An upper level elongated trough with several shortwave impulses resulted in a period of moderate to heavy snow across the mountain zones. Heaviest snow was observed across the east slopes of the Oregon Cascades and northern Blues.
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.
An upper level elongated trough with several shortwave impulses resulted in a period of moderate to heavy snow across the mountain zones. Heaviest snow was observed across the east slopes of the Oregon Cascades and northern Blues.
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 23, 9:05 AM PST, 1 hour 55 minutes earlier.
Area Forecast Discussion
National Weather Service Pendleton OR
1005 AM PDT Thu Mar 23 2023
Updated Aviation Discussion
.AVIATION...18z TAFs...Mostly VFR conditions are expected through
the period, however shower activity at times through the early
evening could send cigs down to MVFR levels. These conditions are
most likely to occur at PDT/ALW, but may occur at BDN/RDM as
well. Shower intensity expected to be light. Winds will also be
breezy, with widespread gusts of 20-25 kts, mainly out of the
SW/W. Could see localized gusts exceed 30 kts as well, before
winds decrease overnight. Evans/74
MORNING UPDATE...A Winter Storm Warning is in affect from now
until 5 am Saturday for the East Slopes of the Oregon Cascades
with heavy snow expected above 3500ft with accumulations of 10 to
20 inches (80%). A Winter Weather advisory in affect and will
remain in affect until 5 am Saturday for the Northern Blue
Mountains of Oregon- Northwest Blue Mountains and Upper Slopes of
the Eastern Washington Cascades Crest with snow accumulations of 6
to 10 inches in the Blues and 6 to 12 inches above 2500 ft for
the Wa Cascades (80%). Current radar imagery is showing some
showers picking up over the Blue Mountains with some scattered
showers over parts of the Cascades with a band of precipitation
following close behind. Ground observations confirm the
precipitation and also that these are scattered showers. Next up
is the cold front that will swing through the region later today
brining an increase in the winds. There is currently a wind
advisory set to begin around 2 pm this afternoon and remain in
affect until 11 pm this evening across Foothills of the Southern
Blue Mountains of Oregon- North Central Oregon- Eastern Columbia
River Gorge of Washington- Simcoe Highlands as well as the
Foothills of the Northern Blue Mountains of Oregon- Lower Columbia
Basin of Washington-Foothills of the Blue Mountains of
Washington. Winds are expected to range between 20 to 30 mph with
gusts to 45 mph. Bennese/90
PREV DISCUSSION... /issued 410 AM PDT Thu Mar 23 2023/
SHORT TERM...Today through Saturday night...Radar and
satellite reveals some ongoing showers across the forecast area in
response to a weak shortwave and deep moisture across the region.
This activity will bring mountain areas some light snow and rain
to lower elevations of the Columbia Basin and adjacent valleys.
Rain or a rain/snow mix for central Oregon the Grande Ronde Valley
with light snow for the John Day Basin and Wallowa Valley is
expected with this first wave of precipitation this morning.
More active weather begins in earnest later this morning as an
elongated, negatively tilted trough originating from the Gulf of
Alaska approaches the forecast area. Guidance is in very good
agreement about the overall location and magnitude of the upper-
level trough and timing of a cold front this afternoon and evening.
This system will usher in cold air and bring a return of winter
weather, especially for the mountains. NBM 48-hr probabilities of
snow are suggesting a 80-100% chance of exceeding 6 inches along
the OR/WA Cascade crest with 40-85% chance of exceeding 6 inches
for the northern Blue Mountains. Raising the threshold to 12
inches reduces probabilities significantly across the Washington
Cascades and northern Blue Mountains, but robust chances (60-95%)
remain for the Oregon Cascades. The Winter Storm Warning for the
Oregon Cascades remains in effect 18Z Thursday until 12Z Saturday,
and the Winter Weather Advisory for the Washington Cascades and
Northern Blue Mountains of Oregon and Washington is valid for the
same period. Precipitation will be showery in nature with brief
intense snowfall in showers. As such, some locations will receive
significant snow while others will be missed by shower activity.
A secondary concern with the arrival of the cold front this
afternoon is brief advisory-level sustained winds and wind gusts
for non-mountain zones. Guidance is in good agreement regarding
the magnitude of the wind aloft (35-50 kts at 850 mb), and high-
resolution guidance is showing sustained winds of 20-30 mph with
gusts of 30-40 mph for north-central Oregon, the Simcoe Highlands,
the Eastern Columbia River Gorge, the Lower Columbia Basin of
Oregon and Washington, and the Foothills of the Blue Mountains.
While confidence in long-lived advisory-level winds is low,
thinking is that winds with frontal passage will be very close to,
if not exceeding advisory criteria, so have opted to issue Wind
Advisories for the aforementioned zones for 00Z Friday to 09Z
Friday.
Active weather with sustained breezy to locally windy conditions
looks to continue Friday and Friday night as the elongated trough
remains overhead with strong northwest flow keeping snow showers
across the mountains. Snow levels plummet with the trough overhead
Friday such that light low-elevation snow becomes a concern for
portions of the John Day Basin and central Oregon into the
foothills of the southern Blue Mountains and over to the Grande
Ronde Valley, especially during the overnight hours.
Guidance diverges somewhat for Friday night and Saturday with the
exact progression of the trough, but either solution (progressive
or not) will yield continued snow shower chances with the
northwest flow and cold core aloft. Plunkett/86
LONG TERM...Sunday through Wednesday... An upper level low and
trough over the inland northwest early Sunday will move eastward
and weaken into Monday. A strong upper low will then drop
southward off the coast Monday and move into northern California
by Wednesday morning As this low migrates southward, Monday may be
relatively dry due to the area being between systems, with
precipitation moving in later in the day in southwesterly flow.
Even with the low moving into California, the larger trough will
move over the western states and keep things unsettled through
Wednesday, though by later Wednesday, depending on the position of
the trough, it could be far enough south and east that we could
see some improvement.
Despite there being several times where there could be lower
elevation rain and mountain snow, overall QPF is low. Only a few
hundredths are expected in the lower elevations and mainly 0.10 to
0.20 in the mountains, which translates to only a couple inches of
snow.
Winds will become gusty Monday into Tuesday as the southwesterly
flow increases, but at this point speeds look to mainly be in the
25 to 30 mph range.
As was the case 24 hours ago, guidance continues to showcase the
significantly below normal temperatures. ECMWF EFI guidance for
Sunday high temperatures has almost the whole region, except for
the COlumbia Basin at -0.7 to -0.8 and most of eastern Oregon in
-0.8 to -0.9. The Basin will be -0.6 to -0.7. Low temperatures aren't
expected to be as abnormal, generally -0.5 to -0.7. On Monday,
the EFI has most of eastern Oregon -0.7 to -0.8. Deterministic
guidance has highs around 40 degrees in central Oregon and low to
mid 40s in many locations on Sunday which is anywhere from 10 to
20 degrees below normal. Ensemble guidance is similar to the
deterministic. Temperatures warm up somewhat Monday through
Wednesday, but will still be about 5 to 10 degrees below normal,
though the ensemble guidance does not warm up as much. Confidence
is high (90 to 100%) in the below normal temperatures. However,
the big question is just how cool it will be, especially on
Sunday.
The models are in very good agreement through Wednesday overall,
though the ECMWF 500 mb ensemble mean is in better agreement with
its deterministic run as its 850 mb temperatures as compared to
the GFS, lending a more support to its solution.
High temperatures on Sunday will range from the upper 30s to
around 40 in central Oregon to around 50 degrees in the Columbia
Basin. Monday through Wednesday will see highs in the low to mind
40s in central Oregon to the low 50s most elsewhere and the mid
50s in the Basin. Overnight lows will mainly be in the 20s Sunday
and Monday morning then the 30s Tuesday and Wednesday morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 55 32 48 31 / 50 100 40 40
ALW 56 34 50 33 / 80 70 60 50
PSC 59 36 54 34 / 30 20 20 10
YKM 55 29 51 27 / 20 10 10 0
HRI 59 34 53 33 / 40 40 20 20
ELN 53 29 48 29 / 30 20 20 10
RDM 49 26 41 24 / 50 30 50 20
LGD 47 27 40 26 / 90 90 80 50
GCD 46 23 38 23 / 80 80 80 50
DLS 54 34 51 34 / 70 40 50 40
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening
for ORZ041-044-508-510.
Winter Weather Advisory until 5 AM PDT Saturday for ORZ502.
Wind Advisory from 5 PM this afternoon to 2 AM PDT Friday for
ORZ507.
Winter Storm Warning until 5 AM PDT Saturday for ORZ509.
WA...Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening
for WAZ024-521.
Winter Weather Advisory until 5 AM PDT Saturday for WAZ030-522.
Wind Advisory from 5 PM this afternoon to 2 AM PDT Friday for
WAZ028-029.
&&
SHORT TERM...90
LONG TERM....77
AVIATION...74The national radar mosaic for the moment the first event began.
2 heavy snow. Local standard time, as filed.
A trained spotter 12 miles east of Weston, OR reported 10 inches of new snow in a 24 hour period ending at 0940 PDT on March 24th. The Milkshakes SNOTEL measured 11 inches of new snow in a 30 hour period ending at 1400 PDT on March 24th.
The Hogg Pass SNOTEL measured 9 inches of new snow in a 21 hour period ending at 1000 PDT on March 24th.
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: 1088592, 1088593.