A very moist Pacific weather system interacted with a cold Arctic air mass over western Montana to produce strong gusty winds, cold temperatures, very cold wind chill temperatures, blowing snow and local whiteout conditions.
Every event with a place to put it; 5 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 weather system interacted with a cold Arctic air mass over western Montana to produce strong gusty winds, cold temperatures, very cold wind chill temperatures, blowing snow and local whiteout conditions.
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 Feb 23, 4:11 AM MST, 3 hours 49 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
411 AM MST WED FEB 23 2011
...WINTER WEATHER HIGHLIGHTS HAVE BEEN ISSUED FOR THE ENTIRE
NORTHERN ROCKIES REGION THROUGH THURSDAY...
.DISCUSSION...A MOIST WEST FLOW WILL PERSIST OVER THE NORTHERN
ROCKIES TODAY. INSTABILITY SNOW SHOWERS WILL CONTINUE TO
DEVELOP...BUT THE GREATEST INSTABILITY WILL BE OVER NORTHWEST
MONTANA THROUGH MUCH OF THE DAY. THEREFORE...WILL LEAVE THE WINTER
STORM WARNING IN PLACE FOR THAT AREA. THE REMAINDER OF THE REGION
WILL SEE LESS OF AN IMPACT FROM SHOWERS AS THE DAY PROGRESSES.
EASTERLY FLOW HAS ALREADY BEGUN IN WESTERN MONTANA AS A COLD AIR
MASS PUSHES INTO THE NORTH CENTRAL PART OF THE STATE. THIS WILL
KEEP TEMPERATURES FAIRLY STEADY THROUGH THE DAY.
AN ARCTIC BOUNDARY (OR FRONT) WILL BEGIN TO IMPACT NORTHWEST
MONTANA EARLY THIS EVENING AND SLIDE SOUTHWARD THROUGH THURSDAY
NIGHT. THE MAIN IMPACTS FROM THIS FEATURE CONTINUE TO CENTER
AROUND WINDS/WIND CHILLS...SNOW/BLOWING SNOW...RAPIDLY FALLING
TEMPERATURES...AND TREACHEROUS TRAVEL CONDITIONS.
WINDS/TEMPERATURES...STRONG AND GUSTY EAST WINDS WILL INTENSIFY
DRAMATICALLY IN NORTHWEST MONTANA EARLY THIS EVENING AND BY
THURSDAY MORNING IN WEST CENTRAL/SOUTHWEST MONTANA. GUSTS OF 35
TO 45 MPH WILL BE COMMONPLACE IN AREAS THAT FAVOR CHANNELLED WINDS
THROUGH GAPS IN THE CONTINENTAL DIVIDE. SIGNIFICANT TEMPERATURE
DROPS WILL ALSO OCCUR ALONG AND BEHIND THE ARCTIC FRONTAL PASSAGE
AS IT SLIDES SOUTHWARD. THE COMBINATION OF BITTERLY COLD
TEMPERATURES AND STRONG WINDS WILL CREATE EXTREMELY DANGEROUS WIND
CHILL VALUES OF 20 BELOW ZERO OR LESS WEDNESDAY NIGHT THROUGH
THURSDAY MORNING IN WESTERN MONTANA. LOCATIONS IN THE FLATHEAD
VALLEY AND ALONG THE CONTINENTAL DIVIDE WILL SEE WIND CHILL
READINGS OF 30 BELOW ZERO OR LESS DURING THE SAME TIMEFRAME.
ANYONE VENTURING OUTDOORS SHOULD DRESS APPROPRIATELY BY WEARING
WARM LAYERS AND COVERING ANY EXPOSED SKIN TO PREVENT FROSTBITE.
SNOW...SNOWFALL WILL INTENSIFY ALONG THE ARCTIC BOUNDARY AS
MOISTURE FROM THE WEST IS LIFTED OVER THE COLDER CANADIAN AIR MASS.
AGAIN...NORTHWEST MONTANA WILL FEEL THE EFFECTS EARLY THIS EVENING...
FOLLOWED BY WEST CENTRAL/SOUTHWEST MONTANA BY THURSDAY MORNING.
SNOWFALL WILL BE LIGHT AND FLUFFY...THEREFORE THE COMBINATION OF
SNOW AND GUSTY WINDS WILL PRODUCE WIDESPREAD BLOWING/DRIFTING OF
SNOW AND BLIZZARD CONDITIONS WITH RAPID REDUCTIONS TO VISIBILITY.
TRAVEL WILL BECOME EXTREMELY TREACHEROUS AS DRIVING CONDITIONS
QUICKLY DETERIORATE TONIGHT.
ANOTHER AREA OF CONCERN FOR SNOWFALL TONIGHT THROUGH TOMORROW
MORNING IS NORTHWEST MONTANA NEAR THE IDAHO PANHANDLE AND IN NORTH
CENTRAL IDAHO. THE UPPER LOW OFF THE PACIFIC NORTHWEST COAST WILL
EJECT MOISTURE AND ENERGY INTO THIS AREA ON PREDOMINANT SOUTHWEST
FLOW. NOT ONLY IS THIS A FAVORABLE SET-UP FOR UPSLOPE ENHANCED
PRECIPITATION...BUT IT IS ALSO FAVORABLE FOR HEAVY SNOW OVER THE
CAMAS PRAIRIE FROM OROFINO TO RIGGINS. THE INFLUX OF PACIFIC MOISTURE
WILL ALSO HELP TO AMPLIFY LIQUID PRECIPITATION AMOUNTS...LEADING TO
HIGHER SNOW ACCUMULATION AMOUNTS RANGING FROM 8 TO 12 INCHES IN
VALLEY LOCATIONS.
THURSDAY NIGHT THROUGH SATURDAY...THE MID-LEVEL CIRCULATION
PREVIOUSLY DEPICTED IN SHORT RANGE MODELS THURSDAY NIGHT THROUGH
FRIDAY MORNING IS NOW BEING ABSORBED INTO OBLIVION AND
PRECIPITATION AMOUNTS HAVE COME DOWN DRAMATICALLY. ALTHOUGH PRECIP
DOES NOT APPEAR TO BE AS ORGANIZED OR FOCUSED...CONTINUED THE
TREND OF SHIFTING PRECIPITATION SOUTHWARD OVER TIME AND EVENTUALLY
DRYING FRIDAY NIGHT INTO SATURDAY. MEANWHILE...BITTERLY COLD
TEMPERATURES WILL MAKE FOR EXTREMELY COLD MORNINGS ACROSS THE
REGION FRIDAY AND SATURDAY...WITH TEMPERATURES SLOW TO MODERATE
AND REMAINING WELL BELOW AVERAGE FOR THIS TIME OF YEAR.
A MOIST NORTHWEST FLOW WILL DEVELOP SUNDAY...AND THIS IS GENERALLY
A GOOD LIGHT SNOW PRODUCER FOR THE REGION. THERE IS SOME MODEL
INDICATION OF WEAK RIDGING MONDAY AND EARLY TUESDAY...BUT MODEL
CONSISTENCY HAS BEEN POOR IN THE MEDIUM RANGE OF LATE...SO WILL
NOT STRAY TOO FAR FROM A CLIMATOLOGICAL PRECIPITATION FORECAST.
TEMPERATURES WILL STEADILY RECOVER FROM THE ARCTIC TEMPERATURES
THROUGH THIS PERIOD.
&&
.AVIATION...A MOIST WEST FLOW WILL PERSIST OVER THE NORTHERN
ROCKIES TODAY. INSTABILITY SNOW SHOWERS WILL CONTINUE TO
DEVELOP...BUT THE GREATEST INSTABILITY WILL BE OVER NORTHWEST
MONTANA THROUGH MUCH OF THE DAY. THEREFORE...KGPI WILL LIKELY SEE
PERIODIC VISIBILITY AND CEILING REDUCTIONS. EAST WINDS WILL
CONTINUE TODAY AT KGPI...AND TO A LESSER EXTENT AT KMSO...AS AN
EASTERLY PRESSURE GRADIENT HAS DEVELOPED WITH ARCTIC AIR INVADING
NORTH CENTRAL MONTANA. HOWEVER...THE REAL ARCTIC PUSH WEST OF THE
DIVIDE WILL OCCUR EARLY THIS EVENING AT KGPI AND LATE THIS EVENING
AT KMSO. SURFACE WINDS COULD GUST TO 45 MPH AT KGPI...AND BLOWING
SNOW WILL GREATLY REDUCE VISIBILITIES THROUGHOUT NORTHWEST AND
WEST CENTRAL MONTANA.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 5 PM MST
THURSDAY BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER STORM WARNING FROM 11 PM THIS EVENING TO 5 PM MST
THURSDAY BUTTE/BLACKFOOT REGION.
WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING
MISSOULA/BITTERROOT VALLEYS.
WINTER STORM WARNING FROM 8 PM THIS EVENING TO 2 PM MST THURSDAY
MISSOULA/BITTERROOT VALLEYS.
WINTER STORM WARNING UNTIL 11 AM MST THURSDAY LOWER CLARK FORK
REGION.
WINTER STORM WARNING UNTIL 11 AM MST THURSDAY FLATHEAD/MISSION
VALLEYS.
WINTER STORM WARNING UNTIL 5 AM MST THURSDAY WEST GLACIER REGION.
WINTER STORM WARNING UNTIL 5 AM MST THURSDAY KOOTENAI/CABINET
REGION.
WINTER STORM WARNING UNTIL 11 AM MST THURSDAY POTOMAC/SEELEY
LAKE REGION.
ID...WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 5 PM MST
THURSDAY EASTERN LEMHI COUNTY...WESTERN LEMHI COUNTY.
WINTER STORM WARNING UNTIL 4 AM PST EARLY THIS MORNING FOR WHITE
BIRD GRADE.
WINTER STORM WARNING FROM 4 PM THIS AFTERNOON TO 4 PM PST
THURSDAY LOWER HELLS CANYON/SALMON RIVER REGION...NORTHERN
CLEARWATER MOUNTAINS...OROFINO/GRANGEVILLE REGION...
SOUTHERN CLEARWATER MOUNTAINS.
WINTER STORM WARNING UNTIL 4 AM PST EARLY THIS MORNING
OROFINO/GRANGEVILLE REGION.
WINTER STORM WARNING UNTIL 4 AM PST EARLY THIS MORNING NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
&&
DEROSA/WHITMOREThe national radar mosaic for the moment the first event began.
2 cold/wind chill, 1 blizzard, 1 strong wind, 1 extreme cold/wind chill. Local standard time, as filed.
Snow and blowing snow created white out conditions on highway 93 between Florence and Lolo.
Strong wind gusts uprooted an 18 to 22 inch diameter spruce tree, that hit an apartment complex.
A wind chill temperature of 20 below zero was recorded by the ASOS at the Missoula airport.
Fielding RAWS reported a wind chill temperature of 32 degrees below zero, MDOT at Essex reported a wind chill temperature of 24 degrees below zero.
The ASOS at Glacier International airport in Kalispell reported a wind chill reading of 20 degrees below zero.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2011Every state in 2011This day in weather historyWarnings in Montana, February 2011
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: 282312, 282313, 282314, 282315, 283810.