Warm & Dry July Continues, Plus Some Good Fire News

July 21, 2021

8pm Wednesday…

We’ve been in a surprisingly stable weather pattern ever since the heat wave ended in late June. Warmer than normal, but not much heat. We are three weeks into July; every day has ended up between 75 and 90 in Portland. Today was especially nice with partly cloudy conditions all day long. We’ve seen lots of days in the mid-upper 80s in Portland, but only hit 90 once (on the 6th). That’s due to a persistent weak onshore flow; that cooler ocean air pouring inland each evening. It tends to come up the Columbia River to Longview and then the metro area. That’s different than the “southwest push” coming in over the Coast Range we saw right at the end of the heat wave.

Salem and Eugene, farther removed from those cool northwest breezes, have each seen 9 and 10 days above 90. That’s quite a difference! Although none of those days made it above 92 in Salem. Right now Salem is seeing it’s 4th warmest July on record; due to consistently warm temperatures vs. a series of hot spells.

A very consistent upper-level pattern remains in place the rest of the month (if models are correct). Right now a hot ridge of high pressure is right over the Rockies. At the same time a weak trough is moving by to our north; thus the cooler weather the past two days, even up in the mountains.

By this weekend, the last full weekend of July, the high edges a bit closer. So we turn a bit warmer as onshore flow backs off again. We might even hit 90 in Portland…maybe.

Then the ridge moves farther away, back into the Great Plains early next week. 9 days from now, Friday the 30th shows us in the “Goldilocks Zone” west of the Cascades. Warm, but no heatwave and not much “hot” weather.

All models agree with this general setup the next 7-10 days.

What This Means

  1. Temperatures remain above normal, but a heat wave is unlikely through the end of July west of the Cascades
  2. Most fire smoke will continue to remain over/east of the Cascades. That southwest flow carries most of it well east of us. I don’t expect any sort of “smoke episode” in the Portland area the next 7-10 days
  3. A widespread outbreak of thunderstorms is very unlikely in this pattern, even east of the Cascades
  4. No chance for rain, guaranteed dry weather continues next 7-10 days

Speaking of rain, we’ve only seen a TRACE so far in Portland this month. It was a few spots of drizzle out of the marine layer on the 1st. A trace means it can’t be measured…less than 0.01″. July is our driest month of the year in Portland; we only average 0.50″! August is close behind at 0.54″. We almost never have a truly “wet” July. But I remember both 1983 and 1993 were showery and cool; quite rare indeed. Those were “green tomato” summers…

FIRE WEATHER

Fire season is off and running big-time this year. Numerous large (greater than 100 acre) fires have burned in both Oregon and Washington. This has been fueled by 3 years of drought in southern Oregon plus the driest spring on record for many areas. Then an unprecedented extreme heat wave baked the region in late June; a perfect setup for a bad fire season. At this moment there are 5 large fires burning in Oregon

There is one fire grabbing all the attention right now, the Bootleg Fire burning through the Fremont National Forest. That’s between Bly, Summer Lake, & Paisley

The Jack and Elbow Creek fires are large as well, but notice they aren’t growing quickly. Good news there. The Bootleg Fire is about to become Oregon’s 5th largest on record, passing up the Buzzard Complex

And I had better mention the “Tillamook Burn” because each time I show this graphic, someone accuses me of forgetting that one. Actually there were THREE large Tillamook Burns (and one smaller), beginning in 1933; it was called the “six year curse”. All in the north Coast Range between Banks and Tillamook.

The bad news, of course, is that we don’t have any cool/rainy weather systems headed into the region. We wouldn’t expect that in July anyway. Extremely dry fuels will remain that way until further notice.

The good news?

  1. We don’t see a real heatwave coming for the region over the next week or so.
  2. Lightning activity has been minimal to almost non-existent so far this season and will remain that way through the foreseeable future.

Considering the current very dry fuel conditions, IF we get a widespread outbreak of dry thunderstorms, then fire season could explode. Let’s hope that doesn’t happen. Typically that setup would involve a southerly or southeast flow in the upper-atmosphere. For now I’m not seeing that over the next 7-10 days.

That’s it for now; enjoy the near-perfect summertime weather west of the Cascades. Yes, a bit on the warm side, but no heatwave!

Chief Meteorologist Mark Nelsen