Why is it so warm in the Pacific Northwest of North America right now – mid April 2021?

Remember That Warm Spell in the Pacific Northwest Back in April 2021? Here’s What Happened

Do you recall that surprisingly pleasant weather we had in the Pacific Northwest in mid-April 2021? It wasn’t quite the scorching heatwave we saw later that June, but it was definitely warmer than usual, leaving many of us scratching our heads. So, what was behind it? Well, it turns out a few different weather factors teamed up to give us that taste of early summer.

The main culprit? A big, stubborn ridge of high pressure parked itself along the West Coast. Think of it like a giant invisible shield deflecting storms and bringing sunny skies. This ridge acted like a roadblock, preventing cool, moist air from the Pacific Ocean from reaching us. Instead, we got dry air flowing down from the northwest. High pressure means sinking air, and as air sinks, it warms up – simple as that! Plus, with clear skies, there were no clouds to block the sun’s rays, so the ground heated up even faster.

Meteorologists look at something called the “500 MB pattern” to understand these things. Basically, it’s a way of measuring pressure in the middle of the atmosphere. And guess what? The 500 MB pattern for April 2021 showed that ridge sitting pretty over the West Coast, doing its thing for weeks.

Now, here’s another piece of the puzzle: it was unusually dry that April. I remember thinking my garden was already parched! Turns out, many weather stations reported record-low rainfall. When the ground is dry, it heats up much quicker. All that sunshine wasn’t used to evaporate water; it just went straight into warming the soil and the air above it.

Interestingly, while the daytime temperatures were definitely above average, the nighttime lows were actually cooler than normal in most places. This makes sense, though. With those clear skies, all the heat we gained during the day radiated back out into space at night. It’s like the desert – scorching hot during the day, freezing cold at night.

It’s funny, because the long-range forecasts for April had actually predicted cooler temperatures for the Pacific Northwest! Goes to show you how tricky long-term weather predictions can be. Forecasters were probably looking at weakening La Niña conditions and colder ocean temperatures up in the Gulf of Alaska, which often lead to cooler weather around here. But sometimes, short-term weather patterns just take over and do their own thing.

So, to sum it all up, that warm spell in April 2021 was a result of a high-pressure ridge setting up shop over the West Coast, bringing dry conditions and lots of sunshine. It just goes to show that even when the big-picture climate patterns point one way, the day-to-day weather can still surprise us.