Toward the end of April, snowmelt runoff caused flooding along Tenmile Creek in the Helena area.
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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.
Toward the end of April, snowmelt runoff caused flooding along Tenmile Creek in the Helena area.
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 Apr 27, 3:30 AM MST, 3 hours 57 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 430 AM MDT Fri Apr 27 2018 ...Updated Aviation Discussion... .SYNOPSIS... High pressure will provide dry and mild weather Friday and Saturday with afternoon highs well into the 70s to near 80. A spring storm will arrive by Saturday evening and last through the rest of the weekend and into early next week. Expect increased chances for showers and thunderstorms through this time frame, with some mountain snow possible through at least Monday before drying out and warming back up by late next week. && .DISCUSSION... Increasingly warm temperatures under mostly sunny skies are expected through Saturday afternoon as high pressure gradually gives way to a front moving our way late Saturday. Expect winds to trend more east to south or some combination thereof as this front slowly approaches over the next 24 to 36 hours. A strong upper level disturbance arrives Saturday evening from the southwest, and with fairly decent instability across the entire region, it seems likely there would be some showers and possibly a few thunderstorms across the region, some perhaps lasting into the early overnight hours before diminishing. For Sunday into the middle of next week, model agreement decreases significantly with the evolution of a large, slow- moving upper level low pressure system that will move across the northwestern US. The only thing to say with confidence during this time period is that there will be areas of precipitation almost constantly over our region from Sunday through at least Tuesday, and possibly Wednesday, but confidence in precipitation amounts (both rain and snow) seems to be decreasing with the latest model consensus. Toward later next week, models seem insistent on strong upper level ridging building into the western United States, likely resulting in a warmer and drier pattern. CC && .AVIATION... Updated 1030z. VFR conditions with clear skies will continue across the forecast area at least Saturday morning due to lingering high pressure. Winds will be light for most of the period, but a Pacific cold front approaching from the west and an increased easterly pressure gradient will cause winds to shift more easterly and increase after 18z Fri. CC/Coulston && .HYDROLOGY... The areal flood advisory continues for Meagher County. The most impacts currently are around Ringling. However, with warmer temperatures expected over the next few days, some additional impacts could develop. For Hill/Blaine counties, the areal flood warning will continue. Water is receding in Hill county and this area might be dropped from the warning on Friday. In Blaine county, widespread impacts continue, with numerous roads affected by flowing water. The point flood warning also continues for the Milk River near Harlem. It will take several more days before the Milk River falls below flood stage. A spring storm will move through the region Sunday into Monday, Widespread precipitation amounts of 0.50 to 1 inch will be possible over portions of North Central MT, with a few isolated spots near 2 inches. Thus additional flood impacts could develop in areas of heavier rainfall. Brusda && .PRELIMINARY POINT TEMPS/POPS... GTF 76 45 80 49 / 0 0 10 20 CTB 75 40 79 47 / 0 0 10 50 HLN 77 45 79 45 / 0 0 20 50 BZN 74 41 79 44 / 0 0 10 30 WEY 60 31 61 33 / 0 0 20 20 DLN 74 41 75 39 / 0 0 10 50 HVR 75 42 83 49 / 0 0 0 20 LWT 71 42 81 48 / 0 0 10 20 && .TFX WATCHES/WARNINGS/ADVISORIES... Areal Flood Warnings continue for Hill and Blaine Counties until further notice. Flood Warning continues for the Milk River near Harlem until further notice. Areal Flood Advisory continues for Meagher County until further notice. && http://www.weather.gov/greatfalls
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
NWS Great Falls Warning Coordination Meteorologist reported flooding along Tenmile Creek at Green Meadow Country Club in Helena.
NWS Great Falls Warning Coordination Meteorologist reported additional flooding along Tenmile Creek, near the intersection of McHugh Drive and Mill Road on the north side of Helena.
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, April 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: 763406, 763407.