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Spring Flood Outlook |
PROBABILISTIC HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE ST. LOUIS MO 350 PM CST Thu Mar 09 2023 ...Spring Flood and Water Resources Outlook Number 3... ...Moderate flooding likely along the upper Mississippi River... ...Minor flooding likely along most of the Missouri River... ...Near-normal flood chances along most local tributaries... This outlook uses the term St. Louis service area to refer to the Mississippi River from above Canton, Missouri to below Chester, Illinois, the Missouri River above Jefferson City, Missouri to its confluence with the Mississippi River, the Illinois River downstream from Beardstown, Illinois to its confluence with the Mississippi River, and for tributaries of these rivers in central and eastern Missouri and in west central and southwest Illinois. The probabilities within this outlook are not skewed by any ongoing flooding nor by any anticipated excessive rainfall. While we experienced heavy rainfall and minor flooding last weekend, the peak runoff from this event has already moved out of the area. This outlook is based on current streamflows and soil moisture over the area, upstream snowpack in the Mississippi, Missouri, and Illinois river basins, and forecast rainfall over the next two weeks to three months. More-than-expected rainfall could cause additional flooding over the area, while less-than-expected rainfall could keep rivers from reaching crests we consider likely. While drought conditions have improved considerably across the state of Missouri, the Missouri River basin upstream of Missouri continues to experience widespread persistent drought across most of the Great Plains into Montana, particularly across Kansas and Nebraska. Fortunately, the Great Plains welcomed significant snowfall this winter, a nice improvement over last winter`s snow drought. As a result, there is a fair amount of water content in place for melting across the basin, particularly across North Dakota and eastern South Dakota. Still, with below-normal flow in place along the Missouri for most of the winter, only minor flooding appears to be likely through early June. This is what we typically expect along the lower Missouri River. These minor flood probabilities range from 1 to 19 percent below historical norms. In the Mississippi River basin, the headwaters continue to have above normal snow water content on the ground across most of Minnesota and northern Wisconsin. But as the river winds south, snowpack disappears south of southeastern Minnesota and southern Wisconsin, though these areas are expecting signficant snowfall replenishment today. This snowpack combined with increased flow from recent precipitation has resulted in flood probabilities well above historical averages, making minor flooding a virtual certainty at all forecast points, and moderate flooding is likely at Quincy, from Saverton to Grafton, and at Chester. Moderate flood probabilities are between 12 and 37 percent above historical norms. With recent rainfall, soil moisture has returned to near-average levels across the St. Louis service area. This translates into near- average flood chances along most local streams in the St. Louis Service Area over the next 90 days. The primary exceptions to this rule would be for gages located adjacent to the Mississippi River, as backwater has a big impact at several locations. For the St. Louis service area, outlooks from the Climate Prediction Center indicate a likelihood of below-normal temperatures and near- normal precipitation for both the 6-10 day and the 8-14 day periods. For the next 3 months of April through June, the outlook favors a slightly higher likelihood of above-normal temperatures and above- normal precipitation. In Table 1 below, the current (CS) and historical (HS) or normal probabilities of exceeding minor, moderate, and major flood stages 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 more 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: 03/13/2023 - 06/11/2023 : 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 -------- ----- ----- ----- : --- --- --- --- --- --- :Mississippi River Canton 15.0 20.0 25.0 : 93 63 49 16 6 <5 LaGrange 17.0 23.0 25.0 : 91 53 25 9 8 <5 Quincy 19.0 22.0 26.0 : 91 56 63 28 26 9 Lock & Dam 21 18.0 21.0 25.0 : 91 55 62 27 26 9 Hannibal 17.0 22.0 24.0 : 92 60 48 14 26 9 Saverton 16.0 20.0 24.0 : >95 65 72 38 31 10 Louisiana 15.0 20.0 25.0 : >95 73 68 35 12 8 Clarksville 25.0 31.0 33.0 : >95 73 64 28 43 13 Winfield 26.0 30.0 34.0 : >95 67 74 42 26 9 Grafton 20.0 24.0 29.0 : >95 67 66 19 27 6 Mel Price LD 21.0 29.0 34.0 : 94 72 44 21 16 9 St. Louis 30.0 35.0 40.0 : 84 56 46 34 20 14 Chester 27.0 35.0 40.0 : 94 78 60 41 26 22 :North Fabius River Ewing 11.0 17.0 20.0 : 56 54 15 15 10 10 :Middle Fabius River Ewing 12.0 17.0 20.0 : 50 47 14 14 11 10 :South Fabius River Taylor 10.0 14.0 19.0 : 48 49 16 16 <5 <5 :North River Palmyra 13.0 16.0 22.0 : 26 26 11 11 <5 <5 :Mid Fork Salt River Holliday 17.0 22.0 26.0 : 56 51 <5 <5 <5 <5 :Salt River New London 19.0 25.0 27.0 : <5 <5 <5 <5 <5 <5 :Cuivre River Troy 21.0 25.0 29.0 : 53 53 21 22 7 7 Old Monroe 24.0 27.0 30.0 : 89 60 55 26 28 14 :Dardenne Creek St. Peters 18.0 20.0 23.0 : 34 34 25 25 7 7 :Meramec River Steelville 12.0 20.0 25.0 : 49 41 6 <5 <5 <5 Sullivan 11.0 20.0 29.0 : 72 66 17 12 <5 <5 :Bourbeuse River Union 15.0 22.0 26.0 : 52 50 11 11 <5 <5 :Meramec River Pacific 15.0 23.0 27.0 : 52 42 8 7 <5 <5 :Big River Byrnesville 16.0 20.0 28.0 : 55 49 22 22 <5 <5 :Meramec River Eureka 19.0 26.0 31.0 : 45 42 18 17 7 7 Valley Park 18.0 21.0 27.0 : 48 48 41 37 26 25 Fenton 23.0 29.0 32.0 : 59 50 27 24 17 14 Arnold 24.0 35.0 38.0 : 92 78 31 28 25 22 :Kaskaskia River Vandalia 18.0 24.0 26.0 : 83 83 33 36 18 18 Carlyle 16.5 23.0 27.0 : 60 76 <5 <5 <5 <5 :La Moine River Ripley 22.0 23.0 27.0 : 42 43 32 35 11 10 :Moreau River Jefferson City 17.0 25.0 29.0 : 72 75 50 50 30 28 :Maries River Westphalia 10.0 15.0 20.0 : 40 39 23 23 <5 <5 :Gasconade River Rich Fountain 20.0 25.0 30.0 : 39 40 25 25 10 10 :Missouri River Jefferson City 23.0 25.0 30.0 : 53 68 43 51 19 25 :Osage River St. Thomas 23.0 30.0 35.0 : 12 17 <5 <5 <5 <5 Mari-Osa Campgrou 19.0 22.0 25.0 : 48 60 29 31 16 22 :Missouri River Chamois 17.0 28.0 31.0 : 78 79 17 17 6 10 Hermann 21.0 26.0 33.0 : 75 79 32 48 21 21 Washington 20.0 28.0 31.0 : 54 73 21 21 17 19 St. Charles 25.0 30.0 36.0 : 55 74 23 25 9 14 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: 03/13/2023 - 06/11/2023 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Mississippi River Canton 14.8 16.5 17.1 20.0 22.1 23.8 25.1 LaGrange 15.7 17.4 18.0 20.9 23.0 24.7 26.0 Quincy 17.8 19.7 20.6 23.9 26.3 28.2 30.1 Lock & Dam 21 16.7 18.4 19.3 22.8 25.3 27.5 29.4 Hannibal 16.6 18.1 19.3 21.9 24.4 26.6 29.3 Saverton 16.2 18.2 19.5 22.4 24.8 26.7 28.7 Louisiana 16.4 18.0 19.3 21.6 23.6 25.3 27.4 Clarksville 26.6 28.4 29.8 32.2 34.2 35.6 37.2 Winfield 26.8 28.5 29.9 32.1 34.1 35.7 37.6 Grafton 20.3 22.4 23.0 25.6 29.1 30.7 34.5 Mel Price LD 20.3 22.6 24.7 27.8 31.0 36.9 38.2 St. Louis 23.4 27.5 30.7 34.8 38.7 44.9 46.6 Chester 24.4 28.2 32.6 37.0 40.5 47.6 48.4 :North Fabius River Ewing 6.9 7.0 8.9 11.3 14.9 19.9 22.6 :Middle Fabius River Ewing 5.9 6.7 8.6 11.9 15.3 20.2 22.3 :South Fabius River Taylor 5.3 6.1 7.7 9.9 13.0 16.3 18.4 :North River Palmyra 6.4 7.0 8.2 10.4 13.2 16.4 18.2 :Mid Fork Salt River Holliday 10.2 12.5 15.4 17.3 19.0 20.6 21.7 :Salt River New London 7.6 9.1 9.5 10.0 11.3 12.9 13.5 :Cuivre River Troy 11.6 12.7 16.8 21.8 24.7 27.3 29.2 Old Monroe 22.5 23.9 25.4 27.9 30.2 32.9 33.9 :Dardenne Creek St. Peters 7.7 8.8 10.5 15.1 20.3 22.2 23.9 :Meramec River Steelville 4.8 5.7 7.8 11.7 14.5 16.3 20.1 Sullivan 7.4 8.8 10.7 14.7 18.5 21.6 26.8 :Bourbeuse River Union 9.1 10.4 11.7 15.3 19.6 22.9 25.7 :Meramec River Pacific 8.7 9.2 11.2 15.1 18.6 22.3 26.6 :Big River Byrnesville 9.6 10.5 13.6 16.9 19.7 23.1 25.8 :Meramec River Eureka 11.8 12.1 15.0 17.9 24.1 29.7 36.0 Valley Park 12.3 13.8 15.3 17.8 27.2 37.2 40.9 Fenton 17.0 18.3 20.7 23.8 29.5 36.7 40.0 Arnold 21.9 25.4 28.2 32.2 38.0 42.0 44.5 :Kaskaskia River Vandalia 13.5 16.5 19.7 22.4 25.2 27.2 28.6 Carlyle 14.8 15.1 15.9 17.2 20.0 21.7 22.0 :La Moine River Ripley 12.4 13.9 17.2 20.4 24.3 27.3 28.4 :Missouri River Jefferson City 13.2 18.2 19.8 23.6 27.1 35.8 36.3 :Osage River St. Thomas 6.6 8.7 11.5 13.0 15.8 24.0 25.2 Mari-Osa Campgrou 9.9 14.4 16.3 19.0 22.6 28.2 31.6 :Missouri River Chamois 10.0 14.7 17.1 20.6 24.9 29.9 31.1 Hermann 14.3 18.7 20.9 24.7 29.1 35.0 35.9 Washington 12.1 15.4 17.4 20.8 24.6 31.7 34.1 St. Charles 18.8 21.5 23.1 25.4 29.2 35.9 37.0 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: 03/13/2023 - 06/11/2023 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Mississippi River Canton 9.2 8.8 7.7 7.0 5.8 4.5 3.8 LaGrange 10.1 9.7 8.6 7.9 6.7 5.4 4.7 Quincy 12.9 12.8 12.6 12.4 12.2 11.7 11.4 Lock & Dam 21 10.1 9.5 8.3 7.5 6.3 5.0 4.4 Hannibal 12.6 12.3 11.7 11.3 10.8 10.2 9.9 Saverton 10.0 9.4 8.5 7.9 7.0 5.9 5.2 Louisiana 12.1 12.1 12.1 12.0 12.0 11.9 11.9 Clarksville 20.6 19.7 19.0 18.4 17.1 15.7 14.8 Winfield 20.7 19.7 18.9 18.2 17.0 15.5 14.7 Grafton 15.9 15.7 15.6 15.6 15.4 15.3 15.3 Mel Price LD 13.9 13.2 11.6 10.5 9.2 8.9 8.5 St. Louis 14.8 13.9 12.2 10.4 8.8 8.2 7.3 Chester 17.0 15.9 14.7 13.0 11.9 10.6 9.6 :North Fabius River Ewing 3.8 3.7 3.6 3.5 3.4 3.2 3.2 :Middle Fabius River Ewing 3.2 3.2 3.1 3.0 2.9 2.8 2.8 :South Fabius River Taylor 1.4 1.3 1.2 1.1 1.0 0.9 0.7 :North River Palmyra 4.1 4.1 4.0 3.9 3.8 3.8 3.7 :Mid Fork Salt River Holliday 4.8 4.8 4.8 4.7 4.6 4.5 4.5 :Salt River New London 6.3 5.0 4.4 2.7 2.1 2.1 2.1 :Cuivre River Troy 6.5 6.2 6.1 5.8 5.6 5.5 5.5 Old Monroe 16.2 15.1 14.7 14.2 13.0 11.4 10.3 :Dardenne Creek St. Peters 2.0 1.9 1.8 1.7 1.6 1.5 1.5 :Meramec River Steelville 2.3 2.2 1.9 1.7 1.6 1.4 1.4 Sullivan 4.1 3.9 3.6 3.3 3.1 3.0 3.0 :Bourbeuse River Union 2.7 2.6 2.5 2.4 2.2 2.1 2.0 :Big River Byrnesville 3.7 3.4 2.8 2.5 2.2 2.0 1.9 :Meramec River Eureka 4.6 4.2 3.8 3.5 3.4 3.2 3.2 Fenton 6.9 5.8 4.6 3.6 2.5 1.9 1.8 Arnold 12.9 12.1 11.0 10.0 7.9 7.0 6.8 :Kaskaskia River Vandalia 7.9 6.6 4.2 3.1 2.9 2.7 2.7 Carlyle 14.7 14.7 12.1 5.5 5.5 5.5 5.5 :La Moine River Ripley 6.2 5.7 5.5 5.2 4.8 4.7 4.5 :Missouri River Jefferson City 6.1 5.8 4.4 3.1 2.3 2.1 2.1 :Osage River St. Thomas 3.8 3.8 3.1 2.5 2.5 2.0 1.5 :Missouri River Hermann 7.7 6.5 5.7 4.7 3.9 3.6 3.4 Washington 5.5 4.3 3.6 2.7 1.9 1.5 1.3 St. Charles 12.5 11.2 10.3 9.3 8.3 7.9 7.7 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/lsx for more weather and water information. The next outlook will be issued March 23rd. $$ Fuchs |