Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 212147

Area Forecast Discussion
National Weather Service Seattle WA
247 PM PDT WED SEP 21 2016

.SYNOPSIS...An upper trough will gradually shift south of the
region on Thursday for dry weather across Western Washington. A
weak front will move inland on Friday for some rain. A strong
ridge will bring dry and warmer weather Saturday through Tuesday.


.SHORT TERM...Isolated showers may develop over the Olympics and
Cascades late this afternoon and evening, with dry weather
elsewhere. Temperatures will drop into 40s overnight with a few
upper 30s possible, like Shelton and Olympia.

Thursday is looking like a dry day as an upper level trough over
the Pac NW shifts south and east, while a ridge nudges in from the
west. We`ll likely see patchy low clouds and fog again during the
morning, then mostly sunny skies in the afternoon. High
temperatures will remain near or slightly below normal.

A weak, splitting front will push inland on Friday bringing rain
to the coast...with a chance of rain in the interior. Showers will
mainly affect the Cascades in the afternoon and evening.

A few light showers may linger along the west slopes of the
Cascades Saturday morning. Otherwise, drier weather is expected
in the afternoon as an upper level ridge starts to build over the
region. 33

.LONG TERM...An upper level ridge will bring dry and mild weather
to the region early next week. A thermal trough will form along
the coast for offshore flow Sunday and Monday. Temperatures will
trend above normal with highs in the 70s to lower 80s. The ridge
will shift inland on Tuesday with a return to onshore flow. Cooler
and showery weather is possible next Wednesday and Thursday as an
upper level trough moves in. 33


.AVIATION...A weak upper level trough over Western Washington will
move slowly southeast out of Washington tonight and Thursday. Light
flow aloft tonight will become more northerly Thursday as a ridge of
high pressure aloft briefly builds off the coast. Northerly flow at
the surface will become more onshore Thursday. The air mass is
mostly dry and stable except for cumulus over the mountains. This
cumulus will fade after sunset tonight. Conditions will be VFR
tonight. Patchy fog and stratus will likely return overnight.

KSEA...VFR conditions. There is some chance of stratus or fog at the
terminal 12Z-16Z. Northerly wind 10-15 KT will decrease by 03Z, then
turn southerly Thursday morning. CHB


.MARINE...Mesoscale models continue to highlight small craft
advisory criteria winds over the central and southern coastal zones
this evening and an advisory remains in effect. Onshore flow will
develop Thursday with small craft advisory strength westerlies
possible in the strait Thursday afternoon and evening.

Models show a front reaching the coastal waters Friday. Widespread
small craft advisory southerly winds will develop Thursday night
then become northwesterly Friday afternoon and evening. Surface
gradients and winds will be considerably lighter through the weekend
as high pressure develops over the region. CHB


.SEW Watches/Warnings/Advisories...
PZ...Small Craft Advisory until 5 AM PDT Thursday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 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.



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