A cold Arctic air mass moved over western Montana. As the cold air moved south out of Canada, a strong surface pressure gradient produced gusty winds, causing cold wind chill temperatures.
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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 cold Arctic air mass moved over western Montana. As the cold air moved south out of Canada, a strong surface pressure gradient produced gusty winds, causing cold wind chill temperatures.
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 24, 7:26 AM MST, 3 hours 24 minutes earlier.
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE MISSOULA MT
726 AM MST THU FEB 24 2011
.UPDATE...ISSUED A WIND CHILL WARNING FOR GLACIER PARK AREA
THROUGH THIS EVENING.
&&
.DISCUSSION...COLD ARCTIC AIR WILL CONTINUE TO PUSH OVER THE
DIVIDE AND PRODUCE EXTREMELY LOW WIND CHILLS THROUGH TODAY. IN
GLACIER PARK...WIND CHILLS WILL BE 20 TO 35 BELOW ZERO MAKING THIS
A VERY DANGEROUS SITUATION FOR PEOPLE AND ANIMALS EXPOSED.
CONDITIONS ARE EXPECTED TO PERSIST WELL INTO THIS EVENING BEFORE
WINDS FINALLY LESSEN TONIGHT. THE MAIN IMPACT WILL CONTINUE TO BE
THE GUSTY EAST WINDS AND RESULTING WIND CHILLS...HOWEVER SOME
LIGHT ADDITIONAL SNOW ACCUMULATIONS ARE POSSIBLE. SNOW WILL TAPER
OFF AS THE DAY CONTINUES.
&&
.AVIATION...THE CURRENT WINTER STORM OVER THE NORTHERN ROCKIES WILL
CONTINUE TO IMPACT AIR TERMINALS DURING THE NEXT 24 HOURS. FOR
KGPI...THE MAIN IMPACT WILL BE STRONG NORTHEAST WINDS GUSTING TO
35 MPH. BLOWING SNOW WILL REDUCE GROUND VISIBILITY AT TIMES. FOR
KMSO...SNOW AND BLOWING SNOW WILL PERIODICALLY DECREASE VISIBILITY
THROUGH THIS AFTERNOON. FOR KBTM...THERE WILL BE SOME BURSTS OF
SNOW AND WIND THAT WILL DECREASE VISIBILITY THROUGH 25/0000Z.
NORTH WINDS WILL BE GUSTING TO 30 MPH FOR A TIME DURING TODAY. FOR
KSMN...A COMBINATION OF SNOW AND VARIABLY GUSTY WINDS WILL BE
PRESENT BETWEEN 24/1800Z AND 25/0600Z. BRIEF REDUCTIONS IN
VISIBILITY AND CEILINGS WILL BE PRESENT DURING THIS TIME.
&&
.PREV DISCUSSION... /ISSUED 540 AM MST THU FEB 24 2011/
UPDATE...ADDED WINTER WEATHER ADVISORIES FOR KOOTENAI/CABINET AND
WEST GLACIER REGIONS THROUGH LATE THIS MORNING.
DISCUSSION...SNOW AND GUSTY EAST WINDS WILL CONTINUE TO CREATE
AREAS OF BLOWING/DRIFTING SNOW...RAPID REDUCTIONS TO
VISIBILITIES...DANGEROUS WIND CHILLS OF 10 TO 30 DEGREES BELOW
ZERO AND HAZARDOUS DRIVING CONDITIONS THROUGH LATE THIS MORNING. A
WINTER WEATHER ADVISORY HAS BEEN ISSUED TO ACCOUNT FOR THESE
CONDITIONS.
AVIATION...THE CURRENT WINTER STORM OVER THE NORTHERN ROCKIES WILL
CONTINUE TO IMPACT AIR TERMINALS DURING THE NEXT 24 HOURS. FOR
KGPI...THE SNOW THREAT WILL BE QUICKLY DIMINISHING DURING THIS
TIME...HOWEVER STRONG NORTHEAST WINDS GUSTING TO 35 MPH WILL BE
PRESENT THROUGH 25/0000Z. BLOWING SNOW WILL REDUCE GROUND VISIBILITY
AT TIMES. FOR KMSO...SNOW AND BLOWING SNOW WILL PERIODICALLY
DECREASE VISIBILITY AND CEILINGS THROUGH 24/1800Z. STRONG EAST WINDS
GUSTING TO 40 MPH WILL BE PRESENT DURING THIS MORNING THROUGH
25/0600Z. FOR KBTM...THERE WILL BE SOME BURSTS OF SNOW AND WIND THAT
WILL DECREASE VISIBILITY AND CEILINGS FOR A TIME BETWEEN 24/1200Z
AND 25/0000Z. NORTH WINDS WILL BE GUSTING TO 30 MPH FOR A TIME
DURING TODAY. FOR KSMN...A COMBINATION OF SNOW AND VARIABLY GUSTY
WINDS WILL BE PRESENT BETWEEN 24/1800Z AND 25/0600Z. BRIEF
REDUCTIONS IN VISIBILITY AND CEILINGS WILL BE PRESENT DURING THIS
TIME.
PREV DISCUSSION... /ISSUED 413 AM MST THU FEB 24 2011/
.TREACHEROUS WINTER CONDITIONS ACROSS THE NORTHERN ROCKIES TODAY...
.BITTERLY COLD WITH DANGEROUS WIND CHILLS TONIGHT THROUGH FRIDAY...
DISCUSSION...
THE COMBINATION OF SNOW...GUSTY WINDS AND BITTERLY COLD TEMPERATURES
WILL CREATE THE FOLLOWING IMPACTS TODAY THROUGH FRIDAY MORNING:
* BLOWING AND DRIFTING OF SNOW
* LOCAL BLIZZARD CONDITIONS
* RAPID REDUCTIONS TO VISIBILITIES
* TREACHEROUS DRIVING CONDITIONS
* DANGEROUS WIND CHILLS OF 20 TO 40 BELOW ZERO
THE ARCTIC FRONT IS STRADDLED OVER WESTERN MONTANA EARLY THIS
MORNING. PACIFIC MOISTURE STREAMING INTO THE AREA FROM AN UPPER
LEVEL LOW ON THE WASHINGTON COAST IS ENHANCING PRECIPITATION IN
NORTH CENTRAL IDAHO AND NORTHWEST MONTANA/IDAHO PANHANDLE...
CONTINUING THE THREAT FOR HEAVY SNOW IN THESE AREAS TODAY.
UPSTREAM...THE SPOKANE WFO REPORTED IMPRESSIVE SNOWFALL RATES OF 2
INCHES PER HOUR AROUND 1 AM MST THIS MORNING. AS THIS MOISTURE
FLOWS INTO THE REST OF WESTERN MONTANA...IT WILL INTERACT WITH
THE ARCTIC FRONT AND ENHANCE SNOWFALL...ESPECIALLY THIS MORNING.
STRONG AND GUSTY EAST WINDS WILL ALSO BE THE MOST INTENSE THIS
MORNING BUT WILL REMAIN GUSTY THROUGH THE DAY...GRADUALLY TAPERING
OFF BY FRIDAY MORNING. MEANWHILE...COLD CANADIAN AIR HAS
INFILTRATED WESTERN MONTANA AND WILL CONTINUE TO DRIVE
TEMPERATURES DOWN IN THE NORTHERN ROCKIES THROUGH AT LEAST
SATURDAY MORNING BEFORE MODERATING. THE EXTREME COLD MAY ALSO
IMPACT LIVESTOCK...ESPECIALLY LIVESTOCK YOUNG.
THIS ARCTIC AIR MASS IS ANOMALOUSLY COLD FOR LATE FEBRUARY. HIGH
TEMPERATURES ON THURSDAY AND FRIDAY WILL RUN AROUND 30 DEGREES BELOW
AVERAGE AND LOW TEMPS FRIDAY AND SATURDAY MORNINGS WILL RUN 30 TO 40
DEGREES BELOW NORMAL. FORECAST LOWS ARE APPROACHING RECORD COLD
VALUES IN NORTHWEST MONTANA DURING THIS TIME...AND FORECAST HIGHS
COULD BREAK RECORD LOW MAXIMUM TEMPERATURES IN WESTERN MONTANA AS
WELL. A PUBLIC INFORMATION STATEMENT INDICATING FORECAST
TEMPS/RECORD TEMPS HAS BEEN HEADLINED ON THE
WWW.WEATHER.GOV/MISSOULA HOME PAGE...AND ALSO GIVES AVERAGE
TEMPERATURES AS A COMPARISON.
SATURDAY NIGHT THROUGH MONDAY NIGHT...ALL MODEL GUIDANCE SUGGEST
THAT INTENSE WEST TO EAST FLOW ALOFT WILL DEVELOP OVER THE NORTHERN
ROCKIES DURING OVERNIGHT SATURDAY. THIS RELATIVELY WARM AND MOIST
PACIFIC FLOW WILL QUICKLY MODERATE TEMPERATURES ACROSS THE REGION.
CONSIDERING THAT THE PACIFIC JET STREAM WILL ACCOMPANY THIS PATTERN
CHANGE...AREA MOUNTAIN RANGES WILL BE FAVORED FOR A PROLONGED SNOW
EVENT WITH MODERATE ACCUMULATIONS. WESTERN MONTANA FROM MISSOULA
NORTHWARD HAVE THE BEST CHANCE FOR PRECIPITATION...HOWEVER THE
FLATHEAD AND MISSION VALLEYS ARE LIKELY TO BE IN A RELATIVE
RAIN/SNOW SHADOW FOR MUCH OF THIS TIME.
TUESDAY THROUGH WEDNESDAY...MODELS DEPICTED A RIDGE OF HIGH PRESSURE
BUILDING OVER THE INLAND PACIFIC NORTHWEST...FURTHER WARMING
TEMPERATURES AND DIMINISHING THE THREAT OF PRECIPITATION OVER
NORTHWEST MONTANA. THE RIDGE WILL BE DEVELOPING AHEAD OF A VIGOROUS
PACIFIC STORM SYSTEM.
THURSDAY ONWARD...MODELS ARE IN BASIC AGREEMENT ON THE LARGE
SCALE...DEPICTING A VIGOROUS PACIFIC STORM SYSTEM MOVING OVER THE
NORTHERN ROCKIES BETWEEN THURSDAY AND SATURDAY. SPECIFIC STORM
DETAILS ARE UNCLEAR AT THE MOMENT...HOWEVER THERE IS HIGH CONFIDENCE
OF A CONTINUED STORMY FOR LATE NEXT WEEK AND THROUGH THE WEEKEND.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER STORM WARNING UNTIL 5 PM MST THIS AFTERNOON
BUTTE/BLACKFOOT REGION.
WINTER STORM WARNING UNTIL 2 PM MST THIS AFTERNOON
MISSOULA/BITTERROOT VALLEYS.
WINTER STORM WARNING UNTIL 11 AM MST THIS MORNING LOWER CLARK
FORK REGION.
WINTER STORM WARNING UNTIL 11 AM MST THIS MORNING
FLATHEAD/MISSION VALLEYS.
WIND CHILL WARNING UNTIL 11 PM MST THIS EVENING WEST GLACIER
REGION.
WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING
KOOTENAI/CABINET REGION.
WINTER STORM WARNING UNTIL 11 AM MST THIS MORNING POTOMAC/SEELEY
LAKE REGION.
ID...WINTER WEATHER ADVISORY UNTIL 5 PM MST THIS AFTERNOON EASTERN
LEMHI COUNTY...WESTERN LEMHI COUNTY.
WINTER STORM WARNING UNTIL 4 PM PST THIS AFTERNOON LOWER HELLS
CANYON/SALMON RIVER REGION...NORTHERN CLEARWATER
MOUNTAINS...OROFINO/GRANGEVILLE REGION...SOUTHERN
CLEARWATER MOUNTAINS.
&&
UPDATE...ALLEGRETTO
PREVIOUS DISCUSSION....ZUMPFE
AVIATION...ALLEGRETTOThe national radar mosaic for the moment the first event began.
3 cold/wind chill. Local standard time, as filed.
Montana department of transportation sensor 7 miles east of Kalispell on highway 35 reported a wind chill temperature of 22 below zero.
The ASOS at the Missoula airport reported a wind chill temperature of 20 below zero. Downtown Missoula CWOP station reported a wind chill temperature of 24 below zero.
Wind chill readings of 24 below zero at Deer Lodge, 33 below zero at Helmville, 25 below zero 3 miles north of Avon, 29 below zero at Garrison, 22 below zero at Georgetown Lake and 24 below zero at Homestake Pass were recorded.
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: 282359, 282357, 282362.