####018018391#### FGUS73 KLOT 292041 ESFLOT ILC007-011-031-037-063-075-089-091-093-097-099-103-105-111- 141-197-201-INC073-089-111-127-271700-DDHHMM- PROBABILISTIC HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE Chicago/Romeoville IL 240 PM CST Thu Feb 29 2024 ...2024 Spring Flood and Water Outlook Number 2... ...Locations Covered by this Outlook... This outlook is for rivers and streams within the National Weather Service Chicago Hydrologic Service Area (HSA). The Chicago HSA covers most of northeastern Illinois and a portion of far northwestern Indiana. This includes the Illinois River downstream to just below La Salle, and numerous Illinois River tributaries including the Fox, DuPage, Des Plaines, Calumet, Iroquois, Kankakee, and Vermilion Rivers. This also includes the Rock River from near Rockton downstream to near Dixon, and Rock River tributaries including the Pecatonica and Kishwaukee Rivers. This outlook covers the time period from early March through late May. ...Outlook Brief Summary... Based on current conditions, the risk of flooding ranges from below average to near average across the area. Weather patterns over the next several weeks may change the risk of flooding in later outlooks. ...Risk Factors for Spring Flooding... To determine the relative risk of spring flooding, numerous factors are considered including snow cover, soil moisture, and current river conditions. Snow cover with a high water content can increase the chance of flooding as melting changes the snow to liquid. High soil moisture conditions can increase the chance of flooding by reducing the amount of water that infiltrates into the ground. Above average river levels can increase the chance for flooding because lower amounts of water would be required to reach flood stage. ...Snow Cover and Liquid Water Equivalent... Current snow cover across area river basins is generally near 0 inches, which contains near 0 inches of liquid water equivalent. The only snow cover across the area exists in the upper portions of the Rock River and Kankakee River basins, but is minimal. ...Soil Moisture and Frost Depth... Current soil moisture values across the area are generally near average. Frost depth is near 0 inches across all area river basins. ...Current River Conditions... River levels across the area are generally near average. River ice spotters, river gauges, and satellite imagery indicate no river ice exists on area rivers. The risk of ice jam related flooding is very low this spring based upon current conditions. ...Fall 2023 Weather Summary... Temperatures were near average to above average across northeastern Illinois and northwestern Indiana during fall 2023. Temperatures were 1-2F above average in far northern and northwestern Illinois, with other areas generally within 1F of average. Precipitation was near average in northeastern Illinois and northwestern Indiana during fall 2023. Almost all areas were within 3 inches of average. ...Winter 2023-2024 Weather Summary... Temperatures for winter 2023-2024 through early February have averaged about 5F to 9F above average in northeastern Illinois and northwestern Indiana. Most days have been near average to above average, with one notable period of significant cold weather observed in mid-January. Precipitation in winter 2023-2024 through early February has ranged from 0 inches to 3 inches above average in northeastern Illinois and northwestern Indiana. The first measurable snowfall (>0.1 inches) across northeastern Illinois and northwestern Indiana occurred near the average date, within a range from late October to early November for most areas. Season-to-date snowfall ranges were from about 6 inches to about 24 inches across northeastern Illinois and northwestern Indiana, with the highest snow totals in southern Wisconsin and far northwestern Illinois. Observed snowfall was generally near average in northern Illinois and below average in northwestern Indiana and near the Lake Michigan shore ...Spring Weather Outlook... The long term (next couple months) outlook from the Climate Prediction Center indicates above average temperatures likely during the first several weeks of months. There is a slight signal for above average precipitation during this period. Although snow cover, soil moisture, and recent river levels can provide some indication of the relative risk of spring flooding, any weather system that produces heavy rainfall could cause flooding. Spring flood outlooks are not able to assess the risk of flooding due to heavy rainfall more than a week or so in advance. ...Detailed Flood Outlook... 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: 03/04/2024 - 06/02/2024 : 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 -------- ----- ----- ----- : --- --- --- --- --- --- :Pecatonica River Shirland 12.0 14.0 15.5 : 22 35 <5 14 <5 <5 :Rock River Rockton 10.0 11.0 14.0 : 16 35 13 22 <5 8 Latham Park 9.0 11.0 13.5 : 17 36 8 15 <5 7 Rockford (Auburn 6.0 8.5 10.0 : <5 10 <5 <5 <5 <5 :Kishwaukee River Belvidere 9.0 10.0 12.0 : 7 12 <5 7 <5 <5 :SB Kishwaukee River DeKalb 10.0 11.0 12.5 : <5 10 <5 <5 <5 <5 :Kishwaukee River Perryville 12.0 18.0 22.0 : 24 36 <5 <5 <5 <5 :Rock River Byron 13.0 14.0 16.0 : 11 17 8 14 <5 9 Dixon 16.0 18.0 20.0 : 6 13 <5 7 <5 <5 :North Branch Chicago River Chicago (Pulaski 18.0 20.0 21.0 : <5 <5 <5 <5 <5 <5 :Des Plaines River Russell 7.0 9.0 10.0 : 27 41 <5 8 <5 6 Gurnee 7.0 9.0 11.0 : 31 37 5 10 <5 <5 Lincolnshire 12.5 14.0 15.5 : 18 21 6 11 <5 8 Des Plaines 15.0 18.0 19.0 : 22 26 6 9 <5 <5 River Forest 16.0 17.5 18.5 : <5 <5 <5 <5 <5 <5 Riverside 7.5 8.0 9.0 : 18 20 8 12 <5 <5 Lemont 10.0 13.0 15.0 : 46 46 <5 <5 <5 <5 :WB Du Page River Warrenville 11.5 14.5 17.5 : 14 17 <5 <5 <5 <5 :East Branch Du Page River Bolingbrook 20.0 22.0 24.0 : <5 6 <5 <5 <5 <5 :Du Page River Plainfield 12.0 14.0 15.0 : <5 5 <5 <5 <5 <5 Shorewood 15.5 17.5 19.5 : 30 32 9 10 <5 <5 :Fox River Algonquin Lock & 9.5 10.5 12.0 : 31 48 14 25 5 13 Montgomery 13.5 15.0 16.0 : 8 14 <5 <5 <5 <5 Dayton 12.0 14.0 24.0 : 37 46 14 15 <5 <5 :Kankakee River Dunns Bridge 10.0 12.0 13.0 : 17 30 <5 7 <5 6 Shelby 10.5 11.5 12.5 : 37 49 14 25 9 15 Momence 5.0 6.5 9.0 : 23 30 10 10 <5 <5 :Iroquois River Rensselaer 12.0 14.0 15.0 : 24 30 7 9 6 7 Foresman 18.0 22.0 24.0 : 30 35 5 <5 <5 <5 Iroquois 18.0 24.0 25.0 : 62 63 <5 <5 <5 <5 :Sugar Creek Milford 18.0 22.0 26.0 : 49 49 13 16 <5 <5 :Iroquois River Chebanse 16.0 18.0 20.0 : 15 14 6 8 <5 6 :Kankakee River Wilmington 6.5 8.0 10.0 : 16 18 7 7 <5 <5 :Mazon River Coal City 12.0 16.0 19.0 : 18 19 <5 <5 <5 <5 :Vermilion River Pontiac 14.0 15.0 18.0 : 10 12 9 9 <5 <5 Leonore 16.0 21.0 26.0 : 35 34 11 14 <5 <5 :Hart Ditch Dyer 12.0 13.0 14.0 : <5 <5 <5 <5 <5 <5 :Thorn Creek Thornton 9.0 14.0 15.5 : 19 20 <5 <5 <5 <5 :Little Calumet River Munster (Hohman A 12.0 14.0 17.0 : 46 52 15 20 8 9 South Holland 16.5 18.0 20.0 : <5 <5 <5 <5 <5 <5 :Illinois River Morris 16.0 18.0 22.0 : 28 35 21 25 10 10 Ottawa 463.0 467.0 471.0 : 32 36 14 14 <5 <5 La Salle 20.0 27.0 31.0 : 72 72 17 18 <5 6 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: 03/04/2024 - 06/02/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Pecatonica River Shirland 6.7 7.5 8.0 9.9 11.8 12.5 13.6 :Rock River Rockton 5.4 5.7 6.5 7.8 9.3 11.1 12.8 Latham Park 5.3 5.5 5.9 7.1 8.5 10.3 12.2 Rockford (Auburn 3.0 3.0 3.1 3.2 3.5 4.6 5.8 :Kishwaukee River Belvidere 2.5 3.0 4.1 5.5 7.3 8.4 9.5 :SB Kishwaukee River DeKalb 4.1 4.7 5.7 7.0 8.3 9.4 9.8 :Kishwaukee River Perryville 7.1 7.8 8.8 10.4 11.9 13.4 14.9 :Rock River Byron 7.3 7.9 8.4 10.0 11.3 13.1 14.5 Dixon 9.6 10.0 10.5 11.9 13.0 15.5 16.4 :North Branch Chicago River Chicago (Pulaski 12.6 12.9 13.9 14.8 15.8 17.0 17.6 :Des Plaines River Russell 4.5 4.9 5.7 6.5 7.1 7.7 8.9 Gurnee 3.0 3.9 4.8 5.9 7.2 8.1 9.3 Lincolnshire 7.4 8.1 9.2 10.1 11.8 13.4 14.7 Des Plaines 9.7 10.2 12.0 13.2 14.9 17.0 18.1 River Forest 6.7 7.2 9.8 11.3 13.1 14.5 15.4 Riverside 3.6 4.0 5.1 6.2 7.1 7.9 8.3 Lemont 7.0 7.5 8.8 9.8 10.7 11.6 12.0 :WB Du Page River Warrenville 8.9 9.1 9.7 10.5 11.2 11.6 11.8 :East Branch Du Page River Bolingbrook 16.6 16.9 17.5 18.0 18.8 19.2 19.6 :Du Page River Plainfield 8.2 8.3 8.8 9.7 10.5 11.1 11.6 Shorewood 11.7 12.2 12.7 13.8 15.3 16.4 17.2 :Fox River Algonquin Lock & 6.3 7.0 7.8 8.9 9.8 10.7 12.2 Montgomery 11.8 12.0 12.4 12.8 13.1 13.4 13.6 Dayton 7.5 8.3 9.7 11.5 12.5 14.9 15.5 :Kankakee River Dunns Bridge 6.0 6.5 7.5 8.4 9.5 10.2 10.7 Shelby 7.2 7.8 8.8 9.9 10.9 12.2 13.4 Momence 2.8 3.0 3.5 4.2 4.8 6.4 7.9 :Iroquois River Rensselaer 6.7 7.8 9.6 10.8 11.9 13.1 17.9 Foresman 12.3 13.3 15.2 16.9 18.3 19.6 22.1 Iroquois 13.9 14.4 16.8 18.8 21.0 22.2 23.5 :Sugar Creek Milford 10.6 13.8 16.6 17.9 20.0 22.8 24.6 :Iroquois River Chebanse 7.8 9.1 10.2 12.3 14.9 16.4 19.4 :Kankakee River Wilmington 3.0 3.2 4.1 4.9 5.9 7.2 8.6 :Mazon River Coal City 3.8 5.4 7.5 10.0 11.3 13.4 13.9 :Vermilion River Pontiac 5.2 6.0 7.3 9.6 11.6 14.0 17.5 Leonore 7.7 8.8 10.9 14.0 17.8 21.1 24.2 :Hart Ditch Dyer 3.9 4.1 4.8 5.7 6.7 7.8 8.8 :Thorn Creek Thornton 4.7 5.2 6.2 7.2 8.7 10.2 12.6 :Little Calumet River Munster (Hohman A 9.4 9.9 10.6 11.7 13.4 15.7 18.6 South Holland 9.1 9.7 10.8 12.2 13.9 14.9 15.5 :Illinois River Morris 6.9 8.1 10.9 13.8 16.7 21.9 23.4 Ottawa 459.0 459.2 460.2 461.8 463.7 468.2 469.5 La Salle 13.9 15.6 19.4 22.8 25.7 29.1 30.3 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: 03/04/2024 - 06/02/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Pecatonica River Shirland 6.5 6.2 5.6 4.9 4.5 4.3 4.0 :Rock River Rockton 5.5 5.2 4.5 3.8 3.4 3.0 2.8 Latham Park 5.4 5.2 4.9 4.6 4.4 4.1 4.0 Rockford (Auburn 3.0 2.9 2.8 2.6 2.5 2.4 2.3 :Kishwaukee River Belvidere 1.8 1.8 1.6 1.5 1.2 1.1 1.0 :SB Kishwaukee River DeKalb 3.3 3.3 3.2 3.2 3.1 3.0 3.0 :Kishwaukee River Perryville 6.3 6.2 6.1 5.9 5.7 5.5 5.3 :Rock River Byron 7.2 6.9 6.5 6.0 5.6 5.2 5.1 Dixon 9.5 9.2 8.8 8.4 8.1 7.8 7.7 :North Branch Chicago River Chicago (Pulaski 11.1 11.0 11.0 10.9 10.8 10.7 10.7 :Des Plaines River Russell 3.2 3.1 3.0 2.8 2.7 2.5 2.4 Gurnee 2.2 2.1 1.9 1.8 1.6 1.3 1.2 Lincolnshire 6.9 6.7 6.6 6.4 6.2 6.0 5.9 Des Plaines 8.7 8.6 8.4 8.3 8.1 7.9 7.7 River Forest 4.6 4.4 4.0 3.7 3.2 2.9 2.6 Riverside 2.5 2.4 2.2 2.1 1.9 1.7 1.6 Lemont 5.9 5.8 5.6 5.4 5.2 5.0 4.8 :WB Du Page River Warrenville 7.6 7.6 7.5 7.5 7.4 7.3 7.3 :East Branch Du Page River Bolingbrook 14.5 14.5 14.4 14.3 14.2 14.1 14.1 :Du Page River Plainfield 6.8 6.8 6.7 6.7 6.6 6.6 6.5 Shorewood 10.4 10.3 10.2 10.2 10.1 10.1 10.0 :Fox River Algonquin Lock & 6.1 5.8 5.4 5.1 4.7 4.6 4.6 Montgomery 11.7 11.5 11.4 11.3 11.1 11.1 11.0 Dayton 6.7 6.5 6.1 5.9 5.5 5.3 5.2 :Kankakee River Dunns Bridge 4.3 4.1 4.0 3.7 3.3 3.0 2.8 Shelby 5.9 5.8 5.5 5.3 4.8 4.5 4.2 Momence 2.2 2.1 2.0 1.9 1.7 1.6 1.5 :Iroquois River Rensselaer 4.9 4.8 4.6 4.3 4.1 3.9 3.7 Foresman 7.4 7.3 6.9 6.4 5.9 5.6 5.2 Iroquois 8.7 8.4 7.6 7.0 6.4 5.9 5.2 :Sugar Creek Milford 4.1 4.0 3.8 3.6 3.5 3.3 3.1 :Iroquois River Chebanse 4.5 4.4 4.0 3.7 3.4 3.2 2.8 :Kankakee River Wilmington 2.1 2.0 1.9 1.7 1.6 1.5 1.3 :Mazon River Coal City 1.9 1.9 1.8 1.6 1.4 1.2 0.6 :Vermilion River Pontiac 3.6 3.5 3.4 3.3 3.1 3.0 2.8 Leonore 4.5 4.4 4.3 4.1 3.9 3.7 3.4 :Hart Ditch Dyer 2.1 2.0 2.0 1.9 1.9 1.8 1.8 :Thorn Creek Thornton 3.0 2.9 2.9 2.9 2.8 2.8 2.7 :Little Calumet River Munster (Hohman A 5.7 5.7 5.6 5.5 5.4 5.3 5.3 South Holland 5.8 5.7 5.6 5.5 5.4 5.3 5.3 :Illinois River Morris 5.3 5.2 5.1 5.0 4.9 4.8 4.7 Ottawa 458.7 458.7 458.6 458.6 458.5 458.5 458.5 La Salle 12.0 11.9 11.6 11.4 11.1 10.9 10.7 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/lot for more weather and water information. The next outlook will be issued $$