This wild weather ride that we’re on doesn’t appear to be ending anytime soon. Over the course of the summer, Vancouver has experienced prolonged periods of 90- or near-90-degree weather, often lasting nearly two weeks, followed by a few cooler days before the heat returns.
So don’t let this weekend’s clouds, noticeably lower high temperatures and brief rain fool you: It’ll be back to bright, sunshiny — and hot — days by Monday.
Colin Neuman, a meteorologist with the National Weather Service, explained how the weather was shaped by pressure systems moving through the area. Air wants to move from high-pressure areas to low-pressure areas, Neuman said, and its movement is affected by factors such as the earth’s rotation and the terrain that the system passes over, from forestland to grassland to open water.
“Because of that, you end up getting some areas that warm faster than others, and then basically that ends up causing high and low pressures,” Neuman said. “And then that creates its own circulations.”
This weekend brought a retreat of a high-pressure area, which has been above Clark County for the last week. In high-pressure areas — sometimes called ridges or ridging — warm air disperses clouds, which lets in more sunshine to continue heating up the area.
“If you get day after day of that, then the atmosphere just slowly builds up heat from the ground warming it up each day,” Neuman said. “High pressures can basically remain pretty stationary for several days — sometimes upwards of a week or two.”
An area forecast discussion posted to the NWS’s website Friday said that Saturday’s forecast showed “a decent amount of instability.” Instability is caused by the rising of warm air, which displaces the colder, denser air above it. This in turn is conducive to rain or even thunderstorms.
Just don’t expect the cooler temperatures to stick around.
“We do get stretches of high pressure that produce hot temperatures here, but this summer has been unusual in that we’ve had far more of those than we typically do,” Neuman said.
In fact, Vancouver is on track to break its 112-year record for the most days above 90 degrees in one summer — 27 days in 1906. So far, there have been 24 such days this year; there were 25 days above 90 degrees in 2015 and 2017.
While Neuman said it was “hard to say” if the hotter weather could be attributed to climate change — “that’s something that we’d want to look at more as trends over the course of dozens of years” — he added that the last several summers had been much warmer than most summers over the past century.
“This is entirely possible to happen in any given year,” Neuman said. “But if this keeps happening year after year, then that starts to become more of a signal for something that’s happening at a larger scale.”
