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Area forecast discussion 
National Weather Service Portland or
301 am PST Friday Feb 12 2016

Synopsis...a decent Pacific cold front will move onto the coast middle
morning today and move across the remainder of southwest Washington
and northwest Oregon today for a decent shot of rain. Snow levels
will fall below the Cascade passes tonight as an area of showers
associated with the associated upper trough moves through western
Washington and clips the north part of our forecast area. A warm
front will bring increasing rain to the north part of the area
Saturday afternoon and all of southwest Washington and northwest
Oregon Saturday night and Sunday. The rain will be heavy at times
Saturday night as the first stronger wave along the warm front moves
through...followed by a second weaker wave on Sunday. The warm front
will lift north into western Washington Sunday night and Monday with
rain decreasing from the south. Additional unsettled weather will
produce more valley rain and mountain snow the middle and latter
parts of next week.

Short term...the warm front with the system off the coast brought
some rain to southwest Washington and northwest Oregon Friday
afternoon and evening. The colder cloud tops associated with the
cold front separated from the low level front and brought a period
of decent rain to the coast overnight. The main low level cold front
is still offshore early this morning and will move onshore middle
morning today with one more shot of rain as it moves through the
inland areas today. The front will be east of the Cascades by middle

The associated cool upper trough is offshore this morning...and will
move through western Washington and far northern Oregon tonight for
some showers. Snow levels will fall below the Cascade passes
tonight...but snow amounts will likely stay below advisory criteria.
There is a slight chance of thunder over the northern coastal waters
late today and tonight...and near the north coastal zones tonight.

Attention will then turn to the system now approaching 150w. The
warm front from this system will spread into southwest Washington
and northwest Oregon Saturday afternoon and be over the entire area
Saturday night and Sunday. The first wave riding along the warm
front will move through Saturday night. This wave looks fairly
strong...may produce gale force winds over the coastal waters...and
locally heavy rain over southwest Washington and northwest Oregon. A
second weaker wave will keep the rain going on Sunday. Snow levels
will initially be around the passes late Saturday and a good part of
Saturday night before rising well above the passes Sunday. Given the
model quantitative precipitation forecast...there appears a good chance that portions of the South
Washington Cascades and perhaps the north Oregon Cascades above 4000-
5000 feet will see enough snow...somewhere on the order of 4 to 8 require a Snow Advisory Saturday night before the snow
level rises.

The rain should decrease from the south either late Sunday or Sunday
night as the War front lifts north. Tolleson

Long changes. Previous discussion follows...
Sunday night through Thursday...the progressive weather pattern will
persist into next week. Models continue to show a flat upper level
ridge moving over the Pacific northwest early next week. This could bring a
brief break from the rain Monday...but will maintain some chance probability of precipitation
in the forecast due to lingering instability. A weak shortwave
disturbance looks to ride over the top of the ridge on Tuesday and
will likely push another front across the region late Tuesday/early
Wednesday bringing more rain. Cascade snow looks to return Wednesday
afternoon with snow levels lowering to around 3500 feet. Unsettled
weather and lowering snow levels continue into Thursday as the base
of the trough moves across the forecast area. Monday will likely be
the warmest day...with temperatures trending cooler early next week. /64

Aviation...a very mixed bag in terms of conditions at this hour. Fog
and low clouds have hung around the Willamette Valley and north to
include the Tualatin valley as well. As such have seen vlifr conds at
keug...ksle...and khio at times but with periodic improvements to
just straight IFR cigs/vsbys. Have seen ceilings at kpdx even be rather
inconsistent as a MVFR deck has wavered between 1500 feet above ground level and non
existent. Given the stratus/fog deck is rather nebulous and model/MOS
guidance is far less than helpful..have very low confidence for most
of the inland tafs covering the next several hours. Coastal terminals
saw a decent break in the low clouds and fog...however...there is
just enough onshore flow to push the marine deck onshore. Will likely
see the coastal terminals remain IFR with ceilings 007-010 through at
least 21z. In general...guidance indicates conds improving to VFR
sometime at or after 13/00z.

Kpdx and approaches...low confidence in the forecast as ceilings remain
highly variable. The MVFR 016 above ground level ceilings currently in place show little
sign of moving although gorge outflow winds are probably keeping them
form dropping lower. Web cams of downtown Portland show some lower
clouds banking up against The West Hills. Should the winds ease
before 18z or so...may see some IFR ceilings quickly drift over the field
this morning. Otherwise...expect the ceilings to lift becmg VFR after 21z.

Marine...winds have been very slow to increase tonight and have just
recently seen gusts climb reaching 20-25 knots. Decided to extend the
Small Craft Advisory for winds through 8 am this morning based on loosely better
performance out of the hrrr model thus far and it's timing of
dropping winds below criteria then. Still...this remains a very
marginal wind event. Long period swell continues to build this
morning and should be peaking in the 13-15 feet range shortly.

Next event of note will be a threat for low end gale gusts Saturday
night. Models have continued to back off on the wind speeds over the
last 48 hours. Still have low end gale gusts in the forecast for the
time being. Opted to hold off issuing a watch as the decreasing trend
would give another 12 hours Worth of model runs to see those gusts
fall back toward the lower 30 knots range and thus out of gale criteria.

Surface pressure features thereafter remain highly variable in
location and timing. The trend...though... is for seas to fall below
10 feet Sunday evening with winds becoming less and less eventful.

Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for winds until 8 am PST this morning
for coastal waters from Cape Shoalwater Washington to Florence or
out 60 nm.

Small Craft Advisory for hazardous seas until 4 am PST
Sunday for coastal waters from Cape Shoalwater Washington to
Florence or out 60 nm.

Small Craft Advisory for rough Columbia River bar until
4 am PST Saturday.



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This discussion is for northwest Oregon and southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.

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