Summary: October 17, 2017
It was a dry but cool week for the Upper Colorado River Basin and eastern Colorado. The dry conditions mark a shift in the large scale weather pattern as the last several weeks have been both cooler and wetter than average for much of the Upper Colorado River Basin and eastern Colorado. The last big storm rolled through the region from October 8th to the morning of the 10th. This storm fell as snow in the mountains, which kick-started the snowpack season. Some of the lower elevations saw snowfall as well. Since then, a cool, high pressure airmass has dominated the region, and brought with it impressive swings in temperature between night and day. Westcliffe, CO saw a 55 degree temperature range between night and day on October 16th, which is a remarkable range in the absence of a cold frontal passage.
Despite the dry week, surface water conditions are still holding above average for much of the region thanks to late September and early October's moisture. Streamflows are mostly in the normal to above normal range across the Upper Colorado River Basin and eastern Colorado with a few scattered below normal measurements about the basin. Soil moisture as reported by the variable infiltration capacity model is mostly in the normal range with some below normal conditions along the Green River corridor in eastern Utah and some above normal soil moisture in central and eastern Colorado. USDA in-situ soil moisture is showing some wilting or below wilting levels in southeast Utah near and in the La Sal Mountain Range. Reservoir storage across the basin is decreasing as per usual this time of year. Major reservoirs such as Flaming Gorge, Blue Mesa, Lake Dillon, and Lake Granby are holding normal-to-above normal storage for mid-October.
The Upper Colorado River Basin and eastern Colorado is forecast to be drier and warmer than normal in the coming week with just a few small disturbances rolling through on Thursday night and Saturday. These small, fast-moving weather disturbances will bring moisture totals of mostly less than one tenth of an inch. Increased probabilities of below normal precipitation and above normal temperature are forecast for the last week of October.
UCRB: It is recommended that D0 be added to the San Juans and Four Corners in southwest Colorado. This area did not receive as much moisture as areas to the north, west, and east during late September and early October's wet spell. 60-120 day SPIs are below normal. Reservoir storage from McPhee is still above normal, and storage in Navajo is on the low end of the normal range. Agriculture in this area is primarily irrigated. These areas still have plenty of water. The need to depict drought is not urgent, but D0 appears a prudent move to make the USDM map consistent with nearby D0, and to mark for drought early warning purposes with warm and dry weather in the forecast.
Eastern Colorado: Status quo.
Visit the U.S. Drought Monitor