Warm temperatures and snowmelt caused widespread flooding.
Every event with a place to put it. 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 TFX wrote it up.
Warm temperatures and snowmelt caused widespread flooding.
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 Great Falls, MT wrote its last area forecast discussion before the first event at Mar 17, 8:52 AM MST, 1 hour 8 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 952 AM MDT THU MAR 17 2011 .UPDATE... INCREASED POPS OVER SW MONTANA THIS MORNING...PARTICULARLY OVER THE MOUNTAINS AS WEAK ENERGY MOVES OVER THE AREA. ALSO LOWERED TEMPS WITH MORE CLOUD COVER OVER THE SOUTHWEST VALLEYS. DOWNSLOPE WINDS WILL KEEP NORTH-CENTRAL MONTANA FAIRLY DRY WITH TEMPERATURES AROUND TO SLIGHTLY ABOVE SEASONAL AVERAGES. REMAINDER OF THE FORECAST IS ON TRACK SO MADE NO FURTHER CHANGES. MLS && .AVIATION... UPDATED 1200Z. WESTERLY FLOW ALOFT WILL CONTINUE TODAY AND TONIGHT WITH THE AIRMASS BECOMING SLIGHTLY UNSTABLE THIS AFTERNOON...MAINLY ACROSS SW MT WHERE SOME MID-LEVEL MOISTURE ALSO PRESENT WILL ALLOW FOR CONTINUED SCATTERED MAINLY MTN SNOW-SHOWERS. VFR CONDITIONS WILL GENERALLY PREVAIL WITH OCCASIONAL MVFR AND MTN OBSCURATIONS OVER WESTERN AND SW MT AREAS INCLUDING NEAR THE BOZEMAN AIRFIELD. BREEZY SURFACE WINDS EXPECTED AT TIMES THIS AFTERNOON WILL DIMINISH THIS EVENING. HOENISCH && .HYDROLOGY... MODERATE DAYTIME TEMPERATURES WILL CONTINUE TO BRING WIDESPREAD SIGNIFICANT SNOWMELT ACROSS THE LOCAL FORECAST AREA. SEVERAL SMALL STREAMS AND CREEKS ARE NEARING/EXCEEDING BANKFULL AND FLOWING OVER LOCAL ROADS...PROMPTING MULTIPLE FLOOD ADVISORIES/WARNINGS THAT REMAIN IN EFFECT AT THIS TIME. && .PREV DISCUSSION... /ISSUED 527 AM MDT THU MAR 17 2011/ TODAY THROUGH SATURDAY EVENING...WEAK UPPER LEVEL WEATHER SYSTEM THAT MOVED THROUGH THE REGION YESTERDAY IS NOW MOSTLY IN ERN MT. SMALL AREAS OF RESIDUAL MOISTURE ALONG THE CONTINENTAL DIVIDE IN SOUTHWEST MT AND ALONG THE US/CAN BORDER NEAR HAVRE WILL KEEP A SLIGHT CHANCE OF ISOLATED LIGHT VALLEY RAIN/MTN SNOW SHOWERS THERE THRU AROUND MIDDAY...WHILE REST OF THE FORECAST AREA REMAINS DRY TODAY. HIGH PRESSURE RIDGING ARRIVES ON FRI WITH WIDESPREAD CLEAR TO PARTLY CLOUDY SKIES AND DRY CONDITIONS EXPECTED. THE FAIR CONDITIONS WILL LAST UNTIL EARLY SAT WHEN NORTHERN ROCKIES WILL BEGIN TO BE INFLUENCED BY A SHORTWAVE TROF AND ACCOMPANYING MOISTURE EJECTING FROM A DEEP CLOSED LOW OFF THE PACNW COAST. FORECAST MODELS HAVE SHIFTED BACK TO THE TIMING SEEN IN SOLUTIONS A FEW DAYS AGO...WITH SHOWERS DEVELOPING OVER FAR SOUTHWEST MT BY NOON ON SAT AND THE PRECIPITATION SPREADING OVER CENTRAL & NORTH CENTRAL ON SAT AFTN/EVE. MOST OF THE PRECIP SHOULD BE RAIN AT THE LOWER ELEVATIONS AND A MIX OF RAIN/SNOW TO ALL SNOW IN THE MTNS. A SLIGHT CHANCE OF THUNDERSTORMS IS ALSO IN THE FORECAST FOR SOUTHWEST MT NORTHWARD TO AROUND HELENA AND THE LITTLE BELT MTNS AS MODELS CONTINUE TO INDICATE SOME MARGINALLY UNSTABLE CONDITIONS ON SAT AFTN. DAILY HIGH TEMPERATURES THROUGH THE SHORT-TERM PERIOD WILL REMAIN NEAR TO SLIGHTLY ABOVE NORMAL AS SOUTH/SOUTHWEST FLOW ALOFT KEEPS A MORE TEMPERATE AIRMASS OVER THE REGION. WARANAUSKAS SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODELS CONTINUE TO ADVERTISE AN INCREASINGLY UNSETTLED PATTERN DEVELOPING THIS WEEKEND AND CONTINUING INTO EARLY NEXT WEEK AS A LONGWAVE UPPER LEVEL TROUGH/LOW BECOMES ESTABLISHED ALONG THE WEST COAST. THE FIRST SIGNIFICANT PIECE OF ENERGY TO EJECT OUT OF THE UPPER LEVEL LOW WILL TRACK NORTH THROUGH THE FORECAST AREA SATURDAY NIGHT AND INTO CANADA BY SUNDAY MORNING. THIS SYSTEM STILL LOOKS TO BRING A PERIOD OF RAIN/SNOW TO MUCH OF THE FORECAST AREA WITH SNOW LEVELS FALLING TO NEAR VALLEY FLOORS AND PLAINS BY SUNDAY MORNING. A BREAK BETWEEN SYSTEMS WILL LIKELY OCCUR SUNDAY INTO EARLY MONDAY BEFORE THE NEXT BUNDLE OF UPPER LEVEL ENERGY MOVES INLAND LATE MONDAY AND TUESDAY. MODELS HAVE STRENGTHENED THIS SYSTEM OVER THE LAST FEW RUNS WITH LATEST DATA FROM GFS ECMWF AND GEM MODELS ALL SUPPORTING A FAIRLY VIGOROUS SPRING-LIKE STORM SYSTEM PASSING NEAR THE REGION WITH POTENTIAL FOR MODERATE PRECIPITATION...LIKELY IN THE FORM OF SNOW FOR MANY AREAS...ESPECIALLY OVER NORTH CENTRAL MT. WITH MODEL DATA IN GENERAL AGREEMENT ON A PATTERN THAT WOULD FAVOR THIS KIND OF AMPLIFICATION AND LATE MARCH BEING A TYPICAL TIME OF YEAR FOR THESE TYPES OF SYSTEMS...HAVE GONE WITH RELATIVELY HIGH POPS AND TEMPS NEAR THE COOLER END OF MODEL GUIDANCE FOR THE MONDAY AND TUESDAY PERIOD. AN UPPER RIDGE LOOKS TO BRIEFLY AMPLIFY OVER THE REGION WEDNESDAY INTO THURSDAY IN ADVANCE OF THE NEXT TROUGH DIGGING SOUTH ALONG THE WEST COAST LATE NEXT WEEK. HOENISCH && .PRELIMINARY POINT TEMPS/POPS... GTF 47 26 53 26 / 10 10 0 0 CTB 42 24 47 22 / 10 10 0 0 HLN 48 24 52 28 / 30 10 0 0 BZN 42 21 50 26 / 40 20 0 10 WEY 30 6 37 17 / 50 20 10 40 DLN 40 18 47 27 / 30 20 10 10 HVR 40 20 44 23 / 20 10 0 0 LWT 44 26 49 27 / 20 10 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREAT FALLS MT 447 AM MDT THU MAR 17 2011 MTZ009>011-044>048-181100- NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-TOOLE-LIBERTY- EASTERN PONDERA-BLAINE-SOUTHERN ROCKY MOUNTAIN FRONT- 447 AM MDT THU MAR 17 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL MONTANA. .DAY ONE...TODAY AND TONIGHT FLOOD WARNINGS REMAIN IN EFFECT FOR PORTIONS OF PONDERA COUNTY THROUGH THIS AFTERNOON. FLOOD ADVISORIES REMAIN IN EFFECT FOR PORTIONS OF BLAINE AND HILL COUNTIES THROUGH THIS AFTERNOON. OTHER THAN THE FLOOD CONDITIONS...THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW TODAY. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A VIGOROUS SPRING-LIKE STORM SYSTEM WILL BRING A WIDE AREA OF SNOW MONDAY EVENING INTO TUESDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO RELAY SIGNIFICANT WEATHER REPORTS AND IMPACTS TO THE NATIONAL WEATHER SERVICE FORECAST OFFICE IN GREAT FALLS. MTZ012>014-049>054-181100- CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK- EASTERN TETON-JUDITH BASIN-FERGUS-JEFFERSON-BROADWATER-MEAGHER- 447 AM MDT THU MAR 17 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT FLOOD WARNINGS FOR PORTIONS OF TETON AND CHOUTEAU COUNTIES ARE IN EFFECT THROUGH THIS AFTERNOON. FLOOD ADVISORIES REMAIN IN EFFECT FOR PORTIONS OF CASCADE AND NORTHEASTERN FERGUS COUNTIES THROUGH THIS AFTERNOON. OTHER THAN THE FLOOD CONDITIONS...THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW TODAY. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A VIGOROUS SPRING-LIKE STORM SYSTEM WILL BRING A WIDE AREA OF SNOW MONDAY EVENING INTO TUESDAY. THERE IS A POSSIBILITY THAT SOME LOCATIONS IN NORTH CENTRAL MONTANA COULD SEE SEVERAL INCHES OF SNOWFALL FROM THIS SYSTEM. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO RELAY SIGNIFICANT WEATHER REPORTS AND IMPACTS TO THE NATIONAL WEATHER SERVICE FORECAST OFFICE IN GREAT FALLS. MTZ008-015-055-181100- BEAVERHEAD-MADISON-GALLATIN- 447 AM MDT THU MAR 17 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY UNSTABLE CONDITIONS ASSOCIATED WITH A PACIFIC STORM SYSTEM WILL PRODUCE ISOLATED THUNDERSTORM ACTIVITY ON SATURDAY AFTERNOON AND EVENING. A SECOND WEATHER SYSTEM MONDAY EVENING INTO TUESDAY WILL BRING A CHANCE OF LIGHT SNOW TO THE AREA. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO RELAY SIGNIFICANT WEATHER REPORTS AND IMPACTS TO THE NATIONAL WEATHER SERVICE FORECAST OFFICE IN GREAT FALLS.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
805 AM MDT THU MAR 17 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0600 AM SNOW FORT BELKNAP 48.48N 108.77W
03/17/2011 E1.0 INCH BLAINE MT PUBLIC
1.0 INCHES OF SNOWFALL THIS MORNING. 0.29 LIQUID WATER
EQUIV.
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NJLThe national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Ponding of water reported on area roads and farmland.
Ponding of water occurred on area roads and farmland.
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, March 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: 370028, 370029.