029
FXUS66 KPQR 121158 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
358 AM PST Wed Feb 12 2025

.SYNOPSIS...Wednesday daytime hours remain dry, with cold morning
temperatures.Widespread snow, freezing rain/sleet, and rain are
expected late Wednesday night/early Thursday morning. Also, very cold
overnight temperatures and breezy easterly winds are expected. This
will result in very hazardous conditions across the forecast area
through the end of this week. A pattern change with slightly
warmer temperatures and rain/snow is possible Sunday and looks
to continue into the start of next week.

&&

.SHORT TERM...Wednesday through Saturday...Relatively dry conditions
during daytime hours Wednesday, though cold temperatures are still
expected Wednesday morning as easterly flow continues to push cold
arctic air from over the Cascades into the area. Easterly winds begin
to peak Wednesday afternoon, with peak gusts up to 35-45 mph in the
east Portland metro area, and up to 55-65 mph at exposed areas in the
Columbia River Gorge. A High Wind Advisory has been issued for the
eastern Portland metro area near the Gorge at this time. Going into
Wednesday night, temperatures remain quite cold, with another Cold
Weather Advisory for the entire area remaining on track. Extreme Cold
Warning also still remains on track for the Columbia River Gorge and
Upper Hood River Valley, which could see wind chill values down to
zero degrees.

Hazardous conditions begin Wednesday night as a low begins
approaching the central Oregon coast, bringing significantly
impactful winter precipitation. With cold surface air due to easterly
winds through the Gorge, as well as a warm front overriding over top,
the setup is right for freezing rain and sleet potential, as well as
snow. Precipitation begins around the middle of Wednesday night,
impacting the southern regions first (Lane, Lincoln, Benton, Linn
counties). Precipitation pushes northward over the rest of Wednesday
night, reaching the Portland metro area by early Thursday morning.
This initially begins as mixed snow and freezing rain for all areas
west of the Cascades (likely just snow in the Coast Range), but as
temperatures warm after sunrise Thursday, all areas will see a
transition over to primarily freezing rain during daytime hours
Thursday. Expect the Thursday morning morning commute to be impacted
by winter weather. Sleet may mix in as well during daytime hours, but
primary threat will be snow and freezing rain throughout this event.
Heading into Thursday night, mixed rain and freezing rain continue
for all areas west of the Cascades, with precipitation gradually
turning completely to rain Friday morning.

The early bout of snow Wednesday night should be rather brief, but
accumulations will be possible in the lowlands, with around a 10-20%
chance of 1 inch or greater of snow accumulation in the Willamette
Valley. Closer to 2 inches expected in the Coast Range. Precipitation
type transitions mostly to freezing rain (mixing with regular rain at
times) during daytime hours Thursday. With snow accumulations
possibly already on the ground, ice could accumulate quickly on
roadways and sidewalks. Ice accumulations throughout the whole event
could be up to 0.1 inches in the Portland metro area (20% confidence
of 0.1 inches or greater). However, higher accumulations can be
expected Salem and further south, as well as in the Coast Range. LREF
currently has a 40-70% chance of exceeding 0.1 inches for those
areas,and a 20-50% chance of exceeding 0.25 inches of ice. Highest
accumulations are expected in the southern Coast Range. With mixed
snow and ice accumulations as well as the timing of the event
impacting the Thursday morning commute, a Winter Storm Watch has been
issued for the central and south Willamette Valley, Coast Range, and
Coast Range valleys. With slightly lower ice accumulations in the
northern Willamette Valley (including Portland/Vancouver metro area),
a Winter Weather Advisory has been issued there. With a combination
of potentially gusty winds and ice accumulations, there is a
possibility of power outages for any areas affected by one or both.

The Columbia River Gorge and Hood River County will see slightly
different conditions. While these areas will also see strong easterly
winds and cold temperatures (actually colder than the Willamette
Valley, down to -10 to 0 degrees wind chill), the only precipitation
type expected there will be snow; no threat of freezing rain. 1-3
inches of snow accumulation can be expected over the course of this
event, beginning Thursday morning, tapering off Friday. Still
evaluating the potential for Winter Weather Advisory for snow
accumulations.

For the Cascades as well, only snow is expected as temperatures are
too cold and these areas will generally be above the warm nose.
Around a 50-70% chance of total snow accumulations exceeding 6 inches
from Thursday 4am to Friday 4am; still evaluating the potential for
Winter Weather Advisory for snow accumulations.

By Friday midday, most precipitation west of the Cascades turns
primarily over to rain. The system finishes passing through the area,
and drier ridging conditions are expected the rest of Friday and
Saturday daytime hours. Notably, there is some uncertainty as to
whether or not east winds will really weaken Friday. Model guidance
is indicating as such, and in this scenario, temperatures would begin
to warm going into the weekend. However, should easterly flow
continue, expect the possibility of continued strong gusts through
the Columbia River Gorge, colder temperatures, and continued winter
precipitation at times for the Gorge, Hood River Valley, and Portland
metro area. /JLiu


.LONG TERM...Saturday Night through Tuesday...Another northeast
Pacific system will bring another round of widespread precipitation
to the Pacific NW by Saturday night or Sunday. While at present,
model guidance indicates this to primarily be rain, the possibility
does exist for east winds to continue through the Gorge, allowing for
possible winter precipitation in the northern Willamette Valley.

Now, as discussed in the short term, Hood River and the Columbia
River Gorge will likely hold onto the cold air for a longer
period of time that the majority of our CWA. So, this will
result in a transition for predominately snow to a mixture of
snow and freezing rain/sleet on Saturday. Rain for lower
elevations is not expected to return until late Saturday night.
Sunday morning. As the start of next week comes into view,
expect a slight warming trend with widespread precipitation
remaining in the forecast through at least next Tuesday. /42/JLiu

&&

.AVIATION...VFR through the next 12 hours as high pressure exits
the region. Winds will be easterly but will amplify through the
afternoon. A low pressure system will near the coast after 00Z
Thur which will increase easterly winds inland. After 08Z
Thur, predominate terminals near the Columbia River Gorge,
including KTTD, will experience gusts as high as 45 kt. At 1500
ft, gusts up to 50 kt possible within the Columbia River Gorge.
Shifting west and southward, terminals will see less wind unless
within an east-west aligned valleys or coastal gaps like KAST and
KTMK where higher winds are possible.

In addition to wind, overnight temperatures will be below
freezing, and precipitation will make its way over the forecast
area. Precipitation will start around KEUG and K77S as early as
09Z Thur. Precipitation will initially fall as snow south of KSLE
but transition to freezing rain. This transition could occur as
early as 11Z Thursday. Confidence is very low at this point in
regards to exact timing and precipitation type as it will greatly
be determined by the low pressure track. Please read the "Short
Term" portion of the forecast discussion for more details.

PDX AND APPROACHES...VFR through much of the forecast until after
00Z when high clouds begin to move in ahead of an incoming system.
Lower CIGs not expected until after the 12Z TAF package. Prior to
the front winds will be the main concern. Easterly winds with
elevated gusts up to 30 kt are likely. For approaches though,
gusts as high as 50 kt possible above 1500 ft AGL after 05Z
Thursday. Models continue to struggle on winds aloft, but
something to be aware of. Precipitation is expected moving
forward, but will likely not occur until after 12Z Thursday.

&&

.MARINE...Fairly quiet weather for the next 12 hours or so as
high pressure weakens. A low pressure system will near the
coastline later tonight which will be the weather maker for the
next couple of days. The big impact of this low pressure system on
the marine forecast is in regards to wind. Wind will initially
hover around 10-15 kt with gusts to 20 kt, but quickly increase
late tonight. Initially winds will increase in the outer and
northern waters, then spread southward. The inner waters,
especially around the Columbia River Bar, will experience the
strongest wind speeds as easterly flow is channeled through area
terrain. Will experience gusts as high as 30 kt in the coastal
gaps. Within the outer waters, gusts up to 25 kt expected. Seas
will remain around 5-6 ft at 13 seconds on Thursday.

With the added easterly wind, temperatures will drop. Expecting
freezing conditions along moorages overnight Wednesday, Thursday,
and Friday. With the added precipitation, cannot rule out freezing
rain, snow, or even freezing spray if the winds are high enough
from the east. Confidence is low as to whether any ice will form.

Conditions will become more variable in the post frontal
environment as winds decrease and the westerly swell amplifies.
Seas will build to around 10 ft at 14 seconds by Friday morning,
then slowly ease as ridging occurs. Thus, could see the Small
Craft Advisories extending past the current end time. Another area
of low pressure moves in over the weekend which will again build
seas with the fresh swell.
  -Muessle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Cold Weather Advisory until noon PST today for ORZ101>118-
     123>128.

     Cold Weather Advisory from 7 PM this evening to noon PST
     Thursday for ORZ101>118-123>128.

     Winter Storm Watch from this evening through Friday morning for
     ORZ105>107-114>118.

     Winter Weather Advisory from 4 AM Thursday to 10 AM PST Friday
     for ORZ109>112.

     Wind Advisory from 4 PM this afternoon to 10 PM PST Thursday for

     ORZ112.

     Extreme Cold Warning until noon PST today for ORZ119>122.

     Extreme Cold Warning from 7 PM this evening to noon PST Thursday

     for ORZ119>122.

WA...Cold Weather Advisory until noon PST today for WAZ201>208-211.

     Cold Weather Advisory from 7 PM this evening to noon PST
     Thursday for WAZ201>208-211.

     Winter Weather Advisory from 4 AM Thursday to 10 AM PST Friday
     for WAZ205>207.

     Wind Advisory from 4 PM this afternoon to 10 PM PST Thursday for

     WAZ207.

     Extreme Cold Warning until noon PST today for WAZ209-210.

     Extreme Cold Warning from 7 PM this evening to noon PST Thursday

     for WAZ209-210.

PZ...Small Craft Advisory from 4 PM this afternoon to 7 AM PST
     Thursday for PZZ210-251-252-271-272.

     Small Craft Advisory from 10 PM this evening to 7 AM PST
     Thursday for PZZ253-273.

&&

$$

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