####018012589#### FGUS75 KPUB 011431 ESFPUB COC003-009-011-015-021-023-025-027-041-043-055-061-065-071- 079-089-099-101-105-109-119-311800- PROBABILISTIC HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE Pueblo CO 0730 AM MST Fri Mar 1 2024 ...SPRING FLOOD AND WATER RESOURCES OUTLOOK... This outlook is for the Arkansas River Basin in southeast Colorado and the Rio Grande Basin in south-central Colorado. This outlook is valid from February 27 to May 27, 2024. The potential for spring flooding, caused by snowmelt alone, is near normal for the Arkansas River Basin. The potential for spring flooding, caused by snowmelt alone, is below normal for the Rio Grande Basin. ...OUTLOOK FOR THE ARKANSAS RIVER BASIN... Temperatures have fluctuated between above and below normal levels since the beginning of the water year (Oct 1, 2023) with minimal to no drought conditions present throughout the Arkansas River Basin heading into the winter months. Despite a strong El Nino in effect, mountain precipitation was off to a slow start with only 68 percent of normal basin-wide snowpack snow-water-equivalent (SWE) at the end of December. January and the first half of February, however, have brought beneficial snowfall to the basin with basin-wide mountain snowpack SWE recovering to 97 percent of normal as of February 13. A drier couple of weeks has since brought basin-wide SWE back to 91 percent of normal by the end of February. Mountain snowpack for the mountains along the Continental Divide of the upper Arkansas River Basin and sub-basins draining from the eastern slope of the Sangre de Cristo Mountains are trending at near normal levels for the middle of February. The potential for spring flooding due to snowmelt during the next 90 days is limited and near normal. Any snowmelt flooding that develops will most likely be minor and would only result in minimal property damage and minor public threat or incovenience. Table 1. below, shows 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: 02/27/2024 - 05/27/2024 : 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 -------- ----- ----- ----- : --- --- --- --- --- --- :Arkansas River Leadville 9.0 10.0 12.0 : <5 <5 <5 <5 <5 <5 Salida 8.0 9.0 10.0 : <5 <5 <5 <5 <5 <5 Wellsville 9.0 10.0 11.0 : <5 <5 <5 <5 <5 <5 Parkdale 9.0 10.0 11.0 : <5 <5 <5 <5 <5 <5 Canon City 10.0 12.0 14.0 : <5 <5 <5 <5 <5 <5 Portland 9.0 10.0 11.0 : <5 <5 <5 <5 <5 <5 Pueblo 8.0 9.0 11.0 : <5 <5 <5 <5 <5 <5 Avondale 7.0 8.0 9.0 : 29 15 20 9 13 5 Nepesta 16.5 17.5 18.5 : 20 <5 12 <5 5 <5 Fowler 13.5 14.0 15.0 : <5 <5 <5 <5 <5 <5 Rocky Ford 10.0 11.0 12.0 : <5 <5 <5 <5 <5 <5 La Junta 11.0 13.0 15.0 : 45 20 17 6 <5 <5 Lamar 11.0 13.0 15.0 : <5 7 <5 <5 <5 <5 :Fountain Creek Colorado Springs 11.5 16.0 18.0 : <5 <5 <5 <5 <5 <5 Fountain Creek ne 12.0 14.0 16.0 : <5 <5 <5 <5 <5 <5 Pinon 12.0 14.0 15.0 : <5 <5 <5 <5 <5 <5 Pueblo 10.0 12.0 13.5 : <5 <5 <5 <5 <5 <5 :St. Charles River Vineland 12.0 15.0 18.0 : 7 <5 <5 <5 <5 <5 :Purgatoire River Madrid 7.0 9.0 11.0 : <5 <5 <5 <5 <5 <5 Trinidad Lake 10.0 12.0 14.0 : <5 <5 <5 <5 <5 <5 Trinidad 11.0 12.0 13.0 : <5 <5 <5 <5 <5 <5 Las Animas 9.0 12.0 15.0 : 20 10 7 <5 <5 <5 Legend CS = Conditional Simulation (Current Outlook) HS = Historical Simulation FT = Feet The table above indicates a near normal chance for exceeding flood stage over the next 90 days. The probability of flooding in most years is very low and is considered normal for the Arkansas River Basin. This analysis is for the period ending May 27 with the normal snowmelt period occurring from late April to mid-June. Those locations where the probability of exceeding flood stage is greater than 5 percent do not show a significant difference between the current (CS) conditions and historical (HS) or normal conditions. These results are consistent with a near normal snowpack expected. Any snowmelt flooding that develops will most likely be minor and would result in minimal property damage or threat to the public and only minor inconveniences. Snowmelt flooding should not be confused with other types of flooding such as those associated with heavy rain from storms, releases from reservoirs, or extreme runoff from burn scars. This outlook does not address the potential for those types of floods. Flooding and flash flooding from heavy rainfall or burn scar runoff is always a possibility during heavy rain events. ...OUTLOOK FOR THE RIO GRANDE BASIN... The spring flood potential in the Rio Grande Basin, from snowmelt runoff alone, is below normal. Any snowmelt flooding that develops will most likely be minor and would only result in minimal property damage and minor public threat or inconvenience. Probabilities of exceeding flood stage or various flood categories such as those presented for the Arkansas River Basin are not currently available for the Rio Grande Basin. However, a qualitative assessment of the spring flood potential for the Rio Grande Basin is presented below. After a slow start to the snowpack accumulation season, snowpack conditions for the Rio Grande Basin have steadily improved over January and the first half of February with basin-wide mountain snowpack SWE at 91 percent of normal as of February 13. A drier couple of weeks has since brought basin-wide SWE back to 86 percent of normal by the end of February. Snowpack conditions for sub-basins draining from the eastern San Juan Mountains, La Garita Mountains, and the west slope of the Sangre de Cristo Mountains range from near normal to slightly below normal for the end of February. Soil moisture conditions remain below to well below normal due to widepread drought conditions in place heading into the winter months. Despite closer to normal snowpack conditions, soil moisture deficits will likely reduce the probability of excess snowmelt runoff that would cause flooding for the next 90 days.The probability of flooding in most years is very low and is considered normal for the Rio Grande Basin. Any snowmelt flooding that develops will most likely be minor and would result in minimal property damage or threat to the public and only minor inconveniences. Snowmelt flooding should not be confused with other types of flooding such as those associated with heavy rain from storms, releases from reservoirs, or extreme runoff from burn scars. This outlook does not address the potential for those types of floods. Flooding and flash flooding from heavy rainfall or burn scar runoff is always a possibility during heavy rain events. ...FLOOD ASSESSMENT QUALIFIER... A little over a month of the snowpack accumulation season remains until mountain snowpacks typically peaks in early April for both the Arkansas River and Rio Grande Basins. March and April, however, are often the snowiest months of the accumulation season, and the current outlook for spring snowmelt flooding can change dramatically between now and when the snowmelt season typically begins in mid to late April. In addition to peak snowpack levels, meteorological conditions and snowmelt patterns can also have a substantial influence on the outlook for excess runoff and flood concerns. These flood potential assessments are also based on current conditions and projections of average temperature and precipitation for the coming months. It does not reflect any flood potential due to more extreme weather conditions. If unusually warm or wet weather conditions develop over the region during the next 90 days or during the snowmelt period, then much more severe flooding is possible. ...SUMARRY OF PAST, PRESENT AND FUTURE CONDITIONS... Temperatures this winter have fluctuated between above and below normal through December and mostly below normal temperatures were experienced throughout the state of Colorado for the month of January. In contrast, temperatures in February have ranged from near normal to above normal across the state. Snowpack conditions for the mountains of the Arkansas River Basin remain just below normal conditions for this time of year while snowpack conditions for the Rio Grande Basin range between near normal and slightly below normal for this time of year. As of February 29, basin-wide mountain snowpack SWE was 91 percent of normal for the Arkansas River Basin and 86 percent of normal for the Rio Grande Basin. Precipitation for the Water Year (beginning October 1, 2023), as measured at NRCS SNOTEL stations at the higher elevations, is normal for the Arkansas River Basin and slightly below normal for the Rio Grande Basin. As of February 29, the water year-to-date precipitation was 101 percent of normal for the Arkansas River Basin and 84 percent of normal for the Rio Grande Basin. At the end of February, overall reservoir storage was at 105 percent of normal for the Arkansas River Basin while storage for the Rio Grande Basin was above normal at 123 percent of normal. Soil moisture conditions remain favorable for the Arkansas River Basin coming off a wetter than normal summer and beneficial precipitation which fell during the fall and early winter. Although some recent improvement in snow accumulation has been observed, widespread drought conditions continue to persist throughout the Rio Grande Basin with the San Luis Valley being the most impacted by drier than normal soil moisture levels. The National Weather Service, Climate Prediction Center has indicated that strong El Nino conditions will likely transition fairly quickly back to La Nina conditions by the beginning of summer. Due to the expected persistence of El Nino conditions throughout the spring, however, the 3-month climate outlook for the February through April period indicates likely near normal temperatures and near to slightly above normal precipitation for south-central and southeast Colorado. ...SCHEDULE OF OUTLOOKS... This is the second of three scheduled Spring Flood and Water Resources Outlooks for 2024. Additional outlooks may be issued if conditions change significantly. Long range probabilistic outlooks for the Arkansas River Basin are issued near the second and fourth Thursdays of most months. The next probabilistic outlook will be issued on March 14. ...ADDITIONAL INFORMATION... Visit our web site at weather.gov/pub for more hydrologic information including graphs of probabilistic river outlooks. The National Weather Service Pueblo CO hydrology page can be accessed by clicking the Rivers and Lakes tab near the top of the page. $$