An intense and prolonged atmospheric river (AR) impacted the Northern Rockies, directed primarily at North-Central Idaho. This event was characterized by a deep moisture plume and an unseasonably warm air mass, which transitioned mountain snow to a heavy rain-on-snow event.
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 MSO wrote it up.
An intense and prolonged atmospheric river (AR) impacted the Northern Rockies, directed primarily at North-Central Idaho. This event was characterized by a deep moisture plume and an unseasonably warm air mass, which transitioned mountain snow to a heavy rain-on-snow event. Total precipitation across the Clearwater Basin ranged from 2.5 to over 5.0 inches. Impacts from this storm included power outages and impacts to travel. The biggest impact, however, was flooding in Clearwater County near Orofino. By the morning of March 13, several days of moderate rain and mild temperatures had completely saturated the soil. With the ground unable to absorb any more water and temperatures remaining above freezing overnight, continued rainfall and rapid snowmelt triggered immediate runoff. This surge of water overwhelmed culverts, destabilized hillsides, and caused rapid rises on small streams and the Clearwater River.
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 Missoula, MT wrote its last area forecast discussion before the first event at Mar 11, 10:20 AM PST, 5 hours 40 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
1220 PM MDT Wed Mar 11 2026
.DISCUSSION...
KEY MESSAGES:
- Prolonged atmospheric river event from Wednesday night through
Saturday.
- Strong and potentially damaging winds late Wednesday night
through Thursday, with the strongest gusts expected across
northwest Montana and along the Continental Divide.
- Very difficult backcountry conditions due to strong winds and
heavy snow, leading to areas of blizzard conditions.
Changes Over Last 24-Hours:
* Upgraded Glacier Park region to Blizzard Warning late tonight
into Thursday morning; significant impacts from whiteout
conditions from heavy snow and strong winds.
* Replaced High Wind Warning in Butte/Blackfoot region with Winter
Storm Warning; where significant heavy snow, strong winds, and
periods of blizzard conditions are expected across pass areas
and the Montana Highway 1 corridor near Georgetown Lake.
IMPORTANT: A significant wind event remains on track across all
elevations.
* Issued Winter Storm Warning for Seeley Lake/Potomac region
Thursday night into Saturday morning, where snow amounts have
notably trended higher.
Discussion:
A significant and prolonged atmospheric river event remains on
track to impact the Northern Rockies later today through Saturday.
Satellite and regional radar imagery this morning show the
atmospheric river making landfall across the Pacific Northwest,
with precipitation rates beginning to increase along the Idaho and
Montana border. The primary impact window begins tonight into
Thursday morning, as a 990-995 mb surface low tracks along the
USA-Canadian border west-to-east into southern Alberta by Thursday
morning. Model guidance has been very consistent with a
significant threat for strong and damaging winds as a near-record
mid-level jet stream moves across the region after midnight
tonight. Models suggest 700-mb winds (10,000 ft MSL winds) will
reach near 90-100kt (~100-110 mph), which is near the all-time
record climatology within historical data. These strong winds
aloft, coupled with a surface cold front tracking through
northwest Montana early Thursday morning maximize the threat for
strong and widespread damaging winds, particularly north of the
I-90 corridor, with the greatest impacts will focus across
Lincoln, Flathead Counties, and the highest terrain. Further
south, strong and damaging winds will be more localized, driven by
strong winds aloft being mixed down to the surface through
convective gusts and mountain wave activity. This includes areas
along and south of I-90. Historically, the Bitterroot Valley and
the I-90 corridor from Garrison to Anaconda are the most
susceptible to the strongest winds, with gusts up to 70 mph a
concern during this event.
A long duration winter storm will bring major to extreme impacts
across the Glacier Park region, the Bitterroot, Clearwater, and
Sapphire Mountains, and Seeley Lake, Potomac, Butte/Blackfoot
regions tonight into Saturday morning. Storm impacts will peak
after midnight into early Thursday afternoon across mountain
passes and backcountry areas, with periods of blizzard conditions
driven by heavy snow rates and strong winds, with gusts of 50 to
80 mph. The worst conditions and impacts will be felt across the
Glacier Park region, specifically on US Highway 2 east of West
Glacier to Marias Pass and in the higher terrain, where several
hours of whiteout conditions are expected. Model guidance suggests
over a 80-90% probability for snow rates of near 1 inch per hour
and strong winds in excess of 50 mph as the cold front passes.
Lookout, Lost Trail, MacDonald Passes, and the Georgetown Lake
areas will also see blizzard-like conditions late tonight into
Thursday morning. Those planning to travel across these areas
should consider delaying or canceling plans as these conditions
will be life threatening.
The atmospheric river will continue to bring widespread heavy
mountain snow Thursday afternoon through Saturday. Ensemble
guidance has been consistent with a 24-48 hour period of
Integrated Vapor Transport Values of 200-400 kg/ms reaching the
divide. This provides a high confidence scenario for feet of snow
above 4,000-5,000 feet across mountain areas, with the highest
accumulations of 2-5 feet across the Bitterroot and Clearwater
Mountains. The combination of heavy snow, strong winds, and
significant precipitation totals will cause dramatic changes to
the snowpack and those heading into the backcountry and in the
mountains should closely monitor the latest avalanche conditions.
Rising temperatures and snow levels during the atmospheric river
event in Clearwater and Idaho Counties of Idaho will bring the
risk for sharp rises of small streams and creeks as 1 to 5 inches
of precipitation falls below the snow line. Roadways will also be
at risk for rock and mudslides. Please see our hydrologic outlook
for more information.
This storm system will begin to exit the region on Saturday, with
the passage of a Pacific cold front and upper level trough from
the northwest. Snow levels will quickly drop late Friday night
into Saturday morning, with snow showers bringing minor-moderate
winter weather impacts. Valley snow amounts remain variable during
this period; please monitor the forecast closely in the coming
days. /AL
&&
.AVIATION...The atmospheric river will continue to move into the
Northern Rockies tonight and last through Saturday. This moisture
will cause cloud cover to steadily increase and lower over the
next 12 hours at all terminals. Snow levels will be climbing
during the evening hours so any precipitation at the terminals
are expected to be rain. Then tonight a cold front will begin to
push through the region from the north to south causing strong to
damaging winds, all terminals are expected to have gusts in excess
of 35kts on Thursday. Low level wind shear will also be a concern
late tonight through Thursday. The cold front will also cause snow
levels to drop to valley floor, especially across northwest
Montana. Any snow that impacts KGPI, anticipate at least IFR
conditions along with blowing snow.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning from 6 PM this evening to noon MDT Saturday
for Bitterroot/Sapphire Mountains...Lower Clark Fork Region.
High Wind Warning from midnight tonight to 6 PM MDT Thursday for
Flathead/Mission Valleys...Kootenai/Cabinet Region...
Missoula/Bitterroot Valleys...Potomac/Seeley Lake Region.
Winter Weather Advisory until 6 PM MDT this evening for West
Glacier Region.
Winter Storm Warning from 6 PM this evening to midnight MDT
tonight for West Glacier Region.
Winter Storm Warning from 9 AM Thursday to noon MDT Saturday for
West Glacier Region.
Blizzard Warning from midnight tonight to 9 AM MDT Thursday for
West Glacier Region.
Winter Storm Warning from midnight tonight to noon MDT Saturday
for Butte/Blackfoot Region.
Winter Storm Warning from 6 PM Thursday to noon MDT Saturday for
Potomac/Seeley Lake Region.
ID...Winter Storm Warning from 5 PM this afternoon to 11 AM PDT
Saturday for Northern Clearwater Mountains...Southern
Clearwater Mountains.
Wind Advisory from 8 PM this evening to 11 AM PDT Thursday for
Lower Hells Canyon/Salmon River Region...
Orofino/Grangeville Region.
High Wind Warning from midnight tonight to midnight MDT Thursday
night for Eastern Lemhi County...Western Lemhi County.
&&The national radar mosaic for the moment the first event began.
1 winter weather, 1 winter storm, 1 flood. Local standard time, as filed.
Elk Butte SNOTEL recorded 2.80 inches of snow-water equivalent since 0000 PST March 11, 18 inches of snow. Crater Meadows SNOTEL two feet of storm total snow.
Montana Department of Transportation (on the east side of Highway 12) reported severe driving conditions. Lolo Pass Visitor Center reported 59 inches of storm total snow. Rock slides occurred between Grangeville and Elk City. A power outage event was reported in Elk City.
The most significant impact occurred south of Orofino, where a large landslide blocked US-12 between mile markers 44 and 45. The initial slide occurred around 1539MST on Friday, March 13. While crews worked to clear the route, a second slide occurred at the same location at 0920MST on Saturday, March 14. The highway remained closed in both directions until Saturday afternoon. Additional landslides and rockslides were reported on Lower Fords Creek Road, Grangemont Road, Sunnyside, and Bobbitt Bench. Heavy traffic diverted to Sunnyside Road caused that secondary route to begin failing under the saturated conditions.
In Orofino, the urban drainage system reached maximum capacity and overflowed, flooding residential areas. In the Riverside area (115th Street), rushing water surrounded homes and filled basements. Significant damage occurred at the Joint School District 171 bus garage when a nearby creek (likely Flume Creek) blew out, flooding the facility. While officials successfully moved most of the fleet, one school bus and a neighboring food pantry were inundated and suffered major damage.
Small streams and creeks, including Jim Fords Creek and Freeman Creek, crested their banks, threatening homes and washing out culverts. Near Weippe, a creek overflowed onto the roadway, causing significant rutting. The Clearwater River at Orofino saw a dramatic rise of over 8 feet, increasing from 5.78 feet on Thursday to a crest of 13.96 feet on Saturday night staying just below the 16-foot flood stage, though the high water contributed to the drainage backup in the city. Total rainfall between March 10 and 15 included 3.57 in Orofino, 4.00 in Peck, and 4.50 at the Pierce SNOTEL.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2026Every state in 2026This day in weather historyWarnings in Idaho, March 2026
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: 1316449, 1316450, 1320433.