Summary: December 3, 2019
The last week’s precipitation analysis is much more colorful than usual for the Intermountain West in late fall/early winter. Two significant storms tracked across the region. Last Monday and Tuesday heavy snow fell across NE CO, and SE WY. Thursday through Saturday, storms produced heavy mountain snows, and winds on the plains. High elevation areas of the Colorado Rockies, received 2.00″-3.00″ of new moisture. Lower elevations benefitted as well with valley totals largely in the 0.50-1.00″ range.
As expected, temperatures were mostly below normal across the IMW. The Colorado Mainstem and Yampa Basins maintained temperatures a little above normal, likely due to downslope winds from Monday/Tuesday’s storm. The rest of the region was on the cool side of average. SE WY and NE CO were as much as 10 degrees below normal for the week.
With a large boost from last week’s storms, above average snowpack is nearly ubiquitous across the IMW. Subbasins in the Tetons and Wind River Range of WY are still just 80-100% of normal snowpack. While the high snowpack is encouraging, it no guarantee of good April numbers. In fact, it is still early enough in the season that a two-week dry spell could bring down these numbers significantly.
Streamflows across the Upper Colorado River Basin are running above normal for the most part. There is a higher proportion of gauges reporting below normal flows in the San Juan and Dolores River Basins. For the most part, reservoirs in the Upper Colorado River Basin are retaining adequate winter storage. Lake Powell, of course, is still below the long-term average. Most major reservoirs, however, are retaining near-normal to above normal storage thanks to last year’s great snowpack.
The coming week’s forecast calls for warmer temperatures and dry conditions across eastern WY, CO, and NM. This should at least partially melt the snow from last week’s blizzard. The UCRB will be wetter. Another 1.00-2.00″ is expected in the high country with measurable precipitation on the plains. The Four Corners area is forecast to see 0.25-0.75″ of precipitation in the valleys. This continued reprieve from the historically dry late summer/early fall is quite welcome.