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National Weather Service Area Forecast Discussion for Long Beach, WA USA

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Area Forecast Discussion
National Weather Service Portland, OR oregon
1025 am pst fri dec  2 2016

.synopsis...a warm front off the pacific will approach the
coast today, and move inland at the end of the day. a cold front
from the nw will follow fri night, moving se through the area.
another front will move south into the pacific nw sat night and sun,
ushering in a colder air mass for early next week that originated in
the arctic. there is the potential for low elevation snow down to the
valley floor on monday. another system is expected to move through
later next week, which bears watching with the potential for
significant impacts later next week.

&&

.short term...today through sunday... rain is starting to pick up
along the coast this morning associated with isentropic upglide ahead
of the warm front. will see rain spread southeastward across the area
today. snow levels are currently around 3000 feet according to the
troutdale wind profiler, but should be rising with the approach of
the warm front. snow levels are expected to rise above the passes, so
bulk of the precipitation should fall as rain on the passes. the
trailing cold front moves onto the coast this evening, turning rain
over to showers. drying at mid-levels, however, should limit qpf
overnight tonight with this system. snow levels will fall back down
to 3000 to 4000 feet behind the front tonight, but limited qpf should
keep accumulations below advisory criteria.

moisture generally limited to low levels early sat, with forecast
soundings suggesting shallow low level instability best across the
north part of the forecast area. coupled with a weak onshore flow,
will keep a low pop in across most of the forecast area sat.

sat night sees a westerly flow aloft with sagging upper heights.
models agree on a sharp but slow moving front sagging south through
sw wa into nw or sat night. moisture cross sections show the slow
moving system picking up deeper moisture sat night and sun. westerly
flow ahead of this system increases modestly to 20 kt at 850 mb,
which paired with the deeper moisture increases moisture transport.
with good moisture transport and additional dynamic lift associated
with the front will go with categorical pops. with cooling air mass
expect to see a good shot of snow down to passes in the northern
cascades saturday night into sunday. qpf amounts in the cascades on
sunday suggest locations above 5000 feet could see a foot or more of
snow. snow accumulations on the passes could reach 5 to 10 inches
impacting travel through the cascades.

a high surf advisory is in effect for the coast for saturday morning
as large swell out of the northwest is expected to build seas to
around 20 to 24 feet by early saturday morning.       -mccoy


.long term...sunday night through thursday...sunday night we will
start to see significant cool air moving into the region, with our
first chance for significant snow in the cascade foothills starting
sunday night. by monday morning, models show wet-bulb zero heights
getting down below 1000 feet. this coupled with 850 temperatures
around -5c to -6c, means the potential for accumulating snow down to
at least 1000 feet monday morning with a secondary shortwave expected
to move across the region on monday. could see drying behind the
front overnight sunday night which would help temperatures wet-bulb
down monday morning for a chance of snow down to the valley floor.
paved surfaces may be too warm for much accumulation, but can`t rule
out an inch which would impact the monday morning commute in valley
locations from salem northward. south of salem may start as more of a
mix of rain and snow. midday, snow levels should come up a bit
allowing precipitation to turn to rain right around the valley floor,
but could continue to see accumulating snow down to 1000 feet.
precipitation turns back to showers monday night with another brief
period where we may see snow all the way down to the valley floor,
but drying behind the front should limit qpf monday night.

tuesday will be the coldest morning so far this year, with
temperatures generally down below freezing everywhere except along
the coast. will generally remain fairly cold through the day, with
temperatures in inland valley locations possibly not getting out of
the 30s. in addition to cooler temperatures, will also see easterly
winds start to increase tuesday evening, particularly in and near the
columbia gorge, which could make it feel even colder tuesday night.

forecast later next week gets a little more uncertain with another
system expected to move across the area sometime between wednesday
night and friday night. this could be another high impact event,
especially with the earlier scenario which could overrun cold air
trapped in the valley for a freezing rain scenario.  the later
scenarios may be a less impactful cold rain event. stay tuned to the
forecast for later next week as well.      -mccoy

&&

.aviation...mostly vfr conditions this morning will deteriorate
to mvfr this afternoon with the more persistent rain. higher
terrain will be obscured in clouds and rain this afternoon through
this evening. winds will shift from the south to the southwest
between 00 and 03z for the coast, and between 03 and 06z for the
willamette valley. rain will turn to showers late tonight and
2500 to 2000 feet cigs should settle into the interior valleys
early saturday. there may be enough mixing with showers saturday
morning to result in vfr cigs for the coast. except newport may
see fog if there is any clearing overnight.

kpdx and approaches...vfr conditions today will deteriorate to
mvfr late this afternoon with more persistent rain. light winds
will shift from the south to the southwest between 03 to 06z. cigs
will likely lower to around 2000 feet late tonight into early
saturday morning. tj

&&

.marine...a frontal system is generating gusts up to 25 kt this
morning, and will increase to around 30 kt this afternoon and
evening. seas will be between 11 and 13 ft today before a larger
swell builds late tonight. large seas are being observed at the
buoys far offshore this morning. as of 8 am, buoy 46004 (~540
miles away) currently reports 33 ft at 17 seconds, buoy 46036
(~420 miles away) has 19 ft at 14 seconds, and buoy 46005 has 15
ft at 12 seconds. these seas will decay to around 20 to 24 ft at
17 seconds when they reach the wa and or coast early saturday
morning which is quite a bit higher than the 06z enp forecast.
buy more in on observations than models and have increased seas
saturday morning.

seas in the columbia river bar will build to around 20 ft with the
ebb this evening then remain above 17 ft until the next ebb early
saturday morning where seas will be around 24 ft with larger
breakers. tj

&&

.pqr watches/warnings/advisories...
or...high surf advisory from 2 am to noon pst saturday for central
     oregon coast-north oregon coast.

wa...high surf advisory from 2 am to noon pst saturday for south
     washington coast.

pz...small craft advisory for winds until 6 pm pst this evening for
     coastal waters from cape shoalwater wa to florence or out
     60 nm.

     small craft advisory for hazardous seas until 4 pm pst tuesday
     for coastal waters from cape shoalwater wa to florence or
     out 60 nm.

     small craft advisory for rough columbia river bar until 6 pm
     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.

Information courtesy of the National Weather Service - NWS Portland...
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