At 109% despite abundant snowfall in Methow Valley
People in the valley who are certain they’ve spent every spare moment clearing snow from walkways, roofs and driveways will be surprised to learn that the official snowpack numbers for the Methow basin as of Jan. 1 are just 109% of normal, 3 percentage points less than this time last year.
The Snotel snowpack sensors are all located in the mountains, and some years there’s actually less snow at higher elevations than in the valleys, said Water Supply Specialist Scott Pattee at the Washington Snow Survey Office of the Natural Resources Conservation Service (NRCS).
Many factors can cause this disparity. Sometimes there’s an inversion that holds a cloud cover over the valley floor, despite sunnier and warmer conditions at higher elevations. Snowfall amounts also depend on the direction storms come from, and where the cold air meets moister, warmer air, Pattee said.
“What it comes down to seems like sleight of hand — the valley bottoms and mountains are not always the same,” Pattee said. While typically there’s more snow in the mountains, Pattee recalled one year when the town of Conconully had 3 feet of snow, whereas the nearest Snotel site, at 4,460 feet at Salmon Meadows, registered just 10 inches.
Harts Pass, the highest Snotel gauge in the state at 6,500 feet, was at just 99% of normal on Jan. 1, and Rainy Pass was at 91%. Both of those numbers factor into the Methow basin reading of 109% of normal, Pattee said.
As in many basins across the state, the snow-water equivalent actually dropped in the first week of January because there was little fresh snow. Harts Pass and the Upper Columbia basins lost snowpack between Jan. 1 and Jan. 12. Harts Pass decreased from 99% to 94% of normal, and the Upper Columbia went from 133% to 122% of normal, Pattee said.
Still, snow-water equivalent in the Upper Columbia basin is the highest in the state. Statewide, most basins are above normal, an average of 113% of normal at the start of the year, with a few basins slightly below normal, according to the January Washington Water Supply Outlook issued by NRCS.
The snowpack for the Omak basin started the year as the highest in the state, at 229% above normal. The Snotel gauge for the Omak basin is on Moses Mountain, at 5,010 feet, so this doesn’t describe snow in downtown Omak. Last year, the Omak reading was just 78% of normal.
Since we’re less than halfway into the water year, there’s plenty of time for things to change, Pattee said.
Despite all the snow and rain, winter moisture will have a hard time making up for the record-dry conditions that plagued Washington in 2022. “The summer of 2022 was the driest on record and unfortunately carried over until the end of October, leaving a deficit that will be hard to fill,” the Water Supply Outlook said.
The Cascades and eastern slopes and valleys typically get rain in September and October, but in 2022, there was almost no precipitation until the end of October, meaning the ground was extraordinarily dry going into winter.
Soil at Harts Pass usually measures about 20% saturation at the end of the summer. That builds to 60% from fall rains until it starts to snow in November, and it stays at 60% all winter, Pattee said. But this year, soil moisture at Harts Pass was at a severe low of 6% at the start of winter, having gained only 1% from its 5% saturation at the beginning of October, Pattee said.
Not only are those numbers critically low, but they are a conspicuous departure from anything seen in the past. The previously recorded low for soil moisture at Harts Pass was 55%, Pattee said. NRCS has soil sensors at various depths that take measurements on a daily basis.
Normally, fall rains wet the soil, priming it to absorb moisture in the spring as snow starts to melt. But this year’s dry conditions leave questions about spring run-off, since the parched soil may take its share of moisture before the snowmelt filters down from the mountains to replenish streams and rivers, Pattee said. If the melting snow saturates the soil first, it could result in a lower spring run-off, he said.
If the snowpack is at 200% of normal by spring, there’s little to worry about for spring run-off, but if the snowpack is normal or below normal, run-off will be lower than anticipated, Pattee said. Mountain snow doesn’t start melting in earnest until there are sustained temperatures of about 50 degrees, day and night, along with warmth from the sun, he said.
The Methow and Okanogan valleys rely on snowpack to recharge streams and rivers throughout the summer and fall, for household and commercial water use and for agriculture.
Forecast: above-normal precipitation
The forecast for January shows a probability for both temperatures and precipitation to be above normal. Later in the winter, the forecast is for weather to be colder than normal with above-normal precipitation, typical of a La Niña pattern, according to the Water Supply Outlook.
In fact, the U.S. Drought Monitor anticipates the continuation of “abnormally dry” conditions for most of the state later this year, including in all but the southeastern quadrant of Okanogan County. Abnormally dry is the lowest level of drought intensity (just above “none”) on the six-tier scale, which tops out at “exceptional drought.”
Still, the NRCS water report is reassuring, overall. “By no means a record-setting year, but Washington is in pretty good shape overall,” it says.