3 Hot Days Ahead

September 4, 2014

9pm Thursday…

A classic early-fall east wind event has arrived this evening.  This is the time of year when east winds make our temperatures jump up, drop the relative humidity, and give us crystal clear skies (assuming no fires).  The view from our Skyline Camera at 1,900′ in the West Hills (recently upgraded) was stunning this afternoon.  We could easily see into the west end of the Gorge…the sandy hill on Sand Island at Rooster Rock SP showed up clearly 20 miles away!  That’s something we couldn’t do all summer with the haze/smoke filling our skies most of the time.

High pressure is centered well to our east, and a “thermal trough” of low pressure is right along the coast.  So wind flows from east to west, over the Cascades and down into the lowlands.  As a result temperatures warm quickly.  In the case of tomorrow and the first part of Saturday, that wind will make it all the way to the beaches.  Tomorrow will be one of those rare days at the Coast when temperatures soar into the 80s or even 90.

MarkCoast_Pier_Temps

Today we hit 85 at PDX, a 12 degree jump from Wednesday.  Models seem to show 4-5 degrees warming for tomorrow, so I forecast a 90.  Then another 3-5 degrees warming on Saturday as 850mb top out around +20 to +21.  That would put us in the 93-95 degree range.  Saturday is going to be a windy scorcher!

In September last year and in 2012 we hit 95 degrees at PDX.  850mb temps were +23 and +21 degrees at Salem.  Similar offshore flow pattern so I’m pretty confident of the 94 we have in the forecast for Saturday.

What about the big picture?  Is September going to be a blowtorch month?  Two thoughts on that.

1. Yes, the first half of the month looks extremely warm.  The general pattern is the ridge/offshore flow through Sunday, a weakening trough giving us cooling Monday-Tuesday, then a return to ridging and offshore flow the 2nd half of next week. 

2. Things could change quickly the last two weeks!  We’ve seen that in the past.  Flip a coin.  A little bit of information can be gleaned from last night’s maps from the monthly run of the ECMWF. 500za_week1_bg_NA  500za_week2_bg_NA

They show the well above average upper-level heights through the 20th.  That’s a little more than 2 weeks away.  Then the following two weeks:

500za_week3_bg_NA

500za_week4_bg_NA

That last map isn’t real helpful is it?

We didn’t have measurable rain in August here in Portland (officially).  Yes, yes, I fully aware some of us had showers.  But many of us didn’t, just like PDX.  The ECMWF shows no precipitation for the next 10 days, and it would be fair to assume it shows below normal rainfall for the next 5-10 days after that.

ecmwf_10dayprecipSo keep watering…your yards/plants/trees are more stressed now than back in July/August as the soil continues to dry out.

Chief Meteorologist Mark Nelsen