Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 292320 CCA

Area Forecast Discussion
National Weather Service Seattle WA
300 PM PST Tue Nov 29 2016

.SYNOPSIS...A front will bring rain and mountain snow to the region
later tonight into Wednesday. A weak ridge will move through the
area Thursday ahead of a warm front. A mild and fairly wet weather
pattern at the end of the week will turn colder with a chance of
lowland snow showers by next Monday.


.SHORT TERM...A front is just offshore and that will bring some rain
into the area later tonight and Wednesday. A warm front dirty ridge
pattern will set up for Thursday through Saturday with rain at times
and mild weather. The snow level will rise back up above I-90 but
the higher mountains may continue to have snow at times. Looking at
the timing of each front...the GFS shows the front that is offshore
this afternoon reaching the coast in the early morning hours
Wednesday. The low pressure area gradually fills over the region
Wednesday afternoon and night, but there is plenty of onshore flow
so it should be wet. Thursday looks like the main break in the
weather as high pressure builds in--but there are still dribs and
drabs of precip so it looks like a dirty ridge and not much clearing
is likely. Thursday night could be dry, but low clouds will probably
set up or some fog. On Friday warm advection begins in earnest and
the rain starts up again.

.LONG TERM...The front that arrives Friday will probably slow down
and stall while it weakens Friday night and Saturday with rain at
times. The 12z GFS shows a decent frontal wave moving into the area
Saturday night and a cooler air mass should arrive behind the front
on Sunday. After that a much cooler air mass in a showery pattern
looks like about the best bet for now, as a rather cold trough moves
through the area Sunday night and Monday. The snow level could drop
down to sea level by daybreak on Monday and stay low through Tuesday-
-although by Tuesday there might not be much moisture left as an
upper ridge starts to build into the area for a day or two.


.AVIATION...A front will approach the coast tonight and move inland
Wednesday. Flow aloft will become southerly tonight, then westerly
on Wednesday. At the surface, light winds will become increasingly
southerly tonight, then turn onshore Wednesday. The air mass is
moist and stable.

Ceilings are VFR. Rain will develop on the coast this evening and
after midnight over inland areas. Ceilings will trend down to MVFR.

KSEA...Discussion above applies. Southeast wind 6-10 KT today
increasing to 10-15 KT after midnight. CHB


.MARINE...A front will reach the coast late tonight and move inland
Wednesday. Winds will become increasingly southerly, with gales
likely on the coast. Recent mesoscale models including the UW-WRF
and Canadian HRDPS show brief gales at the east entrance and over
the northern inland waters late tonight, so a gale warning is now in
effect there. Small craft advisory strength winds area likely over
most of the rest of the inland waters. Onshore flow will follow on
Wednesday with westerly winds in the strait 20-30 KT.

Higher pressure will rebuild over the area Wednesday night and
Thursday. The next front is forecast to reach western Washington
around Friday. CHB


.CLIMATE...If you live on the north coast and think it has been
raining a lot lately, you`re not wrong. October 2016 was the third-
wettest October at Quillayute (KUIL), with 21.08 inches. The wettest
October was in 1975, with 27.17 inches.  With two days remaining in
the month, November 2016 is already the fourth wettest November,
with 25.08 inches. The wettest November was in 1983 with 29.14
inches.  This year`s October and November is the second wettest
October and November on record at KUIL, with 46.16 inches.  The
wettest was in 1975, with 51.45 inches.


.HYDROLOGY...Any additional rain through Saturday is expected to be
generally light and should not be enough to produce flooding on any
area river. A stronger storm may bring heavier rain Saturday--but
snow level will fall sharply by Sunday. The Skokomish river would
probably be the only river with a chance to approach flood stage.
Also, there is a special weather statment for the chance of isolated
landslides from the recent wet weather.



PZ...Gale Warning coast, east entrance, and north inland waters.
     Small craft advisory all other waters except Puget Sound.
     Small Craft Advisory for rough Grays Harbor bar.



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