Friday, May 6, 2016
Record high April melt decreases snowpacks across Idaho
The Natural Resources Conservation Service (NRCS) has just released the fifth water supply outlook report for the 2016 water year. What a difference a month makes. Near normal snowpack covered the majority of Idaho, and the NRCS monitoring region, at the beginning of April.
The beginning of May, however, tells a much different story. Snow across much of the state has melted at a record high rate during April.
Reservoirs and lakes remain in good shape across Idaho and are capturing this year’s snowmelt runoff to store and put to use as we enter the dry summer months.
April precipitation across the state covered the extremes: from well-below to well-above average depending on location. Most areas received below average monthly precipitation.
The lowest precipitation amounts occurred in the Snake River headwaters above Jackson Lake, while Idaho’s southern border from the Owyhee to the Raft basin received from 112% to 150% of normal.
“Precipitation amounts received since the start of the water year on Oct. 1, 2015 remains encouraging with the whole state reporting 92% of average or better,” said Ron Abramovich, water supply specialist with NRCS. “However, those areas with deficits are worth watching and may not improve much as we move into our dry summer months.”
Streamflow forecasts reflect the early melt, early runoff and dry April by shifting forecasts down a notch and are now 70 to 90% of average across most of the state. The exceptions are the high desert streams south of the Snake River from the Bruneau to Oakley Reservoir inflow which are forecast at 100 to 125% of average.
“One of the key variables to watch now is nighttime air temperatures,” said Abramovich. “If they dip below freezing which will slow down melting of the pack. But, if daytime temperatures approach near record highs, there is still enough snow to generate additional streamflow increases across much of the state.”