A deepening area of low pressure dropping down the BC coastline tracked into the Pacific Northwest, which in combination with the northern edge of an atmospheric river to the south of the CWA lead to heavy mountain snow particularly in the Ochocos and Oregon Cascades. A lee side surface low due to the passing disturbance also enhanced strong winds along the base of the Blue Mountain foothills.
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 deepening area of low pressure dropping down the BC coastline tracked into the Pacific Northwest, which in combination with the northern edge of an atmospheric river to the south of the CWA lead to heavy mountain snow particularly in the Ochocos and Oregon Cascades. A lee side surface low due to the passing disturbance also enhanced strong winds along the base of the Blue Mountain foothills.
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 Mar 9, 3:06 AM PST, 3 hours 54 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
306 AM PST Thu Mar 9 2023
.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...Current radar and
infrared satellite imagery showing light returns confined west of
the Cascades as our area is currently dry under partly cloudy skies.
However, conditions will be changing through the day today as an
upper level low pressure, located off the Oregon/Washington coasts,
proceeds to drive through our area later today into Friday morning.
This will allow for substantial mountain snowfall to occur beginning
this evening along the east slopes of the Cascades, John-Day/Ochoco
Highlands, and Southern Blue Mountains before extending into the
Northern Blues overnight into Friday morning. Snow showers are
likely to continue across the Northern Blue Mountains and Wallowas
through much of the day on Friday until tapering off into Saturday
morning. The main concerns reside at elevations above 4000 feet,
with expected snowfall amounts through Friday totaling 8 to 18
inches along the east slopes of the Oregon Cascades, 4 to 10
inches over the east slopes of the Washington Cascades, 6 to 9
inches for the John-Day/Ochoco Highlands, 5 to 9 inches over the
Southern Blue Mountains, and 8 to 15 inches along the Northern
Blue Mountains. Confidence in these snow amounts are moderate to
high (70-90%) as the NBMv4.1 highlights a 90% chance of 8 inches
or more of snow along the east slopes of the Oregon Cascades, a
60-80% chance of 6 inches or more of snow over the John-Day/Ochoco
Highlands, a 65-75% chance of 10 inches or more of snow over the
Northern Blue Mountains, a 60-70% chance of 6 inches or more of
snow along the Southern Blue Mountains, and a 60-70% chance of 8
inches or more of snow over the east slopes of the Washington
Cascades. Thus, Winter Weather Warnings have been issued for the
east slopes of the Oregon Cascades, John-Day/Ochoco Highlands, and
the Northern Blue Mountains, which are in effect this afternoon
through late Friday evening. Also, Winter Weather Advisories have
been issued for the east slopes of the Washington Cascades and the
Southern Blue Mountains, which are effect at 3PM and 7PM
respectively, and extend through late Friday evening.
The other concern with this passing system resides with breezy to
windy conditions through the Grande Ronde Valley and along the
Northern Blue Mountain foothills. Pressure gradients are still
hinting at only a 5mb difference over the Grande Ronde Valley and
3- 4mb difference over the Northern Blue foothills, but
considerable temperature gradients and downsloping winds off the
Blues will allow for wind gusts of up to 55 mph to occur overnight
tonight into Friday morning. Thus, a Wind Advisory has been
issued for both areas beginning at 3 PM this afternoon and
extending until 4 AM Friday morning, with gusts peaking between
the hours of 10 PM and 4 AM.
The low pressure system's axis passes through our area Friday
morning before pushing east through the afternoon. A weak, upper
level ridge will follow closely behind the departing system into
Friday evening, then will build across the Inland Northwest through
the day on Saturday. This will provide drier conditions for lower
elevations by Friday evening, with mountain showers over the
Northern Blue Mountains and the Cascade crest tapering off through
Saturday morning as drier conditions ensue through the remainder of
the day. This will also allow for a slight warming trend to begin on
Saturday, with highs increasing from the upper 40s to low 50s
Thursday and Friday, into the low to mid 50s for lower elevations on
Saturday. These high temperatures on Saturday are much more
seasonal, aligning with average values expected for this time of
year. However, with the presence of the upper level ridge overhead,
skies will clear through the morning on Saturday and extend into
Sunday. This will allow for efficient radiational cooling to occur
overnight, as Sunday morning lows will plummet into the low to mid
20s for Central Oregon and upper 20s to low 30s through the Lower
Columbia Basin. 75
.LONG TERM...SUNDAY THROUGH THURSDAY...Ensemble and deterministic
models are in good agreement to begin the week with an upper level
trough off the coast and a moist southwest flow over the forecast
area. Deterministic models begin having timing and placement issues
regarding the trough moving inland late Monday into Tuesday.
Regardless, forecast confidence is high that Sunday through Tuesday
will be a wet period with rising snow levels and warmer
temperatures. After some initial snow in the mountains this will
produce a period of rain on existing snowpack leading to some minor
rises on streams and rivers Monday through Wednesday. Ensemble
models bring the upper level trough across the forecast area Monday
night and Tuesday with snow levels lowering Tuesday easing the
snowmelt and runoff feeding into the streams. Ensemble models begin
to diverge Wednesday as the ECMWF has a secondary trough moving onto
the coast followed by a zonal flow. Meanwhile, the GFS indicates a
building ridge pattern. Deterministic models also show this
divergence followed by the ridging pattern on Thursday. NBM tends to
follow the ECMWF ensemble which keeps a wet zonal pattern over the
forecast area Wednesday and Thursday but due to the
model inconsistencies I backed off on the NBM POPs during this time.
Either way forecast confidence drops to poor following the Tuesday
trough passage.
&&
.AVIATION...12Z TAFS...VFR conditions expected to prevail over the
period except for YKM through this morning with expected MVFR CIGs.
Periods of MVFR possible where RA/SN occur over the next 24 hours.
Expected development of showers for BDN/RDM early this morning then
spreading towards other sites through day and evening. Winds
less than 10kts until 18Z then gusting 20-25kts for
BDN/RDM/ALW/PDT.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 48 37 47 29 / 10 80 80 20
ALW 51 40 50 34 / 10 70 90 40
PSC 52 38 50 34 / 0 80 80 10
YKM 46 33 47 24 / 10 90 70 10
HRI 52 37 50 32 / 10 80 70 10
ELN 42 31 43 25 / 20 70 80 10
RDM 44 30 43 22 / 40 90 60 10
LGD 38 32 42 27 / 20 90 90 40
GCD 40 30 43 22 / 50 90 80 20
DLS 48 36 47 32 / 40 90 70 30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 3 PM this afternoon to 4 AM PST Friday for
ORZ049-507.
Winter Storm Warning from 10 PM this evening to 10 PM PST Friday
for ORZ502.
Winter Weather Advisory from 7 PM this evening to 10 PM PST
Friday for ORZ503.
Winter Storm Warning from 3 PM this afternoon to 10 PM PST
Friday for ORZ506-509.
WA...Winter Storm Warning from 10 PM this evening to 10 PM PST Friday
for WAZ030.
Winter Weather Advisory from 4 PM this afternoon to 10 PM PST
Friday for WAZ522-523.
&&
SHORT TERM...75
LONG TERM....91
AVIATION...91The national radar mosaic for the moment the first event began.
2 heavy snow, 1 high wind. Local standard time, as filed.
The SNOTEL Ochoco Meadows measured 12 inches of snowfall between 0800 on March 9th and 1500 on March 10th. The SNOTEL Lake Creek R.S. measured 9 inches of snow between 0200 on March 9th and 1000 on March 10th.
The SNOTEL Hoggs Pass measured 10 inches of snowfall between 1500 on March 9th and 1700 on March 10th. In addition a storm spotter measured 10 inches of snowfall 7 miles SSW of Three River at 1600 on Match 10th which had fallen over the past 24 hrs.
The mesonet station AS881 recorded a gust of 60mph at 2330 on March 9th, and the mesonet station OD181 measured a gust of 59mph at 2337 on March 9th.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2023Every state in 2023This day in weather historyWarnings in Oregon, March 2023
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: 1090700, 1090701, 1090705.