Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 221055

Area Forecast Discussion
National Weather Service Portland Oregon
253 AM PST Sun Jan 22 2017

.SYNOPSIS...Low pressure offshore will slowly drift southward later
today through Monday. One more band of rain early this morning, then
showers. But showers will be decreasing from north to south as the
low moves southward. Minor threat of showers on Monday, but otherwise
building high pressure will bring generally dry weather for Tue
through next weekend. At least we thought. Now, a weak front will
push into the region later Wed and Wed night, with a minor threat of
rain. But still, temperatures generally near seasonal levels for the
coming week.

.SHORT TERM...Today through Tuesday...Impressive low pressure off the
Oregon coast this am, with an estimated central pressure around 965
mb. An occluded front connected with this low now over southwestern
Oregon, and will lift north across the region this am. Will see a 2
to 4 hour long duration of rain with the front as it moves across the
region this am, then quick transition to showers behind the front.
Showers will decrease later this afternoon, with mix of sun and
clouds, though more clouds than sunshine. Will keep some threat of
thunderstorms for the coast, and inland areas to south of Portland,
with the best threat along the coast from Lincoln City southward.
Seems reasonably, as have plenty of lightning strikes off the south
Oregon coast as of 2 am.

Normally, would be concerned about strong winds with such a low, but
not this time. Winds will turn southerly and be gusty for a time
behind the front, but strong winds will remain well offshore.
Pressure gradients stay too southeasterly, which will keep peak wind
gusts in the 25 to 30 mph for most areas later this am into early
this afternoon, and maybe 40 to 45 mph along the Oregon Coast. But
winds will ease and turn back southeasterly later in the afternoon.
Also, the low is now starting to drift back to the west-northwest.
Models have been indicating this would happen, as the low prepares to
move southward towards California.

Offshore pres gradient has strengthened a bit this am, but overall
air mass not a cold as would expect. Likely due to some mixing that
occurred on Sat. But with temperatures around freezing, and models
soundings still supportive of snow, will maintain Winter Weather
Advisory for the Columbia River Gorge and Hood River Valley. But best
threat of snow will be east of Multnomah Falls, and likely above 500
feet. In general, would expect up to 2 inches of snow in the Columbia
Gorge, and 2 to 4 inches for the Hood River Valley. Higher up, likely
to see 3 to 6 inches of snow on the Cascades and higher peaks of the
Coast Range, but no advisory expected. With showers decreasing this
afternoon, likely that accumulating snowfall will end by early to mid
afternoon. But for now, will keep Winter Weather Advisory up until 6
pm today.

On Mon, the low will be much farther to the south, and off the Calif
coast. Will keep some minor threat of showers over the region, but
trend will be a decreasing shower threat on Mon. Dry Mon night into
Tue, with some patchy fog. Models continue to hint at some light
moisture around region later Tue. Will increasing clouds, and put
occasional sprinkles in for Tue afternoon and Tue night.  Rockey.

.LONG TERM...Tuesday night through Saturday...Overall, dry as high
pressure builds over the region. Will see seasonal temperatures for
the region for rest of the week. One fly as appeared in the
ointment...Wed night. Past and previous model runs have hinted at a
front of varying strength moving into the region late Wed and Wed
night. Am convinced now that will see some precipitation, albeit not
much. Will put increased clouds for Wed and Thu, along with an
increasing chance of rain late Wed afternoon and Wed night, then
minor threat of showers on Thu. Rockey.

.AVIATION...Mostly VFR conditions at all terminals this morning.
Only exception is some patchy fog along the Columbia River
impacting KVUO. Rain is starting to move in from the south with
light rain being reported at both KEUG and KSLE. Ceilings and
visibility both appear to remain VFR even after the rain arrives.
The only exception was KONP where ceilings briefly dropped to low
end MVFR, however this was short lived, and ceilings quickly
improved to VFR.

PDX AND APPROACHES...Still cannot rule out MVFR cigs at KPDX
during the heavier precipitation moving into the area in the next
hour or two, but considering there has been little visibility or
cig restriction with the precip moving through KSLE and KEUG,
expect VFR conditions. /Bentley

.MARINE...East winds will continue to strengthen and veer through
the morning hours as a strong surface low continues to strengthen
and move NW off the Oregon Coast. Expect the strongest winds after
the winds switch to southerly once the warm front passes in the
next few hours. Winds are coming up about as expected, so did not
make many changes to the ongoing forecast or headlines.

The forecast for seas is quite complicated. The long period
westerly swell held on much longer than expected, but finally
began to subside around midnight. Seas have now come down to the
14 to 16 ft range but will slowly begin to increase again as the
approaching surface low continues to move northward. Given the
strength of the surface low, one would expect seas to be quite
high today, although, the strongest winds are rarely being
generated towards our waters. In addition, there was little
opportunity for a dynamic fetch to develop with this system,
especially in our area.

Beyond Monday, marine concerns will be quieter as high pressure
builds into the NE Pacific waters which will limit winds. The next
for higher seas won`t arrive until Wednesday night/Thursday as a
swell train arrives from a strong surface low pressure near the
Aleutians. /Bentley


OR...Winter Weather Advisory until 6 pm today for...
 Western Columbia River Gorge
 Central Columbia River Gorge
 Upper Hood River Valley.

WA....Winter Weather Advisory until 6 pm today for...
 Western Columbia River Gorge
 Central Columbia River Gorge.

PZ...Gale Warning until 10 PM today on all coastal waters.

     Small Craft Advisory for Rough Columbia River Bar
 conditions today and tonight.



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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. is the U.S. government's official web portal to all federal, state and local government web resources and services.