A moist Pacific system moved into western Montana and north central Idaho, and dropped some significant snowfall totals mainly at the higher elevations.
Every event with a place to put it; 11 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.
A moist Pacific system moved into western Montana and north central Idaho, and dropped some significant snowfall totals mainly at the higher elevations.
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 17, 3:00 AM MST, 2 hours 30 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
400 AM MDT SAT MAR 17 2012
.DISCUSSION...A RATHER POTENT WEATHER SYSTEM HAS BEGUN TO IMPACT
THE INTERMOUNTAIN WEST THIS MORNING AND WILL CONTINUE ITS
PROGRESSION NORTHWARD. AS IT DOES SO...PRECIPITATION IN THE FORM
OF RAIN WILL PLAGUE VALLEYS OF WESTERN MONTANA AND CENTRAL
IDAHO...WHILE SNOWFALL IS EXPECTED IN THE HIGHER TERRAIN. THE MOST
FOCUSED SNOWFALL POSING THE GREATEST IMPACTS TO TRAVEL WILL BE
ACROSS SOUTHWEST MONTANA...INCLUDING LOST TRAIL PASS. UP TO A FOOT
OF SNOW IS POSSIBLE IN TERRAIN ROUGHLY 6500 FEET AND HIGHER.
DRIVING CONDITIONS WILL BE IMPACTED THROUGH SUNDAY AS A
RESULT...SO THOSE WITH TRAVEL PLANS OVER MOUNTAIN PASSES SHOULD
PLAN AHEAD AND LEAVE PLENTY OF TIME.
ONE PERSISTENT FEATURE WITH THIS PARTICULAR WEATHER SYSTEM HAS
BEEN THE FACTOR OF RISING SNOW LEVELS THROUGHOUT THE DAY TODAY.
THIS WILL RESULT IN LOCATIONS ALONG THE I-90 CORRIDOR THROUGH DEER
LODGE...ANACONDA...AND BUTTE SEEING A TRANSITION TO RAIN OR A
RAIN/SNOW MIX. BY TONIGHT THIS SCENARIO WILL CHANGE
AGAIN...RESULTING IN ANOTHER TRANSITION FROM RAIN BACK TO SNOW
THROUGH SUNDAY. POTENTIALLY DANGEROUS DRIVING CONDITIONS MAY EXIST
ACROSS SOUTHWEST MONTANA DURING THIS TIME.
NORTHWEST MONTANA WILL BE THE FIRST LOCATION TO SEE A BREAK IN
PRECIPITATION THROUGH THE DAY SUNDAY...BUT PRECIPITATION WILL
REMAIN CONTINUOUSLY FOCUSED ACROSS SOUTHWEST MONTANA AND PORTIONS
OF WEST CENTRAL MONTANA SUNDAY AND THROUGH MONDAY MORNING.
A COLD CORE ALOFT WILL MOVE OVER THE NORTHERN ROCKIES DURING
MONDAY...WITH RELATIVELY COLD DAYTIME TEMPERATURES PRESENT.
RELATIVELY DRY CONDITIONS ARE ANTICIPATED MONDAY THROUGH TUESDAY
MORNING...AHEAD OF THE NEXT PACIFIC STORM SYSTEM.
TUESDAY THROUGH THURSDAY...STORM SYSTEMS EMBEDDED WITHIN
SOUTHWESTERLY FLOW ALOFT WILL CONTINUE TO PERIODICALLY MOVE
ACROSS THE NORTHERN ROCKIES. TIMING OF SURFACE COLD FRONTS VARY
WILDLY AMONG MODEL GUIDANCE...HOWEVER ALL GUIDANCE AGREE ON
ABUNDANT MOISTURE BEING PRESENT...PARTICULARLY OVER FAR NORTHWEST
MONTANA. MOUNTAIN PASSES ARE LIKELY TO EXPERIENCE ACCUMULATING
SNOW FROM TIME TO TIME...HOWEVER MORE RAIN THAN SNOW IS EXPECTED
FOR MOST VALLEY LOCATIONS.
FRIDAY THROUGH SATURDAY...MODEL GUIDANCE SHOW LITTLE AGREEMENT
WITH RESPECT TO THE LARGE SCALE WEATHER PATTERN. ECMWF HAS TRENDED
TOWARD RELATIVELY WARM AND DRY HIGH PRESSURE OVER THE NORTHERN
ROCKIES...WHILE GFS HAS MAINTAINED A CONTINUATION OF WARM AND
MOIST SOUTHWEST FLOW ALOFT. THE CURRENT PRECIPITATION FORECAST
REFLECTS MORE CONFIDENCE IN THE ECMWF SOLUTION...WITH EXPECTATIONS
OF PRECIPITATION LOWER THAN CLIMATOLOGY...HOWEVER NOT COMPLETELY
DRY. TEMPERATURE FORECAST HAS BEEN KEPT SEASONALLY MILD DURING
THIS TIME.
&&
.AVIATION...AN INCOMING WEATHER SYSTEM WILL BRING CONTINUOUS
PRECIPITATION ACROSS WESTERN MONTANA AND CENTRAL IDAHO TODAY INTO
TONIGHT. VARIABLE PRECIPITATION IS EXPECTED...WITH TRANSITIONS
BETWEEN RAIN AND SNOW EXPECTED THROUGHOUT THE DAY. PRECIPITATION
SHOULD CHANGE TO ALL SNOW BY TONIGHT HOWEVER...WITH PERSISTENT
LOWERED CEILINGS AND VISIBILITIES IN AREAS OF HEAVIER SHOWERS.
EXPECT THESE INTERMITTENT REDUCTIONS DUE TO SNOW AND RAIN THROUGH
SUNDAY.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO MIDNIGHT MDT
SUNDAY NIGHT BUTTE/BLACKFOOT REGION.
WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM MDT SUNDAY
FOR LOST TRAIL PASS.
ID...WINTER STORM WARNING FROM 6 AM THIS MORNING TO 6 PM MDT SUNDAY
ABOVE 6500 FEET FOR THE EASTERN LEMHI COUNTY.
&&
SHORT TERM...ALLEGRETTO
LONG TERM....ZUMPFE
AVIATION...ALLEGRETTOThe national radar mosaic for the moment the first event began.
11 heavy snow. Local standard time, as filed.
Lost Trail ski resort measured 7 inches of snow at 7000 feet, near Highway 93 over Lost Trail Pass.
Snowfall total for 36 hours was measured at 8.8 inches 4 miles west northwest of West Valley.
A trained spotter in Anaconda measured 10 inches of snow.
Snowfall of 7.5 inches was measured 4 miles west northwest of Anaconda.
Total snow accumulation of 9 inches was measured in Anaconda, with 4 inches falling between noon and 110pm.
A trained spotter in Anaconda measured 11.2 inches of snow today.
Snowfall of 6 inches was measured in Deer Lodge, visibilities were down to 1/4 mile.
A spotter measured 5.5 inches of snow, with 3 inches falling between 1236pm and 220pm, 3 miles west southwest of Newcomb at an elevation of 6200 feet.
A 24 hour snowfall total at Georgetown was measured at 16.5 inches.
In a three hour period 9 inches of snow was measured 3 miles southwest of Ovando.
Snowfall between 3 pm and 7 pm was measured at 6 inches, 4 miles east northeast of Blacktail at Marias pass.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2012Every state in 2012This day in weather historyWarnings in Montana, March 2012
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: 370242, 370253, 370244, 370249, 370250, 370252, 370246, 370247, 370256, 370245, 370254.