A Historic Hot Day Across Eastern Oregon & Oregon

June 28, 2015

11pm Sunday…

The heatwave west of the Cascades ended up pretty reasonable, except for the sweaty overnight lows of course.  Here in Portland we just had 3 days at/above 90 degrees.

MarkTemp_Last12Days

Of course we were “robbed” of the 100 degree day Saturday by the thick cloud cover, only hitting 92 degrees instead.  That’s okay, except for the weather geeks I’m pretty sure no one else was complaining.

But east of the Cascades the heat has been extreme, even by midsummer standards.  Pendleton the past three days has been 104, 109, & 109 again today!  Here are some other numbers today:

MarkHot_HeatWave_100_Temps

Walla-Walla at 113 was only 1 degree off their all-time high!  Meacham’s 101 is the hottest day in at least the past 15 years.  Many locations recorded their June all-time record of course.

The extreme heat has been caused by an unusually strong upper-level high pressure area that’s been centered just west of the Great Salt Lake.  Keep in mind that a week ago models were putting that high directly over us with easterly wind and a hotter atmosphere.  If that would have occurred, west of the Cascades we would be having all-time June high temps in the 103-107 degree range!  So we dodged the bullet this time around.

We didn’t dodge the warm nights with the cloud cover though.  Portland only dropped to 71 Saturday morning which was the warmest June morning on record.  This morning it was 70, although at 11pm we’ve dropped to 71 already, so even though we set a record, it remains to be seen if we ended up with back to back 70+ lows.  If we do, that’ll be the first time since the heat wave of 2009.  High and low temperatures are calculated based on a calendar day; so if you drop to 70 at 6am, but that evening at 11:50pm west wind comes in and it cools off to 69, then that 69 is the low for the day, not the morning low.  Got it?

The big ridge is being “dented” by a weak low moving around the western periphery of it tonight, thus the cooler temps today, tomorrow, & Tuesday.  But the ridge pops back up again Wednesday-Friday…POSSIBLY through the weekend.  As a result hot weather returns.  At this point we don’t see higher pressure at the surface east of the Cascades to give us a scorching hot east wind.  So it’s unlikely we get up around 100 again unless that pattern develops.  Regardless, a bunch of days 90+ are on the table as heat wave #2 arrives.

Chief Meteorologist Mark Nelsen