SPRING FLOOD OUTLOOK NATIONAL WEATHER SERVICE MISSOURI BASIN RIVER FORECAST CENTER PLEASANT HILL, MO March 09, 2022 NARRATIVE PART 1 OF 1 ATTN WFO'S SERVED BY MBRFC. This Spring Flood Outlook is not for public release until Thursday, 10 March 2022. This Spring Outlook is for the Missouri River drainage which includes rivers in Montana, Wyoming, Colorado, North and South Dakota, Nebraska, Kansas, Iowa, Minnesota, and Missouri. SPRING FLOOD OUTLOOK Flood risk this Spring within the Missouri River basin is generally below normal. To provide context, a normal risk indicates that a location that typically experiences Spring time flooding is likely to see flooding again this year. However, a normal risk for flooding does not necessarily mean that a location is expected to flood. For those locations which do not typically experience flooding, a normal risk simply indicates that flooding is again not expected this year. By the same token, a reduced risk of flooding does not necessarily mean that flooding is not expected. A good example is the Platte River in northwest Missouri. Normally there is a 86 percent chance for flooding during the Spring. This year the likelihood has been reduced by 35%, down to 51%. The Platte River in Missouri will still likely experience flooding, although the risk has been significntly reduced. In a similar fashion, an increased risk does not necessarily indicate flooding is likely. Mountain snowpack overall is generally near-to-below normal. Therefore, widespread, significant flooding in the mountainous west is not likely due to mountain snowmelt alone. Current Water Supply Forecasts produced by the National Weather Service project lower than average April-September runoff volumes for the mountainous west. More information regarding current Water Supply Forecasts can be accessed at weather.gov/mbrfc/water The only appreciable plains snowpack is found in eastern North Dakota and extreme northeastern South Dakota. Highest reports of snow water equivalent in this area are upwards of 3.5 inches in the headwaters of the James River basin. Water Year 2021, extending from October 2020 through September 2021, was the 17th driest in the 126 year record for the Missouri River basin. So far, Calendar Year 2022 is the 6th driest on record. As far as temperatures go, the 3-month period extending December 2021 through February 2022 has been the 30th warmest December through February on record. The mild and dry conditions this winter are thought to have precluded the development of a deeply frozen ground condition. Frost depths are indeed impressive in some regions, however reports indicate that the ground remains workable in most areas. Therefore soils, while indeed cold, are thought capable to absorb some of any future runoff produced by plains snowmelt, rain-on-snow, or rain events this Spring. The Dakotas may be the exception to this generalized assumption. Precipitation received in October, December, and January benefited soil moisture, especially in the eastern portion of North Dakota and the extreme northeastern corner of South Dakota. It is possible that the available soil moisture in in this area of the Dakotas may have been able to produce a deeply frozen ground condition. If this is the case, runoff generated by future springtime plains snowmelt, rain-on-snow, and/or rain events would be dramatically increased, as the soil infiltration capacity would be curtailed. Dry and mild conditions have also resulted in an overall lower than normal ice jam break up flood risk for the 2021-2022 season. That is not to say that ice jam flood risk is nonexistent. Elevated stages due to river ice action have already been reported this season along the Middle Loup and North Platte Rivers in Nebraska, the Jefferson and Gallatin Rivers in Montana, and the Wind River in Wyoming. Impacts thus far have been minor and localized. Ice jam induced flooding will remain possible in the northern and western portions of the basin for the next few weeks. Please note, the probabilistic quantifications that form the basis for this Spring Flood Outlook can not take into account the presence of river ice. Springtime flooding in the lower one-third of the basin, including southeastern Nebraska, southern Iowa, eastern Kansas, and the state of Missouri, is driven by typical thunderstorm activity. Flooding is projected to occur again this Spring in this region of the basin. Minor flooding due to convective activity has already occurred within the Gasconade River basin located in the Missouri Ozarks. This demonstrates that flooding can, and does occur, any time of the year within the Missouri River basin. The following state by state flood potential discussions are based on long-range probabilistic river outlooks developed this week. Again, it must be stressed, these outlooks do not take into account the presence of river ice. In South Dakota, the Columbia to Stratford reach of the James River is expected to see minor to moderate level flooding. In Iowa, the upper reach of the Little Sioux River could possibly see minor flooding. In Kansas, Stranger Creek is expected to have moderate flooding, while the Marais des Cygnes and Little Osage Rivers are expected to have minor flooding. In the state of Missouri, the Grand, Crooked, Blackwater, Moreau, Tarkio, and South Grand Rivers will experience moderate level flooding. Wakenda, Petite Saline, and Big Creeks will also have moderate flooding. The Chariton, Lamine, Big Piney, Gasconade, Little Osage, Sac, Marmaton and Platte Rivers are all likely to see minor level flooding, as are Moniteau and Roubidoux Creeks. As this latest Outlook covers early June, the Missouri River downstream of Kansas City to the mouth is likely to see episodic, on-again off-again minor flooding over the next 3 months. Again, this is due to thunderstorm activity that commonly occurs in this period. These projections of river stages are based on current observed states of streamflow, soil moisture, and snowpack, coupled with future precipitation and temperature patterns and anticipated operational hydrologic changes such as reservoir releases and canal diversions. "Outlooks" are provided for long-range (weeks to months) projections based on climatological patterns of precipitation and temperature. "Forecasts" are provided for short-term (days) projections based on forecast patterns of precipitation and temperature. The uncertainty of these products varies from season to season and location to location. The uncertainty of forecasts tend be less than the uncertainty of outlooks due to their shorter lead time. Users of these products are encouraged to contact their nearest National Weather Service Forecast Office for continued updates of meteorological conditions which can have significant impacts on flood preparedness planning and flood fighting activities. For additional quantitative information please refer to AHPS products for probabilistic outlooks of potential flooding. Refer to short-term flood forecasts and products, if any are currently issued, for information about ongoing or near-term anticipated flooding. This is the last scheduled Spring Outlook of the season. Should significant changes occur subsequent to this Outlook, additional Outlooks can be released to update expected conditions. Additional river information, including the monthly Water Supply Outlook, can be accessed at the following URL: http://weather.gov/mbrfc Current Snow Conditions The conditions listed below are based on observations and model data as of Wednesday morning, March 9th. Colorado, Montana, and Wyoming Plains Snow depths of 1 to 3 inches are being reported across the plains of Montana, northern Wyoming, and Colorado with water equivalents generally less than 0.5 inches. Higher snow depths of 3 to 6 are being reported across the plains of southern Wyoming with water equivalents generally less than 1.0 inch. Mountainous West Snowpack conditions in the mountainous areas of the basin are generally near to below normal. In Montana, the Jefferson, Musselshell, Missouri headwaters, Sun, Teton, and Marais River basins are reporting a near normal snowpack (85-110%). The St. Mary and Milk basins are reporting a near normal snowpack (100-110%). In Wyoming, the Tongue, Bighorn, Powder, Wind, and Yellowstone River basins are reporting a below normal snowpack (80-95%). The higher elevations of the North Platte River basin are reporting a near normal snowpack (90-100%). In Colorado, the higher elevations of the South Platte River basin are also reporting a near normal snowpack (95-105%). North Dakota Snow depths of 5 to 12 inches are being reported across eastern North Dakota with water equivalents in the 1.0-3.5 inch range. Snow depths of 1 to 5 inches are being reported across the remainder of North Dakota with water equivalents less than 1.0 inch. South Dakota The Black Hills in South Dakota have 5 to 10 inches of snow depth with water equivalents in the 0.5-2.0 inch range. Snow depths of 2 to 6 inches with water equivalents generally in the 0.5-1.5 inch range are being reported across the extreme northeastern corner of the state. The remainder of the state has 1 to 3 inches of snow with water equivalents less than 0.5 inches. Iowa Snow depths of 1 to 3 inches are being reported across extreme southern Iowa with water equivalents generally less than 0.3 inches. Little to no snow is being reported across the remainder of Iowa. Nebraska Snow depths of 2 to 4 inches are being reported across the western half of Nebraska with water equivalents generally less than 0.5 inches. Little to no snow is being reported across the eastern half of Nebraska. Missouri Snow depths of 2 to 4 inches are being reported across the northern half of Missouri with water equivalents generally less than 0.5 inches. Little to no snow is being reported across the southern half of Missouri. Kansas Snow depths of 1 to 2 inches are being reported across Kansas with water equivalents less than 0.5 inches. Current Soil Moisture Conditions The US Drought Monitor indicates that much of the Missouri River basin is experiencing below normal soil moisture conditions. Extreme to exceptional drought is indicated across much of Montana. Moderate to extreme drought is indicated across Wyoming, western Dakotas, western Nebraska, and western Kansas. Abnormally dry to moderate drought is indicated across much of the remainder of the Missouri River basin. Isolated frost depth reports suggest that soils across Montana, Wyoming, South Dakota, and North Dakota have frost penetration ranging from 1-4 feet. Frost depths of less than 1 foot are being reported across Nebraska, Iowa, Colorado, Kansas, and Missouri. Current River Conditions A large majority of rivers across the northern half of the Missouri River basin are iced over. Generally, river levels across the basin are currently running near to below normal, or estimated to be so if the rivers are frozen. The exception is across southern Missouri where rivers are running near to above normal. A summary of river flow conditions at selected river stations for March 9th follows: Long Term Current Mean (CFS) (CFS) James River - Huron, SD 210 60 (EST) Big Sioux River - Akron, IA 950 450 (EST) Platte River - Louisville, NE 8350 7620 Kansas River - Desoto, KS 3440 1840 Gasconade River - Jerome, MO 2470 8290 Missouri River - Omaha, NE 19600 14800 Missouri River - Rulo, NE 30200 24400 Missouri River - St. Joseph, MO 35200 25600 Missouri River - Waverly, MO 42200 32500 Missouri River - Hermann, MO 70500 50600
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