A dynamic spring storm system brought heavy rain and snow to parts of central and Southwest Montana over a multi-day period. Rainfall amounts exceeded three inches for some and snowfall amounts of one to two feet were reported.
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.
A dynamic spring storm system brought heavy rain and snow to parts of central and Southwest Montana over a multi-day period. Rainfall amounts exceeded three inches for some and snowfall amounts of one to two feet were reported. Various impacts stemmed from this spring storm.
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 17, 4:40 AM MST, 1 hour 20 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 540 AM MDT Wed May 17 2017 Updated Aviation Discussion .SYNOPSIS... A potent spring storm system will continue to deliver widespread rain through the day on Wednesday. Rain could become moderate to heavy at times, with the heaviest precipitation occurring along the Rocky Mountain Front. Mountain snow is also likely, as snow levels lower from around 6000 feet early this morning to around 5000 feet by Wednesday evening, impacting travel over most mountain passes. This storm system finally departs on Thursday with drier conditions likely into Friday. && .DISCUSSION... Today through Friday...Deep mid to upper level low is now centered in southern ID as of early this morning with surface low pressure from SW MT/WY and trough axis/TROWAL (TRough of Warm Air aLoft) extending from WY NW into central MT. Models remain in good agreement with little change from previous thinking for overall depiction of precipitation/amounts and winter weather impacts expected through today and tonight as the mid-upper level circulation center drifts SE into northern UT while the Trowal feature and deep/moist easterly flow focus moderate to heavy precipitation across north-central and central MT. Precipitation amounts of 1-2 over the next 24 hrs are most likely from areas along the Rocky Mtn Front SE through eastern portions of Meagher and Gallatin counties where upslope easterly flow will maximize precipitation amounts. Snow levels have lowered to around 5000 feet in SW MT where snow is being observed at Butte and is in the process of changing over to snow at Dillon as of 3AM. Snow levels have fallen to around 6000 feet across NW portions of the forecast area including the Glacier NP area with relatively milder air across central MT where snow levels remain around 7000 feet. Expect some additional lowering of snow levels through this morning as the atmospheric column continues to cool. Still looking at 1 to 2 feet of snow accumulation across the highest elevations (above 7000ft) across western and central MT today. Greatest potential for snow impacting roadways will be across SW MT where temperatures and snow levels are lowest. Higher precipitation amounts across central and NW portions of the forecast area will be counter-balanced by somewhat higher snow levels and warmer temperatures, but snowfall rates may overcome this at times and allow for accumulations on road surfaces here as well, particularly later this morning. Even without Ongoing Winter weather statements highlight these impacts well, but will need to watch impacts at Bozeman pass and Kings Hill closely as the day progresses for potential upgrades if accumulating snow occurs at a larger rate at these elevations than currently anticipated. Precipitation diminished from north to south tonight through Thursday morning as the upper low drifts south across UT/CO. Dry conditions are expected thursday afternoon through Friday as weak high pressure extends across the region at the surface and aloft. Hoenisch Friday Night through Wednesday...Unsettled northwesterly to northerly flow aloft is expected Friday night through Monday. Multiple shortwave troughs embedded within the flow should traverse the CWA, but the exact timing of each shortwave is uncertain at this time. Moderating temperatures and an overall decreasing trend in POPs are then forecast for Tuesday into Wednesday of next week, courtesy of upper-level ridging building eastward into our region. However, a potent shortwave trough may dig southeastward and begin to break-down the aforementioned ridge by Wednesday afternoon, which would cause POPs to increase over the CWA. Lows should be near- normal throughout the period. Highs should be near or slightly below- normal this weekend through Monday, while highs look to be near or slightly above-normal by Tuesday and Wednesday of next week. Jaszka && .AVIATION... Updated 1140Z. Upper level low centered over southern ID will wrap deep moisture into the region from the S and E with widespread precipitation across much of the forecast area this morning and locally moderate to heavy precipitation across central MT. MVFR conditions and Mtn obscuration will persist across all of central and SW MT with periods of IFR and lower cigs/vsby during periods of heavier precipitation. Gradual improvement can be expected after 00Z in diminishing precipitation intensity but mountains will remain obscured with lower ceilings slowly improving later tonight. Hoenisch && .HYDROLOGY... The main message at this point regarding hydro is that significant flooding is not anticipated at this time. However, given the higher precipitation amounts forecast and already elevated streamflows due to seasonal snowmelt, we will continue to closely monitor area streams and rivers, particularly areas that drain the east slopes of the Rockies. By next week, streams/rivers full from the upcoming rain and mountain snowfall may begin to respond a bit more with added snowmelt. Those with interests along rivers/streams are encouraged to monitor river levels through next week as well as any additional statements from our office. Flash flood guidance values are fairly high at this time, and small streams/urban areas should be able to handle the expected precip. Martin/Hoenisch && .PRELIMINARY POINT TEMPS/POPS... GTF 49 38 56 37 / 100 90 10 10 CTB 44 37 56 36 / 100 60 10 10 HLN 48 40 57 38 / 100 100 30 10 BZN 44 36 51 32 / 90 80 30 10 WEY 37 26 46 26 / 80 70 30 10 DLN 42 36 50 32 / 90 80 20 10 HVR 58 35 60 37 / 80 20 0 0 LWT 51 37 53 34 / 100 60 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM MDT Thursday above 5500 feet for Broadwater...Central and Southern Lewis and Clark... Gallatin...Meagher. Winter Storm Warning until 6 AM MDT Thursday above 5500 feet for Beaverhead...Jefferson...Madison. Winter Storm Warning until 3 AM MDT Thursday above 5000 feet for Northern Rocky Mountain Front...Southern Rocky Mountain Front. Winter Weather Advisory until 3 AM MDT Thursday Eastern Glacier...Northern Rocky Mountain Front. && weather.gov/greatfalls
2 winter storm. Local standard time, as filed.
Eastbound Interstate 90 is closed over Homestake Pass. Prior to closure, there were multiple reports of jack-knifed semis due to snow and ice conditions.
KBZN media reports around 10 slide-offs over Bozeman Pass. DOT webcam shows poor visibility and snow-covered conditions over the pass.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2017Every state in 2017This day in weather historyWarnings in Montana, May 2017
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: 703073, 703078.