A deep trough in the Gulf of Alaska moved southeast across Washington, Oregon, and northern California with a trio of fronts. Snow levels gradually lowered with each disturbance.
Every event with a place to put it; 1 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 MFR wrote it up.
A deep trough in the Gulf of Alaska moved southeast across Washington, Oregon, and northern California with a trio of fronts. Snow levels gradually lowered with each disturbance. Eventually, light valley snow was produced. But, warning amounts were limited to elevations above 2500 feet.
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 Medford, OR wrote its last area forecast discussion before the first event at Mar 31, 7:45 PM PST, 4 hours 15 minutes earlier.
Area Forecast Discussion
National Weather Service Medford OR
845 PM PDT Fri Mar 31 2023
.DISCUSSION...The latest satellite image shows the upstream upper
trough making headway into our area. So far the radar is showing
scattered precipitation mainly in Douglas, Curry and northern
Cascades from about Prospect north. At the surface, a cold front
will reach the coast around midnight tonight, then move southeast
during the overnight hours. A colder air mass will follow the front
with snow levels lowering. Precipitation will be heaviest during the
overnight hours tonight into Saturday morning. Showers will continue
into Saturday afternoon, with moderate to heavy showers expected
along the Cascades and coastal mountains.
Another upper trough will approach the area Saturday night with
plenty of energy out ahead of it. The upper trough will then settle
in over the area Sunday night into Monday morning, with a
reinforcing short of colder air moving in, with snow levels dropping
down to around 2000 feet Sunday night into early Monday morning,
could could briefly lower to 1500 feet in heavier showers.
There's also good agreement among the data, we'll see a net increase
in showers Sunday with moderate to occasionally heavy showers lasting
into Monday morning. For this reason we decided to extend the end
time of the Winter Storm Warnings into Monday morning. We also made
some adjustments to the Winter Storm Watch. However, precipitation
amounts many not be enough to warrant an upgrade to a warning, but
more towards a Winter Weather Advisory above 2000 feet where we
currently have the Winter Storm Watch. The only difference would be
to include an advisory above 2,000 feet for Jackson County. We'll
let the night shift take a look at this in the event new data sheds
more light on the situation. -Petrucelli
&&
.AVIATION...01/00Z TAFs...Gusty southwest winds are present for
most areas and wind shear is also of concern along the coast while
the front is approaching. Rain is beginning to spread inland and
will continue to become more widespread through this evening. Snow
is anticipated for KLMT and other areas east of the Cascades tonight
too. As rain/snow expands in coverage, MVFR conditions in CIG/VIS
will become more common. When heavier rain/snow showers move in
around the 12z TAF window, IFR conditions could become more
widespread. Snow levels will also begin to lower as heavier showers
move through tonight from around 3500-4000 feet down to 2700-3300
feet. -Miles
&&
.MARINE...Updated 800 PM PDT Friday, March 31, 2023...Southerly
winds will continue to build to gale force north of Cape Blanco this
evening ahead of a strong cold front, bringing high and very steep
wind-driven seas. The front will move inland late tonight, with
winds turning westerly and diminishing behind it.
The pattern is expected to remain active and hazardous to smaller
craft through this weekend with high and steep seas. Seas are
generally expected to be around 10 feet with a period around 8 to 10
seconds. Weak high pressure builds in briefly by Tuesday night with
wave heights lowering into Thursday. -CSP
&&
.PREV DISCUSSION... /Issued 454 PM PDT Fri Mar 31 2023/
UPDATE...Updated aviation discussion for 00z TAF issuance.
SHORT TERM...This afternoon there has been rain passing northern
Douglas County that is moving east. It is not until later this
evening and overnight that more precipitation arrives. Snowfall
levels east of the Cascades start at 3,000 to 3,500 feet this
evening. After, snow levels fall below 3,000 feet Saturday evening
and will be between 2,000 and 2,500 feet Saturday night through
early Sunday afternoon. With these lowering snow levels, have
included a Winter Storm Watch for portions of Josephine, Coos,
Curry and Douglas Counties. This has been issued for the hazard of
snow and strong winds. However, periods of heavier precipitation
could lead snow levels to fall to valley floors, especially the
Illinois Valley, Sunday. A Wind Advisory is in effect for portions
of eastern Lake County. Overall, wind gusts with this system will
reach 40 to 50 mph. -Hermansen
LONG TERM...The extended portion begins Monday with an upper low
swinging down the back of a strong ridge well offshore. In this
pattern a cold air mass is sliding down in the northwesterly flow.
In this cold airmass snow levels Monday morning are expected to
to drop down to the valley floors west of the Cascades. However,
in this more northerly flow in the absence of an atmospheric river
contribution amounts are expected to be light to very light.
Another upper low swings down the back of the upper low in the
continued cold air mass in a very similar track to Monday's system.
However, the BL flow begins southwesterly, with the 700 mb flow
being almost westerly. This will bring increased moisture with
higher amounts, but the higher amounts will be in the higher
terrain, mostly in the Cascades and the coastal ranges, with the
valleys along the I-5 corridor seeing generally light amounts.
This general offshore ridge and great basin upper trough pattern
remains into Wednesday, but in the absence of an upper low swinging
down the back of the upper ridge, precipitation amounts will be
lighter with snow levels once again down to most of the west side
valleys.
From there into the end of the week deterministic models are showing
a weak upper ridge, but ensemble spread increases with a slight
chance of showers resulting mostly at the coast. The spread on the
possible temperatures also increases in this time frame, but all
indicate an increase in temperatures into the end of the week.
-Sven
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 11 AM PDT Monday for ORZ027>030.
Winter Weather Advisory until 11 AM PDT Monday for ORZ027-
029>031.
Wind Advisory from 5 AM to 11 PM PDT Saturday for ORZ030-031.
Winter Storm Watch from Saturday evening through Sunday evening
above 2000 feet for ORZ021-023-024.
Winter Storm Warning until 11 AM PDT Monday above 2500 feet for
ORZ025-026.
CA...Winter Storm Warning until 11 AM PDT Monday for CAZ080.
Winter Weather Advisory until 11 AM PDT Monday for CAZ085.
Wind Advisory from 5 AM to 11 PM PDT Saturday for CAZ085.
PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT Sunday
for PZZ356-376.
Gale Warning until 2 AM PDT Saturday for PZZ350-370.
Small Craft Advisory from 2 AM Saturday to 11 PM PDT Sunday for
PZZ350.
Small Craft Advisory until 11 PM PDT Sunday for PZZ370.
&&The national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
National gridded snowfall analysis indicated 4 to 13 inches of snow at elevations above 2500 feet, with heaviest amounts west and southwest of Happy Camp.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2023Every state in 2023This day in weather historyWarnings in California, April 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: 1092954.