####018016954#### FGUS75 KBOU 142137 ESFBOU COC001-005-013-014-019-031-035-039-047-049-057-059-069-073-075- 087-093-095-115-117-121-123-162145- Water Supply Outlook National Weather Service Denver CO 337 PM MDT Thu Mar 14 2024 ...SPRING FLOOD AND WATER RESOURCES OUTLOOK FOR NORTH CENTRAL AND NORTHEAST COLORADO... ...Spring Flood and Water Resources Outlook for North Central and Northeast Colorado Issuance Number 3... This is the third 2024 spring runoff outlook for North Central and Northeast Colorado covering all or portions of the Upper North Platte...Upper South Platte and Upper Colorado River Basins. Flood and Water Supply Outlook Summary -------------------------------------- Spring flood potential is near to slightly below normal at this time for the South Platte River Basin, the Upper North Platte River Basin and the far Upper Colorado River Basin. Any widespread, significant flooding is not likely due to snowmelt alone. It should be emphasized that snow typically accumulates into April, therefore conditions may change before the runoff begins. Water supply forecasts issued by the National Weather Service in early March have slightly increases from the mid-February forecasts and project generally near to just slightly below average April through July runoff volumes for Upper Colorado and South Platte Basins. The Upper North Platte basin, and the Fraser River Basin continue to show a slightly above average runoff volume if current conditions persist. Appreciable mountain snowmelt runoff in a normal year starts in late April to early May. Mountain snowmelt generally peaks in mid- May to mid-June. It is still early to make long range predictions on the magnitude of flooding from mountain snowmelt runoff. Heavy rainfall, a cold spring, or unseasonably warm temperatures during the snowmelt season can affect total runoff volume and peak flow, increasing the threat of flooding. Observed Precipitation...Snowpack and Temperatures -------------------------------------------------- The average higher elevation total water year precipitation for the Upper Colorado, Upper South Platte and the Upper North Platte Basins are near to slightly below normal with and Cache La Poudre Basin below normal. For the water year the percent of normal precipitation is still below normal for the central and northern part of the Denver metro area extending out into most of the northeastern plains. The exception with along the north Weld county border and most of Sedgwick and Phillips counties with near normal precipitation. Southern part of the Denver metro area into the Palmer Divide and adjacent foothills are near to slightly above normal. Precipitation in October through November was well below normal for most of Northeastern Colorado including the eastern plains, the urban corridor and mountains. In December the far eastern plains over to the Palmer Divide and into the foothills had above normal precipitation for the month. The northern part of the metro area east and north had much less than normal precipitation. Weld and Morgan counties had the least precipitation. January continued the dry trend over most of the eastern plains and Denver metro area. The Palmer Divide and portions of the mountains received some much needed moisture and spotty areas above normal for the month. The very end of January and through February brought much needed precipitation to the area. The eastern plains and into the foothills have received well over normal precipitation for the month of February. The mountains also received much needed snow and increased the snowpack to near to slightly below normal for the water year. The first part of March has well above normal precipitation for the far northeastern plains and over the northern Front Range Mountains. The central plains and urban corridor were dryer than normal. A current storm will bring additional moisture to the urban areas into the foothills and Front Range Mountains. Temperatures on average since the beginning of the water year have been above normal. In January temperatures were below normal. February temperatures have been above normal with the exception of the northern Gore and southern Park Ranges. The northern part of the Front Range mountains has had less snow and precipitation than normal although the last month saw slight improvements, including the St Vrain, Big Thompson, and Cache La Poudre Basins. Basin snowpack conditions for the period October 1 2023 to March 13 2024: --------------------------------- (Snow is percent of Median) (Total precipitation is percent of Average) Basin Snow Precip ----- ---- ------ Upper Colorado 105 104 South Platte 98 94 Upper North Platte 109 110 Subbasin Snow Precip -------- ---- ------ Colorado Headwaters 107 106 Blue 109 102 South Platte Headwaters 106 98 Clear Creek 103 105 St Vrain 93 92 Big Thompson 94 91 Cache La Poudre 94 89 North Platte Headwaters 100 98 Climate Outlook --------------- The current ENSO pattern is El Nino and is forecast to transition to the neutral phase later this spring. The chance of ENSO changing to neutral later this spring reaches 79 percent. The outlook for March favors equal chances of either above, below or normal temperatures with a better chance of above normal precipitation over the mountains and along the urban corridor with a slightly smaller chance of above normal precipitation on the far eastern plains. Farther out, the March through May seasonal outlook favors equal chances of either above, below or normal temperatures and equal chances of either above, below or normal precipitation for Northeastern Colorado. Numerical River Outlooks ------------------------ In Table 1 below, the current (CS) and historical (HS) or normal probabilities of exceeding minor...moderate...and major flood stage 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 greater 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: 03/16/2024 - 09/30/2024 : 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 -------- ----- ----- ----- : --- --- --- --- --- --- :South Platte River South Platte 7.0 8.5 9.5 : 5 5 <5 <5 <5 <5 Denver 11.0 13.0 15.0 : <5 <5 <5 <5 <5 <5 Henderson 11.0 13.0 15.0 : <5 <5 <5 <5 <5 <5 Fort Lupton 11.0 13.0 15.0 : 6 5 <5 <5 <5 <5 Kersey 10.0 11.5 13.5 : 24 15 12 8 <5 <5 Weldona 10.0 11.0 12.0 : 16 9 10 8 8 6 Fort Morgan 17.5 19.5 21.5 : 17 13 13 10 9 7 Balzac 10.0 11.0 12.5 : 16 12 13 11 11 9 Atwood 11.5 13.0 14.5 : 14 11 11 10 5 <5 Julesburg 10.0 11.0 12.5 : 12 10 <5 <5 <5 <5 :Plum Creek Sedalia 8.0 10.0 12.0 : 14 <5 5 <5 <5 <5 :Bear Creek Morrison 9.0 10.0 10.5 : <5 <5 <5 <5 <5 <5 Sheridan 8.0 10.0 10.5 : <5 <5 <5 <5 <5 <5 :Clear Creek Golden 8.5 9.5 10.5 : <5 <5 <5 <5 <5 <5 Derby 10.5 11.5 12.5 : <5 <5 <5 <5 <5 <5 :N Fk Big Thompson River Drake 5.5 6.0 7.0 : <5 <5 <5 <5 <5 <5 :Cache la Poudre River Fort Collins 9NW 7.5 9.0 10.5 : 12 10 5 6 <5 <5 Fort Collins 10.5 11.5 13.0 : 5 <5 <5 <5 <5 <5 Greeley 8.0 9.5 10.5 : 18 17 11 12 6 7 :North Platte River Northgate 8.0 9.5 11.0 : 6 13 <5 <5 <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: 03/16/2024 - 09/30/2024 Location 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :South Platte River South Platte 3.9 4.1 4.3 4.8 4.9 5.7 7.1 Denver 4.9 5.1 5.5 6.1 6.6 7.5 8.1 Henderson 5.5 5.9 6.8 7.4 8.1 9.0 9.3 Fort Lupton 5.4 6.0 7.2 8.1 9.3 10.8 11.5 Kersey 4.6 5.0 6.9 7.9 9.6 12.4 13.4 Weldona 3.9 4.2 5.9 6.7 8.4 10.9 14.0 Fort Morgan 10.8 10.9 12.6 13.8 16.4 21.1 23.1 Balzac 4.3 4.3 6.0 6.9 8.9 13.1 14.1 Atwood 5.1 5.1 6.7 7.8 9.5 13.7 14.6 Julesburg 6.6 6.7 7.8 8.1 8.8 10.5 10.9 :Plum Creek Sedalia 4.5 4.7 5.0 5.5 6.4 8.2 10.0 :Bear Creek Morrison 6.5 6.7 6.9 7.1 7.4 7.6 7.7 Sheridan 3.3 3.5 3.8 4.3 4.9 5.3 5.3 :Clear Creek Golden 5.0 5.3 5.9 6.2 6.8 7.1 7.4 Derby 5.0 5.2 5.6 6.4 6.9 7.2 7.6 :N Fk Big Thompson River Drake 3.0 3.1 3.2 3.5 3.9 4.1 4.7 :Cache la Poudre River Fort Collins 9NW 4.2 4.3 5.0 5.6 6.3 8.2 9.0 Fort Collins 2.5 2.9 4.2 5.3 6.2 8.8 10.3 Greeley 2.1 2.2 4.6 6.1 7.5 9.7 11.5 :North Platte River Northgate 4.4 4.8 5.9 6.5 7.2 7.8 8.4 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: 03/16/2024 - 09/30/2024 LOCATION 95% 90% 75% 50% 25% 10% 5% -------- ------ ------ ------ ------ ------ ------ ------ :South Platte River South Platte 2.8 2.8 2.8 2.8 2.8 2.8 2.8 Denver 3.2 3.1 3.1 3.0 3.0 3.0 3.0 Henderson 4.0 4.0 3.9 3.9 3.8 3.6 3.6 Fort Lupton 3.8 3.7 3.7 3.5 3.3 3.2 3.2 Kersey 3.2 2.5 2.3 2.2 2.1 2.0 2.0 Weldona 2.7 2.5 2.2 2.2 2.1 2.1 2.0 Fort Morgan 9.4 9.1 8.6 8.5 8.4 8.4 8.4 Balzac 2.8 2.5 2.1 2.0 1.6 1.6 1.6 Atwood 3.4 3.1 2.4 2.2 1.7 1.7 1.6 Julesburg 3.3 3.3 3.3 3.3 3.3 3.3 3.3 :Plum Creek Sedalia 3.7 3.7 3.7 3.6 3.6 3.5 3.5 :Bear Creek Morrison 5.7 5.7 5.7 5.7 5.7 5.6 5.4 Sheridan 2.5 2.5 2.5 2.4 2.2 2.0 2.0 :Clear Creek Golden 3.3 3.3 3.3 3.3 3.3 3.3 3.3 Derby 3.0 2.9 2.7 2.7 2.7 2.7 2.7 :N Fk Big Thompson River Drake 2.4 2.4 2.4 2.4 2.4 2.4 2.4 :Cache la Poudre River Fort Collins 9NW 3.0 3.0 2.9 2.8 2.8 2.7 2.7 Fort Collins 0.1 0.1 0.0 0.0 0.0 0.0 0.0 Greeley 0.9 0.8 0.8 0.7 0.7 0.7 0.7 :North Platte River Northgate 2.4 2.4 2.4 2.4 2.4 2.4 2.3 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. Following are the forecasts for selected locations: Median Forecast Volume Percent Stream and Station Period 1000 AF of Avg __________________ ______ _______ _______ South Platte River Antero Reservoir inflow Apr-Sep 13 91 Spinney Mtn Res inflow Apr-Sep 48 106 11-Mile Canyon Res inflow Apr-Sep 52 104 Cheesman Lake inflow Apr-Sep 94 101 South Platte Apr-Sep 182 89 Bear Creek Morrison Apr-Sep 20 75 Clear Creek Golden Apr-Sep 111 85 South Boulder Creek Eldorado Springs Apr-Sep 38 96 Boulder Creek Orodell Apr-Sep 56 108 Saint Vrain Creek Lyons Apr-Sep 80 73 Cache La Poudre River Canyon Mouth Apr-Sep 229 109 North Platte River Northgate Apr-Sep 374 127 Colorado River Granby Apr-Jul 196 87 Willow Creek Willow Creek Res Apr-Jul 51 102 Fraser River Winter Park Apr-Jul 21 113 Williams Fork River Williams Fork Reservoir Apr-Jul 86 89 Blue River Dillon Res Apr-Jul 152 91 Green Mtn Res Apr-Jul 268 96 Muddy Creek Wolford Mtn Res Blw Apr-Jul 54 103 Colorado River Kremmling Apr-Jul 835 96 These forecasts reflect natural flow only. Actual observed flow will likely be affected by upstream water management. It should be emphasized that snow accumulation and snow pack conditions could change before the runoff begins. Changing hydrometeorological conditions can have a significant impact on water supply forecasts. Additional products will be issued as conditions evolve. Additional supportive information --------------------------------- - Visit the Missouri Basin RFC information webpage for water supply forecasts east of the divide at weather.gov/mbrfc/water. - Visit the Colorado Basin RFC for water supply forecasts west of the divide at cbrfc.noaa.gov/lmap/lmap.php?interface=wsup. - Visit our website at weather.gov/bou for additional local weather...climate and stream information. - Long range precipitation and temperature outlooks are available at www.cpc.ncep.noaa.gov/products/predictions/. - Snowpack and reservoir data are available from the Natural Resources Conservation Service at www.wcc.nrcs.usda.gov/snow/. $$ as