Strong thunderstorms produced gusty winds in Beaverhead County. Wind gusts to 59 mph were reported.
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The episode as NWS TFX wrote it up.
Strong thunderstorms produced gusty winds in Beaverhead County. Wind gusts to 59 mph were reported.
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 May 21, 1:57 PM MST, 2 hours 50 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 257 PM MDT MON MAY 21 2012 .DISCUSSION... TONIGHT THROUGH WEDNESDAY...UPPER TROF WILL MOVE TO WESTERN MONTANA TONIGHT. MOIST AND UNSTABLE SOUTHWEST FLOW ALOFT AHEAD OF THE TROF CONTINUES TO SPAWN SHOWERS AND ISOLATED THUNDERSTORMS. THUNDERSTORMS WILL END LATER THIS EVENING BUT MODELS BRING ANOTHER SURGE OF SHOWERS ACROSS THE AREA AFTER MIDNIGHT. WESTERLY...DOWNSLOPE FLOW ALOFT...WILL LESSEN CHANCES OF PRECIPITATION ACROSS THE NORTH ON TUESDAY AND TUESDAY NIGHT. SURFACE WINDS WILL BECOME BREEZY ACROSS THE PLAINS. A BROAD UPPER TROF WILL RESIDE OVER THE AREA WEDNESDAY AND SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL REMAIN A POSSIBILITY. COOLER AIR WILL DROP TEMPERATURES FOR THE NEXT COUPLE OF DAYS. SNOW LEVELS WILL DROP TO AROUND 5500 FEET ACROSS THE NORTH ON WEDNESDAY AND SOME SNOW IS POSSIBLE AT THE HIGHER ELEVATIONS. TEMPERATURES WILL DROP BELOW SEASONAL AVERAGES BY WEDNESDAY. WEDNESDAY NIGHT THROUGH MONDAY...FOR THE FIRST PART OF THE PERIOD MODELS POINT TO AN UPPER LOW OVER SOUTHERN CANADA WITH A BROAD UPPER TROUGH OVER THE FORECAST AREA. IT LOOKS LIKE THE AIRMASS WILL BE WEAKLY UNSTABLE SO WILL CONTINUE THE IDEA OF SCATTERED SHOWERS FOR THURSDAY. MODELS CONTINUE THE IDEA OF DEVELOPING AN UPPER LOW OVER THE SOUTHWEST U.S. BY LATE IN THE WEEK. THIS UPPER LOW IS NOW FORECAST TO MOVE NORTHEAST AND INTO MONTANA OVER THE WEEKEND. WHEREAS YESTERDAY THE ECMWF AND GEM (CANADIAN) MODELS WERE IN FAIR AGREEMENT WITH UPPER AIR FEATURES AND THE GFS WAS AN OUTLIER..THIS SUNDAY NIGHT THE GFS AND ECMWF MODELS ARE IN FAIR AGREEMENT AND THE GEM IS AN OUTLIER. MODEL CONSISTENCY OVERALL IS NOT GOOD SO CONFIDENCE IN THE TRACK AND TIMING OF THE UPPER LOW IS LOW AT THIS POINT. BASED ON LATEST MODEL GUIDANCE HAVE MADE ADJUSTMENTS TO THE CHANCES OF PRECIPITATION FOR LATER THIS WEEK. IN PARTICULAR HAVE LOWERED THE CHANCES OF PRECIPITATION OVER PORTIONS OF THE WESTERN ZONES FOR THURSDAY NIGHT AND LOWERED THE CHANCES OF PRECIPITATION IN THE NORTH ON FRIDAY. THIS IS BASED ON THE MODELS IDEA OF BEING SLOWER SPREADING PRECIPITATION NORTH. THE GFS AND ECMWF TAKE THE UPPER LOW INTO CANADA BY LATE SUNDAY SO BEGAN THE TREND OF LOWERING THE CHANCES OF PRECIPITATION SUNDAY. THERE IS SOME INDICATION FROM GUIDANCE THAT THE UPPER LOW MIGHT BE SLOWER TO MOVE NORTHEAST THAN WHAT THE GFS AND ECMWF FORECAST SO WILL NEED TO MONITOR THIS. LIKE YESTERDAY MODELS FORECAST A COOLER AIRMASS TO MOVE SOUTH OVER THE PLAINS THURSDAY. EXPECT BELOW NORMAL TEMPERATURES AT LEAST INTO THE EARLY WEEKEND WITH NEAR NORMAL TEMPERATURES POSSIBLE LATE IN THE WEEKEND. BLANK && .AVIATION... UPDATED 1740Z. GENERALLY VFR CONDITIONS WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING THIS AFTERNOON. THERE WILL BE A RISK OF GUSTY WINDS TO 40 KTS AND SMALL HAIL ASSOCIATED WITH THE THUNDERSTORMS. EXPECT LOCAL IFR CEILINGS AND VISIBILITIES IN STRONGER THUNDERSTORMS THIS AFTERNOON AND EARLY AFTERNOON. SUK && .PRELIMINARY POINT TEMPS/POPS... GTF 52 65 41 58 / 60 40 10 30 CTB 47 62 38 56 / 60 40 10 30 HLN 52 65 41 57 / 60 50 30 40 BZN 47 64 36 55 / 50 60 50 40 WEY 40 56 31 45 / 40 70 60 50 DLN 47 63 35 53 / 50 60 30 30 HVR 51 70 40 62 / 50 50 10 30 LWT 48 63 37 55 / 40 50 10 20 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...EMANUEL LONG TERM...BLANK AVIATION...SUK WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREAT FALLS MT 530 AM MDT MON MAY 21 2012 MTZ008>015-044>055-221130- BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL- CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON- TOOLE-LIBERTY-EASTERN PONDERA-BLAINE- SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS- JEFFERSON-BROADWATER-MEAGHER-GALLATIN- 530 AM MDT MON MAY 21 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY IS LOW FOR WIDESPREAD HAZARDOUS WEATHER. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY A COOL AND WET PATTERN IS EXPECTED BEGINNING TUESDAY THROUGH THE MEMORIAL DAY WEEKEND. WHILE LIGHT RAIN IS EXPECTED OVER THE PLAINS AND VALLEYS...SOME SNOW ACCUMULATIONS ARE POSSIBLE IN THE MOUNTAINS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
525 PM MDT MON MAY 21 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0521 PM HEAVY RAIN WHITE SULPHUR SPRINGS 46.54N 110.90W
05/21/2012 M1.13 INCH MEAGHER MT TRAINED SPOTTER
1.13 INCHES OF RAIN IN ABOUT AN HOUR WITH STRONG WINDS
BENDING SOME TREE TOPS.
&&
GUSTAFSONThe Pocatello radar (KSFX), 212 km away, was scanning. The volume nearest the first event began at 23:48 UTC.
1 thunderstorm wind. Local standard time, as filed.
A thunderstorm produced a wind gust to 59 mph at Grant 8WSW (the Brenner RAWS site).
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2012Every state in 2012This day in weather historyWarnings in Montana, May 2012
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: 382508.