A warm front brought a round of heavy mountain snow to the forecast area Christmas Day through the 26th.
Every event with a place to put it; 2 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 warm front brought a round of heavy mountain snow to the forecast area Christmas Day through the 26th.
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 25, 3:35 AM PST, 3 hours 25 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
335 AM PST Wed Dec 25 2024
Updated Aviation Discussion
.SHORT TERM...Today through Friday...
Bottom Line Up Front
1. Winter Storm Warnings & Winter Weather Advisories
2. Wind Advisories
3. Widespread low elevation rain
The short term will be characterized by multiple highlights.
Lingering precipitation from the previous system has since tapered
off and the current radar is showing nothing over the region.
Nighttime microphysics satellite is showing some areas of lingering
fog around Yakima to Prosser with a dense fog advisory in effect
through 10 AM. Also some patchy fog is lingering across the northern
border of Franklin county.
Short term models show that there will be some lingering showers
over the Blue as the upper level shortwave makes its way east of the
region. A very brief upper level ridge is wedged in between the two
systems and will allow for Christmas Day to see some reprieve from
all the rain. However, that will be short lived as the next incoming
system will reach the region by later this afternoon bringing with
it a wet warm front. Mountains snow will begin near 10 AM with the
bulk of the snow occurring through the day and overnight. CAMs show
decent amounts of snow accumulation with probabilities of 70-90% for
6-18 inches of snow along the eastern slopes and 6-12 in for the
lower east slopes of the Cascades. The system will also bring snow
across the OR Cascades with probabilities of 60-80% for 4 to 8
inches. As the system traversed the region, orographic lift will
allow the Northern Blues to also receive a round of snowfall above
4000 feet with 50-80% probabilities of 6-10 inches. A Winter Storm
Warning has been issued for 1 PM Wednesday through 6 PM Thursday for
the upper slopes (above 3000 feet) of the WA Cascades, 3 PM
Wednesday through 3 PM Thursday for the lower east slopes (above
3000 feet) of the WA Cascades. A Winter weather advisory has been
issued for the OR Cascade east slopes (above 4000 feet) 1 PM
Wednesday through 10 PM Thursday and also for the Northern Blues of
OR and WA 10 PM Wednesday through 4 PM Thursday.
Models show the system to not only be a wet one, but a strong one as
well. The bulk of the upper level winds aloft are out of the
southwest and switching a bit to the south as the system continues
to cross the region. Looking at the pressure gradient tool as well
as surface deterministic models, there is a definite tightening of
the pressure gradients along the Blues between Baker and Pendleton
with a 6 mb tightening. There is also a tightening of the gradients
along the OR Cascades. This will lead to increased downsloping winds
along the foothills of the Southern and Northern Blues, through the
Ladd and Pyles Canyons in the Grande Ronde Valley as well as through
central and North central OR. Probabilities of central and north
central OR seeing 45 mph gusts is 60-80%, 70-90% for the southern
and northern foothills of the Blues and 70-80% in the Grande Ronde
Valley.
Lastly, widespread low elevation rain will accompany this system as
well. Timing on the precipitation is a bit off with the models but
confidence in the ensembles of precipitation amounts is high.
Thursday afternoon models show the bulk of the precipitation
overhead. Looking at the raw ensembles, 24 hour precipitation
amounts have probabilities of 45-65% that 0.20-0.30 inches of rain
will fall over the Basin, 70-90% have 0.50 inches falling through
the Gorge, and 30-60% falling across north central and central OR
skipping Redmond which will only see 0.10-0.15 inches. Rain will
continue to remain steady through Friday bringing 60-80% chances
the entirety of the region will see a minimum of 0.25 inches with
mid elevations seeing up to an additional 0.40 inches. Saturday
shows things slowing, at least for the Basin as the upper level
system flattens out with the bulk of the energy along the southern
portion of the region and along the mountains. Another 0.25-0.35
inches of rain occurring again Saturday with 60-80% probabilities.
Its gonna be a wet weekend. Bennese/90
.LONG TERM...Saturday through Wednesday...Active weather in store
for the region through the long term forecast as a series of upper
troughs bring periods of rain and mountain snow across the
forecast area.
Saturday will begin with a shortwave trough swinging north into
BC, while a warm front lifts north across the PacNW through the
late evening hours. Snow levels will hover between 3.5kft to 5kft,
with lowest snow levels along the WA Cascade east slopes during
this period. At pass level, chances of 4 inches of snow will be
less than 25% through Sunday morning. In the lower elevations,
NBM probabilities of rain accumulations greater than 0.1 inches
will be 40-70%. As for liquid equivalent QPF, the eastern
mountains will see a 50-70% chance of greater than 0.25 inches,
while the Cascade east slopes will see upwards to 60-90% of 0.5
inches of liquid equivalent QPF. The warm front passage late
Saturday will result in increasing winds across the Blue Mountain
foothills, central OR, and portions of the Cascade east slopes,
with a 55-70% chance of 45mph gusts developing both Saturday night
and Sunday morning.
Sunday into early Monday, ensemble guidance is in good agreement
of an upper trough sliding across the PacNW and snow levels
falling to between 2kft to 3kft, however, there is some
disagreement in how far south the trough will travel. Overall, the
favored solution amongst ensemble cluster guidance is for the
main shortwave energy associated with the trough to travel just
south of the OR/WA border, which will result in heavy snow
accumulations along the OR Cascade crest and lighter accumulations
along the WA Cascade crest. Looking at NBM probabilities shows a
50-70% chance of 8 inches of snow or greater in the Santiam and
White passes as well as interior northern Blues, while
probabilities are 40-60% in Snoqualmie pass for 4 inches of snow.
Monday through Tuesday, there is good agreement that upper level
ridging will build over the region. However, there remains
disagreement in the amplitude of the upper ridge, resulting in
uncertainty in the strength of cold air advection into the PacNW
and snow amounts through Tuesday. In the leading solution, made up
of 40% of ensemble cluster members, the ridge axis is amplified
across the region, resulting in poor cold air advection and low
accumulations of snow along the Cascade crest and interior Blues.
Meanwhile, the other ensemble cluster solutions have a lower
amplified(weaker) upper ridge, resulting in higher snow
accumulations along the Cascade crest and interior Blues the
weaker the ridge across the region. At the moment, confidence is
moderate (50-70%) in upper ridging developing in some form during
this period and for light mountain snow across the Cascades and
interior Blues.
One thing to note through the period is that ensemble atmospheric
river guidance does indicate moderate-high (70-90%) confidence in
a weak atmospheric river (AR) accompanying the shortwave trough
passage over the weekend, with the AR axis across southern OR.
With a westerly flow accompanying the AR through the weekend,
there is moderate(50-60%) confidence in seeing some upslope
enhancement of snow, and therefore higher snow accumulations,
along the OR Cascade crest during this period. Lawhorn/82
.AVIATION...00Z TAFs...VFR conditions to prevail into this
afternoon at sites DLS/PDT/RDM/BDN/ALW/PSC, with VLIFR conditions
to continue at site YKM through this morning. While prevailing VFR
conditions are favored (70-80% confidence) at site PSC, a fog
layer developing north of the site could bring periodic reductions
in vsby through the morning hours. Otherwise, an incoming weather
system will spread precipitation impacts from west to east across
the region. Rain is expected to impact all sites, with a brief
rain/snow mix at site YKM 23Z-3Z. Precip impacts will also reduce
vsby/CIGs to MVFR or lower overnight. Winds will be light, less
than 12kts, through the period at sites DLS/PDT/YKM/PSC through
the period. Winds are expected to increase to 15-25kts with gusts
30-35kts at sites RDM/BDN after 3Z and between 3Z-9Z at site ALW
this evening. Lawhorn/82
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 45 39 50 37 / 20 100 60 60
ALW 47 41 51 39 / 20 100 80 60
PSC 44 41 52 41 / 20 100 40 60
YKM 38 33 47 33 / 60 100 50 60
HRI 45 40 53 39 / 20 100 40 60
ELN 37 32 43 31 / 70 100 60 60
RDM 41 36 46 35 / 30 90 60 90
LGD 40 35 45 32 / 10 100 90 60
GCD 40 34 44 33 / 20 100 80 80
DLS 43 40 51 40 / 80 100 80 90
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 10 PM this evening to 10 AM PST Thursday for
ORZ049-507-508-510-511.
Winter Weather Advisory from 10 PM this evening to 4 PM PST
Thursday for ORZ502.
Winter Weather Advisory from 1 PM this afternoon to 10 PM PST
Thursday for ORZ509.
WA...Wind Advisory from 10 PM this evening to 10 AM PST Thursday for
WAZ029.
Winter Weather Advisory from 10 PM this evening to 4 PM PST
Thursday for WAZ030.
Dense Fog Advisory until 10 AM PST this morning for WAZ027.
Winter Storm Warning from 1 PM this afternoon to 10 PM PST
Thursday for WAZ522.
Winter Storm Warning from 4 PM this afternoon to 10 AM PST
Thursday for WAZ523.
&&
SHORT TERM...90
LONG TERM....82
AVIATION...82The national radar mosaic for the moment the first event began.
2 heavy snow. Local standard time, as filed.
Starr Ridge Snotel recorded 7 new inches of snow depth in 24 hours by the morning of the 26th. A Cocorahs observer also recorded 7.4 inches of new snow 9 miles NW of Seneca.
ODOT road report from Santiam Pass recorded 13 inches of new snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2024Every state in 2024This day in weather historyWarnings in Oregon, December 2024
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: 1226377, 1226585.