A large amount of runoff from the melting of a significant snowpack contributed to prolonged flooding along the Milk River and its tributaries during mid to late April 2018.
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The episode as NWS TFX wrote it up.
A large amount of runoff from the melting of a significant snowpack contributed to prolonged flooding along the Milk River and its tributaries during mid to late April 2018.
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 18, 11:00 AM MST, 0 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 1200 PM MDT Wed Apr 18 2018 ...Corrected WWA Section... .UPDATE... No major changes appeared necessary in this morning's forecast package. Only small features to note were some lingering areas of clouds across Chouteau, Liberty and Toole Counties, but should diminish shortly. Otherwise, pleasant day in store for the day today with temperatures reaching the lower to mid 50's across the Plains while remaining dry. Additionally, latest guidance this morning continues to suggests the potential for areas of dense fog to develop early tomorrow morning across northern and central MT, and have continued this mention in the morning update. KLG && .SYNOPSIS... Ridge of high pressure will build into the area today. This will bring mainly dry conditions...although an isolated mountain shower is possible. Temperatures will remain below normal today...with highs in the 40s and 50s. Slightly warmer temperatures are then expected for Thursday...with a few isolated to scattered rain or snow showers possible across the southwest...and dry conditions elsewhere. Mostly clear skies and near to above average temperatures are then expected for Friday. Some areas may even see highs in the 60s for Friday. Flooding from snowmelt will remain a concern for areas along the Hi-Line...see current flood products for more details. && .AVIATION... Updated 1800Z. VFR conditions and mostly clear skies as high pressure moves in over the region today. Some areas of patchy fog are possible after 10Z Thursday morning, mostly across Central and North Central Montana. Confidence was high enough to mention it in the KCTB and KHVR TAF. Any fog should be short lived and clear out around 15Z as light winds shift more easterly at many locations. && .PREV DISCUSSION... /ISSUED 542 AM MDT Wed Apr 18 2018/ Today through Friday...Ridge of high pressure will build into the area today. This will be more of a dirty ridge...with lingering moisture trapped underneath it. The result will be some increased cloud cover and perhaps an isolated rain or snow shower at times. Overall the threat for precipitation is minimal today...and in many areas was to low to include in the forecast. Temperatures will continue to be below normal today...with highs in the 40s and 50s. Mainly dry conditions will then be found tonight...with near normal lows in the 20s and 30s. Some areas may see areas of patchy fog develop tonight into Thursday morning...mainly across northern portions. A large upper level disturbance will push the mentioned ridge eastward for Thursday. This disturbance will be well to our south and take more of a Four Corners track. Some scattered rain or snow showers are possible in the southwest...with dry conditions and still below normal temperatures expected for the remainder of the area. Dry and warmer air then moves into the CWA on Friday under another brief ridge. This will bring mainly dry and warming conditions to the area. Some areas across the central and north may see their first 60 degree temperature readings since November. Although warmer temperatures will bring a more spring like feel...this will continue to bring hydro concerns across the area. See the hydro discussion for more details. Anglin Friday Night through Wednesday...Forecast models are continuing their consistent solutions. A fast-moving shortwave trough will bring a good chance of showers to the mountains Saturday into Saturday night. A Pacific cold front associated with this shortwave will also sweep a narrow band of showers east across the area on Saturday, then gusty west winds will follow the front Saturday afternoon and evening. High winds are possible with this front, but they do not appear to be likely at this time. Above normal temperatures on Saturday will also cool back closer to normal on Sunday. Another shortwave trough will move through the northwest flow aloft in the wake of the earlier shortwave, which will move a Canadian cold front south through Montana Sunday night, which will keep temperatures near to slightly below normal for Monday. This front will also bring another good chance of showers to the mountains, as well as to much of central and southwest Montana Sunday night into Monday. Models are in better agreement tonight with keeping a weak high pressure ridge over the area for Tuesday into Wednesday, which will keep the region dry as temperatures warm back above normal. Coulston && .HYDROLOGY... Updated 315 AM Wednesday (4/18). Flood advisories continue across much of north central Montana due to persistent lowland snowmelt flooding and areas of water over roadways. However, we have received reports from Hill and Blaine Counties of a few roads being washed out and several inches of water on other roads (making them impassable). As a result, areal flood warnings have been issued for those counties. Gradually warming temperatures with plenty of strong spring sun this week will continue to melt the snow, likely continuing or possibly increasing flooding coverage for many areas well into next week. Runoff will also continue areas of significant river flooding along the Hi-Line. A flood Warning will continue at least through today for Battle Creek near Chinook, as its river level remains just above Minor flood stage. It may fall below flood stage this evening. Lodge Creek north of Havre along the Canadian border is also hovering around flood stage, so the flood warning there will continue through today. Big Sandy Creek spiked above Major flood stage Tuesday afternoon and evening and, although it is falling as of Wednesday morning, it will likely remain above Major flood stage for much of today and then stay above Moderate flood stage for the next week or so. Along the Milk River, the gauge site at Havre will likely remain above Minor flood stage for the next week or so, while the site near Harlem is expected to stay above Moderate stage for at least the next week and possible even reach Major flood stage for a time. This persistent flooding will be helped along by increased water releases (and water flowing over spillways) from Fresno Reservoir, which will increase the threat to the towns of Havre, Chinook, and Harlem. River/creek levels will continue to be closely monitored in case any additional river flood warnings are required. && .PRELIMINARY POINT TEMPS/POPS... GTF 53 28 55 32 / 0 10 10 10 CTB 49 27 50 29 / 10 10 10 0 HLN 52 29 57 33 / 10 10 10 10 BZN 51 26 54 30 / 10 10 10 10 WEY 41 20 46 23 / 10 0 20 20 DLN 48 27 52 29 / 10 10 20 10 HVR 49 29 50 31 / 10 10 10 10 LWT 50 30 55 31 / 10 10 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Flood Warning in effect until further notice for Big Sandy Creek near Havre. Flood Warning in effect until further notice for Milk River near Havre. Flood Warning in effect until further notice for Battle Creek near Chinook. Flood Warning in effect until further notice for Milk River near Harlem. Areal Flood Warning in effect until 815 PM MDT Sunday for Hill...Blaine Counties. Areal Flood Advisory in effect until 345 PM MDT Friday for Glacier County. Areal Flood Advisory in effect until 815 AM MDT Thursday for Teton County. Areal Flood Advisory in effect until 830 PM MDT Thursday for Liberty County. Areal Flood Advisory in effect until 715 AM MDT Friday for Fergus County. Areal Flood Advisory in effect until Noon MDT Friday for Eastern Pondera...Southern Toole Counties. && http://www.weather.gov/greatfalls
The national radar mosaic for the moment the first event began.
4 flood. Local standard time, as filed.
Chouteau and Blaine County DES (Disaster and Emergency Services) conducted helicopter flyover and reported floodwaters surrounding Chinook. This flooding continued until receding around April 30th. The floodwaters never entered downtown Chinook since roadways acted like levees.
NWS Great Falls hydrologist reported and photographed flooding along Thirty Mile Creek just north of downtown Harlem.
Public reported flooding along Cottonwood Creek in Chester.
KRTV reported a high water rescue along US-2 near Dunkirk. Exact location unknown, but rescue occurred around 12 AM MDT on April 19th. Good Samaritan rescued woman from her car after it became stranded in floodwaters.
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: 763403, 763402, 763404, 763405.