Heavy Snow in Washington, February 3 to 5, 2025

Area Forecast Discussion
National Weather Service Portland OR
338 PM PST Mon Feb 3 2025

.SYNOPSIS...Scattered showers continue through tonight, increasing to
widespread showers on Wednesday as the low pressure
system offshore brings another front to our area. Mountain snow
and overnight lowland rain/snow continues through most of the
week. Temperatures get colder Tuesday through the end of the week,
with continuing chances for light lowland rain/snow, favored
more towards snow. However, expected snow amounts remain
uncertain.

&&

.DISCUSSION...Now through Sunday...The upper level trough continues
to stay offshore, with continued rain/snow showers (just snow in the
mountains) throughout the region. Presently just seeing rain as
daytime temperatures have come up well above freezing, but around
9-10pm Mon, snow mixes back in to the lowlands; areas above 500-1000
feet should just continue seeing snow throughout Monday afternoon and
evening. Winds gradually shift more offshore over the course of
Monday night, though remaining under 10-15 kt gusts. This will
contribute to slightly cooler temperatures, better facilitating
accumulating snow for the rest of the week. That said, much of the
Willamette Valley and SW Washington lowlands will likely be shadowed
from precipitation; only around a 10-20% chance of any accumulating
snow between 10pm Mon to 10pm Tue. The coast and northern Coast Range
likely see slightly more impactful snow as upsloping allows for
slightly stronger moisture; expecting 0-2 inches at the coast and 1-3
inches in Coast Range and Willapa Hills tonight and Tuesday morning.
As a result, Winter Weather Advisory has been issued for those
regions through 1pm Tue. Those planning to travel through coastal
mountains and the Cascades should prepare for winter weather
conditions and refer to ODOT/WSDOT for road conditions and
restrictions.

A slightly more defined front swings through early Wednesday morning,
with slightly more precipitation expected during daytime hours on
Wednesday, particularly early morning. Easterly flow continues
throughout this time, creating slightly colder conditions that would
better facilitate accumulating snowfall. Between 10pm Tue and 10pm
Wed, NBM ensemble guidance has a 20-60% chance in the lowlands of 1
inch or more of snow accumulations, with the highest likelihood in
the SW Washington lowlands, slowly decreasing as you go further
south. Chances in the Portland metro area around right around 50% of
1 inch or more during this period. The Cascades will also see
stronger accumulations Tue night/Wed; from 10pm Tue to 10pm Wed, much
of the Cascades see a 60-80% chance of accumulations over 6 inches.
Will be watching carefully for a potential Advisory or Warning in the
next few model runs.

Snowfall potential on Thursday and Friday has come down a bit as
models are trending towards shifting moisture slightly southward
towards SW Oregon and northern California. Overall a low confidence
forecast; temperatures will be in the upper 20s, supporting potential
for accumulating snow, but overall QPF may just be too low and
moisture misses the area. Lowland areas see <10% chance of 1 inch of
snowfall or more during this period, but the Coast Range and Cascades
see better snowfall, potentially somewhere between 3-8 inches.
Regarding cold weather, see around a 60-80% chance of temperatures
falling below 25 degrees in the lowlands/Willamette Valley. Of
particular note is the upper Hood River Valley, which looks likely to
dip into the upper teens (80%+ confidence) each night from Wednesday
night onwards. Easterly flow through the Columbia River Gorge also
picks up Thursday, with gusts of 25-35 mph possible.

Generally lower confidence in snow forecast going into the weekend.
Cold temperatures continue, and the potential for snow mixing into
the lowlands remains possible during overnight and early morning
hours. QPF looks to remain generally low during this period, though
any showers that fall during overnight hours could produce snow, in a
similar pattern as the workweek. Early indications are that cold
temperatures remain through the weekend and into next week. /JLiu

&&

.AVIATION...Broad area of low pressure remains offshore with
southwest flow aloft across the area. This will maintain scattered
showers across the region through the period. A mix of VFR and
MVFR cigs continues at area terminals through this afternoon.
Snow begins to mix in again 03-06z Tuesday as temperatures fall
back closer to freezing. Guidance suggests cigs trend toward MVFR
after 12z Tuesday. South-southwest winds generally below 10 kt
through the period, except light east winds through the Gorge.

PDX AND APPROACHES... Scattered showers continue through the
period. Low-end VFR with intermittent bouts of MVFR likely in
passing showers through this evening. Snow mixing in at times
after 03z Tue. Little or no accumulation expected on paved
surfaces. Southeast winds around 4-7 kt expected through the
period. /DH

&&

.MARINE...Not much change as low pressure lingers near Vancouver
Island today. Southwest winds 10-15 kt becoming more southerly on
Tuesday as the low retrogrades farther offshore and slowly drops
south. Winds expected to increase slightly on Wednesday up to
15-20 kt as the low slides near the coastal waters. Seas around 8
to 9 ft this afternoon will continue to gradually subside to
around 4 to 6 ft through the middle of the week, with little
change through the end of the week. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory from 10 PM this evening to 2 PM PST
     Tuesday for ORZ101-102-104.

     Winter Weather Advisory from 10 PM this evening to 1 PM PST
     Tuesday for ORZ106.

WA...Winter Weather Advisory from 10 PM this evening to 2 PM PST
     Tuesday for WAZ201-202.

     Winter Weather Advisory from 10 PM this evening to 1 PM PST
     Tuesday for WAZ203.

PZ...None.

&&

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