####018026634#### FGUS73 KILX 292015 ESFILX ILC009-017-025-033-057-079-095-101-113-123-125-129-137-143-147- 155-159-167-169-179-183-203-092200- PROBABILISTIC HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE Lincoln IL 215 PM CST Thu Feb 29 2024 ...2024 Spring Flood and Water Resources Outlook Number 2... ...Near normal to below normal likelihood for flooding across central and southeast Illinois this spring... This flood outlook covers the Lincoln Hydrologic Service Area (HSA) which encompasses 35 counties in central and southeast Illinois. It includes the following rivers... - Illinois River from Henry to Beardstown - Spoon River from London Mills to Seville - Mackinaw River at Congerville - Sangamon River from Monticello to Chandlerville - Salt Creek at Greenview - Little Wabash River near Clay City - Embarras River from Ste. Marie to Lawrenceville These flood outlooks are issued in late winter and early spring, in addition to the 7 day river forecasts that are issued when river forecast locations are in flood or are forecast to rise above flood stage. They are based on multi-season scenarios from more than 30 years of climatological data, current streamflows, soil conditions, snow pack, as well as short/long range weather forecasts. FLOOD OUTLOOK HIGHLIGHTS... - Risk of flooding this spring is near normal to below normal across central and southeast Illinois. - Factors limiting flood potential this spring include: near normal to below normal streamflows, no local or upstream snowpack, thawed soils, deep layer soil moisture deficits. - Springtime rains expected to be the primary driver for flooding. WINTER WEATHER REVIEW... --December-- Statewide Temperatures/Precipitation: Information, courtesy of the Illinois State Climatologist, shows that the preliminary statewide average December temperature was 39.2 degrees, 7.6 degrees above normal and the 3rd warmest on record going back to 1895. For the second time in three years, Illinois experienced an extremely mild December. All but three days were warmer than normal in Decatur, and several days in the second and fourth weeks of the month were 10 to 20 degrees warmer than normal. This was the 2nd warmest December in Rockford, the 3rd warmest in Peoria, and the 4th warmest in Chicago and Moline. None of the more than 120 NWS observing stations in Illinois recorded a low temperature in the single digits. Many places hit the freezing mark only a handful of nights. December average temperatures ranged from the low 30s in northern Illinois to the low 40s in southern Illinois, between 6 and 10 degrees above normal. The warmest place in the state was Du Quoin with an average December temperature of 46.1 degrees. The coolest was Stockton in Jo Daviess County with an average December temperature of 33.9 degrees. It is important to note that the nighttime low temperatures in December were much higher than normal. The preliminary average December minimum temperature is 32.2 degrees, which would be the 2nd highest on record statewide. The mild December weather broke 20 daily high maximum temperature records and 99 daily high minimum temperature records across Illinois! No daily low maximum or daily low minimum temperature records were broken. The preliminary statewide average total December precipitation was 2.99 inches, 0.56 inches above normal and the 30th wettest on record statewide. The first month of climatological winter brought a more active storm track to the Midwest than for most of the fall. December total precipitation ranged from just over 4 inches in parts of northern Illinois to less than 1 inch in parts of far southern Illinois. Most of northern Illinois was around 1 inch wetter than normal, while most of the state south of Interstate 64 was 1 to 3 inches drier than normal in December. As is often the case in milder Decembers, snowfall was hard to come by across Illinois. Total snowfall ranged from around 4 inches in far northwest Illinois to less than a tenth of an inch in southern Illinois. This was between 1 and 8 inches below normal. Local Temperatures/Precipitation/River Conditions: Temperatures for December were above normal across the ILX Hydrologic Service Area (HSA). They generally ranged from 7.5 degrees to 9 degrees above normal. Daily high temperatures ranged from the teens to the upper 60s. Normal highs for December typically range from the low 30s to the mid 40s. Low temperatures across the area ranged from the mid 30s to the low 50s. They typically range from the teens to the upper 20s. Rainfall totals across most of the ILX HSA were above normal for the month of December. However, far southeastern areas saw below normal precipitation. Monthly precipitation ranged from 1.68 inches in Hutsonville to 4.07 inches in Fisher. These totals ranged from 1.38 inches below normal to 1.62 inches above normal, respectively. This equates to roughly 55 to 165 percent of normal precipitation for the month. The above normal precipitation in northern Illinois allowed for drought improvement in those areas. In contrast, conditions worsened across southern sections of the state, due to below normal precipitation. While D0 (Abnormally Dry) and D1 (Moderate Drought) conditions improved overall, areas of D2 (Severe Drought) expanded from 6 percent to 19 percent month over month. This was most evident across portions of west-central Illinois as well as the southern third of the state. With low streamflows and below normal soil moisture conditions, the above normal December precipitation was not enough to cause flooding issues across central and southeast Illinois. U.S. Geological Survey (USGS) monthly average streamflow values for December show overall near normal streamflows across mainly the northern half of Illinois. Flows across the southern half of the state were overall in the below normal to much below normal categories. --January-- Statewide Temperatures/Precipitation: The Illinois State Climatologist notes that the preliminary statewide average January temperature was 25.7 degrees, 1.0 degree above normal and tied for the 57th coldest on record going back to 1895. The very mild December weather spilled over into the new year as the first 10 to 12 days of January had temperatures near to slightly above normal. Extremely cold air moved into Illinois following a series of winter storms and brought frigid weather across the state for the middle part of the month. Daily temperature departures from normal showed average temperatures were 10 to 30 degrees below normal. Some of the coldest temperatures from that week included -25 degrees in Altona and -19 degrees in Moline. Strong northerly and northwesterly winds added to the cold and pushed wind chills into the -30 to -40 degree range. Water main breaks were reported across the state, and several school districts closed for multiple days because of the cold. Numerous deaths in the state were attributed to the cold as well. Temperatures moderated in the final week of the month, providing a well-deserved break from an Arctic winter. January temperatures ranged from the low 20s in northern Illinois to the mid 30s in southern Illinois. The southern half of the state was 1 to 3 degrees colder than normal. Despite the extreme cold mid- month, northern Illinois was 1 to 2 degrees warmer than normal. The coldest point in the state in January was Stockton in Jo Daviess County at 20.1 degrees. The “warmest” point was Olmstead in Pulaski County at 32.7 degrees. The preliminary statewide average total January precipitation was 4.50 inches, 2.19 inches below normal and tied for the eighth wettest on record statewide. Precipitation was hard to come by for much of Illinois during the last few months of 2023. Drought impacts are usually minimal in winter, but there were many reports of unusually dry soils and low streams and ponds at the start of the new year. While January did not completely replenish all water lost last year, it took a big bite out of the drought. January total precipitation ranged from around 2.5 inches in northwest Illinois to nearly 10 inches in far southern Illinois. Everywhere in Illinois was wetter than normal in January, to the tune of 1 to 4 inches, between 150% and 300% of normal monthly precipitation. It was the eighth wettest January on record in Champaign and Centralia, both with over 5 inches total. Depending on where you are in Illinois, January is either the first or second snowiest month of the year. If you live north or west of the Illinois River, this was the case this past January. For the rest of Illinois, January just brought more cold rain. Total January snowfall ranged from less than half an inch in southern Illinois to over 25 inches in northwest Illinois. The latter was 4 to 15 inches above normal. Most of the snow in January came immediately ahead of or during the extreme cold in the middle of the month. Moline picked up more snowfall between January 8 and January 18 than in all of 2023. January was the second snowiest on record in Moline, only less than 2019. The 12th of January was also the second snowiest day on record in Moline, with 15.4 inches. It was only less than on January 3, 1971. The heavy snowfall in mid-January pushed the northwest corner of Illinois 1 to 6 inches above normal on season-to-date snowfall. Meanwhile, most of central and southern Illinois had 2 to 8 inches below normal snowfall by that time. Local Temperatures/Precipitation/River Conditions: Temperature averages for January were overall near normal across the ILX Hydrologic Service Area (HSA). Temperatures generally ranged from 1 degree below normal to 1 degree above. Daily high temperatures ranged from the single digits below zero to the mid 50s. Normal highs for January typically range into the low to mid 30s. Low temperatures across the area ranged from low teens below zero to the mid 30s. They typically range into the teens. Liquid precipitation totals across the ILX HSA were well above normal for the month of January. Monthly precipitation ranged from 2.87 inches in Mackinaw to 6.32 inches in Casey. These totals ranged from 0.70 to 3.07 inches above normal, respectively. This equates to roughly 130 to 195 percent of normal precipitation for the month. The above normal precipitation for January continued to erode drought coverage across the state. Only areas of D0 (Abnormally Dry) conditions remain across portions of southern and west-central Illinois. Drought coverage dropped from to 54 to 17 percent of the state. With the above normal precipitation, we did see minor to moderate river flooding. However, it was not widespread and began in the latter half of the month. Flooding was seen along the Illinois River, and portions of the Little Wabash and Sangamon rivers and largely continued into February. Bitterly cold temperatures mid-month caused appreciable ice development on area rivers. This was followed by a rapid warm-up along with widespread heavy rain. The frozen ground led to significant runoff, which caused area rivers to swell and mechanically break up the ice. The higher flows caused downstream movement of the ice. As a result, there were a few instances of ice jams along portions of the Mackinaw and Sangamon Rivers. Thankfully, impacts from these ice jams were minor and short-lived. USGS monthly streamflow for January shows overall near normal streamflows across mainly the southern half of Illinois as well as areas in the northwest. Flows across remainder of the state were overall in the above normal to much above normal categories. --February-- Local Temperatures/Precipitation/River Conditions: The month of February, has seen daily average temperatures that are well above normal. They generally ranged from around 8 to 12 degrees above average across the ILX Hydrologic Service Area (HSA). In contrast, precipitation for February has been well below normal... generally ranging from 1 to 2 inches below average. Overall, precipitation for the month ranged from 10 to 50 percent of normal. The below normal precipitation for February has caused worsening drought conditions across much of the Illinois. Some form of drought is now reflected for 80 percent of the state, according to the latest drought monitor. With the overall drier conditions, river flooding that carried over into February came to an end by the third week. Streamflows have continued to decline and currently range in the normal to below normal categories across central and southeast Illinois. SOIL MOISTURE AND FROST DEPTH CONDITIONS... Shallow soil moisture conditions across Illinois are near normal for this time of year. However, deep layer soil conditions (down to 39 inches) continue to show an appreciable deficit across nearly the entire state. Drought conditions in Illinois have notably improved through the winter season as a whole. The drought recovery is thanks to overall above normal temperatures that minimized periods of frozen soils in addition to precipitation that fell in form of rain. In late November, nearly 40 percent of Illinois was experiencing D0 (Abnormally Dry) conditions with about 40 percent in the D1 (Moderate Drought) category...or worse. Only pockets of D0 conditions remained by mid-February, covering portions of west-central and southern Illinois and encompassing only about 20 percent of the state. Since then, conditions have been overall dry. As a result, drought conditions have expanded significantly across Illinois. The February 29th Drought Monitor issuance now shows nearly 75 percent of the state within the D0 (Abnormally Dry) category with an additional 7 percent in the D1 (Moderate Drought) category. With overall above normal temperatures this winter, frost was afforded little opportunity to develop or persist across the area. One exception was the Arctic outbreak we had in mid-January. That stretch of frigid temperatures caused frost to develop down to 6 to 10 inches across our service area. However, the return to above normal temperatures quickly thawed the soils across the area. As of this issuance, Illinois remains free of frost. Frost is not a concern going forward into the spring. The lack of frost will allow for deeper infiltration of rainfall into the soil. As a result, runoff potential will be reduced until soils moisten up more thoroughly. If we get into a longer duration, wet weather pattern then runoff potential and risk of flooding can increase with time. RIVER CONDITIONS... As of this issuance, there is no river flooding that is currently impacting Illinois. Information, courtesy of the U.S. Geological Survey (USGS), shows that streamflow conditions are overall near normal across most of northern and central Illinois. In contrast, portions of central and most of southern Illinois are in the below normal to much below normal categories. Thanks to the above normal temperatures the past few weeks, river ice is not currently present on area rivers. With above normal temperatures continuing as we head into the spring, ice jam flooding will not be a concern. WEATHER OUTLOOKS... The weather pattern over the next 2 weeks will be somewhat active and will bring a couple opportunities for precipitation across Illinois over that time. As we look toward this weekend and into next week, high temperatures will generally range into the 50s and 60s with lows well above freezing. The next best chance for widespread precipitation comes early to mid-next week. The warm temperatures should allow this to fall mainly as rain across central and southeast Illinois. The 8 to 14 day outlook (Mar 7 to Mar 13) favors above normal temperatures in Illinois with the highest likelihood across the northern half of the state. Above normal precipitation is also favored across Illinois over the same time period. The most recent outlook for this spring (March / April / May) favors above normal temperatures across Illinois with the highest likelihood across far northeastern portions of the state. As for precipitation, most of Illinois is favored for above normal precipitation this spring with the highest likelihood across the southern third of the state. FLOOD OUTLOOK SUMMARY... The risk of flooding this spring is near normal to below normal across central and southeast Illinois. Any flooding that does occur would most likely be in the minor category with isolated moderate flooding possible. Currently, there is no river flooding that is impacting Illinois as streamflows are currently near normal to below normal. Soils are thawed with shallow moisture conditions near normal. However, deeper soils continue to show an appreciable deficit. As a whole, these conditions are not contributory toward enhanced flood potential this spring. Spring rains will be the primary driver of flooding this year since other hydrometeorological conditions are not significant contributing factors. Again, expectations are for isolated minor to moderate flooding this spring. However, if we get into a very wet springtime pattern then more widespread flooding is possible, but would most likely be minor in severity. -------------------------------------------------------------------- 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 -------- ----- ----- ----- : --- --- --- --- --- --- :Illinois River Henry 23.0 24.0 31.0 : 54 56 42 52 <5 <5 Peoria 18.0 22.0 28.0 : 64 66 28 36 <5 <5 Peoria L/D 447.0 449.0 455.0 : 52 59 31 38 <5 <5 Havana 14.0 17.0 23.0 : 82 84 63 62 9 22 Beardstown 14.0 18.0 28.0 : 76 79 52 60 <5 7 :Mackinaw River Congerville 13.0 14.0 20.0 : 19 21 14 16 <5 <5 :Spoon River London Mills 15.0 21.0 24.0 : 43 47 6 5 <5 <5 Seville 22.0 25.0 30.0 : 35 40 19 17 <5 <5 :Sangamon River Monticello 13.0 17.0 20.0 : 61 70 5 6 <5 <5 Riverton 23.0 26.0 29.0 : 14 12 <5 <5 <5 <5 Petersburg 23.0 24.0 33.0 : 21 24 17 15 <5 <5 :Salt Creek Greenview 16.0 17.0 20.0 : 15 17 11 11 <5 <5 :Sangamon River Oakford 471.0 472.9 478.5 : 26 38 17 19 <5 <5 Chandlerville 456.6 459.0 462.0 : 42 49 19 23 <5 <5 :Embarras River Lawrenceville 30.0 37.0 41.0 : 70 75 23 19 <5 <5 Ste. Marie 19.0 20.0 27.0 : 35 35 24 23 <5 <5 :Little Wabash River Clay City 18.0 22.0 25.0 : 85 85 18 21 <5 <5 :Vermilion River Danville 18.0 22.0 28.0 : 15 23 5 12 <5 <5 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% -------- ------ ------ ------ ------ ------ ------ ------ :Illinois River Henry 16.4 16.7 20.3 23.3 25.8 27.3 28.9 Peoria 13.0 13.2 16.1 19.7 22.3 23.6 25.5 Peoria L/D 436.1 436.5 443.6 447.1 449.8 450.9 452.9 Havana 11.0 12.5 15.0 18.1 21.3 22.8 25.5 Beardstown 11.2 12.0 14.3 18.2 22.9 25.4 27.3 :Mackinaw River Congerville 3.8 4.3 6.2 9.3 11.7 14.9 16.3 :Spoon River London Mills 5.4 6.3 9.8 13.1 18.4 20.3 22.1 Seville 9.7 10.4 14.7 17.5 24.4 26.6 27.9 :Sangamon River Monticello 9.0 9.9 12.1 13.5 14.8 16.1 17.0 Riverton 9.3 12.3 16.2 18.5 21.1 23.2 25.9 Petersburg 8.1 10.4 13.7 16.6 21.0 24.9 27.3 :Salt Creek Greenview 4.3 4.9 7.7 10.5 12.5 17.4 20.0 :Sangamon River Oakford 460.1 461.9 464.7 468.2 471.6 473.9 475.5 Chandlerville 447.5 449.5 452.3 455.7 458.5 460.5 461.8 :Embarras River Lawrenceville 24.6 26.3 29.4 32.6 36.7 38.8 39.5 Ste. Marie 6.6 9.2 12.5 17.7 19.9 21.4 22.9 :Little Wabash River Clay City 16.4 17.3 19.6 20.8 21.6 22.4 23.7 :Vermilion River Danville 6.9 8.2 10.1 12.1 15.3 19.4 22.3 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% -------- ------ ------ ------ ------ ------ ------ ------ :Illinois River Henry 15.3 15.2 15.0 14.9 14.7 14.5 14.3 Peoria 12.4 12.3 12.1 12.0 11.6 10.6 10.6 Peoria L/D 434.2 433.9 432.9 432.1 431.2 430.6 429.9 Havana 7.4 7.1 6.3 5.6 5.0 4.9 4.8 Beardstown 10.7 10.3 10.2 9.9 9.7 9.3 9.1 :Mackinaw River Congerville 1.9 1.7 1.5 1.4 1.2 1.0 1.0 :Spoon River London Mills 3.7 3.3 3.0 2.8 2.4 2.0 1.8 Seville 7.0 6.6 6.4 6.0 5.6 5.2 5.0 :Sangamon River Monticello 7.0 6.8 6.4 6.1 5.7 5.2 4.9 Riverton 6.5 6.1 5.7 5.1 4.4 4.0 3.8 Petersburg 6.8 6.7 6.2 5.8 5.4 5.3 5.2 :Salt Creek Greenview 2.2 2.0 1.9 1.6 1.4 1.1 1.0 :Sangamon River Oakford 458.4 458.1 457.7 457.4 456.9 456.5 456.4 Chandlerville 445.8 445.5 445.1 444.8 444.3 443.9 443.8 :Embarras River Lawrenceville 18.7 18.4 17.8 17.7 17.6 17.4 17.1 Ste. Marie 2.7 2.6 2.2 2.1 2.0 1.7 1.4 :Little Wabash River Clay City 6.6 5.8 4.8 4.7 4.6 4.4 4.2 :Vermilion River Danville 3.7 3.6 3.5 3.3 3.2 3.0 2.9 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. -------------------------------------------------------------------- FLOOD TERMINOLOGY... Minor flooding is used to indicate minimal or no property damage. However, some public inconvenience is possible. Moderate flooding is used to indicate some inundation of structures and roads near the river. Transfer of property to a higher elevation or another location may be necessary. Some evacuations may also be required. Major flooding is used to indicate extensive inundation and property damage, usually characterized by the evacuation of people and livestock and closure of both primary and secondary roads. FOR MORE INFORMATION... Visit our web page at www.weather.gov/ilx for more official NWS river and weather information. To view graphical AHPS information, including forecasts, select Rivers and Lakes from along the top menu bar. Full AHPS graphics are available for all forecast points in the ILX Hydrologic Service Area. For 30 to 90 day temperature and precipitation outlooks, visit the web page of the Climate Prediction Center at www.cpc.ncep.noaa.gov. The third and final issuance of the Spring Flood Outlook for central and southeast Illinois will be on Thursday, March 14th. The NOAA National Spring Flood Outlook will be issued on Thursday, March 21st. $$ DRH