A strong low pressure system moved southeast to just offshore from far northern California then continued southeast along the California coast. This brought heavy, low elevation snow to much of southern Oregon and northern California.
Every event with a place to put it; 7 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 strong low pressure system moved southeast to just offshore from far northern California then continued southeast along the California coast. This brought heavy, low elevation snow to much of southern Oregon and northern California.
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 27, 1:18 PM PST, 2 hours 42 minutes earlier.
Area Forecast Discussion
National Weather Service Medford OR
218 PM PDT Mon Mar 27 2023
.Updated marine section
.SHORT TERM...Mon Mar 27 to Tues Mar 28...At a glance, our short
term period begins with a deepening low pressure system approaching
the region from the west. Ahead of the low, a strong front will move
over the area this afternoon into Tuesday afternoon, with light pre-
frontal precipitation spreading eastwards from the coast and
increasing in intensity as the front approaches. Frontal passage will
bring strong southerly winds, especially over exposed terrain and to
north-to-south oriented valleys, as well as moderate to heavy
precipitation to northern California and elevations over 2000 feet.
Precipitation begins to lighten and taper off in south Oregon
Tuesday night as the front moves out of the area, but additional
impacts to northern California (especially the I-5 corridor and
areas along it from Gazelle south) are expected through early
Wednesday afternoon as the surface low spins down the coast.
Radar/satellite imagery shows light showers coming onshore the Curry
County coast from the southwest. Offshore, the counter-clockwise
flow around a strong low pressure system is visible as it continues
to spin down the coast well offshore. This will lift an occluding
frontal boundary across the region beginning later this afternoon.
As it approaches, strengthening precipitation will spread across the
area from the southwest. The heaviest precipitation will be across
coastal counties (Coos, Curry, western Douglas), over high terrain
in south Oregon (Siskiyous and south-central Cascades into Klamath
and western Lake Counties) and in northern California (southern and
western Siskiyou County into western Modoc). Snow levels will hover
around 3000 feet this evening into tonight, lowering briefly
overnight to around 2000 feet west of the Cascades in the early
morning hours of Tuesday, before coming up to 2000-2500 feet again
in the afternoon.
Gusty winds are also expected during this period, with winds
increasing through this afternoon and peaking later tonight. Models
indicate a strong 60-65 kt 925 mb jet will push onto the coast from
Cape Blanco south late this afternoon into tonight, with models
supporting gusts of 50-60 mph along the coast south of Cape Blanco
and gusts up to 70 mph over coastal headlands in the same area.
Inland, the southern Rogue Valley, the Shasta Valley, over high,
exposed terrain, and areas east of Cascades are forecast to also
experience gusty winds. Models continue to show a moderate to strong
mid level jet (SW 45 to 65 kt at 700 mb and S 40 to 50 kt at 850 mb)
moving across the area this evening through Tuesday morning. This
will bring strong winds, gusting to 55 to 65 kt in the Shasta Valley
and to higher mountains, with winds gusting to around 40 to 50 mph
in the southern Rogue Valley, and gusting to around 35 to 55 mph
east of the Cascades. Of note, the downslope winds in the southern
Rogue Valley may result in light or little rainfall until the front
pushes through Tuesday morning.
Significant impacts from this system are expected from the
combination of snow and winds. In western and southern Siskiyou
County into western Modoc County, especially in the Mt. Shasta area,
very heavy snow (1 to 3 feet of total accumulation). High-resolution
models like the HREF have been very consistent in showing snowfall
rates of 1-2" per hour late this evening through Tuesday. Combined
with gusty winds, very poor visibility will result and may produce
white out conditions at times. The HREF also indicates 1" per hour
snowfall rates in northern and central Klamath into western Lake
county Tuesday morning along with gusty winds, so poor visibilities
in these areas are also likely.
Winter weather advisories/winter storm warnings are out for these
areas: please see the detailed hazards/WSWMFR for more specifics.
The front moves out of the area Tuesday afternoon, but additional
precipitation from the surface low moving down the coast will occur
through late Wednesday. There will be additional precipitation at
the south Oregon coast Tuesday evening before the low continues
southwards. Again the majorly impacted area here is the Mt. Shasta
area, where the southwest direction of the wrap-around precipitation
favors more orographic enhancement and additional heavy
precipitation is expected Tuesday night through Wednesday morning.
Elsewhere, light to moderate showers through the region will persist
through Tuesday night. There is a chance for thunderstorms Tuesday
afternoon into the night, which could result in localized small hail
and strong, gusty winds. -CSP
.LONG TERM...(Wednesday through Monday)...In general, we'll
remain locked in a cool to cold and showery pattern through at least
early next week, possibly longer.
Wednesday, the upper and surface low will continue to slowly move
south. However enough energy around the north end of the upper low
will be enough to bring showers to the area, especially in the
afternoon as we get further into max daytime heating. Also upslope
flow with enhanced precipitation is expected in the the Mount Shasta
Area, however it's not expected to be anything like were expecting
tonight through Tuesday morning.
Dry weather is expected Wednesday night, then a weak upper trough
will drop down along the Oregon coast Thursday which could trigger
some showers Thursday afternoon. However, were not expecting
anything significant.
The operational ECMWF and GFS continue to show differences with the
timing of a stronger front Friday into Saturday. The ECMWF is at
least 6 hours faster than the GFS. Looking further into the ECMWF
individual ensemble members show varying solutions with the timing
of the front, thus suggesting, there is nothing clear cut regarding
the timing. Meanwhile the individual GFS ensemble members are pretty
much lock in step with the operational. Bottom line is there is low
confidence on the timing, but when the front does come in it will be
followed by a cold upper trough coming in from the Gulf of Alaska.
Thus, its' a good bet this weekend will be cool to cold with
scattered showers, and mountain snow showers.
As alluded to in the beginning, all signs are pointing to a
continuation of cool to cold and unsettled weather that could last
into the first week of April. There are some signs the pattern may
change to where we'll get slight ridging or at least a zonal flow in
our area with drier (not necessarily flat out dry) weather and
milder temperatures as we get into the second week of April.
-Petrucelli
&&
.AVIATION...27/18Z TAFs...VFR conditions will prevail for the early
portions of this TAF period. However, showers are starting to pop
up ahead of the incoming low. We are expecting MVFR ceilings to
spread into the coast this afternoon into this evening. Rain will
also generate lower visibilities and brief periods of IFR
visibilities along the coast. Farther inland, VFR will remain
likely for most of the afternoon into the early, especially near
KMFR.
Eventually, frontal boundaries will push onshore later this evening
into tonight. Wind shear will be a partial concern along the coast
and within valleys west of the Cascades. Ceilings within the
Umpqua Basin are anticipated to fall within MVFR levels. Mountain
obscurations are anticipated later tonight into Tuesday morning as
more moisture
&&
.MARINE...Updated 200 PM PDT Monday, March 27, 2023...Conditions
continue to deteriorate this afternoon as gale force winds are being
reported near buoy 27. There is a higher expectation now of storm
force wind gusts across the majority of the waters beyond 10 nm from
shore this evening. Data shows that the chance of wind gusts in
excess of 55 knots is about 70% between Pt. St. George and Cape
Blanco beyond 10 nm from shore. Those probabilities lower to about
50 percent North of Cape Blanco and beyond 10 nm from shore. Closer
to shore, gale force winds are about 95 percent, although those
probabilities lower significantly as one nears Coos Bay and travels
northwards. Very high wind driven waves will develop from these
gale and storm force winds.
Once the surface low moves south of the area Wednesday morning,
conditions will gradually improve as winds ease and wind driven seas
gradually diminish. Northwest winds with relatively light seas will
persist through the end of the week as we catch a break in the
weather. Active weather and hazardous conditions likely return late
Friday into the weekend. -Smith
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 8 PM this evening to 2 PM PDT Tuesday for
ORZ030-031.
High Wind Warning until 8 PM PDT Tuesday for ORZ021-022.
Winter Weather Advisory until 11 AM PDT Tuesday above 2000 feet
for ORZ024.
Winter Weather Advisory until 11 AM PDT Tuesday above 2500 feet
for ORZ025-026.
Wind Advisory until 8 PM PDT Tuesday for ORZ026.
Winter Storm Warning until 11 AM PDT Tuesday above 5000 feet for
ORZ027-028.
Winter Weather Advisory until 11 AM PDT Tuesday below 5000 feet
for ORZ027-028.
Winter Storm Warning until 11 AM PDT Tuesday for ORZ029-030.
Winter Weather Advisory until 11 AM PDT Tuesday for ORZ029-030.
CA...Winter Storm Warning until 11 PM PDT Tuesday above 3000 feet for
CAZ080.
Winter Weather Advisory until 11 PM PDT Tuesday above 2000 feet
for CAZ080.
High Wind Warning until 8 PM PDT Tuesday for CAZ081.
Wind Advisory until 8 PM PDT Tuesday for CAZ081.
Winter Storm Warning until 5 AM PDT Wednesday for CAZ081>083.
Winter Weather Advisory from 11 PM this evening to 5 PM PDT
Tuesday for CAZ083-084.
Wind Advisory from 8 PM this evening to 2 PM PDT Tuesday for
CAZ085.
Winter Storm Warning from 11 PM this evening to 5 PM PDT Tuesday
for CAZ085.
Winter Weather Advisory from 11 PM this evening to 5 PM PDT
Tuesday for CAZ085.
PACIFIC COASTAL WATERS...Gale Warning until 11 PM PDT Tuesday for
PZZ350-356-370-376.
Storm Warning until 2 AM PDT Tuesday for PZZ350-370-376.
&&The national radar mosaic for the moment the first event began.
7 winter storm. Local standard time, as filed.
National gridded snowfall analysis indicated 4 to 8 inches of snow at elevations above 1500 feet, including the vicinity of Camas Mountain.
National gridded snowfall analysis indicated 3 to 7 inches of snow at elevations above 1500 feet.
National gridded snowfall analysis indicated 3 to 8 inches of snow at elevations above 1500 feet, including the passes on Interstate 5 in the southern portion of the zone.
National gridded snowfall analysis indicated 1 to 6 inches of snow at valley elevations above 1500 feet, including 5 inches measured at Selma. But, 5 to 18 inches were indicated in the surrounding foothills and mountains.
National gridded snowfall analysis indicated 6 to 12 inches of snow at elevations above 1500 feet.
National gridded snowfall analysis indicated 9 to 20 inches of snow.
National gridded snowfall analysis indicated 7 to 17 inches of snow.
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: 1089841, 1089842, 1089843, 1089844, 1089845, 1089846, 1089847.