A heavy wet snow fell over portions of the area, knocking out power and disrupting travel and calving operations.
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 GGW wrote it up.
A heavy wet snow fell over portions of the area, knocking out power and disrupting travel and calving operations.
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 Glasgow, MT wrote its last area forecast discussion before the first event at Apr 21, 7:13 PM MST, 3 hours 47 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 813 PM MDT THU APR 21 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY... UPDATE...NONE TONIGHT. ALL ELEMENTS ARE ON TRACK THIS EVENING. PRECIPITATION IS MOVING INTO THE SOUTHWESTERN ZONES ON TIME AND SHOULD SLOWLY SPREAD TO THE NORTH AND EAST OVERNIGHT. PROTON ANOTHER CHALLENGING STORM SYSTEM WILL AFFECT THE AREA OVER THE NEXT 24 TO 36 HOURS. THE MODELS SEEM TO BE SLOWING THIS SYSTEM UP...WHICH OCCURS OFTEN THIS TIME OF YEAR. SHOWERS AND THUNDERSTORMS ARE STARTING TO SPREAD INTO WESTERN WYOMING AND SOUTH-CENTRAL MONTANA THIS AFTERNOON. THIS PRECIP WILL CONTINUE TO BLOSSOM AS IT MOVES EAST-NORTHEAST ACROSS EASTERN MONTANA AND INTO THE DAKOTAS. THE DEFORMATION ZONE WITH THIS SYSTEM WILL SPREAD INTO THE SOUTHERN ZONES LATE TONIGHT BRINGING THE HIGHEST QPF/S IN EASTERN MT PROBABLY JUST SOUTH OF THE SOUTHERN ZONES WITH TOTALS CLOSE TO AN INCH LIKELY. TEMPS DON/T SUPPORT SNOW UNTIL LATE TONIGHT WHERE ENOUGH COLD AIR MOVES INTO MAINLY THE WESTERN HIGHER ELEVATIONS (I.E THE LITTLE ROCKIES AND PETROLEUM COUNTY). ON FRIDAY...COLDER AIR MOVES IN AT THE MID LEVELS AND INTENSITY MAY KEEP PRECIP AT LEAST MIXED WITH SNOW IN PARTS OF THE SOUTHERN ZONES. ENOUGH SNOW LOOKS TO FALL IN WIBAUX COUNTY THAT A WINTER WEATHER ADVISORY IS WARRANTED...AND WILL ISSUE WITH THIS PACKAGE. PRECIP LOOKS TO WIND DOWN FROM NORTHWEST TO SOUTHEAST WITH THE NAM HAVING THE BEST TIMING (AGAIN SLOWER IS BETTER) FRIDAY NIGHT. ON SATURDAY...CONDITIONS START OUT MUCH MORE CALM BUT WITH A NORTHWEST FLOW ALOFT (AND A BIT UNSTABLE)...CUMULUS CLOUDS WILL QUICKLY BUILD AND SOME SHOWERS COULD OCCUR BY THE AFTERNOON. JAMBA .LONG TERM...SATURDAY NIGHT THROUGH THURSDAY... THE MAIN JETSTREAM IS TO OUR S MOST OF THE TIME...HOWEVER ENOUGH ENERGY IN THE N BRANCH OF THE JET WITH AN INCOMING SYSTEM TUE/TUE NIGHT FOR A CHANCE OF SHOWERS. CMC GEM IS AN OUTLIER WITH A MUCH WETTER AND STRONGER SYSTEM. THICKNESSES ARE IN THE 540S DM...INDICATIVE OF TEMPS THAT WILL BE AROUND NORMAL...WITH PRECIP TYPES SHOULD BE LIQUID FORM. SHORTWAVE RIDGING FOLLOWS THIS SYSTEM. AT THE END OF THE PERIOD THOUGH...MODELS INDICATING A MODERATELY STRONG SHORTWAVE SYSTEM FROM THE W FOR A CHANCE OF SHOWERS. TIMING DIFFERENCES AS WOULD BE EXPECTED...MODELS PROBABLY TOO FAST IN GENERALLY...SO CURRENT POPS GRIDS ARE OK. SIMONSEN PREVIOUS LONG TERM ...SATURDAY NIGHT THROUGH THURSDAY...A RIDGE ACROSS THE PACIFIC NORTHWEST WILL MOVE ONTO THE PLAINS RAISING TEMPERATURES. MEANWHILE...ANOTHER PACIFIC TROUGH WILL BEGIN THROWING OFF SHORTWAVE ENERGY WITH THE MAIN ONE COMING THROUGH MONDAY EVENING THROUGH TUESDAY. THIS MAY BE ABLE TO SPARK OFF SOME THUNDER DURING THE AFTERNOONS WITH INTERMITTENT RAIN SHOWERS MONDAY AND TUESDAY. THE FULL TROUGH SHOULD MOVES THROUGH BY TUESDAY WITH A SLIGHT COOL DOWN BEHIND IT. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT... FLOW BECOMES SPLIT WITH MONTANA EXPERIENCING MORE OF THE NORTHERN RIDGE OF THE FLOW. TEMPERATURES SHOULD RISE TO NEAR NORMAL FOR THE SEASON WITH REDUCED CHANCES FOR RAIN. THURSDAY ONWARD... PACIFIC TROUGH MOVES ONSHORE... BRINGING A SOMEWHAT FAST MOVING SYSTEM THROUGH THE AREA. ASSOCIATED COLD FRONT SHOULD BRING A CHANCE FOR PRECIPITATION MID DAY THURSDAY INTO FRIDAY MORNING. DROPPED TEMPERATURES SLIGHTLY ON THURSDAY AND THURSDAY NIGHT COMPARED TO MOST GUIDANCE DUE TO THE COLD FRONT AND PRECIPITATION CHANCES IN THE REGION. JB/GAH && .AVIATION... INITIAL VFR CONDITIONS WILL GRADUALLY WORSEN TO MVFR AFTER MIDNIGHT AS INCREASING MID/HIGH LEVEL CLOUDS SIGNAL BETTER CHANCES FOR RAIN AND SNOW DEVELOPING ACROSS MOST OF THE AREA THROUGH THIS TAF PERIOD. SHOULD SEE CEILINGS LOWER AROUND 2K FT AGL...WITH VISIBILITIES OF 3 TO 5 MILES...AND A FEW IFR AREAS BELOW 3 MILES. SIMONSEN/BMICKELSON && .HYDROLOGY... MODERATE TO MINOR FLOODING CONTINUES ON THE MILK RIVER. HOWEVER... LEVELS ARE SLOWLY FALLING AND SHOULD CONTINUE TO GENERALLY IMPROVE FOR THE NEXT COUPLE WEEKS. SIGNIFICANT SNOW IS STILL ON THE GROUND OVER SOUTHWEST SASKATCHEWAN...NORTHERN BLAINE... PHILLIPS... AND VALLEY COUNTIES... AND THIS SNOW MELT WILL IMPACT THE LOWER MILK RIVER OVER THE NEXT COUPLE WEEKS. WATER LEVELS WILL CONTINUE TO SLOWLY FALL ALONG THE MILK RIVER AT TAMPICO...GLASGOW AND NASHUA. TAMPICO FELL BELOW THE MAJOR FLOOD STAGE OF 27 FEET ON WEDNESDAY. GLASGOW IS EXPECTED TO CONTINUE DROPPING THROUGH THE WEEK...POSSIBLY REACHING THE MINOR FLOODING STAGE THIS WEEKEND. NASHUA WILL REMAIN ABOVE MINOR FLOOD STAGE OF 20 FEET INTO NEXT WEEK. THE AREAL FLOOD WARNING FOR EASTERN PHILLIPS AND MOST OF VALLEY COUNTIES CONTINUES. WATER LEVELS ON THE UPPER REACHES OF CREEKS FLOWING INTO THE MILK VALLEY HAVE SUBSIDED... WITH FLOODING CONTINUING WHERE THESE CREEKS ENCOUNTER THE MILK RIVER. THIS INCLUDES BEAVER CREEK FROM THE SACO FLATS THROUGH HINSDALE. THE WATER LEVELS ON THE FRENCHMAN RIVER NEAR THE CANADIAN BORDER HAVE BEEN DROPPING BUT THESE LEVELS ARE EXPECTED TO FLUCTUATE OVER THE NEXT FEW WEEKS AS SNOW MELT TO THE NORTH CONTINUES. IN BLAINE COUNTY RECENT SNOWMELT HAS OCCURRED AND IS RUNNING OFF INTO SMALLER CREEKS AND STREAMS THAT ARE TRIBUTARIES TO THE MILK RIVER. WATER LEVELS WILL RISE ON THE MILK RIVER OVER THE NEXT FEW DAYS. THE HIGHER WATER IS EXPECTED TO REACH MALTA BY EARLY NEXT WEEK. AT THIS TIME IT IS EXPECTED TO REMAIN BELOW FLOOD STAGE. AES && .GLASGOW WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 9 AM FRIDAY TO MIDNIGHT MDT FRIDAY NIGHT FOR WIBAUX. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GLASGOW MT 302 PM MDT THU APR 21 2011 MTZ016-017-059-061-221200- CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY- NORTHERN PHILLIPS-NORTHERN VALLEY- 302 PM MDT THU APR 21 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT A FLOOD WARNING REMAINS IN EFFECT FOR VALLEY AND NORTHEAST PHILLIPS COUNTIES. FLOODING WILL CONTINUE ON THE MILK RIVER AND THE NORTHERN TRIBUTARIES FOR THE NEXT FEW WEEKS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ021>027-060-221200- PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-PRAIRIE-WIBAUX- SOUTHWEST PHILLIPS- 302 PM MDT THU APR 21 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT NO HAZARDOUS WEATHER EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A STORM SYSTEM WILL AFFECT THE AREA TONIGHT AND FRIDAY. THERE IS A POTENTIAL FOR ACCUMULATING SNOW...DEPENDING ON TEMPERATURES FRIDAY. THE AREAS MOST LIKELY TO SEE ACCUMULATING SNOW FROM THIS STORM WILL BE HIGHER ELEVATION AREAS LIKE THE LITTLE ROCKY MOUNTAINS...BIG SHEEP MOUNTAINS...WIBAUX...PETROLEUM AND WESTERN GARFIELD COUNTIES. A WINTER WEATHER ADVISORY IS IN EFFECT FOR WIBAUX COUNTY FOR FRIDAY AND FRIDAY EVENING. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
The national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
In the southern portion of the county, spotters reported that the storm began with rain that changed to sleet, then snow. 1.5 inches of new snow fell, and coupled with strong winds, visibilities were down to a quarter of a mile.
Eleven power lines were downed between Winnett and Mosby from the wet/heavy snow. Visibility was also reported to be down to 300 yards. 4 power poles were snapped on Highway 244 due to the heavy snow and 20 to 30 mph winds. 4 inches of snow was reported in the Winnett and Flatwillow areas. At 2044 MST, the Winnett Fire Cheif reported at least 6 to 8 inches of new snow.
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, April 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: 309159, 290230.