A very moist Pacific storm moved into north central Idaho from the southwest. This storm followed a previous storm that moved through the region 2 days earlier.
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.
A very moist Pacific storm moved into north central Idaho from the southwest. This storm followed a previous storm that moved through the region 2 days earlier. With abundant moisture this storm dropped some very significant snowfall totals.
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 20, 12:54 PM PST, 6 hours 6 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
254 PM MDT TUE MAR 20 2012
.DISCUSSION...MULTIPLE WINTER HIGHLIGHTS HAVE BEEN ISSUED ACROSS
THE NORTHERN ROCKIES AS A STRONG WEATHER DISTURBANCE PUSHES
THROUGH THE REGION. THIS SYSTEM CONTAINS A LOT MOISTURE AND STRONG
WINDS.
SEVERAL IMPACTS ARE EXPECTED THROUGH WEDNESDAY MORNING
HEAVY MOUNTAIN SNOW AND BLOWING SNOW (HIGH CONFIDENCE) OVER:
LOOKOUT PASS......6-12 INCHES
LOLO PASS.........6-12 INCHES
MARIAS PASS.......4-8 INCHES LOST
TRAIL PASS...3-6 INCHES
MODERATE TO HEAVY SNOW IN CENTRAL IDAHO (MODERATE TO HIGH CONFIDENCE)
PIERCE............6-12 INCHES
GRANGEVILLE.......1-3 INCHES
GREER GRADE.......2-5 INCHES
WHITEBIRD GRADE...2-5 INCHES
ACCUMULATING SNOWS IN THE LOWER VALLEYS ACROSS WESTERN MONTANA:
TUESDAY NIGHT AND THE WEDNESDAY MORNING COMMUTE:
(LOW TO MODERATE CONFIDENCE WITH AMOUNTS)
I-90 CORRIDOR ST. REGIS TO FRENCHTOWN........2-4 INCHES
HIGHWAY 93 HAMILTON TO KALISPELL.............1-3 INCHES UP TO 4 INCHES
EVARO HILL...................................2-5 INCHES
HIGHWAY 200 BONNER TO OVANDO.............. ..1-3 INCHES
HIGHWAY 83 INCLUDING SEELEY LAKE.............2-5 INCHES
MODELS ARE INDICATING A STATIONARY BOUNDARY OF PRECIPITATION TO
DEVELOP THIS EVENING THROUGH WEDNESDAY MORNING ACROSS NORTH
CENTRAL IDAHO THROUGH WEST CENTRAL TO NORTHWEST MONTANA. SNOWFALL
WILL BEGIN TO ACCUMULATE ON ROADWAYS AT LOWER ELEVATIONS AFTER
SUNSET. THE BIGGEST IMPACT WILL BE THE MORNING COMMUTE. CONFIDENCE
IS HIGH FOR PRECIPITATION OR SNOWFALL BUT LOW ON THE WHERE THE
HEAVIEST AMOUNTS OF SNOW IN THE VALLEYS WILL OCCUR. IT IS QUITE
POSSIBLE THAT HEAVY SNOW COULD OCCUR IN LOWER ELEVATIONS WHERE
THIS BOUNDARY FORMS. STAY TUNED FOR FURTHER UPDATES.
BY WEDNESDAY AFTERNOON THE LOW OFF THE COAST WILL AMPLIFY AND
AND PUSH THE MAJORITY OF PRECIPITATION INTO FAR NORTHWEST MONTANA.
SLIGHTLY WARMER TEMPERATURES WILL PRODUCE A MIX OF RAIN/SNOW IN
THE VALLEYS BY NOON.
THURSDAY THROUGH TUESDAY...SOUTHWEST TO SOUTHERLY FLOW WILL
DOMINATE THE EXTENDED FORECAST PERIOD. ONE CHANGE TO THE FORECAST
IS FOR FRIDAY MORNING WHERE MODEL GUIDANCE HAVE ABOVE AVERAGE
AGREEMENT ON THE LOCATION OF PRECIP. AT THIS TIME THERE IS AN AREA
OF SNOW POSSIBLE FROM A LINE EXTENDING FROM DIXIE...IDAHO AND
NORTHEAST THROUGH MISSOULA AND SEELEY LAKE. THE AMOUNT OF PRECIP
IS UNCERTAIN BUT CHANCES FOR SNOW HAVE BEEN INCREASED TO ACCOUNT
FOR MODEL AGREEMENT. NUMEROUS SHORTWAVES WILL PASS THROUGH THE
SOUTHWEST FLOW PATTERN...THAT WILL BRING ON AND OFF CHANCES FOR
PRECIP AND A WAVERING BOUNDARY BETWEEN WARMER AIR TO THE SOUTH AND
COOLER AIR TO THE NORTH. THE PLACEMENT OF THIS BOUNDARY WILL DETERMINE
THE LOCATIONS WITH ABOVE AVERAGE AND BELOW AVERAGE TEMPERATURES.
&&
.AVIATION...THE STRENGTHENED PRESSURE GRADIENT OVER THE REGION THAT
IS CREATING STRONG AND GUSTY WINDS AT CURRENT TIME WILL WEAKEN
THROUGH THIS EVENING. AFTER THE PRESSURE GRADIENT WEAKENS THE WIND
AT AREA TAF SITES WILL DECREASE AND SNOW POTENTIAL WILL INCREASE.
A STRONG WEST TO SOUTHWEST FLOW OVER THE REGION IS BRINGING
ABUNDANT MOISTURE TO IDAHO AND WESTERN MONTANA. THE HIGH TERRAIN
AND MOUNTAIN PASSES HAVE BEEN AND WILL CONTINUE TO BE THE HARDEST
HIT WITH GUSTY WINDS...SNOW AND LOW VISIBILITY/CEILINGS THROUGH
WEDNESDAY. ALL ELEVATIONS FROM WESTERN IDAHO THROUGH MISSOULA AND
NORTHWARD IN NORTHWEST MONTANA ARE EXPECTED TO ACCUMULATE SNOW.
REDUCED CEILINGS AND VISIBILITIES THROUGH THE VALLEYS CAN BE
EXPECTED THROUGH TONIGHT AND INTO WEDNESDAY.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...HIGH WIND WARNING UNTIL 8 PM MDT THIS EVENING BUTTE/BLACKFOOT
REGION.
WINTER STORM WARNING UNTIL NOON MDT WEDNESDAY
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER STORM WARNING UNTIL NOON MDT WEDNESDAY LOWER CLARK FORK
REGION.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM MDT
WEDNESDAY FLATHEAD/MISSION VALLEYS...MISSOULA/BITTERROOT
VALLEYS.
WINTER WEATHER ADVISORY UNTIL NOON MDT WEDNESDAY WEST GLACIER
REGION.
WINTER WEATHER ADVISORY UNTIL NOON MDT WEDNESDAY
KOOTENAI/CABINET REGION.
WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON MDT
WEDNESDAY POTOMAC/SEELEY LAKE REGION.
ID...WINTER STORM WARNING UNTIL 11 AM PDT WEDNESDAY SOUTHERN
CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 9 AM PDT WEDNESDAY LOWER HELLS
CANYON/SALMON RIVER REGION...OROFINO/GRANGEVILLE REGION.
WINTER STORM WARNING UNTIL 11 AM PDT WEDNESDAY NORTHERN
CLEARWATER MOUNTAINS.
&&
SHORT TERM...RPN
LONG TERM....KITSMILLER
AVIATION...KITSMILLERThe national radar mosaic for the moment the first event began.
2 heavy snow. Local standard time, as filed.
A spotter in Pierce measured 12 inches of snow.
A spotter in Weippe measured 9 inches of snow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2012Every state in 2012This day in weather historyWarnings in Idaho, 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: 370267, 370266.