Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 090525
AFDPQR

Area Forecast Discussion
National Weather Service Portland Oregon
925 PM PST Thu Dec  8 2016

.SYNOPSIS...Warmer air will continue to slowly move northward as east
winds decrease tonight across the northern half of our area. East
winds will remain strong enough to keep areas near and west of the
Columbia River Gorge below freezing. Is decreasing tonight into
Friday morning, but there will be areas with light freezing drizzle
in the areas influenced by the east winds through the gorge. A
series of low pressure systems will maintain cool and showery weather
into next week with the snow level around 2500 feet.

&&

.SHORT TERM...Tonight through through Sunday...The bulk of the
forcing has passed to our north, with precipitation decreasing across
our area. Areas south of Salem inland, and south of Tillamook along
the Coast have switched to an onshore more southerly wind, warming
temperatures up above freezing. Southerly winds will slowly progress
northward into Salem overnight. East winds through the Columbia Gorge
will likely keep southerly winds from reaching the north Willamette
Valley until mid-morning tomorrow, so the Portland/Vancouver metro
area will likely remain below freezing and icy through the first half
of the Friday morning commute, especially on the east side. The
central Gorge and Hood River Valley however, will likely hold on to
sub-freezing temperatures into a good part of the day tomorrow, with
snow continuing to accumulate continuing to make travel through the
Gorge difficult. Hood River may not get above freezing all day
tomorrow.

Precipitation overnight looks to be fairly light, being mainly
drizzle as moisture is limited to lower-levels, with dry air up
around and above -10C. Only minor accumulations are expected west of
the Cascades after midnight tonight. We will probably be changing the
winter storm warnings to freezing rain advisories which will last
through the morning commute. Snow will continue for the Washington
and North Oregon Cascades, the Columbia River Gorge and the Upper
Hood River through Friday.

Showers continue Friday as an upper level trough approaches the area
with snow levels gradually rising to 2500-3000 feet except for near
the Columbia River Gorge and Upper Hood River Valley area where they
will remain down near the surface. By Friday night the showers will
mostly be over the Cascades where they will continue into Saturday
morning. The Cascades can expect an additional 4 to 8 inches of snow
from Friday afternoon through Saturday afternoon. The Upper hood
River Valley and Central Columbia Gorge will see another 1 to 3
inches of snow, but forecast confidence on these amounts are low at
this point. Snow levels up around 2500 to 3500 feet should keep snow
from accumulating except at higher elevations in the Coast Range.

Another front will bring additional rain and mountain snow Saturday
and Saturday night, with post-frontal showers continuing into Sunday.
 -McCoy

.LONG TERM...Sunday night through Thursday...No changes. Previous
discussion follows...Onshore flow for the start of next week when
maintain shower chances across the region early next week. The
overall weather pattern remains rather progressive, with several
impulses passing across the region and providing for increased
precipitation chances. Snow levels remain around 2,500 feet through
the start of next week, so expect continued snow to pile up in the
Cascades, and a chance for some additional snowfall down in the
higher Cascade foothills and the highest parts of the Coast Range.
Forecast models are in good agreement in bringing a plume of enhanced
moisture to the West Coast around midweek, but still some significant
uncertainty in the strength and timing of the upper trough. This may
result in a dry time of a day or so later in the week, but given
significantly different solutions, will continue to utilize a blend
of model solutions and the previous forecast to generalize decreasing
PoPs across the north but higher across the southern portion of the
CWA for midweek with the idea that the core of moisture will stay in
southern Oregon and northern California. There is some potential for
a much colder air mass in place by the end of the week that could
bring lowering snow levels, but will wait for more continuity in the
overall pattern before moving too far this direction. Cullen
&&

.AVIATION...Do not expect a lot of change with temperatures
overnight except for a very gradual warming for areas along the
coast and in the southern half of the Willamette Valley. Most
locations that are currently at or below freezing appear likely to
remain at those readings until daybreak. Occasional light showers
streaming onshore will as a result produce brief periods of light
freezing rain in the northern half of the Willamette Valley and
snow and LIFR conditions in the Columbia River Gorge. Otherwise,
expect a lot of MVFR and high end IFR conditions through 06z
Saturday as moisture streams over the top of cold temperatures
near the surface.

KPDX AND APPROACHES...Temperatures should hold near freezing
overnight, which will leave the terminal susceptible to light
freezing rain showers through 12-15z Friday. As east winds subside
Friday, lingering low level moisture and the cold temperatures
near the surface will promote a lot of IFR and low end MVFR
conditions
through 06z Saturday. /Neuman

&&

.MARINE...Winds are in the midst of turning to out of the
southwest and decreasing some. Have replaced the Gale Warning for
tonight with a Small Craft Advisory for Winds. Winds will come
back up out of the west starting Friday afternoon as low pressure
moves north of the local waters. Have issued a Gale Warning from
Friday afternoon through the day Saturday for those winds.

Seas running 7 to 10 ft this evening with swell beginning to come
in from the south. Have issued a Small Craft Advisory for
Hazardous Seas, but only for the waters south of Cascade Head.
North of there, it looks like seas will be slower to come up and
may not hit 10 ft until around the time the Gale Warning starts
Friday. Seas will continue to build into Saturday with westerly
swell, peaking in the upper teens to near 20 ft during the day
Saturday. Winds as seas both look like they`ll come down rather
quickly overnight Saturday, leaving nearly benign conditions for
Sunday and possibly into early next week. Bowen

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 4 PM PST Friday for Central Columbia
     River Gorge-Upper Hood River Valley-Western Columbia River
     Gorge.

     Winter Storm Warning until midnight PST tonight for Coast Range
     of Northwest Oregon-Greater Portland Metro Area-Lower
     Columbia-Northern Oregon Cascade Foothills.

     Winter Storm Warning until 4 AM PST Friday for Northern Oregon
     Cascades.

     Winter Weather Advisory until 10 PM PST this evening for North
     Oregon Coast.

     Freezing Rain Advisory until 4 AM PST Friday for Central
     Willamette Valley.

WA...Winter Storm Warning until 4 PM PST Friday for Central Columbia
     River Gorge-South Washington Cascades-Western Columbia
     River Gorge.

     Winter Storm Warning until midnight PST tonight for Greater
     Vancouver Area-I-5 Corridor in Cowlitz County-South
     Washington Cascade Foothills-Willapa Hills.

     Winter Weather Advisory until 10 PM PST this evening for South
     Washington Coast.

PZ...Small Craft Advisory for winds until 1 PM PST Friday for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Gale Warning from 1 PM Friday to 4 PM PST Saturday for Coastal
     Waters from Cape Shoalwater WA to Florence OR out 60 nm.

     Small Craft Advisory for hazardous seas until 1 PM PST Friday
     for Coastal Waters from Cascade Head OR to Florence OR out
     60 nm.

     Small Craft Advisory for Rough Columbia River Bar from 11 AM to
     3 PM PST Friday.

&&

$$

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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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