It’s a slow go for moisture throughout the state and within North Central Idaho.
According to the February Water Supply Outlook, released by the Natural Resources Conservation Service (NRCS) in Idaho, the snowpack continues to increase slowly across all basins during water year 2021. Despite a few large storms at the beginning and end of January, snowpack and precipitation totals are below normal across all basins as of Feb. 1. A few large storm events during January raised the snow water content (SWE) in all basins from 0.8” to 13” during the month.
As of Feb. 1, basins that gained more snow and moved closer to a normal snowpack included two covering the North Central Idaho region: Salmon River, 86 percent, and the Clearwater River, 81 percent.
The Salmon Basin received 93 percent of normal precipitation for January, and the Clearwater Basin received 64 percent. All other basins were well below normal, and only received 57 to 88 percent of the normal amount of precipitation that typically occurs in the month. Water-year-to-date precipitation, as of Feb. 1, was 89 percent of average for the Clearwater and 79 percent for the Salmon.
According to the report, as of Feb. 1, total water year precipitation is 80 to 100 percent of normal in the basin. Precipitation during January was below normal (60 to 75 percent). Snowpack in the sub-basins is 75 to 85 percent of normal, with the majority of increases in precipitation and snowpack occurring during the first half of January. A Jan. 13 storm event increased total precipitation and SWE, however, according to the report, warm temperatures and rain resulted in some snowmelt and SWE loss.
Peak snowpack is typically reached around April 11, leaving less than 70 days in the average snow accumulation season. According to the report, in order to reach normal precipitation conditions by April 11, this needs to be above average (70th percentile) during February and March.
Snowpack analyses as of Feb. 1 show basin amounts all down in comparison to this time in 2020: North Fork Clearwater, 79 percent (down 20 percent); Lochsa River, 76 percent (down 17 percent); Selway River, 85 percent (down 23 percent); and South Fork Clearwater, 77 percent (down 32 percent).
Salmon River Basin:
The report states, in order for the basin to reach normal precipitation conditions by April 1, these need to be above average (70th to 90th percentile) during February and March. La Nina conditions continue, and NOAA Climate Prediction Center’s 30-day forecast predicts slightly increased chances of above normal precipitation and relatively cool temperatures in Central Idaho. The typical date of peak SWE in the basin occurs on April 4, leaving two months in the snow accumulation season.
Snowpack analyses as of Feb. 1 show basin amounts down slightly across the board, in comparison to this time in 2020: Salmon River, above Salmon, 79 percent (down 7 percent); Lemhi River, 81 percent (down 14 percent); both the Main Fork and South Fork of the Salmon River, 85 percent (down 1 percent); Little Salmon River, 101 percent (down 11 percent); and Lower-Middle Salmon, 80 percent (down 12 percent).