The July #Climate Briefing is hot off the presses from the Western Water Assessment

Click here to go to their website to read the briefing. Here’s an excerpt:

  • Despite above average rain in some portions of the region, drought conditions expanded slightly and worsened by one drought category across the region. During June, areas of above average precipitation fell in parts of eastern Utah and western Colorado and Wyoming; much of Colorado, southwest Utah and eastern Wyoming saw below average precipitation. After extremely warm regional temperatures in April and May, the western half of the region experienced near-normal temperatures while eastern Colorado and Wyoming saw temperatures 2-6 degrees above normal.
  • June precipitation was much above average in northern and eastern Utah, western Wyoming and northwestern Colorado Western US Seasonal Precipitation. Although June precipitation was 150% – 300% of average in many locations, it is important to note that average June precipitation is typically low (1 -2”) and above-average June precipitation was not significant enough to overcome long-term deficits needed to improve drought conditions. Very little precipitation fell in southwestern Utah, and precipitation was much below normal in eastern Wyoming and much of Colorado except for isolated storms that produced pockets of near-normal precipitation.
  • Temperatures in the Intermountain West were generally near average in Utah, western Wyoming and northwestern Colorado in June (+/- 2 degrees of normal) Western US Seasonal Precipitation. June temperatures in eastern Wyoming and much of Colorado were 2 – 6 degrees above normal. High temperatures in Colorado and Wyoming contributed to the persistence and exacerbation of long-term drought.
  • All Snotel sites in the Intermountain West have melted out and most rivers have returned to near-baseflow conditions. Rivers in much of Utah, Wyoming and northern Colorado are flowing at near-average volumes. Below-average streamflows are occurring in rivers of western Colorado, central and eastern Utah and southwestern Wyoming. The NOAA CBRFC July 1st forecast for the April-July inflow to Lake Powell on the Colorado River is 3.93 MAF (55% of average). Since April 1st, the seasonal inflow forecast for Lake Powell decreased by over 1.5 MAF from an April 1st forecast of 5.7 MAF and 79% of average. The large decrease in forecasted streamflow volume for Lake Powell was due to far-below-normal precipitation and above-normal temperatures for the Upper Basin in April – June.
  • During June, drought conditions in large areas of Utah and Wyoming worsened by one drought category and the overall coverage of abnormally dry or drought conditions expanded slightly in the region WY Drought Monitor. Drought or abnormally dry conditions now cover 96% of Utah, 84% of Colorado and 74% of Wyoming by land area. Although areal coverage of drought expanded only slightly during June, drought conditions significantly worsened in all three states, especially in Wyoming where D1 drought expanded from only 1% of the state on June 2nd to over 50% of the state by July 7th. In Colorado, D2 and D3 drought expanded to cover 22% and 34% of the state, respectively. D3 drought now covers nearly all of southern Colorado. In Utah, abnormally dry or drought conditions cover the entire state except the northeast corner and a sliver of northern Utah. Aside for the northern Wasatch Front (Cache and Box Elder Counties) where drought conditions improved by one category, drought conditions worsened in much of the state. D2 drought expanded across all of central Utah and D3 drought emerged in Juab County during June.
  • Pacific Ocean temperatures continued a slow cooling trend during June and ranged from 0.5°C above normal to 1.0°C below normal. Sea surface temperatures are projected to remain slightly below normal, but still in a neutral ENSO phase throughout the remainder of the summer and into early fall. ENSO has near equal probabilities (40-55%) to be in its neutral or La Niña phase through the summer and fall . The NOAA Climate Prediction Center issued a La Niña Watch on July 9th. The La Niña Watch indicates that there is a 50-55% chance of La Niña conditions developing in fall 2020 and a 50% chance of La Niña conditions The NOAA one-month temperature outlook for July shows slightly enhanced odds of above-average temperatures for all of the region except northern Utah and northwestern Wyoming. Except for northern Wyoming, there are also slightly enhanced odds of below-average precipitation in July. Over the next three months (July–September), temperatures are more likely to be above average for the region, with the highest probability of higher-than-normal temperatures in Utah and southwestern Colorado. There is a slight tilt towards below-average precipitation for much of the region during the July-September period.
  • Significant weather event for June. On June 6-7, a rare derecho swept northeastward through eastern Utah, much of Colorado and Wyoming, and then through western Nebraska, South Dakota and North Dakota. A derecho is a fast-moving and extensive line of thunderstorms associated with long-duration and destructive winds. The storm produced 272 reports of wind gusts greater than 50 knots, 44 reports of gusts greater than 65 knots, 67 reports of wind damage, and a maximum wind gust of 110 miles per hour in northern Colorado. Two tornadoes and hail up to 1.75” in diameter were also reported. Only two other derecho events have been reported in the western United States: one in 1994 and the other in 2002.
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