Over the course of four days, a slow-moving storm system brought multiple rounds of rainfall to central and northeast Montana.
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.
Over the course of four days, a slow-moving storm system brought multiple rounds of rainfall to central and northeast Montana.
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 20, 7:49 PM MST, 4 hours 11 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 849 PM MDT TUE MAY 20 2008 .SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH THURSDAY... THINGS UNFOLDING ABOUT AS PLANNED WITH SOME SEVERE WEATHER OCCURRING WEST OF THE CWA IN THE GREAT FALLS VICINITY...AND MOVING NORTH. SURFACE PRESSURE GRADIENT ACROSS EASTERN MONTANA TIGHTENING IN RESPONSE TO THE LOW PRESSURE OVER CENTRAL MONTANA BUCKING UP AGAINST THE HIGH PRESSURE EXTENDING SOUTH OVER THE DAKOTAS INTO NORTHEAST MONTANA. FOR THIS REASON WILL RAISE THE WIND SPEEDS JUST A BIT FOR THE OVERNIGHT...ESPECIALLY FOR THE GLASGOW AREA WHERE OROGRAPHICS ESPECIALLY FAVOR AND ENHANCE EASTERLY WIND. OTHERWISE REMAINDER OF THE FORECAST PRETTY MUCH LEFT UNTOUCHED WITH PERHAPS SOME SHOWERS AND A THUNDERSTORM OR TWO POSSIBLY SNEAKING INTO THE WESTERN HALF OF THE CWA TONIGHT. PREVIOUS DISCUSSION... UPPER TROF MOVING INTO THE PACIFIC NORTHWEST WITH LEE TROF OVER CENTRAL MONTANA. STRONG HEIGHT FALLS IN ADVANCE OF THIS TROF COMBINED WITH A PLUME OF PACIFIC MOISTURE SHOULD SUPPORT SOME THUNDERSTORM DEVELOPMENT ALONG THE HIGHER TERRAIN IN CENTRAL MONTANA THIS AFTERNOON BEFORE SPREADING NORTHEAST THIS EVENING. FORECAST SOUNDINGS CONTINUE TO INDICATE A WELL-MIXED BOUNDARY LAYER...SO CERTAINLY SOME POTENTIAL FOR GUSTY WINDS...BUT GIVEN LATE ARRIVAL OF THIS ACTIVITY BELIEVE WIND THREAT SHOULD BE DIMINISHED SOMEWHAT AFTER SUNSET. LEE CYCLONE DEVELOPS ACROSS NORTHERN WYOMING LATE TONIGHT WITH INVERTED TROF OVER EASTERN MONTANA AS UPPER TROF CLOSES OFF OVER THE GREAT BASIN. BEST PRECIPITATION CHANCES WILL BE GENERALLY TO THE WEST OF THE INVERTED TROF AND WILL BE SLOW TO MOVE EAST AS UPPER FLOW PARALLELS THE SURFACE BOUNDARY. ALL MODELS AGREE IN AN OMEGA BLOCK STRENGTHENING JUST TO OUR EAST BY THURSDAY MORNING. CONVERGENCE LINE LINGERS ACROSS THE WESTERN ZONES WHERE BEST CHANCE OF RAIN WILL CONTINUE. LESSER CHANCES STILL TO THE EAST. EBERT .LONG TERM...THURSDAY NIGHT THROUGH TUESDAY... A VERY BLOCKING TYPE OF UPPER PATTERN ENSURES THAT THE UPCOMING WET WEATHER PATTERN WILL BE SLOW TO CHANGE. MODELS INDICATE THERE WILL BE A GRADUAL FILLING AND FRAGMENTING OF THE LARGE UPPER LOW COMPLEX OVER THE WESTERN STATES. TIMING IS AN ISSUE AND THE ECMWF IS QUICKEST TO DRY THINGS OUT. IN THIS BARELY-MOVING PATTERN...AND AT THIS TYPICALLY MOIST...LATE IN MAY...TIME OF THE YEAR...PREFER THE SLOWER SOLUTION...WITH SCATTERED SHOWERS LINGERING AND JUST A GRADUAL LOWERING OF POPS. THE LATEST MODELS LOOK SIMILAR TO PREVIOUS RUNS WITH NOTHING REALLY NEW TO ADD. THE CURRENT FORECAST COVERS THE SITUATION WELL...SO FEW CHANGES MADE. SIMONSEN PREVIOUS LONG TERM...THURSDAY NIGHT THROUGH THROUGH TUESDAY. A VERY LARGE UPPER LOW DRAPED ACROSS THE WESTERN UNITED STATES WILL BE THE DOMINANT FEATURE OF THE EXTENDED. MODELS CONTINUE TO STRUGGLE IN HOW TO HANDLE THE FEATURES EMBEDDED IN THE LOW...AND HOW AND WHEN TO MOVE IT OUT. GIVEN THE PLACEMENT OF THE LOW OVER THE GREAT BASIN AND AN UPPER RIDGE EXTENDING OVER THE DAKOTAS...THE BEST POTENTIAL FOR PRECIPITATION WILL LIE ACROSS THE WESTERN ZONES THURSDAY NIGHT INTO FRIDAY. TEMPERATURES WILL ALSO BE COOLER TO THE WEST AND WARMER TO THE EAST UNDER THIS PATTERN. FRIDAY NIGHT AND BEYOND CONTINUED A BROADBRUSHED APPROACH WITH NEAR CLIMATOLOGICAL POPS...WHICH GIVEN THE UNCERTAINTY SEEMS THE BEST CHOICE UNTIL CONFIDENCE GROWS. GILCHRIST && .AVIATION... VFR WITH BROKEN CEILINGS AT AROUND 10K FT AGL TONIGHT...LOWERING TO AROUND 5K AGL BY WEDNESDAY AFTERNOON. ANY SHOWER AND ISOLATED THUNDERSTORM ACTIVITY TONIGHT SHOULD REMAIN WEST OF THE TERMINALS. SCATTERED SHOWERS THEN DEVELOP WEDNESDAY WITH THE CAPABILITY OF REDUCING VISIBILITY BRIEFLY TO 5 MILES IN THE HEAVIER SHOWERS. SIMONSEN/MCZ && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && WEATHER.GOV/GLASGOW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GLASGOW MT 430 AM MDT TUE MAY 20 2008 MTZ016>027-059>062-202100- CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY- DANIELS-SHERIDAN-WESTERN ROOSEVELT-PETROLEUM-GARFIELD-MCCONE- RICHLAND-DAWSON-PRAIRIE-WIBAUX-NORTHERN PHILLIPS- SOUTHWEST PHILLIPS-NORTHERN VALLEY-EASTERN ROOSEVELT- 430 AM MDT TUE MAY 20 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHEAST MONTANA. .DAY ONE...TODAY AND TONIGHT A COLD FRONT WILL SWEEP THROUGH THE TREASURE STATE TUESDAY NIGHT BRINGING COOLER AND WETTER CONDITIONS FOR THE REMAINDER OF THE WEEK. THUNDERSTORMS WILL FORM AHEAD OF AND ALONG THE FRONT OVER CENTRAL MONTANA TUESDAY AFTERNOON BEFORE MOVING INTO NORTHEAST MONTANA TUESDAY EVENING AND OVERNIGHT. SOME OF THESE STORMS MAY BE STRONG WITH GUSTY WINDS AND SMALL HAIL. PLEASE CONTINUE TO MONITOR THE LATEST FORECAST FOR DETAILS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY NO HAZARDOUS WEATHER EXPECTED AT THIS TIME. .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 heavy rain. Local standard time, as filed.
A trained spotter recorded 7.04 inches of rain from May 21 to May 24. The heavy rain washed out gravel roads in the Zortman area.
A trained spotter measured a total of 4.70 inches of rain.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2008Every state in 2008This day in weather historyWarnings in Montana, May 2008
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: 105599, 102191.