Rainfall in the state — and the region — has been the story of two Januarys.
The first week of January brought heavy thunderstorms and normal to above normal precipitation. Then there’s the rest of the month — where significant storms have been rare, Natural Resources Conservation Service officials said in a news release Friday.
But NRCS officials said there was still plenty of winter left – and the chance of significant rainfall in the state. Less than desirable January precipitation dampened some of the previous optimism for an anti-drought snowpack and subsequent effective runoff, the snowpack is still near or above normal, they said in the report on February 1 Idaho water supply outlook.
“While temperature inversions and cloud cover dominated in January for most of Idaho’s lower elevation valleys, the mountains largely received the opposite: slightly warmer than normal temperatures and many days of bluebird,'” said Daniel Tappa, hydrologist and data collection manager for NRCS Snow Survey. in Idaho.
Warmer temperatures, combined with little snowfall during the month, resulted in an unusually dense snowpack for this time of year, Tappa said. The season’s low sun angle limits early runoff and additional snowfall will also help limit earlier than normal snowmelt.
While the state saw less rainfall in the second half of January, NRCS officials said the Panhandle fared slightly better than most of Idaho. The area experienced 85-105% of normal rainfall in January.
Despite little rainfall during this period, NRCS officials said the year was still trending towards normal in the region, with rainfall totals hovering between 105% and 115% of normal. Snow accumulation is also near normal, ranging from 100 to 105% of normal for February 1.
The snowpack was cold enough and had a low enough density to withstand several rain-on-snow episodes. However, such events increase snow density and warm the snowpack, reducing the overall amount of energy needed to produce snowmelt runoff, NRCS officials said.
“Although it is too early to predict the timing of snowmelt for this region, Panhandle Basins still have near-normal snow density, which should help prevent early snowmelt,” they said. officials said in the report.
At most elevations in the Panhandle Basins, the snowpack is just over 50% of normal peak conditions, which typically occurs between April 5 and April 14.
“Having 50% of normal peak conditions is expected for this time of year, but this suggests there is still plenty of time for conditions to change,” officials said.
National Oceanic and Atmospheric Administration forecasts suggest an even chance for normal rainfall
The Panhandle lakes are 65-95% of normal storage, with Coeur d’Alene Lake at 64%, Pend Oreille Lake at 85%, and Priest Lake at 94%. The April through July flow forecast ranges from 110% to 115% of normal at the 50% exceedance level for the Panhandle basins.
“The start of disappointment…but cautiously optimistic,” NRCS officials said in the report. “That’s how we can describe the statewide February 1 snow and water supply situation. As we get closer to spring, we’re still hoping for late December and early January will come back – at least for a few more rounds to give us some extra drought relief.”
The active weather pattern that brought heavy snowfall to the state abruptly ended in mid-January, leaving a “high and dry” weather pattern in its place. While the northern half of the state fared better, southern Idaho saw record to near-record rainfall in the second half of the month.
Thanks to heavy rainfall in the fall and early winter, NRCS officials said the severity of the drought in the state has diminished. Less than 1% of Idaho faces extreme drought conditions, down from more than 40% three months ago.
These early weather patterns help offset January’s dry spell, officials said, but current weather forecasts suggest the same will happen in early February – high pressure and little rainfall.
“Conditions are still favorable for at least one normal runoff season,” NRCS officials said in the report. “However, if the January dry spell is a premonition of weather to come, normal stream runoff will be unlikely.”