December 2021 Hydrologic and Precipitation Summary

December 2021 Hydrologic & Precipitation Summary

Summary

December 2021 precipitation was highly variable across the upper Mississippi River Valley. Precipitation departures were up to 1" drier-than-normal south of Interstate 90 to 1.5" wetter than normal north of this Interstate. Precipitation totals ranged from 0.69" near Stewartville, MN (CoCoRaHS observer) and Fayette, IA (COOP observer) to 3.29" at the Austin Waste Water Treatment Facility (COOP observer). December precipitation typically ranges from 1.2 to 2".

Flood Conditions

No flooding occurred in the La Crosse Hydrologic Service Area (HSA) during December 2021.

River Conditions

USGS average monthly streamflows were above normal for the Yellow River near Ion, IA. Elsewhere, the monthly streamflows were near normal across the NWS La Crosse Hydrologic Service Area (HSA).

The Mississippi River at La Crosse, WI had an average 7 AM stage of 5.36 feet. This was 0.12 feet above the 1937-2021 long-term average of 5.24 feet. 7 out of the last 8 Decembers have averaged above the December long-term average. The only one that did not average above long-term average was December 2019 (average flow 5.18 feet). This was the first month to be above the long-term average since August 2021.

In 2021, the Mississippi River at La Crosse, WI had an average 7 AM stage of 5.61 feet. This was 0.44 feet below the long-term average of 6.05 feet. This was the lowest average since 2009 (5.45 feet).

Drought

Drought expanded in the NWS La Crosse Hydrologic Service Area (HSA) by 1.86% from 13.38% in early December to 15.14% by late December.

During mid-December, severe (D2) drought was added to Adams and Juneau counties in central Wisconsin. This was due to precipitation deficits up to 5” since early September. At the same time, moderate (D1) drought was added to eastern Vernon County (due to precipitation deficits up to 4” during this same time frame).

By the end of December, abnormally dry (D0) conditions to moderate drought continued in parts of Clayton, Floyd, and Mitchell counties in northeast Iowa; and in Grant, Jackson, Monroe, and Taylor counties in southwest and central Wisconsin. Abnormally dry conditions continued in Chickasaw and Fayette counties in northeast Iowa; Dodge, Mower, Olmsted, and Wabasha counties in southeast Minnesota; and Clark, Crawford, and Richland counties in Wisconsin.