A series of storms brought heavy snow and strong winds to some parts of northern California. This particular storm caused accidents and breakdowns that closed Interstate 5 in northern California for 23 hours between 15/1330 PST and 16/1230 PST, and thus Interstate 5 was closed from Ashland south to the Oregon/California border as well.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 MFR wrote it up.
A series of storms brought heavy snow and strong winds to some parts of northern California. This particular storm caused accidents and breakdowns that closed Interstate 5 in northern California for 23 hours between 15/1330 PST and 16/1230 PST, and thus Interstate 5 was closed from Ashland south to the Oregon/California border as well.
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 14, 9:13 PM PST, 5 hours 47 minutes earlier.
Area Forecast Discussion
National Weather Service Medford OR
913 PM PST Tue Dec 14 2021
.DISCUSSION... A solid cirrus deck is moving ahead of the front
at this time. Current timing of the lower clouds and the
precipitation continue on track, and with the cold air in place at
the onset, the possibility of brief light snow in the Rogue
valley continues on track before sh=now levels rise slowly
through the day as heavier precipitation moves in. -Sven
&&
.MARINE...Updated 800 PM PST Tuesday, 14 December, 2021...
Steep seas will become very steep early Wednesday morning as storm
force south winds accompany a very strong front. Seas peak around 15
to 18 ft at 8 to 9 seconds out of the south-southwest late Wednesday
morning. West swell will then build to another peak with seas around
16 to 19 ft at 13 seconds late Wednesday night. Swell dominated seas
will remain steep while they gradually subside Thursday. Seas
continue to diminish Friday ahead of a seasonably strong front on
Saturday. Gales are possible on Saturday. -DW
&&
.PREV DISCUSSION... /Issued 505 PM PST Tue Dec 14 2021/
DISCUSSION...December continues to be an active month as another
storm takes shape over the Northeast Pacific, due to impact the
forecast area Wednesday. We have high confidence in impactful
snowfall in portions of Siskiyou County including the Mount Shasta
City area (Warning issued for Western Siskiyou and Mount Shasta
City), Cascades and Siskiyous, and some areas east of the Cascades
(mainly Highway 97 just north of Klamath Falls and passes east of
that area). Regarding snowfall, some cold air ahead of this system
presents the possibility for low elevation snowfall on Wednesday and
much of today's focus was on this.
Model data has trended away from valley snowfall and pushed more
towards expected snow levels around 2000 feet. One of the reasons is
increasing southerly flow ahead of this next system which should
help to mix out some of the colder air and generally will keep
precipitation to a minimum during the morning. Because of the
uncertainty with these low elevation snow systems, we'll put our
forecast in some simple probabilistic terms. The Illinois Valley has
a better chance for accumulating snows because of existing snow and
a colder lower atmosphere, but its still not high. There's about a
90 percent chance for between a dusting of snow and less than an
inch in the Illinois Valley and about a 40 percent chance for 1 to 2
inches there. For the Rogue Valley, there's an 80 percent chance
that we'll see some snowfall but less than an inch, and about 20
percent chance of 1 to 2 inches on the valley floor. Higher up,
above 2000 feet, we've issued Winter Weather Advisories with snow
levels expected to fluctuate between 2000 and 2500 feet.
East of the Cascades there does look like a sharp gradient from
significant, impactful snow to off and on snowfall with less
impacts. This will be right around Klamath Falls--significant snow
to the north and much less so to the south. Windy conditions will
align with snowfall east of the Cascades to result in drifts and
very low visibility, and this will also be the cast near Weed along
Interstate 5 on Wednesday, with gusty winds, snow, and occasional
very low visibility.
Showers linger Thursday morning, with the Cascades likely seeing
additional snow accumulation.
The following details expected wind impacts on Wednesday into
Wednesday night: A strong frontal system will bring moderate to strong
winds over a good portion of the area Wednesday morning into
Wednesday evening. Details on the areas that could be impacted the
most will follow below.
Along the coast, guidance is pretty consistent showing pressure
gradients from Arcata to North Bend peaking out between 8 and 10 mb
Wednesday morning which typically results in high winds. Winds are
expected to be strongest for a 3-6 hour period before diminishing
around midday after the front moves onshore. Because of the above
and high confidence, the High Wind Watch has been upgraded to a High
Wind Warning.
Moderate to strong winds are also likely in the Shasta Valley with
winds strongest near Weed from Wednesday morning until Wednesday
afternoon. Pressure gradients between Medford and Redding are
expected to peak out just over 10 mb around midday. Winds could
easily exceed high wind warning criteria from about Yreka south
along I-5. Even though no high wind warning has been issued for that
area, the details have been outlined in the Winter Storm Warning and
Winter Weather Advisory for this area. Please see WSW for more
details. Gusty winds will continue into Wednesday evening, but at
the same time will gradually diminish as wind direction shifts
southwest which typically become less favorable for strong winds in
this area.
At the same tine winds are in a favorable alignment (southeast) for
gusty winds to develop in the Rogue Valley Wednesday morning. Winds
are expected to be strongest between from mid morning until early
afternoon, and could reach advisory criteria and a Wind Advisory has
been issued. Winds should quickly diminish once the front moves
through by early Wednesday afternoon.
East of the Cascades, winds will start to increase during the
morning hours Wednesday with the strongest winds expected between
noon and 5 pm pst. Models show 700mb winds peaking out close to 70
kts early Wednesday afternoon which will likely yield in High Wind
Warning criteria being meet, especially over the higher terrain and
along highway 31 between Summer Lake and Paisley. Gusty winds will
continue into Wednesday evening, but the general consensus is for
winds to diminish once they peak out late Wednesday afternoon. Winds
will continue to diminish Wednesday night, except for the ridges
where they could persist into the overnight hours. Please see NPWMFR
for more details on the wind headlines.
After Wednesday, winds are not expected to be a concern until
Saturday afternoon ahead of another potentially strong cold front.
-Petrucelli
Long term...Thursday Afternoon through Tuesday...A few lingering
snow showers will be possible across the Cascades with some light
rain possible in the Umpqua Basin. The area will see a day break
before the next system arrives Friday afternoon and evening. This
system will keep the active pattern going. This system will mimic
that of a front/atmospheric river hybrid. Precipitation will begin
with low snow levels around 1500 to 2500 feet and rise to around
6000 to 7000 feet by Saturday with the heaviest precipitation. Then
the front moves inland and snow levels fall to around 3000 feet by
the time the precipitation tapers off in showers on Sunday. The
heaviest precipitation looks to be confined to areas along and west
of the Cascades. Otherwise, snow levels will be much lower east of
the Cascades. Please stay tuned to the forecast for additional
impacts upcoming.
Then, a brief break is expected Sunday night into Monday before the
active weather pattern continues as a low pressure system offshore
spins up moisture and rainfall into southern Oregon and northern
California for most of the rest of the week. Precipitation is
expected to be relatively light, and snow levels will hover between
3000 and 5000 feet with impacts possible for passes as travel begins
increasing ahead of winter holidays. -Schaaf
AVIATION...15/00Z TAFs...
Quiet conditions exist this evening, but a cold air mass in place is
yielding some scattered to broken cloudiness in the MVFR range this
evening. Overnight a warm front will begin to push into the area
with a general wind from the southeast expected. This and some lower
level instability are likely to result in mainly VFR conditions
beginning around 03Z this evening. Low level wind shear is likely to
develop at airfields along the coast after midnight and across the
interior west side late tonight into Wednesday morning and then
persist through about 18Z. MVFR to IFR conditions are likely to
develop with precipitation that will fall in the form of snow down
to around 500 to 1000 foot elevations late tonight through Wednesday
morning and higher terrain will become obscured after midnight at
most locations. Wednesday afternoon snow levels are most likely to
rise into the 1500 to 2500 foot range at most locations while IFR to
MVFR in snow will continue at other locations.
An Airport Weather Warning for both wind and snow is likely to be
needed for KLMT for Wednesday, most likely in the daylight hours.
~BTL
MARINE...Updated 455 PM PST Tuesday, 14 December, 2021...
Steep seas will continue this evening before seas build and steepen
further due to a strong frontal system that will impact the coastal
waters later tonight through Wednesday. Southerly gales are expected
and a period of storm force winds are likely along with very steep
seas Wednesday, strongest during the daylight hours of the morning.
West swell will then build Wednesday afternoon and night and
gradually subside during the day on Thursday. Pressure will then
rise Thursday into Friday before a seasonably strong frontal system
moves through Friday night through Sunday morning. ~BTL
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 10 AM to 7 PM PST Wednesday for
ORZ030-031.
Winter Weather Advisory from 7 AM Wednesday to 1 AM PST Thursday
for ORZ029>031.
Wind Advisory from 10 AM to 7 PM PST Wednesday for ORZ029>031.
High Wind Warning from 4 AM to 10 AM PST Wednesday for
ORZ021-022.
Winter Weather Advisory from 8 AM Wednesday to 8 AM PST Thursday
above 1500 feet in the for ORZ024.
Winter Weather Advisory from 8 AM Wednesday to 8 AM PST Thursday
above 2000 feet in the for ORZ023-026.
Wind Advisory from 7 AM to 1 PM PST Wednesday for ORZ026.
Winter Weather Advisory from 7 AM Wednesday to 10 AM PST
Thursday for ORZ025.
Winter Weather Advisory from 7 AM Wednesday to 10 AM PST
Thursday for ORZ027-028.
CA...High Wind Warning from 10 AM to 7 PM PST Wednesday for
CAZ084-085.
Wind Advisory from 10 AM to 7 PM PST Wednesday for CAZ084-085.
Winter Storm Warning from 4 AM to 10 PM PST Wednesday for
CAZ080.
Winter Storm Warning from 4 AM to 10 PM PST Wednesday for
CAZ082-083.
Winter Weather Advisory from 4 AM to 10 PM PST Wednesday for
CAZ080.
Winter Weather Advisory from 4 AM to 10 PM PST Wednesday for
CAZ081.
Winter Storm Warning from 4 AM to 10 PM PST Wednesday for
CAZ081.
Winter Weather Advisory from 4 AM to 10 PM PST Wednesday for
CAZ083.
Winter Weather Advisory from 10 AM to 10 PM PST Wednesday for
CAZ085.
Pacific Coastal Waters...
Small Craft Advisory until 1 AM PST Wednesday for
PZZ350-356-370-376.
Storm Warning from 1 AM to 1 PM PST Wednesday for
PZZ350-356-370-376.
Hazardous Seas Warning from 1 PM Wednesday to 4 AM PST Thursday
for PZZ350-356-370-376.
SBN/SBN/SBNThe national radar mosaic for the moment the first event began.
4 heavy snow. Local standard time, as filed.
A spotter 5NNE Selma at elevation 1170 feet reported 5.0 inches of snow in 12 hours ending at 15/1457 PST.
A spotter 5WNW Klamath Falls reported 12.0 inches of snow in 24 hours ending at 16/0900 PST.
The cooperative observer at Odell Lake East reported 18.0 inches of snow in 24 hours ending at 16/0900 PST.
A CoCoRaHS observer 5.4NNW Gold Hill reported 6.4 inches of snow in 24 hours ending at 16/1000 PST.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2021Every state in 2021This day in weather historyWarnings in Oregon, December 2021
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: 989789, 989786, 989788, 989787.