Snowpack continues to melt this spring but still time until melt-out


PORTLAND, Ore. (KOIN) – There comes a time when the snow must go, but are we ready to give it up?

A view from our Mt. Hood Meadows camera Monday afternoon paints a picture of change. With very little moisture moving through the region this spring, we’ve only had a few spring snowstorms, with only a few opportunities from April 1 to now. We are approaching the second half of May and this is typically the time that conditions just start to change, especially in lower elevations. We’re cruising through the snowpack very quickly though. Snow Water Equivalent (SWE) numbers continue to drop from update to update.


Mt. Hood Meadows 5.17.21

Not much of a surprise here as the SWE has been decreasing quickly this month, with all the basins coming in below 50% with the exception of the Hood, Sandy, Lower Deschutes basin, which is holding in there at 80% of the 1981-2010 median. Would you believe that we were doing just fine at the start of the spring season, with our SWE well above the median, now quickly below.

You can follow that with the graph below, where the SWE at the start of the day is plotted in blue, with the median SWE in red. A drastic drop at the start of May, where the current SWE passes right through the median from 1981-2010. That trajectory likely not to change at this point of the season, with the projected chute in place for that blue line to ride. Here is the deal, there have been a few years that we have nearly reached the melt-out point by this time of May. We are still currently sitting at 43.5 inches out of the Mt. Hood Test Site as of today. When that total is down near zero, we have wrapped things up. However, during those years that we have reached ground zero, we didn’t have the same type of winter and early spring. The SWE already started at much lower value. This year, we are watching that snowpack melt hastily.

Courtesy: NWCC Report Generator

Below is a chart, where the SWE and the Snow Depth are recorded at the start of the day. It goes back a month to April 18. We can track the SWE drop and the snow depth over that period of time. Focus your attention to the last 5 days, where the SWE dropped from 51.0 inches to 43.5 inches in five days. Over that stretch of time the air temperature was in the upper 50s to lower 60s. The snow depth dropped from 105 inches to 88 inches. I like to also think of that in the other direction, where if we had picked up 17 inches over that period of time, it would have been a considerable stretch of snowfall for even an earlier moment in spring. A reminder that this site, is part of the basin that is doing better than others in the state. Many locations to the south and east may have a snow depth of 0 inches at this point.

Information provided by: NWCC

Just miles to the north, the SWE is doing much better in Washington. Heavyweight totals coming out of the basins near Seattle through the Cascades in Washington. Outside of the the lower Yakima basin, the others are holding strong. You can actually see how the weather pattern was directed to the north and then came cutting down through the Rockies towards this spring. More moisture and cooler temperatures for these locations. California, Idaho (central/southern), Nevada, Oregon and Utah took the brunt of the dry conditions this spring. All this may lead to a struggle to refill the reservoirs this spring and summer. An update will be given later this week from the U.S. Army Corps of Engineers, but right now they are expressing concern about the deteriorating water year.

As warm, dry weather continues, the U.S. Army Corps of Engineers, Portland District is seeing a worsening water year as it strives to refill 13 Willamette Valley reservoirs for the upcoming recreation season.

US Army Corps of Engineering

Temperatures dropping through the week and that also means it will be cooler for the mountains. In fact, some weather models are showing some minor snow for the higher elevations by midweek. This may help slow down the snowmelt for the time being. Preventing the SWE from dropping another 5 to 6 inches this week.

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