Nice Independence Day Weather Ahead; But July Starts Cool

June 29, 2020

9:45pm Monday…

We had quite a stretch of warm weather last week, topping out at 93 Tuesday. As models had forecast, a cold upper-level low dropped out of Canada over the weekend. Not much rain, but highs 15-20 degrees cooler

Today was a pleasant day but the constant onshore flow kept us in the lower 70s. A weak cold front passes overhead late tonight, thickening the marine layer and producing spots of drizzle/sprinkles the first half of Tuesday. The GRAF model shows this well for the morning commute; no significant showers but anyone west of the Cascades could wake up to wet.

What’s ahead?

  1. A relatively cool start to July; if our 7 day forecast holds, it would be the coolest first week of July in 10 years!
  2. There’s no sign of a wet spell and/or any unusually wet weather. Actually little to no rain falls in the next week. Just those sprinkles or light showers tomorrow and Wednesday morning.
  3. Not a single model produces any sort of summer heat in the next 7-10 days. No need for air-conditioning!

A deep and cool upper-level low is centered over Idaho right now. That brought us cool weekend showers. Rain totals the past 24 hours in the Wallowa Mountains have been amazing as the northeast flow coming around the low has been getting “scooped up” by the north-facing slopes. Enterprise and Joseph both picked up 1-2″ rain, with 2-5″ around Wallowa Lake! Above 7,000′ or so it was snow during the night with temps at freezing.

That low moves away from us the next 5 days, but it’s replaced by strong onshore flow at the surface tomorrow through early Thursday. Lots of clouds and sprinkles/drizzle are the outcome west of the Cascades. Upper-level troughing weakens by this weekend, but it’s still centered over the Pacific Northwest by fireworks time Saturday evening. This means weak onshore flow, comfortable temps, and plenty of sunshine after brief morning clouds for Independence Day.

But by next Monday (the 6th), the trough is deepening again

GEM (Canadian) model

and it’s still there 10 days from now (Thursday the 9th)

GEM (Canadian) model

This means the marine layer likely thickens again early-mid next week = cooler. The overnight run of the monthly ECMWF shows the pattern returning to a more typical summer setup just after 10 days out…we’ll see. Just for fun and to scramble your brain a bit…here’s the ensemble forecast for max temperature at Salem for the next 46 days.

Notice there is an uptick right around the 11th as the trough weakens. We’ll see how that plays out. But as of now there’s not reason to think this is going to be a cool and cloudy summer.

On the flip side, we are overdue for a cooler than average summer; we haven’t seen one of those in many years. Portland has seen 6 consecutive warm (or hot!) summers. Last summer was a bit warmer than normal, mainly due to unusually warm Pacific ocean water leading to warm nights. But no heat waves or 100 degree days, that was nice.

Chief Meteorologist Mark Nelsen