We are about to encounter a meteorological roller coaster in the form of heat wave spike, a day-long warm spell during which temperatures will rise above 15F. And then, cool quickly as it warms up.
In western Washington and Oregon, spring is the time for heat wave spiked.
The air above is still quite cold, but the sun is getting stronger. Remember that the sun this week has the same strength as early September!
The key to all the west/OregonWashington heatwaves is having high pressure build up east of us, creating winter (eastward) winds. These winds warm by compression as they descend on the western slopes of the Cascades. And winter currents isolate land from the cooling influence of the Pacific Ocean.
Below is Central Europe’s current temperature forecast for Seattle Tacoma Airport. A predicted high of 56 today, but 73 tomorrow…. roughly FIFTEEN above normal. Then back to 55 on Friday and in forty on the weekend.
The Seattle Times even talked about snowflakes! (don’t worry, that’s not likely).
The latest 5 p.m. surface air temperature forecast Thursday should inspire you to dig into your t-shirts and fans (see below). 70s (light pink) from Willamette Valley to Puget Sound country. Warmer east of Puget Sound, where the downflow is strongest.
Note that this is a situation where western Washington is WINNER rather than eastern Washington.
You’re probably asking yourself: what would cause such a heatwave tomorrow?
Let me show you, using some weather maps with sea level pressure, lower atmospheric temperature (about 800 meters above sea level) and surface winds.
At 5 p.m. Tuesday, high pressure was just offshore, pushing cool air inland (white and blue are the coldest).
Today, the high pressure moved inland (map at 5pm today is shown below). An offshore pressure gradient develops that accelerates winds from the east. As the air sinks over the western slopes of the Cascades, it warms up….and you can see a stream of warmer air (red/orange) moving northwest of the Cascades.
Warming causes the air to become less dense, causing pressure to drop to western Oregon.
Warming continued on Thursday (see below), with orange (warmer air) extending into western Washington.
But the warmth won’t last!
By Friday afternoon, the high had moved inland and a strong Pacific cold front was making landfall (note the cold air behind it… lots of light and dark blue).
So enjoy the warmth tomorrow…..next week will be a cool, wet one.
