouds should be prevalent on Thursday although there
might be some lower ceilings in the evening as a weak weather
system brushes the area. South wind 10-15 knots tonight will ease
on Thursday. Schneider

&&

.MARINE...A front will move inland tonight with moderate onshore
flow in its wake. Small craft advisory winds are expected most
waters tonight with gales in the Central and Eastern Strait of
Juan De Fuca.

Winds will gradually ease Thursday and Friday then another
frontal system will move through the waters Friday night and
Saturday. A surface low will move onshore early Saturday
somewhere between the central Washington coast and central
Vancouver Island. There is a good amount of uncertainty with the
details and this will have a big impact on the winds.

Offshore flow will develop Sunday and Monday. A weak frontal
system may reach the area on Tuesday. Schneider

&&

.HYDROLOGY...
Flood Warnings remain in effect for the following rivers: Snoqualmie
River near Carnation, Cowlitz River at Randle, and the White River
at R Street (affecting Auburn and Pacific). The flow at the R Street
Bridge in Auburn is forecast to remain near 6500 cfs for at least a
couple of days.

A Flood Watch is in effect for the Skokomish River in Mason County.
Additional heavy rain the end of this week, could drive the
Skokomish River above flood stage again. The threat of flooding on
the Green River has ended.

Meanwhile, more rain on nearly saturated soils will result in an
elevated threat of landslides for much of the CWA the rest of this
week.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Warnings and/or Watches are in effect for parts of the
  CWA.

PZ...Gale Warning until 5 AM PDT Thursday for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
  Juan De Fuca.

 Small Craft Advisories are in effect for the remaining waters.

&&

$$

www.weather.gov/seattle

An illustrated version of this forecast discussion can be seen at
www.weather.gov/seattle/gafd/latest_webafd.html



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