MISSOURI BASIN: CHANCE OF REACHING FLOOD STAGE IN 2021 AS COMPARED TO HISTORICAL 31 percent decrease in chance to reach flood stage during next 3 months NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 1 MISSOURI BASIN: Mountain Snowpack As of 10 February 2021 Mountain snowpack running near average in the north to well below average south. NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 2 MISSOURI BASIN: Mountain Runoff Volume April-September Mountain runoff volume projected to be below normal • Upper Missouri abv Ft. Peck: 86% • Yellowstone: 80% • North Platte: 60% • South Platte: 66% NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 3 MISSOURI BASIN: Plains Snowpack as of 11 February 2021 NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 4 MISSOURI BASIN: River Ice Conditions….and a new unfolding threat Photo courtesy Patrick Lonergan NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 5 MISSOURI BASIN: Flood Potential Outlook Nebraska Wahoo Creek: minor NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 6 MISSOURI BASIN: Flood Potential Outlook Iowa Little Sioux River: minor Big Sioux River: minor NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 7 MISSOURI BASIN: Flood Potential Outlook Kansas Big Blue River: minor Black Vermillion: minor Stranger Creek: moderate Little Osage R: moderate Marais des Cygnes: minor NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 8 MISSOURI BASIN: Flood Potential Outlook Missouri Tarkio River: moderate Chariton River: minor Grand River: moderate Wakenda Creek: minor Crooked River: moderate Moniteau Creek: minor Blackwater R: moderate Moreau River: minor Lamine River: moderate Marmaton R: minor Petite Saline Ck: moderate Big Piney River: minor Sac River: moderate Gasconade River: minor South Grand R: moderate Little Osage R: minor Big Creek: moderate Osage River: minor Platte River: minor NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 9 MISSOURI BASIN: Flood Potential Outlook: Missouri River Below Gavins to St. Louis Minor flooding expected below Kansas City NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 10 MISSOURI BASIN: Flood Potential Outlook: Summary Points • Mountain snowpack is near-to-below average this year. We still have roughly 35% of snow accumulating period remaining. • Plains snowpack widespread, but generally shallow. Heaviest plains SWE found in eastern Nebraksa and southwestern Iowa with 1 to 2+ inches. • Soils very dry over most of the basin. Ground getting cold…but still porous. • Recent arctic blast heightens river ice concerns. • Overall, spring flood risk is lower than normal. • Significant flooding due to mountain snow runoff alone is not likely. • Episodic minor-to-moderate level flooding likely in the lower portion of the basin (southeastern NE, eastern KS, southern IA, MO) due to Spring-time thunderstorm activity. This is typical whether soils are dry or not. • River ice going into March is concerning, especially in the southern portion of the basin. March can bring quick warm-ups (i.e. cause plains snowmelt) and rain events. River ice break-up jams could result. Outlook probability numbers DO NOT take ice jam flooding risk into account. NATIONAL WEATHER SERVICE Building a Weather-Ready Nation // 11.