A series of weather systems beginning Nov. 12th moved through the forecast area with moderate to heavy snow to mountains and light to moderate snow accumulations to higher elevation valleys.
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 PDT wrote it up.
A series of weather systems beginning Nov. 12th moved through the forecast area with moderate to heavy snow to mountains and light to moderate snow accumulations to higher elevation valleys.
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 Pendleton, OR wrote its last area forecast discussion before the first event at Nov 12, 9:50 PM PST, 2 hours 10 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
950 PM PST Thu Nov 12 2020
Updated Aviation Discussion
.UPDATE...Changes were made to the forecast to add wind
advisories for the Lower Columbia Basin, Blue Mtn Foothills, the
Kittitas and Yakima Valleys, Simcoe Highlands, the eastern
Columbia River Gorge, and North Central Oregon. Areas of blowing and
drifting of snow were also added to the mountain zones. Although
models have backed off on the winds compared to several days ago,
the tight pressure gradients will cause very windy conditions to
develop in the advisory areas. HRRR and other high resolution models
are showing 10m winds around 25 kts, and there are hints of
isentropic descent that could bring 50kt winds at 850mb near the
surface. No changes were made to the current winter storm warnings
and winter advisories. Wister
&&
.AVIATION...06Z TAFs...CIGS will lower tonight and Friday morning
with varying VFR and MVFR conditions in light rain. KRDM and KBDN
will have a few hours of a rain/snow mix Friday morning before
changing to rain. Winds will increase on Friday with westerly winds
18-25 kts gusting to 30-40 kts for most of the terminal airports.
Pilots may observe low level wind shear Friday due to 40-50 kt winds
just above 2000 feet, and this was included at KRDM, KBDN, KPDT,
KALW, and KPSC TAFs. Wister
&&
.PREV DISCUSSION... /issued 223 PM PST Thu Nov 12 2020/
SHORT TERM...Tonight through Saturday...A weather system will move
into the area overnight initially as a weak warm front followed by a
cold frontal passage on Friday. This system will bring some
significant snow accumulations in the mountains where winter warning
and advisories will be in effect. Will also see some increasing
southerly winds overnight warranting a windy advisory for the
southern Grande Ronde Valley. There could be some blowing and
drifting snow issues late tonight and early Friday in the southern
Grande Ronde valley. The cold frontal passage Friday will bring some
breezy to windy conditions across the entire forecast area through
Friday night then decreasing slowly Saturday. Precipitation will
taper off to showers Saturday mainly over the mountains. Another
system will arrive from the west late Saturday and overnight as a
warm front. Precipitation will be snow above 2000-3000 feet
initially Saturday afternoon and then rising overnight especially in
central Oregon. Still there will be some more snow accumulation
before changing to rain going into Sunday. More highlights may be
needed for this event but will hold off on any until current
highlights have ended.
LONG TERM...Sunday through Thursday...models in fairly good
agreement for the long term. Moist westerly flow for Sunday with
mountain rain/snow showers expected with mainly dry and locally
breezy conditions in the basin. Highs 40s to low 50s. Rain and high
mountain snow chances increase Sunday night into Monday with strong
warm air advection over the region and plume of deep Pac moisture
working onshore and lifting north. Precip expected to end south to
north Monday night as ridging builds in. Flow turns more southerly
on Tuesday as the ridge shifts east as another upper level
trough/low approaches the coast. Mild temps for Mon/Tue with highs
generally in the 50s. Some breezy southerly winds possible, esp in
the Grande Ronde valley and the foothills of the Blues/Wallowas. The
next system is expected to impact the region Wednesday into
Thursday. Models showing mainly rain and high mountain snow
overspreading the region Wednesday afternoon as deep Pacific
moisture working from the south and front passing through. Precip
expected to become more showery Thursday into Friday as the upper
trough is expected to work overhead. Snow levels remain fairly high
only expected to drop down to 4000-5500ft. Slightly cooler Wed/Thu
with highs in the mid 40s to lower 50s.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 37 51 35 47 / 60 90 30 10
ALW 38 51 37 49 / 60 90 40 10
PSC 39 54 39 52 / 50 60 20 10
YKM 32 51 32 50 / 30 60 20 10
HRI 38 55 39 52 / 40 70 20 10
ELN 29 45 31 44 / 40 60 30 10
RDM 35 49 30 44 / 20 90 60 40
LGD 32 42 31 40 / 40 100 70 30
GCD 35 43 30 38 / 30 100 70 40
DLS 39 51 39 50 / 50 90 50 30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 4 AM PST Saturday for ORZ509.
Wind Advisory from 4 PM Friday to 4 AM PST Saturday for ORZ041-
044-507-508-510.
Winter Weather Advisory from 10 PM this evening to 4 AM PST
Saturday for ORZ049-050-506.
Winter Storm Warning from 10 PM this evening to 4 AM PST
Saturday for ORZ502-503.
Wind Advisory from midnight tonight to 3 PM PST Friday for
ORZ049.
WA...Winter Storm Warning until 4 AM PST Saturday for WAZ520.
Wind Advisory from 4 PM Friday to 4 AM PST Saturday for WAZ024-
026>029-521.
Winter Storm Warning from 10 PM this evening to 4 AM PST
Saturday for WAZ030.
&&
SHORT TERM...85
LONG TERM....84
AVIATION...85The national radar mosaic for the moment the first event began.
4 winter storm. Local standard time, as filed.
A trained spotter in Tollgate measured 16 inches of snow accumulation between 12am PST on 11/13 and 2pm PST on 11/13. The Milkshakes snotel recorded 10 inches of snow accumulation between 12am PST on 11/13 and 2pm PST on 11/13.
At the Ochoco Meadows snotel, 9 inches of new snow was measured between 1 am to 1 pm PST on 11/13. At the Lake Creek R.S. snotel, 9 inches of new snow was measured between 4am to 1pm PST on 11/13.
A trained spotter SSE of Granite, OR measured 7.5 inches of new snow between 2am 11/13 to 12pm on 11/13. The Bowman Springs snotel measured 7 inches of new snow between 2am on 11/13 to 11am on 11/13.
The Hogg Pass Oregon snotel measured 13 inches of total snowfall between 4am on 11/13 and 4am on 11/14. The Oregon department of highways measured 8 inches of new snow from 10pm on 11/13 to 3:49am on 11/14 near La Pine, OR.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2020Every state in 2020This day in weather historyWarnings in Oregon, November 2020
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: 923894, 923888, 923891, 923889.