Freezing Fog in Oregon, December 12, 2020

Name: Freezing Fog in Oregon, December 12, 2020
Start: 2020-12-12T09:05
End: 2020-12-12T09:15
Location: Oregon

December 12, 2020 · NWS MFR · 1 event in 1 county or zone

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 1
Injuries: 2
Property damage: None recorded
Crop damage: None recorded
Events: 1

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.

What happened

The episode as NWS MFR wrote it up.

At around 9:10 AM PST on 12/12/20, a pickup truck on Highway 97 just north of the OR/CA border crossed the median and hit a southbound semi-truck. The driver of the pickup was killed, and his passenger and the semi-driver were seriously injured. As traffic backed up behind the scene, six more vehicles crashed and more than 10 left the roadway, including several semis. The highway was closed for more than four hours. Around the same time, Klamath Falls police were responding to another accident on Highway 97 just north of town, when another semi lost control and struck three police cars and a fire engine. The driver fled the scene and has not been apprehended as of the night of 12/12/20. Minutes after the first collision, another semi collided with the same fire truck, resulting in heavy damage. Oregon state police also reported numerous crashes on an icy Highway 39 near Merrill, OR (also just north of the CA/OR state line). Police reports stated nearly all involved were travelling too fast for icy road conditions. Road conditions at the time of the accident were reported to be icy due to overnight snow and ongoing freezing fog. The KLMT ASOS reported visibility of less than a quarter of a mile and freezing fog at the time of the accidents, with a temperature of 17 degrees. A Co-Op observer at Keno, OR, around the same time as and near the scene of the fatal accident, reported 2.5 of snow in the previous 24 hours, with freezing fog and a temperature of 19 degrees at the time of observation.|Highway 97 was closed for over 4 hours. Three police cars and a fire truck, along with many civilian and commercial vehicles were heavily damaged. There were numerous injuries. A Freezing Fog Advisory issued for Klamath Falls and surrounding areas at 9:18 AM, effective until Noon PST.

What forecasters said that day

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 Medford, OR wrote its last area forecast discussion before the first event at Dec 12, 3:49 AM PST, 5 hours 16 minutes earlier.

Area forecast discussion, Dec 12, 3:49 AM PST, 5 hours 16 minutes before

Area Forecast Discussion
National Weather Service Medford OR
349 AM PST Sat Dec 12 2020

.DISCUSSION...It was anticipated that the showers would continue
more steadily over the Warners and Modoc County, but the Cascades
really took the punch out of the back end of them. Similarly
showers everywhere else have pretty much subsided. Will be
ending the Advisories early after writing this discussion.

Saturday will begin dry but by late afternoon a warm front will
will bring rain showers to the coast. Before the warm front has
time to advance inland a cold front will collapse upon the warm
front driving both of them up to the Cascades. A tongue of warm
air will move over the west side and dam up against the Cascades,
but make little advancement to the east side, except in Siskiyou
County where we expect warm air to sneak through the gap between
Parker Mountain and Mt. Shasta. Snow levels in the warm tongue
will be between 6,500 and 8,000 feet, and behind it heading into
Sunday morning, snow levels will be about 5,000 feet becoming
4,000 to 4,500 feet by Sunday evening over the whole area.

With warm air followed by a sharp cold front, the atmosphere will
be more than conducive for thunderstorms over the ocean and along
the coast. Convective storms could propagate as far inland as
Josephine and central Douglas Counties according to the 00z HREF
run, this seems a little excessive though. Expect eastern Coos and
Curry to be as far inland as these types of storms would go before
weakening. CAPE in the near shore environment is between 300 and
600 J/kg, with lapse rates approaching 8 C/km. If this were
summer, concern would be quite high for accumulating small hail
and lightning. In winter, it's not impossible, certainly expect
the unexpected with this system with hail and a few stray
lightning strikes possible.

Snow will start high in the Cascades and rapidly lower as the
precipitation acts to drive down the snow levels. Amounts range
from 5" to 13" inches in the Cascades and 4" to 9" in the
Siskiyous. This will bring winter related impacts to the usual
areas around Diamond lake and along route 140 between Medford and
Klamath Falls. Also, route 140 east out of Lakeview could see
advisory level snowfall. In north Cal., snow levels are just above
I-5, but snow will impact the road west from Etna, towards
Sawyers Bar, and route 89 from I-5 south through McCloud. We also
expect route 299 over the Warner mountains to be impacted again.
The heaviest snowfall is expected mid-day on Sunday, possibly
lingering into the night along the Cascades. Expect the day shift
to begin issuing warning products for this system.

Winds with the cold front will also be stronger than this last
event. Winds Sunday morning and afternoon will near advisory
criteria in Lake County.

Post frontal showers with this Sunday system could linger through
Monday morning, especially along the higher terrain of Douglas
County and the Cascades. As a whole though, Monday will be fairly
dry through the afternoon and night. Tuesday, another shot of rain
and snow will come in, but is expected to be less impactful, and
lacking the momentum to the east side.

A stronger system will come in after it on Wednesday and this
will bring the punch to get precipitation to the east side.
Moderate winds Thursday morning appear to get near advisory
criteria in Lake County again. Snow amounts do not look to be
overly impactful at this time.  -Miles

&&

.AVIATION...For the 12/06Z TAFs... IFR is expected to develop this
evening at all TAF locations, lowering to LIFR fog and low clouds in
some areas overnight into the morning. Conditions are likely to
improve during the daylight hours of the morning to around midday
across the forecast area as high pressure moves through between
weather systems and winds pick up enough to mix out low level
inversions. Clouds will increase over the coastal waters and along
the coast by the end of the TAF period as the next front
approaches the region. ~BTL/BPN

&&

.MARINE...Updated 243 AM PST Saturday 12 Dec 2020...Winds will
approach gale force strength this afternoon and evening as a cold
front moves through the region. In addition, seas will steepen to 10
to 12 feet as the front moves through the waters Saturday evening.
Then, a 16 to 18 foot swell will move in behind the front on Sunday.
 This high and steep swell will generate some high surf conditions
along the coast, so bar crossing will be more hazardous from Sunday
into Monday.  The steep seas will remain in place Monday and
gradually diminish into Tuesday.  Another warm front and cold front
will swing through the waters Tuesday keeping seas high and steep.

-Smith

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST early this morning for
     ORZ030-031.
     High Surf Advisory from 10 AM Sunday to 4 PM PST Monday for
     ORZ021-022.
     Winter Weather Advisory until 4 AM PST early this morning above
     2500 feet in the for ORZ025.
     Winter Weather Advisory until 4 AM PST early this morning above
     2500 feet in the for ORZ026.

CA...Winter Weather Advisory until 4 AM PST early this morning above
     4000 feet in the for CAZ082-083.
     Winter Weather Advisory until 9 AM PST this morning for CAZ085.

Pacific Coastal Waters...Small Craft Advisory from 4 PM this afternoon to 10 AM PST
     Sunday for PZZ350-356-370-376.
     Hazardous Seas Warning from 10 AM Sunday to 4 PM PST Monday for
     PZZ350-356-370-376.

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 freezing fog. Local standard time, as filed.

Freezing Fog, Klamath Basin

When: December 12, 9:05 AM PST to 9:15 AM PST
Where: Klamath Basin forecast zone
Deaths: 0 direct, 1 indirect
Injuries: 0 direct, 2 indirect
Reported by: Law Enforcement
Coordinates: 42.686, -121.650 (the zone’s center; the record gives no point)

At around 9:10 AM PST on 12/12/20, a pickup truck on Highway 97 just north of the OR/CA border crossed the median and hit a southbound semi-truck. The driver of the pickup was killed, and his passenger and the semi-driver were seriously injured. As traffic backed up behind the scene, six more vehicles crashed and more than 10 left the roadway, including several semis. The highway was closed for more than four hours. Around the same time, Klamath Falls police were responding to another accident on Highway 97 just north of town, when another semi lost control and struck three police cars and a fire engine. The driver fled the scene and has not been apprehended as of the night of 12/12/20. Minutes after the first collision, another semi collided with the same fire truck, resulting in heavy damage. Oregon state police also reported numerous crashes on an icy Highway 39 near Merrill, OR (also just north of the CA/OR state line). Police reports stated nearly all involved were travelling too fast for icy road conditions. Road conditions at the time of the accident were reported to be icy due to overnight snow and ongoing freezing fog. The KLMT ASOS reported visibility of less than a quarter of a mile and freezing fog at the time of the accidents, with a temperature of 17 degrees. A cooperative observer at Keno, OR, around the same time as and near the scene of the fatal accident, reported 2.5 of snow in the previous 24 hours, with freezing fog and a temperature of 19 degrees at the time of observation.|Highway 97 was closed for over 4 hours. Three police cars and a fire truck, along with many civilian and commercial vehicles were heavily damaged. There were numerous injuries. A Freezing Fog Advisory issued for Klamath Falls and surrounding areas at 9:18 AM, effective until Noon PST.

The people who died

As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.

Event	Date	Age	Sex	Where	Kind
Freezing Fog, Klamath Basin	2020-12-12	82	Male	Vehicle/Towed Trailer	Indirect

What these are

Freezing Fog: Fog that froze on contact with roads, vehicles or structures.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Oregon in 2020 Every state in 2020 This day in weather history Warnings in Oregon, December 2020

Sources

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 2026-09-30. Each event’s entry at NCEI: 925612.