Summary: March 10, 2020
Mostly dry, warmer than average conditions prevailed across the IMW over the last week. Some exceptions include northeastern Colorado where they received 0.25-1.00” of precipitation with the greatest accumulation over Weld County. Northern San Juan basin and southern Gunnison basin did see about 0.10-0.25’ with some areas seeing up to 1.00”, however this is low for early March and SPI values are continuing to show degrading conditions in this area. Northern Utah also received decent precipitation, northern Cache county received 1.0-1.50” of precipitation over the last week.
The high elevations of the IMW by and large had a drier week than normal for early March. Snowpack is still strong through most of the IMW with a few stations already over 100% of normal peak values such as Upper Colorado River Basin and the Yampa and White River Basins. However, recent dryness has led to a regression in snowpack values for the southern portion of the region. The San Juans in Colorado have regressed to 88% of average for this point in the season. Snowpack is also below normal in Arizona and western New Mexico. The Colorado Basin River Forecast Center is anticipating low cumulative runoff numbers for this spring and summer from the San Juan Basin southward due to low snowpack and very low soil moisture prior to the start of the cold season. Snowpack numbers are above normal east of the Continental Divide.
Surface water supplies are in generally average to above average conditions for small-to-medium reservoirs across the IMW. This is thanks in large part to a high snowpack in 2019. The giant exceptions are Lake Powell, and Lake Mead, which have been consistently lower than normal for years. Powell and Mead would need an anomalous cool, wet period spanning multiple years to return to levels seen in the 1980s and 90s.
Grasslands east of the Continental Divide are seeing mixed surface conditions, but things have been trending drier. According to the NLDAS NOAH model from nationalsoilmoisture.com, northeastern Colorado is seeing widespread dry topsoils and root zone soils. This is adversely impacting winter wheat and rangeland condtitions prior to greenup. Soil moisture in northeast Wyoming and Utah are in better condition.
Dry weather is in the forecast for much of eastern Colorado but the remainder of the UCRB is forecast to see decent precipitation in the next week. The Tetons, Uintahs, and western Colorado Rockies are forecasted to receive 1.00-3.00” of moisture in the week to come. The 8-14 day outlook will be important to keep an eye on. NOAA’s Climate Prediction Center currently favors below average temperatures and an increased chance of above normal precipitation over the IMW region with highest probability over southern Utah, southern Colorado, all of Arizona and northern New Mexico. Given the persisting drought conditions, and deteriorating snowpack, in the four corners region, a widespread precipitation event over this area would be valuable.