The latest #climate briefing is hot off the presses from the Western Water Assessment

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Latest Briefing – April 8, 2021 (UT, WY, CO)

  • A large upslope storm led to above average March precipitation in eastern Colorado, eastern Utah and southeastern Wyoming. Drought conditions east of the Continental Divide generally improved by one category and many river basins in these areas have near normal seasonal runoff forecasts. March was dry for much of the Upper Colorado River and Great Basins, drought conditions persisted and seasonal runoff forecasts are below to much-below normal.
  • Precipitation was a mix of much-above normal and below normal during March. Western US Seasonal Precipitation Much-above normal precipitation in eastern Colorado, southeastern and central Wyoming and eastern Utah was driven largely driven by a large upslope storm in Colorado in mid-March. Below normal precipitation fell in many areas of Utah, including the Wasatch and western Uinta Mountains, western and northern Wyoming and the Colorado Rocky Mountains west of the Continental Divide.
  • Regional temperatures during March were mostly near average. Western US Seasonal Precipitation There was a slight southwest to northeast gradient in regional temperatures with March temperature slightly below normal in southwestern Utah and slightly above normal in northeastern Wyoming. This pattern in monthly temperatures is the opposite from what was observed in November 2020 and February 2021.
  • April 1st snowpack conditions were a mix of above and below normal in Colorado and Wyoming and generally below normal in Utah. Western US Seasonal Precipitation There was below normal snowpack in southwestern Colorado, near normal in northern Colorado and above normal conditions in the Rio Grande and Arkansas River basins. Western US Seasonal Precipitation Except for the northeastern Uinta Mountains, where conditions were near normal, Utah snowpack was below normal. Snowpack in eastern Wyoming benefitted from a large upslope storm in mid-March and was above average on April 1st. Snowpack conditions in other areas of Wyoming were generally near normal.
  • Seasonal streamflow volume forecasts for April 1st by NOAA CBRFC were below normal to much-below normal for the entire Upper Colorado (25 – 80% normal) and Great Basins (10 – 75%). Western US Seasonal Precipitation Low seasonal streamflow forecasts are due to below average snowpack for most basins and extremely low soil moisture. Because of very low soil moisture across the region, the 2021 runoff will be an inefficient runoff. Regionally, the lowest seasonal runoff forecasts are for Utah river basins (Duchesne, Provo, Virgin and Weber) and the highest are for river basins in Colorado and Wyoming east of the Continental Divide. (Forecast by basin_040121) Western US Seasonal Precipitation Major reservoirs of the Upper Colorado River Basin are forecasted to have below normal inflow for Fontanelle (59%), Flaming Gorge (54%), Blue Mesa (65%), McPhee (44%), Navajo (54%) and Lake Powell (45%). Streamflow during March was much below normal for much of the region and record low monthly streamflow was observed for the siteas along the American Fork, Bear, Dolores, Sevier, Virgin and Weber Rivers in Utah Western US Seasonal Precipitation and the Animas, Dolores, Mancos, Roaring Fork, and San Miguel Rivers in Colorado. Western US Seasonal Precipitation
  • Drought conditions continue to cover nearly the entire Intermountain West Western US Seasonal Precipitation with 44% of the region in extreme (D3) or exceptional (D4) drought, but there was a one category improvement of drought conditions in eastern Colorado and Wyoming. Drought conditions did not change in Utah during March; 90% of the state is still in D3 or D4 drought. A strong upslope storm on March 13-14th dropped several inches of SWE across a wide swath of Colorado east of the Continental Divide and eastern Wyoming. At the beginning of March, D3 or D4 drought covered 60% of Colorado, but by the end of March, only 30% of the state was in D3-D4 drought.
  • Weak La Niña conditions still exist in the eastern Pacific Ocean, but neutral conditions are expected to return during spring. Western US Seasonal Precipitation Seasonal predictions of climate from NOAA suggest there will be an increased probability for above average temperatures Western US Seasonal Precipitation and below average precipitation Western US Seasonal Precipitation at one and three month timescales for the entire region. The increased probability of above average temperatures and below average precipitation will likely cause drought conditions in the Intermountain West to persist and perhaps worsen.
  • Significant March weather event. A significant upslope snowstorm hit the Front Range of Colorado and southern Wyoming on March 13-14th. Snowfall totals from Colorado Springs to Cheyenne Wyoming and west to the Continental Divide ranged from 18 – 40”. Denver International Airport reported 27.1”, making this storm the 4th largest snowfall in Denver since 1881. Cheyenne recorded a 36” storm total; 22.7” fell on 3/14 which broke the daily snowfall record for Cheyenne. The highest storm totals occurred in southeast Wyoming’s Snowy Range at 7,900 feet where 52.5” fell and in the foothills north and west of Fort Collins at Buckhorn Mountain where 48.5” was recorded. The storm closed Denver International Airport and 2,800 flights were canceled on March 13-15. Parts of Interstates 25 and 70 in Colorado and I-80 in Wyoming were also closed on 3/13-14. Approximately 25,000 customers lost power in northern Colorado as a result of the storm. Nearly all of Colorado and Wyoming were in drought prior to the storm, with large areas of both states in extreme drought. The storm did not bring an end to drought, but significantly improved drought conditions east of the Continental Divide in Colorado and in southern Wyoming.
  • #Drought-plagued #California and western U.S. may see another devastating fire season — The Washington Post

    US Drought Monitor April 6, 2021.

    From The Washington Post (Diana Leonard and Becky Bolinger):

    California and the West are falling deeper into drought and, with summer approaching, that portends another severe fire season.

    As a disappointing wet season comes to a close and hope for spring rain fades, conditions are worse now than they were at this time last year, with exceptional and extreme drought now found throughout the region.

    In California, that doesn’t bode well, given that last year’s more moderate rainfall deficits, combined with extreme heat waves, ushered in a record-setting fire year. It brought 5 of the 6 largest fires in modern state history, 10,488 destroyed structures and 33 fatalities. Some 4.2 million acres were torched.

    More frequent drought, hotter summers and warmer and drier autumns, tied to climate change, are stacking the deck for large and destructive fires during the heart of the fire season. And this year, a lack of rain in spring could mean fires arrive early in some areas…

    …despite a significant late-January storm [in California], the 2021 winter and spring months have failed to deliver even normal precipitation, and much of April is forecast to be very dry. In fact, the current water year is now tied for the third driest on record…

    For the last two wet seasons, a persistent ridge of high pressure in the central and eastern Pacific has diverted most storms out of the state. In Northern California, many of the wettest, forested regions have missed over 20 inches of precipitation in that time period…

    Precipitation deficits since April 9. 2020 via the High Plains Regional Climate Center.

    Statewide mountain snowpack, currently at less than 50 percent of normal, is expected to melt off early, leaving Sierra forests prone to burn earlier and hotter…

    Drought deepens across the West, and fire risk follows

    Large wildfires in the West are driven by a complex relationship between shorter-term weather and longer-term climate variability. The West’s descent into the current severe and widespread drought began in the fall of 2019, when a dry pattern emerged over Oregon, northern California, central Nevada and into parts of Idaho, Utah and Colorado. The hot and dry summer of 2020 quickly followed, which brought devastating fires to California and the Pacific Northwest, and set the stage for Colorado’s biggest wildfire season on record beginning in August and continuing through October…

    This concerning situation continues: Not only is drought persisting over the same areas, it’s expanding to areas that weren’t as dry in the winter. Extremely warm and dry conditions from October to March extended across California and Oregon, and eastward across Idaho, Nevada, Utah, Arizona, and entering Wyoming, Colorado, and New Mexico…

    Changes in drought categories over the course of the last year, from March 2020 to March 2021. US Drought Monitor one year change map ending April 6, 2021.

    Combining this longer-term climate signal with expected weather as we move into summer dictates the location of greatest fire risk. Based on low snowpack and early snowmelt already occurring in Arizona and New Mexico, and expected early snowmelt around the Four Corners, the risk for significant wildfires is high in Arizona and New Mexico, and is extending into southern Utah and southern Colorado. That risk moves northward as the summer continues into central Nevada, Utah and western Colorado, but should be reduced to the south if monsoon rains arrive as expected.

    @Northern_Water increases Colorado-Big Thompson quota to 70%

    Cache la Poudre River drop structure. Photo credit: Northern Water

    Here’s the release from Northern Water:

    Adequate native water supplies coupled with improved Front Range soil moisture from March snowstorms prompted the Northern Water Board of Directors to increase its 2021 quota allocation for the Colorado-Big Thompson Project to 70 percent.

    The Board unanimously approved the allocation at its meeting Thursday, April 8, 2021, with several board members participating remotely because of the ongoing pandemic. The Board also directed Northern Water staff to update them in May and June to determine whether an additional allocation would be advisable during the peak demand season.

    Emily Carbone, Water Resources Specialist at Northern Water, outlined snowpack and forecasted streamflows, and the Board also heard about the available native water supplies in regional reservoirs. In addition, the Board heard a presentation about the potential water resources impacts caused by the 2020 East Troublesome Fire. Public input was also considered.

    The Board has been setting C-BT quota since 1957 and 70 percent is the most common quota declared. It was also the quota set for the 2019 water delivery season, while the 2020 quota was set at 80 percent. The quota reflects the amount of water to be delivered through the C-BT Project.

    The quota increases available C-BT Project water supplies by 62,000 acre-feet from the initial 50 percent quota made available in November. Water from the C-BT Project supplements other sources for 33 cities and towns, 120 agricultural irrigation companies, various industries and other water users within Northern Water’s 1.6 million-acre service area. According to recent census figures, more than 1 million residents now live inside Northern Water’s boundaries. Learn more about the C-BT quota.