A warm frontal boundary on the northeastern periphery of an undercutting shortwave trough combined with locally cooler temperatures and a period of offshore flow to produce locally lower snow-levels and warning level snow amounts across the Hood River Valley the night of January 1st into January 2nd.
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The episode as NWS PQR wrote it up.
A warm frontal boundary on the northeastern periphery of an undercutting shortwave trough combined with locally cooler temperatures and a period of offshore flow to produce locally lower snow-levels and warning level snow amounts across the Hood River Valley the night of January 1st into January 2nd.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Portland, OR wrote its last area forecast discussion before the first event at Jan 1, 3:12 PM PST, 2 hours 48 minutes earlier.
Area Forecast Discussion
National Weather Service Portland OR
312 PM PST Wed Jan 1 2025
.SYNOPSIS...Showers will once again ramp up as a weak short wave
moves over the region. A warm front moves over the region on
Friday causing snow levels to rise and easterly winds to
increase. Will be colder in Hood River County and Skamania
County near the Gorge which will bring a wintery mix of
precipitation. High pressure builds keeping conditions generally
dry through early next week.
&&
.SHORT TERM...Now through Saturday...Satellite imagery shows the
main low center that brought precipitation overnight to the
south, and a weak mesoscale low up in the northeast Pacific. A
few waves are extending from the low in the south which is
producing some light drizzle over the forecast area.
Accumulation is minimal and thus have cancelled the Winter
Weather Advisory for the Cascades. Tonight, another shortwave
trough will move over the area which will bring another round of
precipitation. One difference between this and previous systems
are the snow levels. This is a fairly warm pattern and snow
levels will rise well above pass level. A majority of the
precipitation will also fall south of Lane County, so our
southern portions of the forecast area will see the most
rainfall. Up north, where snow levels are lower, very little
precipitation is expected. Could still see around 1-4 inches
along the mountains, and higher amounts along the peaks. While
snow is not necessarily a concern, there was ample melting of
snow on roadways today. As temperatures drop overnight, some
refreezing is possible. Still important to prepare for winter
conditions if traveling through the Cascade Passes tonight into
Thursday morning.
Precipitation peters off on Thursday but will be short lived.
Come Friday, the weather pattern becomes a bit more messy and
uncertain. Some things we have high confidence in: precipitation
returns on Friday with a wintery mix in the Upper Hood River
Valley, east-west aligned drainages above 3000 feet, and in
Skamania County; Rain elsewhere. Moderate confidence: Gusty
winds through the Columbia River Gorge and along the mountain
tops. Low confidence: whether the precipitation in the "wintery
mix" areas will trend towards all snow, rain or freezing rain.
The main driver for this uncertainty lies with the synoptic
pattern. The main feature is another North Pacific low pressure
system that is swinging down over the forecast area. Each model
is really handling this low differently both in the organization
and the track of it's motion. For example, the ECMWF is keeping
it as a closed low and moving it north over Vancouver Island.
Within it's ensembles, there is high consistency from run to
run. The GFS and NAM are attempting to split it into two low
systems but even in this case, they differ with where they are
moving with the ensemble members having low consistency.
Ultimately, the location of the low pressure will determine two
things: strength of the east winds through the Columbia River
Gorge, and precipitation.
In the scenario where we get a stronger north-south gradient
through the Columbia River Gorge, can expect higher easterly
winds (the GFS/NAM scenario). The GFS and the NAM are projecting
around a -8 mb gradient between Troutdale and the Dalles which
is at the upper end of what we typically see this time of year.
The easterly winds will bring in cooler air from the Columbia
Basin, settle into the Upper Hood River Valley and Skamania
County, and cause temperatures to drop at the low levels. As
the low moves in, it will push in warmer air aloft causing rain
to fall. However, if there is a longer period of these east
winds that cold air pool will cause the precipitation to fall
as freezing rain. Soundings are showing a mixed bag with the
mean trending towards a rain scenario, and the lowest 10% of
models trending towards a freezing rain outcome. Decided to
trend towards a wintery mix of rain, snow and freezing rain on
Friday. In the Upper Hood River Valley and foothills of the
south Washington Cascades, freezing rain accumulations up to 0.2
inch is possible but likely would be focused in the upper Odell
area and around the ridges. Freezing rain and snow are not
expected in the interior lowlands. -Muessle
.LONG TERM...Saturday through Wednesday...Showers will persist
through Saturday morning then high pressure builds in. This
high pressure will keep conditions dry and cool with less cloud
cover. Even though high pressure tends to favor cold
temperatures historically during the winter, in this case the
highest probabilities reflect a more moderate temperature
outcome. For inland valleys, the spread ranges from 37-43
degrees F with the lowest 10% of models suggesting a low of 32
degrees on Tuesday in Portland. The highest 10% of members
though show a low temperature around 46 degrees. This is trend
is representative through Wednesday. -Muessle
&&
.AVIATION...Moist westerly flow continues, maintaining plenty of
clouds, with mostly MVFR inland and VFR along the coast. Overall,
not a lot of change through Thu am, as will maintain widespread
MVFR across the interior, and a mix of VFR and MVFR along the
coast. Will see band of rain over Lane County lift northward this
evening, and on into Washington overnight.
Later tonight, will see bit more breakup of clouds. When this
happens, will see IFR stratus and patchy fog form. This mainly
across the interior, and likely will persist well into Thu am.
PDX AND APPROACHES...Predominately MVFR CIGs continue through Thu
am, except to the east where will maintain bit better conditions
with VFR. That east wind with its bit drier air will allow the
MVFR CIGS to slosh back and forth across the field at times, with
MVFR CIGS improving to VFR for a bit, then back to MVFR again.
&&
.MARINE...Overall, active storm track it to the south of the
region for the next 24 hours. As such, pressure gradients not all
that strong, giving winds of 15 kt or less. Seas holding at 8 to
10 ft into tonight, so will maintain current Small Craft Advisory.
Computer models in good agreement with low pressure arriving on
Friday, and staying just offshore as it moves north towards
Vancouver Island. It will push a front across the waters on
Friday, with return to south to southeast winds. But, gradient
does not tighten all that much until Friday evening, as secondary
low pressure moves northward just offshore. This has moderate to
high potential for southerly gales late Friday afternoon into the
evening, along with seas building into the lower to mid teens.
Active weather continues into the weekend, but high pressure
builds next week, with return of more benign conditions.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 10 PM PST this evening for PZZ210-
251>253-271>273.
&&
www.weather.gov/portland
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x.com/NWSPortlandThe national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
At 0700 on 01/02, a trained spotter reported 6in of new snowfall just outside of Parkdale, OR.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2025Every state in 2025This day in weather historyWarnings in Oregon, January 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1227501.