May 8, 2018 (UT, WY, CO)
- An extremely poor runoff season in Utah and the southern half of Colorado is underway, with forecasted outcomes generally worse than 2012 but better than 2002. The Upper Colorado River Basin as a whole is headed for the 5th-worst runoff season since 1964, with 40% of average inflows to Lake Powell expected. Exceptional drought (D4) has emerged in the Four Corners region and the Sangre de Cristo Mountains.
- With above-normal temperatures in April and the first week of May, and significant dust loading from multiple events in April, the snowpack has been melting out rapidly across Utah and southern Colorado, with the % of normal SWE declining to 10-40% . In northern Colorado, new accumulations have slowed the melt, and % of normal SWE is still at 75-90%. In Wyoming, all but a few basins have above-normal SWE, with most basins at 110-150% of normal.
- The seasonal runoff forecasts issued for May 1 by NRCS and NOAA show little change from the previous forecasts. The forecasted runoff for nearly all points in Utah and the southern half of Colorado is in the range of 20-60% of average, while in northern half of Colorado, the forecasted runoff is 60-90% of average. In Wyoming, the forecasted runoff is 100-130% of average at most points. The May 1 NRCS and NOAA forecasts for Lake Powell inflows call for 39% and 42% of average, respectively.
- April precipitation was below normal to well below normal for most of the region, except for northwestern Wyoming, north-central Colorado, and portions of central Utah and eastern Colorado . April temperatures were above normal in Utah, most of Colorado, and southern Wyoming .
- Since early April, drought conditions have worsened in southern Utah and central and southern Colorado, while improving in north-central Colorado and parts of northern Utah. D4 conditions have emerged in the Four Corners region and the Sangre de Cristo Mountains. . As of May 1, 58% of Utah is in D2 or worse, and the remainder in D0 or D1; in Colorado, 54% is in D2 or worse, and 27% in D0-D1; and in Wyoming, only 13% is in D0-D1, with no D2-D4.
- The La Niña event is winding down, and a transition to ENSO-neutral conditions is imminent . The majority of models predict ENSO-neutral conditons to continue through summer 2018, with an elevated chance of El Niño conditions by fall or winter 2018. For the first time in several months, the CPC seasonal precipitation outlook does not show a pattern reflecting La Niña-based expectations .
