A series of deformation bands aided by a closed upper low off the southwest Oregon coastline resulted in light to moderate snowfall through much of the day Dec. 4th and through the morning on Dec.
Every event with a place to put it; 3 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 deformation bands aided by a closed upper low off the southwest Oregon coastline resulted in light to moderate snowfall through much of the day Dec. 4th and through the morning on Dec. 5th. The prolonged snowfall resulted in heavy snow accumulations across the Lower Columbia Basin, portions of the eastern Columbia River Gorge, the Blue Mountain Foothills, and in the Yakima valley.
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 Dec 4, 8:16 PM PST, 1 hour 21 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
816 PM PST Sun Dec 4 2022
.UPDATE...Steady light snow continues to fall from north central
OR eastward to the Blue Mountains and northward across the Lower
Columbia Basin and the Yakima/Kittitas Valleys. These areas have
received anywhere from an inch to as much as 4 to 6 inches.
However, most reports were in the 2 to 4 inch range. This fits the
Winter Weather Advisories well, in which the criteria is 2 to 4
inches in most of these areas, except 4 to 6 inches in the Simcoe
Highlands, which has been added to the advisory area this
afternoon.
A deformation zone continues to persist over the above described
areas this evening, but the area of snow, as a whole, is slowly
shifting northward as it weakens, while individual smaller scale
bands of snow are now moving from the northwest to the southeast.
The southern edge of the snow is now beginning to erode as the
entire area of snow is shifting northward slowly. Even the high
resolution short range models such as the HRRR and HREF are having
a bit of difficulty resolving the overall small scale features
described here. The larger scale models/ensembles slowly weaken
the deformation zone, while the upper low along the southwest OR
coast weakens and moves to the southeast and is replaced by a
cold, but dry northwest flow aloft by late Monday night into
Tuesday morning.
Areas that are still receiving snow will continue to receive
light snow for most of the night with the snow intensity gradually
decreasing and the areal coverage decreasing. This is in line
with what the HREF is showing. All of the Winter Weather
Advisories expire at 10 PM, but some may need to be extended
later into the night as the snow looks to continue beyond the 10
PM time frame. This is especially true for the Lower Columbia
Basin of WA and the Simcoe Highlands as well as the Yakima and
Kittitas Valleys, where perhaps another inch or two are possible.
However, the NBM V4.1 24 hour snowfall probabilities of more than
an inch are less than 50 percent for all these areas, and most
areas are even less than 25 percent of receiving more than
another inch. However, these same areas mostly have greater than a
50 percent chance of receiving between a dusting to an inch of
additional snowfall.
There may continue to be some upslope snow showers over the
eastern and northeast mountains as well as the Cascades on Monday.
However, most areas will be dry and slightly warmer. Low
temperatures tonight will be in the 20s in most areas, except for
teens in the far southern CWA where skies will have more clearing
overnight. Monday's highs will range from the 30s in the lower
elevations where clouds may persist the longest, to the 20s to the
mid 30s in the mountains, where there will be more solar
radiation and less clouds. 88
&&
.PREV DISCUSSION... /issued 233 PM PST Sun Dec 4 2022/
SHORT TERM...Tonight through Tuesday...The closed upper level low
off the SW coast of Oregon continues to lift moisture north into the
forecast area this afternoon resulting in widespread light snowfall.
Snowfall amounts have ranged from a trace to around 3 inches as
reported by spotters and the public. The deformation band will
continue to sit over Washington and northern Oregon into the night
and gradually weaken as it separates from the closed low. This will
result in a continued light snowfall event with some additional
accumulations of 1 to 3 inches across portions of the forecast area.
Therefore, the multiple weather weather advisories will continue
into tonight.
The remnants of the closed low will move into northern California
Monday allowing a northwest flow to become the more dominating
influence to the weather. Whats left of the deformation band will be
picked up in this northwest flow and advected into the eastern
mountains generating some snow showers through the day, otherwise
most of the forecast area will return to dry conditions. The low
moves into the Great Basin on Tuesday and the once pronounced ridging
in the Gulf of Alaska weakens. This will allow the flow to
transition to a more westerly flow Tuesday with some showers along
the Cascade crest and over the mountains of NE Oregon and SE
Washington. This transition to a westerly flow will also cut off
the inflow of cold Canadian air into the region and begin to
moderate towards warming temperatures.
LONG TERM...Wednesday through Sunday...A progressive pattern is in
store for the forecast area as models bring in several systems
through the PacNW between Thursday extending into beyond the next
weekend. Despite the fact that these systems look to be SW to W in
terms of their origin, cold temperatures persisting through the
first half of the work week may inhibit the ability for warmer air
to mix down into the lower elevations as the cold pool maintains its
strength.
Ensemble guidance suggesting Wednesday will be dry with weak N/NW
flow overhead, before bringing a low through during the day
Thursday. Wednesday will be a continuation of relatively cold
temperatures as a result, before another round of precip begins
early Thursday morning in the Cascades, spreading eastward. Little
doubt that our mountain zones will be inundated with precip as these
systems come through, question will be how much the lower elevations
receive and how much warmer air will penetrate into the Basin. QPF
ensembles pretty meager on low-elevation this far out, with values
ranging from a few hundredths to up to a tenth around central OR,
but given the synoptic setup, feeling pretty good on precip chances
for most of the forecast area. Did nudge temps down a little bit
from what the NBM had to compensate for the effect of cold pooling.
Will leave the lower Basin in a mix for now, as suggested by the
NBM, but wouldn't be surprised if future model runs trend colder as
we approach Thursday.
Ensembles then diverge greatly heading into next weekend, as
expected given the overall progressive synoptic pattern.
Deterministic GFS and ECMWF are greatly out of sync by Sunday, with
the GFS depicting westerly flow shifting more SW, while the ECMWF is
more NW. Ensemble clustering hints toward more of a westerly
pattern, possibly as a compromise solution, which would suggest
warming conditions and better chances for rain rather than snow in
the lower elevations, albeit light amounts as shadowing would be
more prominent under westerly flow, while the mountains continue to
receive consistent precip. NBM has a slight chance to chance for
much of the forecast area as a result of this progressive pattern,
so
will leave that in place until models better resolve themselves into
a more consistent solution, but expecting another round of precip
sometime next weekend. NBM has slightly warmer temps by the end of
the period, but given how unseasonably cold November into early
December has been, wouldn't be surprised if cold pooling effects
offset the temperature forecast a bit through the entire period.
Evans/74
AVIATION...00z TAFs...Conditions will improve across all sites
through the evening hours as snow showers taper off. The last of the
snow should linger around nightfall for DLS/YKM, before all sites
are clear by 06z at the latest. Main impact after the snow will be
the potential for low stratus impacts overnight heading into early
Monday morning. Bkn-ovc conditions through the period should keep
the surface insulated enough from fog development. Light winds less
than 8 kts across all sites, with cigs less than 5 kft expected.
Evans/74
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 24 30 25 38 / 90 20 0 0
ALW 24 30 26 38 / 100 20 10 0
PSC 25 30 26 37 / 90 10 0 0
YKM 21 30 20 36 / 90 10 0 0
HRI 26 31 25 38 / 90 10 0 0
ELN 20 29 20 36 / 80 10 0 10
RDM 22 37 22 39 / 20 0 0 0
LGD 27 36 24 37 / 80 20 10 10
GCD 26 38 23 37 / 30 10 10 0
DLS 27 37 28 43 / 90 10 10 10
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 PM PST this evening for ORZ041-
044-507-508-510.
WA...Winter Weather Advisory until 10 PM PST this evening for WAZ024-
026>029-521.
&&
UPDATE...88
PREVIOUS SHORT TERM...91
PREVIOUS LONG TERM....74
PRECIOUS AVIATION...74The national radar mosaic for the moment the first event began.
3 heavy snow. Local standard time, as filed.
A Co-Op observer 1 mile north northwest of Sunnyside, Wa measured 5.5 inches of new over a 24 hour period ending at 0816 PST on Dec. 5th. A Cocorahs observer 2 miles north northeast of Granger, Wa measured 4 inches of new snow over a 24 hour period ending at 0930 PST on Dec. 5th.
A social media post in Richland, Wa indicated 4 inches of new snow accumulations at 0347 PST on Dec. 5th. A Co-Op observer 8 miles north northeast of Hermiston, Or measured 4.8 inches of new snow over a 24 hour period ending at 0705 PST on Dec. 5th.
A public report from Walla Walla, Wa indicated 4 inches of new snow accumulated at 0340 PST on Dec. 5th. A trained spotter 4 miles west of College Place, Wa measured 4 inches of new snow in a 24 hour period ending at 0841 PST on Dec. 5th. A social media report 1 mile east northeast of Walla Walla, Wa indicated 4.3 inches of new snow accumulated in a 24 hour period ending at 1031 PST on Dec. 5th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2022Every state in 2022This day in weather historyWarnings in Washington, December 2022
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: 1072036, 1072037, 1072053.