Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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452
FXUS66 KSEW 262322
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
300 PM PST Sun Feb 26 2017

.SYNOPSIS...Showers will diminish tonight as an upper level low
dissipates over northern Oregon this evening. An upper trough will
move across Washington Monday afternoon and evening. Cool
northwesterly flow aloft will be a good snow producer for the
mountains Wednesday through Friday. An upper level trough will
bring showers Saturday, which will taper Sunday.

.SHORT TERM...The upper level low now over northwest Oregon is
forecast to move east and dissipate over northern Oregon tonight.
Showers associated with the low will gradually shift south. Radar
shows few showers north of about Everett and there has been good
clearing in far northern Washington. Will keep the snow advisory
for the Cascades of Lewis and Pierce counties for another 3 to 5
inches this evening, but have dropped the advisories for the
Cascades of King and Snohomish counties and the Olympics.

Overnight lows tonight will be around freezing. The lowest
temperatures will occur after showers have ended and skies have
cleared a bit, so little additional snowfall is expected. An upper
trough will move through the region Monday, spawning more
showers. Most of the showers will be in the mountains and in a
possible convergence zone. Highs Monday will be in the upper 30s
to mid 40s. The showers could have snow at times, but QPF will be
noticeably lighter and no significant accumulation is forecast in
the lowlands.

Monday night and Tuesday morning will be mostly dry, but an
impulse moving through northwest flow aloft will enhance showers
in the afternoon, especially on the coast and in the mountains.
Highs Tuesday will be in the low to mid 40s. Moist northwest flow
aloft will continue Wednesday, with high pops on the coast and in
the mountains, and the interior lowlands in something of a rain
shadow. Heights will rise Tuesday night and Wednesday, with snow
levels rising to 2000 feet. Highs Wednesday will be in the mid to
upper 40s. Burke

.LONG TERM...Upper flow will turn more westerly on Thursday and
Friday and the air mass will get noticeably more moist. This
pattern will give copious snow to the mountains. The Euro is not
quite as wet as the GFS. Highs will be 45 to 50. On Saturday an
upper trough will move through the region, spawning showers.
Models diverge after that. Burke

&&

.AVIATION...A cold upper trough over the region will move inland.
Showers over Western Washington will decrease this evening. The
air is moist and somewhat unstable, more so over southwest WA and
drying and becoming more stable in the north.

KSEA...Scattered showers will decrease with some partial clearing
at times tonight.

&&

.MARINE...Low pressure near the coast will weaken through Monday.
A front will move ashore Tuesday evening with stronger onshore flow.
The next stronger frontal system is due to arrive Thursday.

&&

.HYDROLOGY...No flooding is expected during the next week.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 10 PM PST this evening for
     Cascades of Pierce and Lewis Counties.

PZ...Small Craft Advisory for hazardous seas until 3 AM PST Monday
     for all the Coastal Waters.

     Small Craft Advisory until 5 AM PST Monday for Grays Harbor Bar.

     Small Craft Advisory until 9 PM PST this evening for Central
     U.S. Waters Strait Of Juan De Fuca.

     Small craft advisory this evening Northern Inland Waters.

&&

$$

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