Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 132246

Area Forecast Discussion
National Weather Service Seattle WA
246 PM PST Fri Jan 13 2017

.SYNOPSIS...High pressure and light winds over the region will
allow a cold dry air mass to persist in place through Sunday, with
mid-high clouds passing by at times. Wetter and warmer west flow
aloft will develop Sunday night and Monday, bringing a series of
frontal systems across the area from Monday through next Thursday.


.SHORT TERM...High pressure and offshore flow will continue
through the weekend for more cool and dry weather across Western
Washington. Low temperatures will be in the teens to 20s with
highs in the mid 30s to lower 40s. Weak systems will split
offshore but will send mid/high clouds inland for partly cloudy

The dense/stable low level air mass is limiting mixing and a few
spots are seeing a decrease in air quality, like Darrington.
Check with local clean air agencies for possible burn bans. 33

.LONG TERM...A pattern change early next week will bring wetter,
warmer and windier weather back to Western Washington. This
change will take place Monday night as a strong jet lines up over
WA. Temperatures Tuesday and Wednesday will spike into the lower
50s as warmer air moves in. Snow levels will also rise over 6000
feet, although east winds will keep snow levels at the surface in
the Cascade passes. It will be wet through the period and the GFS
is showing several inches of precip in the mountains, mostly as
rain. This may force rises on the rivers as we move toward
Wednesday night and Thursday. The ECMWF, however, is lighter on
the QPF but still wet in general. It will be windy through the
period as well, particularly the coast and north interior as low
pressure systems clip through the offshore waters. Snow levels
will drop toward the end of the week as a trough moves
inland...back to around 2000 ft. This trough will maintain showers
across the region with snow showers in the mountains. Temperatures
will return to normal. 33


.AVIATION...High pressure at the surface and aloft will maintain
generally light flow at all levels. A dry and stable air
mass will persist, except for some high cirrus clouds at times.

KSEA...Light variable or northeast wind to 5 kt. Sct-Bkn150-250


.MARINE...Surface high pressure east of the Cascades will give
light offshore flow through Saturday. A weak front will dissipate as
it reaches the area this weekend. A series of stronger fronts will
reach the Pacific Northwest beginning Monday. dtm


.HYDROLOGY...River flooding is not expected through Monday. A period
of heavy rain next Tuesday/Wednesday will cause rises on area
rivers. Minor flooding on a few rivers is possible. Note: Snow is
not a significant contributor to flood flows on western Washington
rivers. Even when there is snow on the ground, river flooding is
almost exclusively caused by runoff from heavy rain.




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