852 FGUS73 KILX 271915 ESFILX ILC009-017-025-033-057-079-095-101-113-123-125-129-137-143-147- 155-159-167-169-179-183-203-281915- Probabilistic Hydrologic Outlook National Weather Service Lincoln IL 115 PM CST Thu Feb 27 2020 ...2020 Spring Flood and Water Resources Outlook Number 2... ...Above normal potential for flooding this spring along portions of the Illinois and Embarras rivers with near normal likelihood across the remainder of central and southeast Illinois... 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... - Above normal likelihood for flooding this spring along portions of the Illinois and Embarras rivers...near normal across the remainder of central and southeast Illinois. - Locations that typically flood in the spring will have similar likelihood this season. - Current soil moisture greater than 95th percentile is a concern for runoff. - Current streamflows are above normal to much above normal across central and southern Illinois. - Minimal to no frost depth across central and southern Illinois is of benefit if conditions allow for drying. - Below normal temperatures with below normal precipitation favored in March. - Any significant flooding will be primarily driven by spring rains. WINTER WEATHER REVIEW... --December-- Statewide Temperatures/Precipitation: Information, courtesy of the Illinois State Climatologist, shows that December temperatures were well above the long-term average across Illinois, breaking dozens of local daily maximum and minimum temperature records. The statewide December average temperature was 35.2 degrees, about 5 degrees above normal and the 18th warmest on record. December was drier than average for most of the state. The statewide average precipitation total was 2.03 inches, 0.66 inches below the 30-year normal. Temperatures during the first half of December were very close to average. This was followed by a brief period of well below average temperatures. On December 20th, southwesterly flow brought warm, dry air into the region. Temperatures between December 20 and 29 ranged from 5 to 25 degrees above normal across the state. In total, 104 daily high maximum temperature records and 27 daily high minimum temperature records were broken over this time period, including a few dozen records on December 25. In fact, it was the warmest Christmas day at 68 stations across the state. A shift in the upper atmosphere and the passage of a cold front late in the month allowed temperatures to moderate. December average temperatures ranged from the low 30s in northern Illinois to the mid-40s in southern Illinois. Monthly average temperature departures ranged from 7 degrees above the long-term mean in northwestern Illinois to just over 1 degree above average in south-central Illinois. December precipitation was below the long-term average for the entire state. Areas in far southern Illinois received 2 to 3 inches less than average in December, approximately 50 percent of normal December precipitation. The statewide average total precipitation was 2.03 inches, approximately 0.66 inches below normal for the month. This was the 50th driest December on record in Illinois and marked the second straight month of below average statewide precipitation. Preexisting wetness and reduced evaporative demand, typical for this time of the year, prevented impacts from the prolonged dry conditions. December snowfall totals ranged from less than a tenth of an inch in far southern Illinois to over 10 inches in south-central Illinois. A strong system came through mid-month and brought several inches of snow to an area spanning the St. Louis Metro East to the Champaign- Urbana area. The December snowfall glut in south-central Illinois turned into snowfall deficits of 8 to 10 inches in northern Illinois. Local Temperatures/Precipitation: Temperatures for December averaged well above normal across the ILX Hydrologic Service Area (HSA). They generally ranged from 3 to 6 degrees above normal. Daily high temperatures ranged from the mid- 20s 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 single digits to the low 50s in December. They typically range from the teens to the upper 20s. Liquid precipitation totals across the ILX HSA were below normal. Monthly precipitation ranged from 0.75 inches in Champaign to 3.36 inches in Olney. These totals ranged from 1.77 to 0.52 inches below normal, respectively. This equates to precipitation that ranged from 30 to 87 percent of normal. Minor flooding was observed across portions of the Little Wabash and Embarras Rivers. However, this came to an end the first week of December. Renewed flooding along the Little Wabash River came at the very end of the month and continued into January. U.S. Geological Survey (USGS) monthly average streamflow values for December were in the normal to above normal range overall across most of the state. The main exceptions were in northwest Illinois and along portions of the Mississippi River, where streamflows were much above normal for the month. --January-- Statewide Temperatures/Precipitation: The Illinois State Climatologist notes that our first month of 2020 was quite a bit warmer and wetter than average across the state. The statewide average January temperature was 31.4 degrees, 5 degrees above the 30-year normal and the 17th warmest on record going back to 1895. The statewide average total January precipitation was 4.41 inches, 2.34 inches above the 30-year normal and the 9th wettest on record. Following a warmer than average December, temperatures remained persistently above average for the first half of January, with only a short cold air incursion between Jan. 15 and 23. January average temperatures ranged from the mid-20s in northern Illinois to the high 30s in southern Illinois, and were 2 to 7 degrees above average across the state. January total precipitation was above normal across the state, with monthly precipitation totals ranging from 2 inches in northwestern Illinois to nearly 8 inches in south-central Illinois. The highest accumulation was along the Interstate 70 corridor between the St. Louis Metro East and Effingham. This region experienced nearly 300 percent of its average January total precipitation. As with most of the wettest parts of the state, most of the January precipitation fell in just three days. Much of this was the result of a single winter storm that moved through the Midwest between the 9th and 12th. Snowfall totals in January ranged from less than a tenth of an inch in southern Illinois to over 12 inches in northwestern Illinois. There was a strong southeast-to-northwest January snowfall gradient across the state, resulting from a similar gradient in air temperature. The highest monthly snowfall total was 15 inches in both Stephenson and Bureau Counties. Rockford experienced the highest 1-day snowfall maximum across the state with 6 inches on Jan. 25. Local Temperatures/Precipitation: Temperatures for January averaged well above normal across the ILX Hydrologic Service Area (HSA). They generally ranged from 5 to 7 degrees above normal. Daily high temperatures ranged from the low teens to the low 60s. Normal highs for January range into the low to mid 30s. Low temperatures across the area ranged from the single digits to the low 50s this month. They typically range into the teens. Liquid precipitation totals across the ILX HSA were well above normal. Monthly precipitation ranged from 2.58 inches in Galesburg to 7.59 inches in Beecher City. These totals ranged from 1.07 to 5.09 inches above normal, respectively. This equates to precipitation that roughly ranged from 170 to 300 percent of normal. There was more widespread river flooding across central and southeast Illinois than had been seen in recent months. We saw minor flooding along portions of the Illinois, Sangamon, Little Wabash and Embarras rivers. However, many other locations saw rises to near- flood levels. USGS monthly average streamflow values for January reflected the above normal precipitation. Overall, values ranged from above normal to much above normal throughout the state. --February-- The month of February, to this point, has seen average temperatures that have ranged from around 1 to 3 degrees above normal across the ILX Hydrologic Service Area. Thus far, precipitation has been variable across the area, but overall near normal. We have ranges from 1.15 inches below normal in Champaign to 1.61 inches above normal in Springfield. As of this issuance, there is minor flooding along portions of the Illinois and Little Wabash rivers. The most recent storm brought rain and a wintery mix of precipitation across the state. A light amount of snow, ranging from 1 to 3 inches, was left behind. However, it will not stick around long...as temperatures are forecast to push into 40s and 50s this weekend into early next week. The recent precipitation and coming snowmelt runoff will keep local rivers and streams elevated in the short term, but will not be of significant impact to central and southeast Illinois. SOIL MOISTURE AND FROST DEPTH CONDITIONS... Soil moisture conditions across Illinois remain well above normal... and greater than the 95th percentile for this time of year. As such, drought conditions in Illinois are not currently a concern and have been non-existent since November 2019. As of the latest Drought Monitor issuance, there continues to be no drought conditions noted in Illinois. The longer duration of above normal temperatures and minimal snowpack has resulted in little, if any, frost across central and southeast Illinois. However, frost depths of up to 8 inches have been reported across northern sections of the state. As we head into spring, the saturated soils will be a significant contributing factor to flood potential. However, thawed soils are of benefit, if optimal conditions allow for some drying. Temperature outlooks over the next 2 weeks continue to favor a warmer than normal trend. Precipitation outlooks favor above normal precipitation... trending to near normal later in the period. Therefore, significant drying is not likely to occur in the short term. RIVER CONDITIONS... As mentioned, there is minor flooding occurring along the Illinois River from Havana to Beardstown and along the Little Wabash River near Clay City. Recent precipitation and coming snowmelt runoff will not significantly impact area rivers and streams. Information, courtesy of the U.S. Geological Survey (USGS), shows near normal streamflows across northern Illinois. However, streamflows across central and southern sections of the state remain in the above normal to much above normal range. There is concern for the next weather system moving through next week. It looks to be warm enough to be all rain, focusing across mainly the southern half of the state. This could cause additional flooding, especially along the Little Wabash and Embarras rivers. WEATHER OUTLOOKS... The latest forecast for Illinois calls for above normal temperatures into the 50s, late this weekend and continuing into next week. The next weather system, impacting Illinois, will arrive early next week. The system is forecast to bring appreciable rain across much of central and southern Illinois. Current expectations are for rainfall amounts of up to 2 inches in southeastern portions of our service area....with decreasing amounts further north and west. The 8 to 14 day outlook (Mar 5th - 11th) indicates a greater than 33 percent likelihood for above normal temperatures across Illinois. Near normal precipitation is currently favored for this time period. The latest outlook for this spring (March, April, and May) indicates a lot of uncertainty for temperatures across Illinois... with no favored trends. However, there is a greater than 40 percent likelihood for above normal precipitation outlined across Illinois. FLOOD OUTLOOK SUMMARY... Probabilities for flooding this spring are overall near normal across central and southeast Illinois. The exceptions are for portions of the Illinois and Embarras rivers, where probabilities are higher than normal. The likelihood for at least minor flooding is highest along portions of the Illinois, Embarras, and Little Wabash rivers...as is typical for the spring season. For central and southeast Illinois, springtime rains will be the driving factor in the evolution of this year's flood season. The saturated soil conditions and elevated streamflows will likely reduce the response time of local rivers and streams, due to efficient runoff. In turn, this would reduce the response time for people living in these areas...should flooding occur. We are currently not expecting widespread flooding across central and southeast Illinois. However, if we trend toward a very wet spring, then more widespread flooding will be possible. --------------------------------------------------------------------- - 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: 03/02/2020 - 05/31/2020 : 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 : 66 56 56 44 <5 <5 Peoria 18.0 22.0 28.0 : 70 65 30 30 <5 <5 Peoria L/D 447.0 449.0 455.0 : 65 54 37 34 <5 <5 Havana 14.0 17.0 23.0 : >95 71 54 42 <5 <5 Beardstown 14.0 18.0 28.0 : >95 79 70 59 <5 6 :Mackinaw River Congerville 13.0 14.0 20.0 : 23 20 18 16 <5 <5 :Spoon River London Mills 15.0 21.0 24.0 : 55 50 8 <5 <5 <5 Seville 22.0 25.0 30.0 : 42 43 22 16 <5 <5 :Sangamon River Monticello 13.0 17.0 20.0 : 65 70 6 7 <5 <5 Riverton 23.0 26.0 29.0 : 13 11 5 <5 <5 <5 Petersburg 23.0 24.0 33.0 : 21 20 17 18 <5 <5 :Salt Creek Greenview 16.0 17.0 20.0 : 17 17 11 10 6 <5 :Sangamon River Oakford 471.0 472.9 478.5 : 39 39 18 17 <5 <5 Chandlerville 456.6 459.0 462.0 : 54 52 21 21 <5 <5 :Embarras River Lawrenceville 30.0 37.0 41.0 : 78 75 20 18 <5 <5 Ste. Marie 19.0 20.0 27.0 : 52 35 39 23 <5 <5 :Little Wabash River Clay City 18.0 22.0 25.0 : 91 85 35 20 <5 <5 :Vermilion River Danville 18.0 22.0 28.0 : 25 24 14 15 <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: 03/02/2020 - 05/31/2020 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Illinois River Henry 20.2 20.2 20.9 24.2 26.0 27.1 27.6 Peoria 16.7 16.7 17.3 20.8 22.6 23.5 24.1 Peoria L/D 444.2 444.2 444.8 448.3 450.0 450.8 451.4 Havana 14.4 14.4 14.9 17.2 19.0 20.8 22.2 Beardstown 15.8 15.8 17.1 20.6 24.1 26.9 27.6 :Mackinaw River Congerville 4.9 5.7 7.1 10.2 12.9 15.7 16.5 :Spoon River London Mills 8.3 8.3 12.0 15.4 18.8 20.7 23.4 Seville 12.5 12.7 16.5 20.5 24.7 26.6 29.5 :Sangamon River Monticello 10.4 10.9 12.4 13.7 15.2 16.4 17.5 Riverton 13.6 13.7 16.9 18.7 21.2 23.3 26.2 Petersburg 12.6 12.7 14.5 17.2 21.9 25.1 28.0 :Salt Creek Greenview 5.6 6.4 8.5 11.4 13.5 17.7 20.7 :Sangamon River Oakford 463.9 464.0 466.1 470.2 472.0 474.1 475.7 Chandlerville 451.6 451.7 453.7 457.2 458.9 460.7 461.9 :Embarras River Lawrenceville 25.8 27.2 30.8 34.1 36.1 39.0 41.0 Ste. Marie 9.1 10.0 14.2 19.4 20.8 22.3 24.1 :Little Wabash River Clay City 16.3 18.4 20.3 21.2 22.5 23.9 24.5 :Vermilion River Danville 8.3 8.5 11.6 13.7 17.9 23.4 25.4 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: 03/02/2020 - 05/31/2020 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :Illinois River Henry 15.5 15.4 15.2 14.9 14.8 14.6 14.4 Peoria 12.6 12.5 12.3 12.1 11.8 10.6 10.6 Peoria L/D 435.1 434.6 433.8 432.5 431.4 430.9 430.4 Havana 8.1 7.8 7.3 6.1 5.3 5.0 4.9 Beardstown 10.9 10.8 10.4 10.0 9.8 9.6 9.2 :Mackinaw River Congerville 2.1 2.0 1.6 1.5 1.3 1.1 1.1 :Spoon River London Mills 4.1 3.8 3.5 3.3 2.9 2.5 2.4 Seville 7.7 7.3 6.7 6.4 5.9 5.6 5.4 :Sangamon River Monticello 7.7 7.2 6.8 6.5 6.1 5.8 5.6 Riverton 7.4 6.5 5.8 5.4 4.7 4.5 4.2 Petersburg 7.6 7.1 6.5 6.1 5.5 5.4 5.3 :Salt Creek Greenview 2.9 2.5 2.1 1.9 1.6 1.4 1.3 :Sangamon River Oakford 459.3 458.7 458.1 457.7 457.1 456.9 456.7 Chandlerville 446.6 446.0 445.4 445.0 444.4 444.1 444.0 :Embarras River Lawrenceville 19.9 19.4 19.2 18.7 18.5 18.3 18.1 Ste. Marie 3.7 3.4 3.1 2.7 2.5 2.3 2.2 :Little Wabash River Clay City 7.5 7.2 6.4 5.8 5.4 5.1 4.9 :Vermilion River Danville 4.3 4.1 3.9 3.7 3.5 3.3 3.3 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 next scheduled issuance of the Spring Flood and Water Resources Outlook for central and southeast Illinois will be on Thursday, March 12th. The NOAA National Spring Flood Outlook will be issued on Thursday, March 19th. Flood Safety Awareness Week is March 16th to the 20th. $$ DRH