Summary: September 10, 2019
For the majority of the Intermountain West, August was much warmer than average (ranging from near average to the northeast in eastern Wyoming and northeast Colorado to record warm in the south in Arizona and New Mexico). August precipitation was above average for eastern WY and parts of eastern CO and much below average for western CO and NM, southwest WY, and most of UT and AZ. Parts of AZ and the Four Corners region have experienced their driest summer on record, largely due to the notable lack of monsoon precipitation.
Last week, hot and dry conditions continued for much of the UCRB. For most of the IMW, temperatures ranged between 2 and 8 degrees warmer than average with areas in central Utah seeing temperatures 10 degrees warmer than average. Some isolated accumulations of precipitation fell in western WY through northern Utah, as well as in southeast WY and northeast CO. However, the four corner region continued to see little to no precipitation over the last week. Across most of the region, SPIs are less than -1.5 on the 30, 60, and 90 day timescales. While the longer-term SPIs show better numbers, the short-term stresses are outweighing those long-term values. Even though some areas will receive near average precipitation for the water year, the last 90 days have taken a toll.
Evaporative demand has been much higher than average. Even though water supplies are still in good condition, reservoir levels are dropping quicker than normal for this time of year, and streamflows have also dropped off.
While temperatures won't be as warm this week, the outlook is that above average temperatures are likely to continue over the much of the IMW with the exception of northern Utah where normal temperatures are forecasted. Some precipitation activity is expected over the next 7 days, to include the four corners region as well as northern Utah. However, little to no precipitation is expected in central through eastern Colorado.
UCRB: It is recommended that D0 be extended east to include Ouray and Gunnison counties in Colorado. The UCRB was mostly dry and warm over the last week with little to no precipitation in the four corners region. This area is showing a combination of August SPIs less than -1.5, 3-month precipitation for June-July-August in the bottom 10th percentile, less than 0.25" accumulation in the last 7 days, and 1-week EDDI at the D2 level or worse.
Eastern Colorado: It is recommended to shave back some D0 over the northern front range in Colorado. This area received over 1.00'' of precipitation over the last week. It is also recommended to extend D0 over Las Animas county north to include Pueblo, Crowley, and Otero counties. This region did not receive precip over the last week. Lack of precip in combination with warmer temperatures has caused evaporative demand to increase. This is also in agreement with short term SPIs.
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