Heavy rain that resulted in swollen tributaries contributed to high river levels on the Milk that lasted well into June in some places.
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 GGW wrote it up.
Heavy rain that resulted in swollen tributaries contributed to high river levels on the Milk that lasted well into June in some places.
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 May 22, 2:52 AM MST, 3 hours 8 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 352 AM MDT SUN MAY 22 2011 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY... THE STRONG LOW PRESSURE SYSTEM THAT HAS BEEN NEARLY STATIONARY OVER OUR AREA...CAUSING A LOT OF RAIN...IS NOW MOVING VERY SLOWLY E...CENTERED OVER SD. THE SURFACE LOW DID A SMALL CIRCULAR LOOP YESTERDAY. WHEN THAT WAS COMPLETED A WEAKENING PROCESS AND SLOW MOVEMENT STARTED. THERE IS A DEFINITE WEAKENING PROCESS SEEN ON SATELLITE AND RADAR LOOPS. HOWEVER...THE AIRMASS IS STILL VERY DEEPLY MOIST WITH E FLOW AT ALL LEVELS IN CYCLONIC FLOW. EXPECT RAIN TO BE SLOW TO TAPER OFF AS MODELS INDICATE...SO POPS REMAIN VERY HIGH TODAY. VERY LITTLE CHANGE IN AIRMASS TEMPS...SO HIGHS TO BE SIMILAR TO YESTERDAY WITH NO SUNSHINE EXPECTED. WE MIX JUST SHORT OF DRY ADIABATIC LAPSE RATES THIS AFTERNOON TO 850 MB...HOWEVER WINDS AT THIS LEVEL TO BE LESS THAN YESTERDAY...SO NO LAKE WIND ADVISORY NEEDED FOR TODAY. WEAKENING DYNAMICS WITH LOW PRESSURE INFLUENCE MOVING FARTHER AWAY TONIGHT WILL RESULT IN RAIN BECOMING SCATTERED SHOWERS...AND THEN ENDING. NOT EXPECTING ANY CLEARING THOUGH AS MOISTURE IS CAUGHT UP IN WEAK FLOW PATTERN. MODELS HAD BEEN BRINGING DRIER AIR IN FROM CANADA TO RESCUE US...BUT ARE SLOWER AND MORE CONSERVATIVE WITH THIS NOW...ALTHOUGH E WINDS DO DEVELOP. THE E WINDS EVENTUALLY DO BRING PARTIAL CLEARING MONDAY. THIS ASSOCIATED WITH A HIGH PRESSURE OVER N CANADA MOVING S...BUT CENTERED WELL TO OUR NE. LITTLE COOLING EFFECT WITH IT...AND AT LEAST BALANCED BY MORE SUNSHINE EXPECTED. WE MAY BE CLOSE TO LAKE WIND ADVISORY IN THE AFTERNOON...BUT MOS MEN GUIDANCE HAS BEEN TOO HIGH LATELY. THE AIRMASS DRYING PROCESS SEEMS TO BE THE MAIN MODEL PROBLEM IN WEAK FLOW PATTERN. PREFER THE CMC GEM HANDLING OF THIS FOR BOTH MON/TUE. THERE IS WEAK NARROW UPPER RIDGING THAT COMBINES WITH CUT-OFF HIGH OVER N CANADA. LITTLE DYNAMICS FOR PRECIP. HOWEVER WITH THE AMOUNT OF MOISTURE...WILL KEEP ISOLATED SHOWERS IN FOR MONDAY. NAM FORMS A WEAK VORTICITY CENTER UNDER THE HIGH...BUT LOOKS UNREALISTIC. MEANWHILE THE APPROACHING SYSTEM FROM THE W GOES MAINLY TO OUR S...BUT THE GFS HAS A WET BULLS EYE OF 0.9 IN OUR S WHICH LOOKS UNREALISTIC. HAVE TO CONSIDER WITH ALL THE LINGERING MOISTURE THAT ANY SYSTEM HAS A LOT TO WORK WITH...SO ISOLATED TO SCATTERED SHOWERS IN OUR S ARE REASONABLE. SIMONSEN .LONG TERM...TUESDAY NIGHT THROUGH SUNDAY... HIGH PRESSURE SYSTEM WILL BE OVER MANITOBA AND NORTH DAKOTA WILL COMBINE WITH AN UPPER RIDGE TO BRING DRY WEATHER TO AT LEAST THE NORTHEAST HALF OF THE FORECAST AREA TUESDAY NIGHT THROUGH WEDNESDAY. COOL AIR MASS WILL KEEP TEMPERATURES BELOW NORMAL. THE SOUTHWEST ZONES ESPECIALLY PETROLEUM COUNTY COULD SEE A FEW SHOWERS AT TIMES AS AN UPPER LOW CENTERED OVER THE PACIFIC NORTHWEST WILL CONTINUE TO BRING MOIST AIR TO CENTRAL MONTANA. MODELS BRING A SHORTWAVE TROUGH OR UPPER LOW ACROSS MONTANA ON THURSDAY. MODELS ARE IN BETTER AGREEMENT IN TIMING SO EASTERN MONTANA SHOULD SEE SOME SHOWERS OR THUNDERSTORMS THURSDAY AND THURSDAY NIGHT FROM THIS SYSTEM THAT COULD LINGER INTO FRIDAY. UPPER RIDGE MOVES THROUGH THE AREA ON SATURDAY WITH MAINLY DRY WEATHER. THE RIDGE MOVES TO THE EAST ON SUNDAY WITH A COLD FRONT. MODELS DIFFER ON TIMING. WILL MENTION A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS FOR NOW. FORRESTER && .AVIATION... RAIN SHOWERS WILL CONTINUE ACROSS THE AREA INTO MONDAY. FLIGHT CONDITIONS WILL VARY FROM VFR TO IFR WITH MVFR CEILINGS BEING THE MOST FREQUENT. VISIBILITIES WILL OCCASIONALLY BE REDUCED TO MVFR LEVELS IN EITHER RAIN OR FOG. && .HYDROLOGY... WIDESPREAD RAIN WILL CONTINUE TODAY WITH ANOTHER HALF INCH TO ONE INCH OF ADDITIONAL RAINFALL LIKELY ACROSS MOST OF THE AREA. FLOODING OF MANY SMALL STREAMS...CREEKS...COULEES...LOW SPOTS...AND POORLY DRAINED AREAS CAN BE EXPECTED TO CONTINUE AND EXPAND AS THE NEW RAINFALL ACCUMULATES OVER AN ALREADY SATURATED SURFACE. NUMEROUS FLOOD WARNINGS ARE IN EFFECT. THE YELLOWSTONE RIVER AT GLENDIVE HAS REACHED 55 FEET AS OF 2 AM SUNDAY WHICH IS 1.5 FEET ABOVE FLOOD STAGE AT GLENDIVE. IT IS THE HIGHEST NON ICE JAM FLOOD RECORDED IN GLENDIVE HISTORY. THE YELLOWSTONE RIVER WILL CONTINUE TO RISE THROUGH MONDAY. THE YELLOWSTONE RIVER AT SIDNEY IS EXPECTED TO GO ABOVE FLOOD STAGE AROUND NOON TODAY. THE MILK RIVER IS ALSO RISING. THE MILK RIVER IS EXPECTED TO RISE ABOVE FLOOD STAGE AT GLASGOW BY THIS AFTERNOON. && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GLASGOW MT 439 AM MDT SUN MAY 22 2011 MTZ017-231200- CENTRAL AND SOUTHERN VALLEY- 439 AM MDT SUN MAY 22 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A FLOOD WARNING IS IN EFFECT FOR THE MILK RIVER AT GLASGOW UNTIL FURTHER NOTICE. FLOOD WARNINGS ALSO REMAIN IN EFFECT ELSEWHERE. RAINFALL WILL CONTINUE OFF AND ON TODAY WITH UP TO HALF AN INCH ADDITIONAL RAINFALL POSSIBLE. MANY SMALL STREAMS...CREEKS...COULEES...LOW SPOTS...AND POORLY DRAINED AREAS ARE FLOODING...OR WILL BE FLOODING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE FLOOD WARNINGS WILL CONTINUE INTO AT LEAST MONDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ024-025-231200- RICHLAND-DAWSON- 439 AM MDT SUN MAY 22 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A FLOOD WARNING IS IN EFFECT FOR THE YELLOWSTONE RIVER UNTIL FURTHER NOTICE. FLOOD WARNINGS ALSO REMAIN IN EFFECT ELSEWHERE. RAINFALL WILL CONTINUE OFF AND ON TODAY WITH UP TO HALF AN INCH ADDITIONAL RAINFALL POSSIBLE. MANY SMALL STREAMS....CREEKS...COULEES...LOW SPOTS...AND POORLY DRAINED AREAS ARE FLOODING...OR WILL BE FLOODING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE FLOOD WARNINGS WILL CONTINUE INTO AT LEAST MONDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ016-018>023-026-027-059>062-231200- CENTRAL AND SOUTHEAST PHILLIPS-DANIELS-SHERIDAN-WESTERN ROOSEVELT- PETROLEUM-GARFIELD-MCCONE-PRAIRIE-WIBAUX-NORTHERN PHILLIPS- SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT- 439 AM MDT SUN MAY 22 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A FLOOD WARNING REMAINS IN EFFECT. RAINFALL WILL CONTINUE OFF AND ON TODAY WITH UP TO HALF AN INCH ADDITIONAL RAINFALL POSSIBLE. MANY SMALL STREAMS...CREEKS...COULEES...LOW SPOTS...AND POORLY DRAINED AREAS ARE FLOODING...OR WILL BE FLOODING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE FLOOD WARNINGS WILL CONTINUE INTO AT LEAST MONDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GLASGOW MT
645 AM MDT SUN MAY 22 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0635 AM HEAVY RAIN 5 SE SACO 48.41N 107.26W
05/22/2011 M3.40 INCH VALLEY MT PUBLIC
STORM TOTAL RAINFALL SINCE TUESDAY...ALSO REPORTED LARB
CREEK SOUTH OF SACO IS RUNNING SLIGHTLY HIGHER THAN
DURING THE SPRING FLOODING
&&
JBThe national radar mosaic for the moment the first event began.
4 flood. Local standard time, as filed.
Gage reading at the Glasgow gage crested at 30.38 feet on May 23rd. Flood stage is 25 feet.
Gage reading at the Nashua gage rose to 23.12 feet on May 31st. Flood stage is 20 feet.
The gage reading at Tampico crested at 25.83 feet on May 28th. Flood stage is 25 feet.
The gage reading at the Bjornberg Bridge (Saco) crested on May 27th at 20.8 feet. Flood stage is 20 feet.
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, May 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: 312534, 321055, 312531, 312530.