Outflow from a thunderstorm near McDonald Pass funneled down to Helena and produced a 59 mph gust. Additionally, a weak shower produced a rogue 59 mph gust at Helena a few hours later.
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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.
Outflow from a thunderstorm near McDonald Pass funneled down to Helena and produced a 59 mph gust. Additionally, a weak shower produced a rogue 59 mph gust at Helena a few hours later.
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 28, 4:41 PM MST, 42 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 541 PM MDT Tue May 28 2024 Aviation Section Updated .SYNOPSIS... Showers and thunderstorms continue today with some isolated severe gusts possible primarily across west Central/North Central, and Southwestern Montana. By Wednesday afternoon, precipitation spreads east to eastern Central/North-Central and Southwest Montana. Gusty winds are possible along the Rocky Mountain Front Wednesday. By Thursday, precipitation shifts north to North-Central Montana. Warmer and drier weather returns for Friday and Saturday. && .DISCUSSION... Tonight Through Tomorrow Morning Current satellite shows cumulus clouds and a few showers popping up along Southwest MT, the Continental Divide. The upper level shortwave and a cold front will continue to initiate afternoon showers and thunderstorms. The Storm Prediction Center has the Inverness to Bozeman corridor and west in a Marginal Risk for some isolated severe wind gusts(5%). Mesoscale analysis shows instability building in (up to 1,000 J/kg of CAPE). This along with deep inverted V's vertical profile soundings support an isolated severe wind gust(58mph) threat. Small hail can also accompany any stronger storm. Another impact we will watch for is for higher mountain snowpack run off with heavier precipitation from thunderstorms along the Continental Divide. Precipitable water(PWAT) along the higher end amounts from models of 0.7-0.8" indicate there can be some heavier rainfall with showers/storms. The Weather Prediction Center has the Continental Divide in a Marginal Risk for excessive rainfall. Meaning, there's a 5%-15% of exceeding flash flood guidance through early Wednesday morning. However, there's a 20-40% of the immediate eastern slopes of the Rocky Mountains receiving a half inch of precipitation. This should keep runoff impacts limited but something we will continue to monitor. Storms wind down as the sun sets tonight, but showers continue to be scattered to widespread along the cold front through Wednesday morning. Wednesday With the upper level trough still in the region and the cold front propagating east across the CWA, there will be redevelopment of widespread precipitation Wednesday afternoon. The bulk of the heavier precipitation will mostly be from southwest Madison County to Lewistown line and to the southeast. Although the thunderstorm risk will be lower tomorrow afternoon, precipitation concerns still linger. The Weather Prediction Center has a Marginal Risk for excessive rainfall(5-15% of exceeding flash flood guidance)along that corridor. Probabilities are showing a 10-20% of precipitation amounts exceeding 1" for the Madison/Gallatin Counties and Big Snowy mountains. Warmer rain falling on the snowpack can melt snow and increase surface run off. Since models keep higher end precipitation amount to 1" of QPF and impacts on rivers don't look to be widespread, I am holding off on Hydrology highlights for now. However, we will continue to monitor the situation. Look in the HYDROLOGY section for more information. In addition to precipitation on Wednesday, gusty conditions are possible along the Rocky Mountain Front. 700mb winds between 30-45kts and a pressure gradient force sets up along the Rocky Mountain Front Wednesday through Thursday morning. Probabilistic guidance shows most of the gusty winds stay along the immediate eastern slopes of the Rocky Mountain Front. Locations along the adjacent plains of the Northern Rocky Front through Cut Bank have a 40-60% of exceeding 55mph (High Wind Warning Criteria). Since the threat of winds reaching High Wind Warning criteria is more isolated, I have hold off of any wind highlights for now. Thursday through Friday As the upper level trough propagates eastwards Thursday, we transition into northwest flow aloft. An upper level disturbance tries to clip North Central MT/Central MT mountains on Thursday, bringing lower end, light precipitation chances. Probabilistic guidance shows a 20-40% of those locations receiving at least a tenth of an inch of precipitation. By Friday, dry and warmer weather moves in, moving temperatures up close to seasonable averages. -Wilson Saturday through next Tuesday... On Saturday a weak upper-level ridge moves over North-central, Central, and Southwestern Montana. This will warm up temperatures and keep most of North-central and Central Montana dry with some precipitation chances for Southwestern Montana. On Sunday cluster analysis shows that an upper-level ridge remains over North-central, Central, and Southwestern Montana which will allow temperatures to warm up on Sunday. On Monday cluster analysis keeps the upper-level ridge over the area. Two of the clusters have a very strong ridge over North-central, Central, and Southwestern Montana. This could cause hot temperatures for the area. This will need to continue to be monitored. Next Tuesday three clusters (81% of ensemble members) keep the upper-level ridge over North-central, Central, and Southwestern Montana. The other cluster (19% of ensemble members) shows an upper-level trough beginning to move over Montana. This indicates that the weather pattern has the potential to change for the middle of next week. -IG && .AVIATION... 29/00Z TAF Period Scattered thunderstorms across North Central and Southwest Montana continue throughout this evening before transitioning over to rain showers tomorrow morning. Primary concerns with thunderstorms this evening are lightning, gusty erratic winds, and heavy downpours that could impact visibility to below VFR conditions. A few lingering showers tomorrow afternoon from KLWT to KWYS and portions of Southwest Montana. Elsewhere, airfields return to VFR conditions for tomorrow afternoon. Webb Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .HYDROLOGY... Showers and thunderstorms today and tomorrow may bring heavier bursts of precipitation. Today, the main focus is along the Continental Divide and tomorrow, it shifts to across Central, North Central, and Southwest Montana. Rain falling on warm winter snowpack can increase the melting of snow and runoff from the mountains. River hydrographs indicate rivers should be able to handle the increased runoff. However, we can't rule out the potential of a few localized areas along smaller streams and creeks for increased flow and minor flooding, especially near the Madison and Gallatin Mountains. We will continue to monitor the situation for possible flood highlights. -Wilson && .PRELIMINARY POINT TEMPS/POPS... GTF 52 65 41 62 / 40 60 0 20 CTB 48 60 38 60 / 80 30 10 20 HLN 52 64 41 63 / 60 50 10 10 BZN 46 59 34 59 / 30 90 50 10 WYS 42 59 30 53 / 30 90 60 10 DLN 46 62 33 60 / 60 80 20 0 HVR 54 67 41 63 / 20 50 10 50 LWT 49 62 36 57 / 20 90 30 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && http://www.weather.gov/greatfalls
Special Weather Statement National Weather Service Great Falls MT 450 PM MDT Tue May 28 2024 MTZ327-290030- Northwest Beaverhead County- Including the cities of Dewey, Wisdom, Wise River, Big Hole Pass, and Chief Joseph Pass 450 PM MDT Tue May 28 2024 ...Gusty Winds From Decaying Showers and Thunderstorms... Showers and thunderstorms moving into northwest portions of Beaverhead county will be capable of producing gusty outflow wind gusts around 50-55 mph over the next couple hours. Be prepared for gusty, erratic winds if outside near any shower or thunderstorm this evening.
Preliminary Local Storm Report
National Weather Service Great Falls MT
454 PM MDT Tue May 28 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0315 PM Tstm Wnd Gst 8 NE Bannack 45.25N 112.88W
05/28/2024 M51 MPH Beaverhead MT Mesonet
Mesonet station MTM14 BLM - Argenta.
&&
AMSpecial Weather Statement
National Weather Service Great Falls MT
522 PM MDT Tue May 28 2024
MTZ308-309-312-290000-
Eastern Pondera and Eastern Teton MT-Cascade County below 5000ft MT-
Southern High Plains MT-
522 PM MDT Tue May 28 2024
...A STRONG THUNDERSTORM WILL IMPACT CENTRAL LEWIS AND CLARK...
SOUTHEASTERN TETON AND NORTHWESTERN CASCADE COUNTIES THROUGH 600 PM
MDT...
At 521 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles southwest of Fairfield, or 23 miles south of Choteau, moving
northeast at 35 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Fairfield, Fort Shaw, Fort Shaw, Power, Vaughn, Simms, and Sun
River.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4732 11205 4750 11228 4783 11186 4761 11137
TIME...MOT...LOC 2321Z 235DEG 29KT 4748 11212
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
AMSpecial Weather Statement National Weather Service Great Falls MT 614 PM MDT Tue May 28 2024 MTZ328-329-290130- Beaverhead and Western Madison below 6000ft- Ruby Mountains and Southern Beaverhead Mountains- Including the cities of Bannack, Dillon, Glen, Waterloo, and Monida Pass 614 PM MDT Tue May 28 2024 ...Gusty Winds from Decaying Showers and Thunderstorms... A line of showers and thunderstorms is shifting eastward across portions of Beaverhead and Madison counties. Wind gusts between 45 and 55 mph have been observed from these showers and thunderstorms. Be prepared for gusty winds in and around showers and thunderstorms this evening.
Special Weather Statement
National Weather Service Great Falls MT
619 PM MDT Tue May 28 2024
MTZ315>317-319-320-322-323-290100-
Helena Valley MT-Little Belt and Highwood Mountains MT-
Elkhorn and Boulder Mountains MT-
Big Belt, Bridger and Castle Mountains MT-
Upper Blackfoot and MacDonald Pass MT-Canyon Ferry Area MT-
Gates of the Mountains MT-
619 PM MDT Tue May 28 2024
...STRONG THUNDERSTORMS WILL IMPACT SOUTHEASTERN LEWIS AND CLARK...
NORTHWESTERN BROADWATER...NORTHWESTERN MEAGHER...NORTHERN JEFFERSON
AND SOUTHWESTERN CASCADE COUNTIES THROUGH 700 PM MDT...
At 619 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 10 miles east of Wolf Creek to 6 miles
northwest of Basin. Movement was east at 25 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Helena, Boulder, East Helena, Montana City, Basin, Wickes, York,
Rimini, Alhambra, Corbin, Spring Meadow Lake State Park, Elkhorn
State Park, Clancy, Black Sandy State Park, and Jefferson City.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4641 11232 4644 11232 4703 11188 4703 11158
4701 11157 4703 11151 4703 11139 4623 11194
4627 11245
TIME...MOT...LOC 0019Z 262DEG 20KT 4698 11184 4635 11232
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
AMPreliminary Local Storm Report
National Weather Service Great Falls MT
623 PM MDT Tue May 28 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0615 PM Tstm Wnd Gst 13 S Marysville 46.56N 112.31W
05/28/2024 M46 MPH Lewis and Clark MT Mesonet
Mesonet station MTMDP MacDonald Pass (MT
DOT).
&&
AMThe Great Falls radar (KTFX), 106 km away, was scanning. The volume nearest the first event began at 00:25 UTC.
2 thunderstorm wind. Local standard time, as filed.
ASOS station KHLN Helena Airport measured a 59 mph gust from outflow.
ASOS station KHLN Helena Airport measured a 59 mph gust from outflow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2024Every state in 2024This day in weather historyWarnings in Montana, May 2024
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: 1180001, 1180000.