May Arrives With More Dry Weather

A new month is here, but the weather pattern hasn’t changed much.

We ended up with .39″ rain at PDX, making it the driest April on record.

At the last minute (the last few hours of Friday) a surge of rain fell throughout the Willamette Valley. That pushed Salem’s total down to only #20 driest. Still near the upper end, but no record. Olympia ended up 3rd driest, Astoria was 2nd driest, North Bend was #4.

Of course spring continues to be the driest on record in Portland. Same in Astoria, Eugene, and Pendleton. It’s the 2nd driest spring on record at Olympia. But only #13 at Salem. IF PDX gets less than 2.20″ or so this month, it’ll still be the driest spring on record there. But it CAN rain a lot in May. One can argue we are overdue. We haven’t seen a “wet” May since 2013! Hopefully this May (or June) we’ll get a good soaking at some point

May in our area sees a gradual transition from the cool spring weather to (usually brief) periods of summer conditions. In many years we see at least a few days in the 80s, or even some brief 90s, before a return to more seasonal temps in the 60s/70s.

What do I see through this first 10 days of May? First we have a very weak/dying front moving overhead tomorrow afternoon. Little or no rain with this one. Then a strong ridge of high pressure pops up briefly Wednesday. A combination of strong offshore flow & thermal trough (in blue) west of the Cascades should give us one day of 80 degree weather Wednesday. Check out the offshore flow for 5pm Wednesday.

We might even get temps 75-80 Wednesday midday/PM on the northern Oregon coastline. Due to 850mb temps forecast between +15 and +17C over Salem, it’s possible we hit 85 and our warmest day of the year.

Then it’s back to onshore flow near sea level for Thursday. At the same time a cool upper-level trough is approaching. This is right overhead Friday/Saturday for lots of showers. Maybe some thunder? We will see. Colors here represent upper-level height anomaly. Red = higher than normal heights

Unfortunately, this doesn’t appear to be a big pattern change. By Sunday the 9th the cold trough is leaving the area and higher than normal heights fill the Gulf of Alaska. This keeps significant wet systems away from us

It’s still there on Thursday the 13th.

This leads me to believe we won’t see a significant wet spell in the first 10+ days of May. Keep watering! If we get lucky, maybe 0.50″ out of the showers Friday/Saturday

By the way, we recorded a fun FOX12 WEATHER podcast last week. We caught up with Stephanie Kralevich! She was a member of the weather team here for about 9 years from 2005-2014. Some great old stories…find it in Apple Podcasts or you can listen directly here: https://www.kptv.com/podcasts/weather/

Chief Meteorologist Mark Nelsen