Memorial Day weather much better than last year; plus summer dry spell has arrived early this year

Do you remember last year’s Memorial Day Weekend? Cool and wet across the region, some snow in the Cascades, and we picked up more than 1/2″ rain in Portland. It was an “indoor” weekend. This year looks MUCH better, with comfortable (not hot) temperatures and mainly dry weather.

HIGHLIGHTS

• After a very wet and cool April, the “faucet” has shut off. We’re entering our 3rd dry week and there’s no real rain in sight.
• That means it’s time to start watering everything as if the summer dry spell has started. It may have arrived early this year.
• After another very warm day tomorrow (in the 80s) a strong marine push keeps us in the 70s for Memorial Day Weekend.
• We’ll see a mix of morning clouds and afternoon sunshine each day during the next week. Days with less cloud cover warm up a bit more; more morning cloud cover = a bit cooler.

THE BIG MESSAGE

We will be in the “Goldilocks Zone” for the next 7-10 days. I think our morning meteorologist Jeff Forgeron coined that phrase. No extremes: hot, cold, wet, or dry east wind. Pleasant late spring or early summer weather with temperatures just a little above normal for this time of year. Many of us would say this is just perfect for late spring in Portland; our 7 Day forecast this evening

WHAT’S AHEAD

So far this May has been one of the warmest on record, mainly due to that 9 day stretch in the 80s and 90s...that was weird. I grew up here and didn’t like the sudden/extreme change from wet/cool to hot/dry/gusty. I prefer the last few days much better.

We picked up just under an inch of rain early in the month, but now no real rain for over 2 weeks. And other than a spot of drizzle Saturday, I think it’s quite likely we remain dry for another week.

We hit 83 in Portland today, making it the 13th day at/above 80 so far this season. Last year at this time we hadn’t hit 80 yet! Each spring is different...

The big/hot upper level ridge that gave us the heat wave has been gone for awhile AND I DON’T SEE THAT RETURNING FOR AT LEAST THE NEXT 7-10 DAYS. Right now the pattern up around 18,000′ looks like this; weak ridge of high pressure overhead, small low to the east, and an approaching upper level trough.

On Saturday that trough is passing overhead; quite weak but strong enough to give us a big push of cooler marine air and possibly a sprinkle.

By later next week (Thursday), we’ve transitioned to a broad upper-level low pressure area way out in the Pacific Ocean.

It’s far enough away to keep rain well offshore; we stay dry. And hot weather is well to our east. Thus the “Goldilocks Zone” with varying morning cloud cover and afternoon sunshine Sunday through the rest of next week. This weekend’s coastal forecast shows that perfect weather with no significant rain and plenty of afternoon sunshine.

There are a few hints that we MAY go into a warmer pattern deeper into the first week of June. Take a look at the 500 millibar anomaly (forecast compared to normal) for the first big Rose Festival weekend (Starlight Parade). Notice a hot upper-level ridge has developed across Canada again; similar to two weeks ago. But this time it’s centered farther east. This is the ECMWF ensemble average, not just one operational model. Other models look similar.

Just for fun, I noticed there are also hints that anomaly may shift a little closer to us heading into the 2nd week of June. About 5 days later...

The result is that this dry pattern will likely continue for another 1-2 weeks. One way to look at it is this “precipitation plume” for the south metro area. Each thin line is one model ensemble member. It’s total rainfall now (left side) to 2 weeks out (right side). The solid green line is the ensemble average. Yep, maybe 1/4″ rain in the next 2 weeks! Very dry. In fact only 4 of those 51 ensemble members produce more than 1/2″ rain in the next two weeks.

Has our summer dry spell begun more than a month ahead of time? We don’t really know at this point, but if we’re to get a soaking it needs to happen in mid-late June. I’m a bit nervous about another very long dry season. If it starts in mid-May, that’s plenty of time for forests to dry out and wells to run low by the time we finally get fall rains.

That’s it for this evening...enjoy your weekend!

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