Whew…how was that rainy, cold weather on Tuesday?!? The Dalles officially registered a high temp of 59, but it was in the low 50s for most of the day with heavy showers and hail at times. (Normal high for May 16, is 73 degrees F.) What’s more, Timberline Lodge recorded 28″ of new snow! There was heavy snow over Government Camp and even a couple inches at Cooper Spur Resort, roughly 3400′ elevation. Pretty damn unusual for the 3rd week of May!

This was caused by a low-pressure system from the polar regions (i.e. Alaska), diving down the Pacific Northwest coast. It’s the kind of pattern that could give us snow very near sea level, anytime between December and early March. When you get a cold airmass in conjunction with a summer-like sun angle (remember, solar summer = early May through early August!), the result is almost always extreme instability, on-and-off showers, hail, and thunder. May is actually our biggest thunderstorm month in the Pacific Northwest, and it usually happens in cool unsettled patterns similar to this.

But the faucet has now shut off for good, and today we begin the transition back to a warm and sunny pattern. In fact, the next 2 weeks are looking more like June, or even early July, than they are like May. Here are the 6-10 day national outlooks from YESTERDAY:

…And here is the 00z “spaghetti chart” from last night’s GFS:

..The green lines at the bottom-right represent rainfall; notice how very few of the model runs are showing much for the next 2 weeks! This is in total contrast to the spaghetti charts from a couple weeks ago. The airmass temperature should gradually ratchet up the next few days, topping out around +20C on Monday and Tuesday. In late May that should easily be good for high temps in the low to mid 90s. Indeed, both airmass temps and surface high temps look to be about 35-40 degrees F warmer next Tuesday, than they were last Tuesday! You don’t get much more dramatic temperature swings than that, at least not in our climate region. East wind late Sunday – Tuesday will ensure that Portland and the Willamette Valley, are near or above 90 degrees as well.

However, the heat may not last. The chart above shows that some model runs want to shift the upper-level ridge further to the west, toward the beginning of Memorial Weekend. That would mean cooler and windier conditions for The Dalles, and more marine clouds for Portland and Salem. But it almost never produces wet weather, at least not at this time of year. (That’s why I say the pattern could be ‘June-like’: the rain will have stopped for the most part, but we’re still not to the point where we see long stretches of days in the 80s or 90s.)

Still…we appear to have turned the corner when it comes to rain. We can still get showery and unsettled periods in June (think of the ‘Rose Festival Low’ if you live near Portland!), but it rarely gets to be anything like what we saw this March and April. Plant those tomatoes, peppers and melons!