@ColoradoClimate: Weekly #Climate, #Water and #Drought Assessment of the Intermountain West

Intermountain West February 2020 precipitation as a percent of normal via the Colorado Climate Center.

Click here to read the current assessment. Click here to go to the NIDIS website hosted by the Colorado Climate Center. Here’s the summary:

Summary: March 3, 2020

Mostly dry, yet cooler than average conditions prevailed across the IMW over the last week. There were two waves of precipitation that impacted the region. A cold front dropping out of the northwest early last week brought up to several tenths of moisture to eastern Wyoming and Colorado. A second system impacted Colorado Sunday into Monday. Neither wave carried large amounts of moisture, and neither gave any more than a glancing blow to areas currently experiencing drought.

The high elevations of the IMW by and large had a drier week than normal for late February/early March. Snowpack is still strong through most of the IMW with a few stations already over 100% of normal peak values. 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 89% 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. This is due not only to low snowpack, but also 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. Soil moisture in northeast Wyoming is in better condition.

Dry weather is in the forecast for much of the UCRB and eastern Colorado. The Tetons, Uintahs, and western Colorado Rockies are forecasted to receive 0.50-1.50″ of moisture in the week to come. Stronger than normal elevational gradients are expected with this moisture. Lower elevations are unlikely to see more than 0.10″. Conditions east of the divide will be dry. The 8-14 day outlook will be important to keep an eye on. NOAA’s Climate Prediction Center currently favors increased chance of above normal precipitation over the Four Corners Region over this time period. Given the persisting drought conditions, and deteriorating snowpack, a widespread precipitation event over this area would be valuable.

And, here is the March climatological contribution to annual precipitation map from Russ Schumacher.

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