Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 180430

Area Forecast Discussion
National Weather Service Seattle WA
830 PM PST Sat Nov 17 2018

.SYNOPSIS...High pressure aloft will maintain the cool dry weather
pattern through Tuesday. Areas of night and morning fog or
freezing fog will give way to afternoon sunshine. A series of
weather systems will bring wet weather by the middle of next week
through the holiday weekend.


No major changes to the previous forecast thinking: An upper
level ridge centered along 130w will shift directly over the
Pacific Northwest through Tuesday. Dry weather will persist along
with some patchy fog night and morning fog or freezing fog in
prone sheltered valleys.

The SEA-EAT gradient may reach -10 mb overnight so there could be
some brief localized gap winds, but gusts to 30 or 35 mph will
likely remain near the pass summits.

The upper ridge finally shifts inland by Tuesday allowing deep
southerly flow to develop over the west coast. This flow direction
could allow wildfire smoke from CA to lift north again into
Oregon/Western WA. This potential for a brief smoke intrusion
around Tuesday of next week could cause some hazy conditions with
worsening air quality for roughly 24 hours. A front on Wednesday
should create a lot of mixing and should improve air quality issues
if any arise.

Models indicate a pronounced pattern change by around Wednesday
of next week, through the holiday weekend. A series of stronger
systems will bring rain at times to the region, but the progressive
flow and pronounced split will likely reduce rainfall amounts.
See the hydrology section below for details. Temperatures will
cool slightly by next Friday and Saturday, but not far off the
average for this time of year. Highs mostly upper 40s to low 50s
with lows in the 30s to around 40. Mercer


No major changes to the previous forecast thinking: High pressure
and offshore flow will lead to dry and stable conditions across
Western WA. The flow aloft is northerly with E/NE winds at the
surface. Skies are clear but may see patchy/shallow fog near the
sound early Sunday morning. Otherwise, expect VFR conditions. 33

KSEA...N/NE winds to 8-15 kt. Patchy low clouds may form near the
Sound Sunday morning but will be shallow and short- lived. 33


No major changes to the previous forecast thinking: Offshore
flow will prevail across Western WA through early next week due
to strong high pressure east of the Cascades. Winds are N/NE over
the waters with Small Craft Advisories in effect, specifically for
the West Entrance and adjacent Coastal Waters. Winds will ease
this evening. The next frontal system will approach the region on
Tuesday then split and weaken as it moves inland on Wednesday. 33


River flooding is not anticipated the next 7 days; however, there
is a slight risk the Skokomish River could flood by the end of
upcoming week.




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