Summary: September 19, 2017
Last week, the Upper Colorado River Basin saw precipitation amounts between 0.25 - 1.00 inch through much of the basin. The southeastern portion of Utah in San Juan County was drier with only 0.25 inch of new precipitation. Portions of the San Juan Mountains and the Upper Gunnison River Basin in Colorado saw over 1.00 inch of new precipitation. Temperatures over the last week in the basin were near normal through the western portions and slightly above normal for the eastern portion of the basin. These warmer temperatures add to a month of September that has seen temperatures at least 2-4 degrees warmer than normal.
SPIs remain on the dry side out to at least the 6 month period. Some near normal SPIs pop up on the 9 month, however there are still a lot of 0 to -1 SPIs on this time.
Despite the recent dryness, streamflows are mostly in the normal range across the UCRB. Some low streamflows are showing up in the White River and the headwaters of the Colorado River.
Across the divide, much of eastern Colorado saw less than 0.25 inch with a large area seeing less than 0.10 inch. There were some isolated spots of 0.25 inch and above. Much of Las Animas, Baca, Weld and the southern Front Range Mountains saw at least 0.25 inch of precipitation. Temperatures last week were much warmer than normal through much of eastern Colorado, in the 4-6 degree above normal range with areas over 6 degrees warmer. Southeastern Colorado only saw 2-4 degrees warmer than normal.
With the recent dryness in eastern Colorado, many SPIs are now showing up between -1 to -2 for the past 30 days. Even drier around the metro area. Back out to the 90 day time step and SPIs in all of southeastern Colorado turn wet, and get better on the longer time steps.
Irrigated agriculture in eastern Colorado has been utilizing the ample reservoir supplies to keep crops from drying up. This is pretty normal this time of year since September is one of the driest months of the year. The current rate of irrigation has been more than would normally be seen this time of year. Some dryland and rangeland impacts are being reported and winter wheat planting has been delayed due to the recent dryness.
Streamflows in eastern Colorado, especially along the Arkansas River, are looking good, with the exception of a flows on the Republican River in Yuma County.
The precipitation forecast for the next 7-days looks promising for eastern Colorado which could see over 1.50 inches this week. Western Colorado and the UCRB should see some precipitation, but will probably be less than 1.00 inch, with the exception of the northern portion of the basin.
UCRB: Status quo. Precipitation in the basin this week was not enough to warrant any improvements, but enough to hold off on further degradations.
Eastern Colorado: Status quo. Southeastern Colorado is on the edge for some short term abnormally dry conditions, however with the longer term wetness D0 introduction can hold off for another week. Given the forecast for next week and the 8-14 day forecast, conditions should hopefully turn around quickly.
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