What appears to be termination dust -- the name for what Alaskans call the first snowfalls in the mountains of what is usually late summer -- has been spotted atop Mount Magnificent, 4,285 feet above Eagle River, a suburb just up the road from Anchorage, Alaska's largest city.
How do we know it's really snow and not some feverish optical illusion?
Well, according to the U.S. National Weather Service Facebook page,"the Anchorage National Weather Service is just one of 92 NWS offices in North America that launch weather balloons with radiosondes to measure the atmosphere overhead." And on Friday morning, the Anchorage office released a balloon that revealed the "freezing level to be 5,221 feet above sea level," but that "the wet-bulb zero height (the level at which air cools to 0ºC once all the moisture is evaporated) was even lower at 4,939 feet above sea level."
Next question: Mount Magnificent's summit is lower than the 5,000ish-foot freezing point, so how does science account for the missing footage?
The National Weather Service says it released its balloon some 30 miles southwest of Eagle River: "The forecast office is located close to Cook Inlet, while Mount Magnificent makes up the north wall of the Eagle River Valley. The two locations are very different microclimates and create very different weather at times."
Still not convinced?
Try "as clouds release precipitation, colder air sinks along with the downdraft created by the falling rain or snow. While that happens, some of the moisture evaporates." Evaporation, you guessed it, creates "even colder air at lower levels," which allows "air at or near 0ºC / 32ºF (the freezing point) to reach Mount Magnificent and the peaks surrounding the Eagle River Valley" just in time for summer to be over.