A warm front moved through northwest Oregon the morning of December 11th, lifting snow levels up high enough for precipitation to fall as rain ahead of the cold front that afternoon. Surface temperatures on Mt Hood, however, were still below freezing so rain froze on contact with surfaces and created a layer of ice.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PQR wrote it up.
A warm front moved through northwest Oregon the morning of December 11th, lifting snow levels up high enough for precipitation to fall as rain ahead of the cold front that afternoon. Surface temperatures on Mt Hood, however, were still below freezing so rain froze on contact with surfaces and created a layer of ice. Once the cold front passed, snow levels dropped, changing precipitation back over to snow, and 10 inches of snow fell overnight December 11 to December 12. Rain falling at lower elevations also caused a landslide in the Columbia Gorge the night of December 11th.
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 Dec 11, 10:28 AM PST, 3 hours 32 minutes earlier.
Area Forecast Discussion...Updated
National Weather Service Portland OR
1028 AM PST Tue Dec 11 2018
Updated Aviation section
.SYNOPSIS...Today and tonight will be rainy as a warm front moves
across NW Oregon this morning, followed by a cold front this evening.
The next warm front stalls over Washington Wednesday and Thursday
keeping most of NW Oregon dry, but maintaining light steady rain for
SW Washington. A cold front will move across the region Friday and
Friday night. Another frontal system is expected for the weekend.
&&
.SHORT TERM...Today through Friday...Light rain ahead of an
approaching warm front is moving into SW Washington and NW Oregon
early this morning. Snow levels will rapidly rise this morning as the
warm front gets closer to the coast. The Astoria profiler shows the
snow level there increased around 1000 feet between midnight and 2
AM. Will keep an eye on the snow levels on the Troutdale Profiler
when the rain reaches there in the next couple of hours to make sure
that the snow levels do indeed rise, and that the forecast reflects
the observed rises. The snow levels should rise to just above the
Cascade passes as the rain reaches the Cascades this morning, then to
6000-7000 feet late this morning. This rapid rise of the snow levels
will minimize snow impacts for the Cascades. The snow levels will be
slightly lower for the south Washington Cascades this morning, and 1
to 3 inches of snow is possible at elevations near 4000 feet before
the warmest air arrives.
The warm front will move onshore late this morning. Gusty west winds
behind the front will help the rain become more orographic as the
trailing cold front spreads heavier rain into the region this
afternoon and evening. The coast, coast range, and the Cascade
foothills will likely measure 1 to 3 inches of rain from this morning
through late tonight, with around 0.75 inch of rain expected for the
interior valleys. Do not foresee any hydrologic concerns, but areas
with poor drainage will likely have some ponding issues. Gusty S-SW
winds can be expected through this evening with gusts up to 45 mph
expected near the beaches and the higher terrain and gusts up to 35
mph for the lower elevations.
Cold air will fill in behind the cold front late tonight and the snow
levels will lower to 3000-3500 feet by sunrise Wednesday morning.
Post-frontal showers will likely result in 2 to 5 inches of snow for
the Cascade passes Wednesday morning through early Wednesday
afternoon. Cool unstable air behind the cold front may provide enough
instability to support isolated thunderstorms near the coast late
tonight into early Wednesday morning. A building upper level ridge
will end showers quickly Wednesday afternoon, except for SW
Washington where another approaching warm front will likely continue
rain through Thursday.
The upper ridge will keep most of this next front north of the
Portland forecast area which is why the rain will be mostly limited
to SW Washington Wednesday night and Thursday. Snow levels should be
above the Cascade passes and limit snow concerns for the South
Washington Cascades. The front changes position very little Thursday
and rain chances will be confined to SW Washington and the coast. THe
warm front lifts north further into Washington Thursday night for a
brief break in rain before the cold front arrives Friday morning.
Friday will be another wet day for the region as the cold front
spreads widespread rain across the region. Gusty winds are expected
with this front similar to what we could see with today's front. ~TJ
.LONG TERM...No Changes. Previous discussion follows...Friday night
through Monday...The active weather pattern will continue well into
next week with a series of fronts moving across the region. There is
some uncertainty in the timing of frontal systems over the weekend
and into next week. At this point in time it looks like there will be
a relative break between systems early Saturday, then another front
moves through late Saturday night and Sunday. Yet another system
arrives sometime Monday into Tuesday bringing more valley rain and
high elevation snow. tw/TJ
&&
.AVIATION...Cigs will continue to lower as a cold front arrives
later this afternoon. Expect IFR cigs at the coast around 20z
and possibly making it inland closer to 22z. However, vsbys
inland may be more of the limiting factor as rain rates increase.
Additionally, southerly winds will increase today with gusts 35
to 45 kt at the coast and around 25 kt later this afternoon.
Post-frontal showers will keep conditions in place for much of
early tonight, with conditions beginning to trend back toward
lower VFR around 04z along the coast and closer to 08z inland.
PDX AND APPROACHES...Gusty southerly winds continue this
afternoon ahead of the the cold front. Expect cigs lowering to
MVFR, and reduced vsbys to 2-4 SM as heavy rain arrives later
this afternoon and into start of evening. Conditions then improve
towards lower VFR around 08z as showers decrease. Cullen
&&
.MARINE...Minor changes as models remain in decent agreement.
Generally, will see gusts in 30 to 40 kt range as a cold front
approaches today. Frequent post frontal wind gusts appear to
remain above gale criteria of 34 kt through a large part of
Wednesday so have extended the Gale warning through then.
Exception looks to be the central inner waters, but even then,
convective gusts may prove too frequent there as well. Models
continue to show a strengthening 972 MB surface low moving
northeast, but well northwest of the waters on Thursday. It does,
however, bring a cold front with stronger gales and possible
storm force gusts across the waters on Friday. No long term
break in sight as additional systems line up across the Pacific
well into next week.
Seas build reaching 14 to 17 ft tonight through Wed night.
Thereafter, details still need to be sorted out, but the overall
message is frequent and mixed swells will arrive to the waters
through early next week. The strong low on Thursday night/Friday
seems to be a more potent swell generator with combined seas
around 25 feet very plausible. Another round is possible later in
the weekend and could bring seas a little higher. Finally, some
models are bringing the strongest storm and highest seas
approaching 30 feet this time next week. Again, fully expect
details to change between now and then, but do want to portray
the overall message of poor conditions for the next several days.
/JBonk
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Warning until 4 AM PST Wednesday for Coastal Waters from
Cape Shoalwater WA to Cascade Head OR out 60 NM.Waters
from Cascade Head to Florence OR from 10 to 60 NM.
Gale Warning until 4 PM PST this afternoon for Coastal waters
from Cascade Head to Florence OR out 10 NM.
Small Craft Advisory for Rough Columbia River Bar until 1 PM
PST Wednesday.
&&
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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the forecast area.The national radar mosaic for the moment the first event began.
1 winter weather, 1 debris flow. Local standard time, as filed.
Freezing rain starting the afternoon of the 11th left a layer of ice on everything, followed by 10 inches of snow overnight into the morning of the 12th. This caused problems on ski lifts at Mt Hood Meadows the morning of the 12th, closing down ski lifts, and leaving over 150 passengers stranded. All were successfully evacuated.
Rain falling on the Eagle Creek burn scar caused a landslide that blocked exit 41 on I-84 for several days.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2018Every state in 2018This day in weather historyWarnings in Oregon, December 2018
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: 798969, 798978.