####018012024#### FGUS73 KBIS 251853 ESFBIS NDC001-007-011-015-021-025-029-031-033-037-041-043-045-047-051-053- 055-057-059-061-065-083-085-087-089-093-103-105-271800- Probabilistic Hydrologic Outlook National Weather Service Bismarck ND 153 PM CDT Thu Apr 25 2024 ...FLOOD AND WATER RESOURCES OUTLOOK... This Flood and Water Resources Outlook is for the James and Missouri basins of North Dakota, covering the period of 27 April through 26 July, 2024. This is a routine monthly issuance of flood probabilities for NWS forecast locations. These probabilities are issued on, or around, the fourth Thursday of every month. The following message has four sections. The first provides some text on the highlights of this outlook and conditions affecting the local hydrology. The second section gives the current and historical risks of flooding as determined by the Ensemble Streamflow Forecast model of the National Weather Service. The third section gives the current probabilities for reaching flood stage at the listed forecast locations. And finally, the fourth section covers the risk of the river sites falling below the listed stages. ...Flood Outlook Highlights... Going into late spring, the region has escaped the normal spring flood season from melting snow. Flood risks generally remain below to near normal for this time of year and should be considered directly related to the region entering its summer severe weather season where large thunderstorms become increasingly common. Indeed, at this point one should expect a few occurrences of minor to moderate river floods somewhere in North Dakota through late summer even though drought concerns will most likely be at the forefront of many residents' thoughts. ...Missouri and Yellowstone Rivers... The snowpack along the Missouri and Yellowstone rivers in western North Dakota and on up through the Montana headwaters for both streams peaked in early April at a value just above the least observed over the past 30 years. This certainly suggests that overall runoff along the Missouri and Yellowstone rivers will fall well short of normal, and that alone will provide challenges for those who maintain and regulate the water levels at lakes Oahe, Sakakawea, and Fort Peck. That being said, a planned "Test Flow" out of Fort Peck is expected to briefly raise water levels along the Missouri River above Sakakawea. Given the currently modest amount of water coming down the Yellowstone, this is not likely to create concerns. ...Snowpack Conditions... No snowpack exists within either the Missouri or James River basins of North Dakota. ...Current Drought Conditions... Timely, but not necessarily plentiful rains over the past few weeks have trimmed the extent and somewhat improved drought conditions. However, without continued timely rains, drought concerns persist and this trend of improvement may be short-lived. ...Reservoirs and Natural Wetlands... Most natural wetlands and smaller man-made water supply features are doing well despite an overall snow deficit across the state this winter. Most rivers and streams are at the lower end of normal for this time of year. The exceptions to this are in the very southwest and very northeastern part of the state where several stream gages are in the 10th to 24th percentile, and even a few streams are below the 10th percentile. ...Soil Conditions... Soil moisture values across the Missouri and James basins are a mixture of somewhat above normal in parts of western and central North Dakota, to well below normal in parts of the James River basin and eastern North Dakota. ...Weather Outlook... Near term, as in the next few days, rain is expected over most of North Dakota. This should put the region on track to enter May with at least a stable position on the drought front. The 6-10 and 8-14 day outlooks favor an above normal temperature and precipitation pattern. The strenth of this above normal temperature and precipitation pattern slightly wanes in the weeks 3-4 outlooks before all of the Missouri and James River basins of North Dakota slide into the equal chances category for above normal, near normal, or below normal temperature and precipitation for the entirety of May and again in the 3-month outlook for May, June and July. ...Ice Conditions... No ice is known to exist on any river or stream in North Dakota. In Table 1 below, the current (CS) and historical (HS) or normal probabilities of exceeding minor...moderate...and major flood stage are listed for the valid time period. CS values indicate the probability of reaching a flood category based on current conditions. HS values indicate the probability of reaching a flood category based on historical or normal conditions. When the value of CS is greater than HS...the probability of exceeding that level is higher than normal. When the value of CS is less than HS...the probability of exceeding that level is lower than normal. ...Table 1--Probabilities for minor...moderate and major flooding... Valid Period: 04/27/2024 - 07/26/2024 : Current and Historical : Chances of Exceeding : Flood Categories : as a Percentage (%) Categorical : Flood Stages (FT) : Minor Moderate Major Location Minor Mod Major : CS HS CS HS CS HS -------- ----- ----- ----- : --- --- --- --- --- --- :Pipestem Pingree 11.0 13.0 15.0 : <5 <5 <5 <5 <5 <5 :James River Grace City 12.0 14.0 15.0 : 5 <5 <5 <5 <5 <5 LaMoure 14.0 16.0 18.0 : 9 5 7 <5 <5 <5 :Missouri River Williston 22.0 24.0 26.0 : 8 43 <5 31 <5 14 :Cannonball River Regent 22.0 24.0 26.0 : <5 <5 <5 <5 <5 <5 :Cedar Creek Raleigh 12.0 14.0 16.0 : <5 <5 <5 <5 <5 <5 :Cannonball River Breien 10.0 20.0 23.0 : 15 38 <5 <5 <5 <5 :Beaver Creek Linton 12.0 14.0 16.0 : 11 31 6 19 <5 13 :Little Muddy River Williston 10.0 12.0 14.0 : 14 60 7 30 <5 8 :Little Missouri River Marmarth 18.0 23.0 30.0 : <5 6 <5 <5 <5 <5 Medora 15.0 18.0 20.0 : <5 18 <5 8 <5 6 Watford City 20.0 24.0 30.0 : <5 9 <5 5 <5 <5 :Knife River Manning 15.0 17.0 20.0 : <5 17 <5 <5 <5 <5 :Spring Creek Zap 14.0 18.0 20.0 : 10 19 6 12 5 11 :Knife River Hazen 21.0 24.0 25.0 : 10 19 5 16 <5 9 :Heart River Mandan 27.0 33.0 38.0 : 5 9 <5 <5 <5 <5 :Apple Creek Menoken 15.0 16.0 17.0 : 30 52 17 41 6 19 Legend CS = Conditional Simulation (Current Outlook) HS = Historical Simulation FT = Feet In Table 2 below...the 95 through 5 percent columns indicate the probability of exceeding the listed stage levels (FT) for the valid time period. ...Table 2--Exceedance Probabilities... Chance of Exceeding Stages at Specific Locations Valid Period: 04/27/2024 - 07/26/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Pipestem Pingree 5.6 5.6 5.6 6.0 7.4 9.5 10.6 :James River Grace City 4.7 4.7 4.7 5.0 6.6 7.7 11.3 LaMoure 7.7 7.7 7.7 8.2 9.3 12.5 17.7 :Missouri River Williston 17.2 17.5 18.2 19.2 19.6 21.6 23.0 :Cannonball River Regent 5.4 5.4 5.7 6.8 7.4 8.3 9.6 :Cedar Creek Raleigh 1.4 2.4 3.0 4.1 5.3 6.3 7.4 :Cannonball River Breien 2.6 3.3 5.1 6.8 8.8 11.0 11.9 :Beaver Creek Linton 5.0 5.1 5.3 6.2 9.6 12.4 14.4 :Little Muddy River Williston 4.8 4.8 4.9 6.5 8.1 10.9 12.2 :Little Missouri River Marmarth 1.1 1.1 1.1 1.5 3.3 7.2 9.5 Medora 1.7 1.7 1.7 2.4 5.5 7.6 10.1 Watford City 7.2 7.2 7.2 8.2 10.1 12.3 13.8 :Knife River Manning 6.4 6.4 6.4 8.1 9.2 10.9 11.6 :Spring Creek Zap 4.8 4.8 4.9 6.4 7.8 14.4 19.9 :Knife River Hazen 1.4 1.4 2.5 6.0 10.2 21.2 23.7 :Heart River Mandan 10.7 10.7 11.4 14.5 18.7 23.8 27.6 :Apple Creek Menoken 5.8 5.8 5.8 10.7 15.3 17.0 18.0 In Table 3 below...the 95 through 5 percent columns indicate the probability of falling below the listed stage levels (FT) for the valid time period. ...Table 3--Nonexceedance Probabilities... Chance of Falling Below Stages at Specific Locations Valid Period: 04/27/2024 - 07/26/2024 LOCATION 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Pipestem Pingree 5.1 5.1 5.1 5.1 5.1 5.1 5.1 :James River Grace City 4.6 4.6 4.5 4.5 4.5 4.5 4.5 LaMoure 7.7 7.7 7.5 7.3 7.2 7.2 7.2 :Missouri River :Cannonball River Regent 5.3 5.3 5.3 5.3 5.2 5.2 5.2 :Cedar Creek Raleigh 1.2 1.2 1.1 1.1 1.0 1.0 0.9 :Cannonball River Breien 2.4 2.3 2.3 2.2 2.1 2.1 2.1 :Beaver Creek Linton 4.9 4.8 4.8 4.8 4.8 4.8 4.8 :Little Muddy River Williston 4.7 4.7 4.7 4.7 4.7 4.7 4.7 :Little Missouri River Marmarth 1.0 1.0 1.0 0.9 0.9 0.8 0.8 Medora 1.5 1.5 1.5 1.4 1.4 1.4 1.4 Watford City 7.1 7.1 7.1 7.0 7.0 7.0 7.0 :Knife River Manning 6.3 6.3 6.2 6.1 6.0 6.0 6.0 :Spring Creek Zap 4.8 4.8 4.8 4.8 4.8 4.8 4.8 :Knife River Hazen 1.1 1.1 0.9 0.9 0.8 0.8 0.8 :Heart River Mandan 10.3 10.0 9.9 9.8 9.8 9.7 9.7 :Apple Creek Menoken 5.1 5.0 4.3 3.9 3.4 3.3 3.2 These long-range probabilistic outlooks contain forecast values that are calculated using multiple season scenarios from 30 or more years of climatological data...including current conditions of the river...soil moisture...snow cover and 30 to 90 day long-range outlooks of temperature and precipitation. By providing a range of probabilities...the level of risk associated with long-range planning decisions can be determined. These probabilistic forecasts are part of the National Weather Service's Advanced Hydrologic Prediction Service. Visit our web site weather.gov/bis for more weather and water information. The next outlook will be issued by the end of May. $$ Schlag