![]() ![]() The latter result is no big surprise since a 36-year record is on the short side for identifying climate trends. Both time series feature prominent year-to-year variations and little in the way of systematic trends. Time series of the composite April 1 SWE, and the composite decrease in SWE from 1 April to 1 June, are plotted in Figure 1. Figure 1: Composite values of the snow water equivalent (SWE) in inches on 1 April (gray, dashed line), and change in SWE from 1 April to 1 June (blue) for 1983-2018. As an aside, it turns out the average of these two temperatures is closely related to the corresponding 850 hPa temperatures from the NCEP Reanalysis (linear correlation coefficient ~.97). The weather data considered are the monthly mean values of temperature and precipitation for April and May from the Cascades Mountains West (#5) and East Slope Cascades (#6) climate divisions of WA. Data are available for all 5 of these stations for the years of 1983 through 2018 from the Natural Resources Conservation Service (NRCS). The present analysis uses SWE data on the first day of the month from 5 sites along the spine of the Cascades (Harts Pass at 6490’, Stevens Pass at 3950’, Stampede Pass at 3850’, White Pass at 4440’ and Lone Pine at 3930’). We assume SWE values are important on 1 June because that is when irrigation demands go up, and freshwater ecosystems can start to become adversely impacted by low streamflows. With that in mind, we have examined recent trends in the melting, arbitrarily defined as the difference in the snow water equivalent (SWE) on 1 June versus 1 April, and how closely mean weather conditions relate to the changes in snowpack over that two-month period. And the latter implies not just less water in the snowpack “reservoir” for summer, but can lead to significant flooding, as for the Okanogan River in north central WA in 2018. Sometimes it hangs around well into summer and other times it melts and runs off quickly. This means that the main issue involving our precious snowpack now is not so much how much there will be but rather how long will it last. Snow can continue to fall in the high country, of course, but the vast majority of the accumulation has generally occurred by that time of year. The date of 1 April is often considered the end of winter for the Cascade Mountains of the Pacific Northwest. ![]() Melting of the Cascade Snowpack in Spring.Loebsack says, if Mother Nature cooperates and there are no equipment issues or other unforeseen delays, the North Cascades Highway should be reopen by next weekend (Friday, May 12), just in time for Mother's Day. That part of the highway is open and this is that rare window for recreationists to get out there and bike behind the closure points before we open for vehicles." ![]() "For bicyclists who enjoy recreation behind the closure points, you are going to be able to get all the way across Rainy and Washington Passes. So clearing work is going to require the rest of this work week and take us into next week."Ĭrews must also clear debris from the roadway and replace or repair guard railing and signage before reopening the highway.ĭespite the road's unreadiness for vehicle traffic, Loebsack says a good portion of it is open to recreationists. "There was some avalanche control work done up there on Tuesday which brought down a substantial amount of snow with several slides that crossed the roadway, including one that was about 25 feet deep. ![]()
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