Click here to read the assessment. Here’s an excerpt:
The latest monthly briefing was posted [April 10, 2018] on the Intermountain West Climate Dashboard. The highlights, also provided below, cover current snowpack and drought conditions, seasonal runoff forecasts, March precipitation and temperature, and ENSO conditions and outlooks.
Snowpack conditions in Utah and the southern half of Colorado remain very poor after below- to near-normal March precipitation. Very low spring-summer runoff is increasingly likely in these basins. Severe to extreme drought conditions have spread and now cover more than half of both states. In nearly all Utah basins, and in Colorado basins south of I-70, the snowpack remains at near-record-low conditions, with 30-60% of normal SWE for early April. The Bear, Upper Green (within Utah), Yampa-White, Colorado River headwaters, South Platte, and North Platte basins have held steady or improved in the past month, with 80-100% of normal SWE. In Wyoming, all but a few basins have above-normal SWE, with most basins at 110-140% of normal. The seasonal runoff forecasts issued for April 1 by NRCS and NOAA provide a grim picture similar to previous months. The forecasted runoff for nearly all points in Utah and the southern half of Colorado is in the range of 20-65% of average, while in northern half of Colorado, the forecasted runoff is 65-90% of average. Wyoming’s outlook is much better, with most points expected to have above-average runoff, and few points below 80% of average. The April 1 NRCS and NOAA forecasts for Lake Powell inflows are down slightly from the previous month and call for 38% and 43% of average runoff, respectively. March precipitation was overall near-normal for Utah and Wyoming, but below normal for Colorado. March temperatures were above normal in Colorado and southern Wyoming, and overall cooler than normal in Utah and northern Wyoming. The first half of this water year (October-March) was the 2nd driest and 6th warmest on record for Utah, and the 4th driest and 5th warmest on record for Colorado. Since early March, drought conditions have worsened in central and northeastern Utah and central and southern Colorado, with D3 (extreme drought) conditions expanding in both states. As of April 3, 59% of Utah is in D2 or D3, and the remainder in D0 or D1; in Colorado, 51% is in D2-D3, and 38% in D0-D1; and in Wyoming, only 14% is in D0-D1, with no D2-D3. Weak La Niña conditions still persist in the central tropical Pacific, with a transition back to ENSO-neutral conditions still likely by late spring. Historically, weak to moderate La Niña events carry increased odds for below-normal March-May precipitation for Utah and Colorado, which is reflected in the CPC seasonal outlook for that period.