Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 230416
Area Forecast Discussion
National Weather Service Seattle WA
916 PM PDT THU SEP 22 2016
.SYNOPSIS...A weak front will move inland on Friday for some
rain. A strong ridge will bring dry and warmer weather Saturday
through Monday with the warmest weather in September possible on
Monday. A marine push will cool things down on Tuesday.
.SHORT TERM...Clouds will increase tonight as a front approaches.
The front will bring rain to the coast in the morning and then
lighter and more spotty rain to the interior in the afternoon as
the front weakens and falls apart over Western Washington. Highs
will cool into the upper 50s or lower 60s.
Showers will taper early Friday evening and effectively end by
late evening as the front dissipates in place. An upper ridge
will build over the area on Saturday for dry weather with highs
returning to near normal. Morning clouds should decrease in the
afternoon for partly sunny weather.
A weather system coming over the top of the ridge might bring some
sprinkles to the north coast Sunday morning. Otherwise, the upper
ridge will continue to strengthen over the area Sunday. A thermal
trough will begin to develop along the coast with low level flow
turning weakly offshore. This should allow highs to warm into the
lower to mid 70s many areas. Schneider
.LONG TERM...Previous discussion...A strong upper level ridge
will remain over the Pac NW on Monday for one more dry and warm
day. Offshore flow will prevail with a thermal trough along the
coast. This will likely be the warmest day of the stretch with
highs in the 70s to lower 80s. A high of 78 degrees would tie the
record at SeaTac.
The upper level ridge and thermal trough will shift east on
Tuesday with a return to onshore flow. This pattern change will
bring cooler marine air inland and temperatures will drop back
into the 60s. A trough over the Pac NW will bring a few showers
next Wednesday and Thursday, mainly coast, the mountains and
north part. Temperatures will trend close to normal. 33
.AVIATION...An upper level ridge will briefly build over the
area tonight. Flow aloft will remain northerly with the ridge,
then become westerly late tonight as a front approaches the coast.
At the surface moderate onshore flow this evening will back to
southerly ahead of the front. The air mass will remain dry and
Mostly clear skies will give way to stratus along the coast this
evening, which will spread inland to the southwest interior, then
through the remainder of the interior Friday morning.
KSEA...VFR conditions this evening, with increasing clouds at all
levels after 12Z. Light rain is possible Friday. Southwest wind
6-10 KT tonight will increase to 10G15 KT Friday afternoon. CHB
.MARINE...Onshore flow with small craft advisory westerlies in the
strait this evening will ease after midnight. A front will approach
the coast late tonight, which will back and strengthen winds out of
the south to small craft advisory levels over the coastal waters
late tonight. Stronger winds, likely small craft advisory levels,
will spread to most waters. Winds will decrease considerably
behind the front and will remain generally light through the
weekend as high pressure builds over the area. Westerly swells
around 10 ft are possible on the coast starting Friday afternoon.
PZ...Small Craft Advisory from 11 PM this evening to 5 PM PDT Friday
for Coastal Waters From Cape Flattery To James Island 10 To
60 Nm-Coastal Waters From Cape Flattery To James Island Out
10 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.
Small Craft Advisory until 2 AM PDT Friday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
Small Craft Advisory from 5 AM to 5 PM PDT Friday for Admiralty
Inlet-Northern Inland Waters Including The San Juan Islands-
Puget Sound and Hood Canal-West Entrance U.S. Waters Strait
Of Juan De Fuca.
You can see an illustrated version of this discussion at