It is now certain that our region (and the entire western US) will experience a “heatwave” welcoming spring, with significant snowmelt causing river levels to rise.
The source of the big change was the development of a large upper ridge along the West Coast this weekend. To illustrate, here’s a forecast high of 500 hPa (think of that as a pressure of about 18,000 ft) at 5 a.m. Friday. Red indicates higher than normal altitude/pressure). This major ridge is associated with warmer-than-normal air that will rapidly sink, warming due to compression.
The National Weather Service’s latest projections for Seattle show temperatures reaching the mid-70s on Friday and Saturday. Another ten degrees for the Columbia Basin.
Recent UW WRF modeling forecasts suggest that some places in the west will enter the ’80s in western Washington, with Portland rising in the mid ’80s.
People will go crazy after one of the coolest springs in Northwest history.
And then the rivers…..
Our snow cover is now above normal and this warmth will cause significant snowmelt, especially on the eastern slopes of the Cascades. Currently, snow and ice are above normal across most of Washington State. Way above normal in Oregon.
The increase in temperature will lead to significant snowmelt, with some rivers rising rapidly. Consider the situation on the Yakima River at Umtahum (see below). River levels will rise to near-record levels during the day by the end of next week. Spring flooding caused by melting snow was a tradition in the Northwest before the dams were built.
People forget that dams save lives and properties by storing water from melting snow in the spring, something the anti-dam crowd should learn more about.
