As a low pressure center aloft consolidated over Washington state, isolated showers and thunderstorms developed over north-central and southwest Montana during the afternoon and early evening of May 10th, 2018. This was especially the case over and near higher terrain.
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 TFX wrote it up.
As a low pressure center aloft consolidated over Washington state, isolated showers and thunderstorms developed over north-central and southwest Montana during the afternoon and early evening of May 10th, 2018. This was especially the case over and near higher terrain. One thunderstorm near Havre managed to generate severe wind gusts as the storm collapsed. Lastly, the combination of rainfall and melting snow led to minor flooding in Jefferson County.
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 10, 2:03 PM MST, 1 hour 8 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 303 PM MDT Thu May 10 2018 .SYNOPSIS... A strong and slow moving Pacific weather system will produce periods of rain and mountain snow tonight through Friday. The heaviest precipitation is expected tonight across central Montana including the Rocky Mountain Front. Precipitation moves away through Southwest Montana Friday night into Saturday. Temperatures trend cooler on Friday with snow levels falling to around 6000 feet. && .DISCUSSION... Tonight through Saturday... A low pressure center aloft consolidates over Washington by this evening and then shifts southeastward to northeastern Nevada by late Friday evening, while cutting-off from the polar front jet stream. This low then looks to move northeastward to southern Idaho by late Saturday evening as high pressure ridging aloft nudges into North-Central Montana. The result should be widespread precipitation redeveloping via large-scale ascent over the CWA this evening into Friday. Northeasterly low- to mid-level upslope flow into the Rocky Mountain Front and central Montana mountains will likely enhance precipitation over portions of North-Central Montana. Precipitation chances then begin to decrease from north to south Friday night into Saturday. A cooling trend today continues into Friday, when high temperatures are expected to be well below- normal. Temperatures then rebound somewhat on Saturday, but will still be below-normal. As a result, today's snow levels near 7000-8000 feet in north-central Montana and near 8000-9000 feet MSL in the southwest will fall to near 6000-7000 feet MSL region- wide by Friday night into Saturday. This should allow about 1-3 inches of snow to fall along Big Hole, Chief Joseph, and Kings Hill passes tonight and again Friday night. Saturday night through Wednesday...Forecast model guidance appears to be coming into somewhat better agreement during this period. In general, the aforementioned cut-off low pressure center aloft looks to meander over northern Nevada and/or southern Idaho through Tuesday as high pressure ridging aloft continues to become established over Montana. On Wednesday, this low should begin to shift northeastward toward southeastern Montana as it gravitates toward a shortwave trough diving southeastward over central Canada. Accordingly, scattered showers and afternoon/early evening thunderstorms remain in the forecast, especially over southwest Montana. Temperatures look to be near or slightly below-normal Sunday before moderating to solidly above-normal by Tuesday and Wednesday of next week. Jaszka && .AVIATION... Updated 1800Z. VFR conditions prevail. However, flight conditions decline this evening through Friday as showers evolve into widespread precipitation. && .HYDROLOGY... Warm temperatures and recent rainfall continue to bring overland flooding. The situation will get more complicated through the weekend as several disturbances could bring areas of increased rainfall across the area. The cooling temperatures with this disturbance may slow down runoff from snowmelt. As a result many river forecasts were slightly lowered today. With the high amounts of QPF possible continued the Flood Watch for Simms and Vaughn along the Sun River, Big Hole River at Melrose, and the Jefferson River near Three Forks. An Areal Flood Warning remains in effect for the Helena Valley and the Lincoln area. Numerous problems have been reported along Tenmile Creek, with impacts possible on Prickly Pear and Sevenmile Creeks. Problems have also been reported in the Lincoln area, with multiple homes having water running through them, especially in the Stemple Pass and Good News Lane areas. An Areal Flood Warning is now in effect for the Deep Creek area in Broadwater County. Emergency Management reports rises in the creek, and potential flooding of homes. All advisories and warnings will remain in effect until the impacts from flooding have diminished. As mentioned...a series of disturbances will bring widespread chances for rain tonight through the end of the week. Rainfall amounts of a half inch to an inch are possible during the next three days. This could bring additional flooding concerns. Those in low lying areas and near rivers or creeks should be alert for additional flooding. Anglin && .PRELIMINARY POINT TEMPS/POPS... GTF 43 48 40 54 / 100 100 50 30 CTB 41 49 36 61 / 80 80 10 10 HLN 42 51 41 54 / 80 80 60 50 BZN 41 53 39 51 / 80 90 80 70 WEY 32 47 31 46 / 70 70 70 60 DLN 37 51 37 49 / 80 60 70 60 HVR 40 54 39 62 / 40 50 10 10 LWT 39 48 37 50 / 80 90 60 60 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 3 AM to 9 AM MDT Friday above 6500 feet for Cascade...Judith Basin...Meagher. Winter Weather Advisory from 3 AM to 9 AM MDT Friday above 6000 feet for Jefferson. Several hydrologic advisories and warnings are in effect across north central and southwest Montana. && http://www.weather.gov/greatfalls
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
129 PM MDT THU MAY 10 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0528 PM TORNADO 6 SW MOORE 46.91N 109.78W
05/09/2018 JUDITH BASIN MT BROADCAST MEDIA
KRTV RELAYED A REPORT OF A BRIEF TORNADO
NEAR MOORE. MULTIPLE PICTURES SHOW THE
TORNADO LOFTED DIRT INTO THE AIR...BUT NO
DAMAGE WAS REPORTED. THE TORNADO WAS
ASSOCIATED WITH A NON-SUPERCELL THUNDERSTORM
THAT PASSED JUST NORTH OF MOORE.
&&
MARTIN/SYNERPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
255 PM MDT THU MAY 10 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0254 PM HEAVY RAIN 1 NNW LEWISTOWN 47.07N 109.43W
05/10/2018 M1.31 INCH FERGUS MT TRAINED SPOTTER
24 HOUR RAINFALL TOTAL THROUGH 8:00 AM, MAY
10.
&&
MARTINSpecial Weather Statement National Weather Service Great Falls MT 341 PM MDT THU MAY 10 2018 MTZ011-045-102230- Liberty MT-Hill MT- 341 PM MDT THU MAY 10 2018 ...STRONG THUNDERSTORM TO IMPACT FAR NORTHEASTERN LIBERTY AND FAR NORTHWESTERN HILL COUNTIES... At 339 PM MDT, Doppler radar was tracking a strong thunderstorm 28 miles north of Joplin, or 31 miles north of Chester, moving east at 25 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. This storm may produce accumulating hail. This storm will remain over mainly rural areas of northeastern Liberty and northwestern Hill Counties. LAT...LON 4885 11048 4884 11098 4900 11104 4900 11049 TIME...MOT...LOC 2139Z 256DEG 21KT 4896 11092 Martin
The Great Falls radar (KTFX), 149 km away, was scanning. The volume nearest the first event began at 22:10 UTC.
2 flood, 1 thunderstorm wind. Local standard time, as filed.
Jefferson County Disaster and Emergency Services (DES) reported water flowing across Hubbard Lane, near Boulder. Flooding was believed to have resulted from a combination of rain and snow melt.
Trained spotter estimated a peak gust of 60 to 70 mph associated with the downdraft of a weakening thunderstorm. The spotter also reported pea-size hail.
Jefferson County Disaster and Emergency Services (DES) reported water flowing across Red Rock Road, near I-15 and the town of Bernice. Flooding was believed to stem from a combination of rain and snow melt.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2018Every state in 2018This day in weather historyWarnings in Montana, May 2018
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: 745815, 745668, 745813.