Click here to read the briefing (Jeff Lukas, Ursula Rick, Ami Nacu-Schmidt, Klaus Wolter). Here’s an excerpt:
September was much drier than normal for Colorado, southeastern Utah, and southeastern Wyoming. The rest of Utah and Wyoming was much wetter than normal. Statewide, Colorado was in the 30th percentile for precipitation, while Utah was in the 91st percentile, and Wyoming, the 89th percentile. For Water Year 2016 that ended on September 30, all three states ended up slightly wetter than average, with Utah in the 69th percentile (105% of the 1981-2010 normal), Colorado was in the 69th percentile (103% of normal) and Wyoming was in the 55th percentile (103% of normal). Temperatures were unusually warm across the region, continuing the overall warming trend. Wyoming was in the 96th percentile for the water year, Colorado was in the 95th percentile, and Utah was in the 93rd percentile. Since early August, drought conditions have eased in northeastern and north-central Wyoming, eastern Utah, and southwestern Colorado, while worsening and/or expanding in northwestern Wyoming, northwestern and central Utah, and north-central Colorado, with little overall net change for the region over the past two months. Despite below-average inflows to Lake Powell for Water Year 2016, total Colorado River system storage as of September 30 was the same as one year ago, at 51% of capacity. Lake Powell was at 12.82 MAF, 53% of capacity. Lake Mead was at 9.63 MAF, 37% of capacity, and flirting with the 1075′ level that is a trigger for declared Lower Basin shortage. While sea-surface temperatures in the tropical Pacific have recently cooled to weak-La Niña territory, the official ENSO status remains ENSO-neutral. ENSO model forecasts have shifted away from the previous consensus towards a La Niña event, with more than half of the models now forecasting ENSO-neutral conditions through the winter.