Heatwave Update: 2 more days plus fire smoke Monday

July 29, 2018

8:30pm Sunday

Yesterday was “reasonably hot” but today the furnace went into “hot blast” mode, hitting 99 degrees in both Portland & Salem.  It was the 2nd hottest day of summer here in Portland.

Todays Observed Highs OrWa 2017

The Dalles and Hermiston both hit at least 107, both the hottest so far this summer

Todays Observed Highs OrWa 2017_2

That puts our streak of 90 degree days up to 8.  That’s rare in Portland

High Temp Last 13 Days

Note we’ve only had one longer stretch…10 days during that brutal July 2009 heatwave.  That year we hit 106 on two consecutive days with lows above 70 for two nights:

90 degree streak history

We didn’t have any offshore flow today, no easterly wind to help drive temps to 100, or higher.  That’s been something interesting about both heatwaves this summer; even with weak onshore flow we’ve been able to get close to or hit 100 degrees.  I’ve been forecasting in Portland coming up on 27 years this fall…seems like it’s “easier” to get hot weather nowadays with the same upper-level setups.   That said, it was +23 deg. Celsius when the weather balloon hit the 850 millibar level about Salem this afternoon.  It doesn’t get much hotter than that.  Easterly wind would have pushed us up into the 101-103 degree range.  Luckily we didn’t get that.

Tomorrow there will only be minor changes.  First the upper-level atmosphere cools just slightly.  Then the onshore flow should be just SLIGHTLY stronger; although I doubt that’ll change much except drop temps maybe 5 degrees.  The 3rd?  Fire smoke is on the way.  Upper-level wind has turned southerly the past 6 hours, which “opens the door” for all those fires in southwest Oregon and northern California to send their smoke northward.  This image is from midday today.  But I can now see the thick smoke approaching from the south on our Skyline Camera.

Mark Smoke FireOrigin

The HRRR experimental smoke modeling shows that it reaches the Columbia River before sunrise


Yuck…expect a sickly yellow-ish sun in most of Oregon and the southern edges of Washington Monday.   As we saw a couple of times last summer, a thick layer of smoke can drop the temperature well below the forecast high.  If the smoke suddenly thickens during the night, it could keep us even warmer than forecast during the nighttime hours.  We’ll see how that turns out tomorrow.

Regardless of exact high temp Monday, we’ll see our 15th day of the month at/above 90 degrees.  We’ve never seen more than 14 in any one month; that will be a new record for PDX

90 Degree July Days

When do we cool off?  All models are in very good agreement that we see some significant cooling Wednesday, down into the 80s.  But wait, an upper-level trough swinging through gives us a big marine push for Thursday & Friday.  Those days could be at least half cloudy with morning clouds lingering until at least noon.  Yes, it’s possible we get a few days only in the 70s…a glorious start to August.  In fact it’s quite interesting that just as August begins on Wednesday, we go into a much cooler weather pattern.   Take a look at the ECMWF ensemble temps for Portland:


This implies the first 10 days of August will actually be BELOW average with plenty of cloud cover.  A huge change.  One more thing, 45 of 51 ECMWF ensemble members give us some significant (think spring) showers the early/mid part of NEXT week. It’s centered around the 6th-9th of August.  I’ll take a closer look tomorrow, but this could impact agricultural interests that are used to dry conditions in early August.

Try to stay cool on Monday!

Chief Meteorologist Mark Nelsen