At Least It’s a Dry Heat

July 3, 2015


I’ve noticed the past few days have been very hot in the afternoon hours as the sun pounds down on me between car-work-store etc…

Yet in the mornings and evenings it’s not so bad…part of the reason is that we’ve had nice low dewpoints (moisture in the air).  They’ve been well down into the 50s most of the time.  That’s our classic “dry heat” here in the Pacific Northwest.  None of that sweaty stuff we had last weekend.

Due to the dry air, the Heat Index (a “feels like” temperature measurement) has been quite low over our area.  Compare that to some notoriously sweaty areas:


Key West (Florida) was 8 degrees cooler than Salem today, yet the heat index value was 10 degrees hotter!  I can attest to the heavy and sweaty feel to the air down there; that’s where I spent a few days early in June on vacation.  One bonus down there is that there’s usually some sort of easterly breeze.

There was a fire today near Mt. Adams and Oca Hoeflein’s Mt. Adams camera captured the smoke plume nicely.

Notice how it died down around sunset.  It’s possible the fire ran into the burned out area from 2012.  All through  September 2012 the Cascade Fire burned out much of the south/west sides of the mountain, eventually reaching 19,000 acres:


When a fire moves into a recently burned area there isn’t much left to burn!  Just grasses and small brush.

You may remember another large fire, the Cold Springs Fire, which burned about 8,000 acres on the SE side of the mountain in 2008.

Fireworks weather looks great tomorrow, temperatures in the 70s to around 80 right as most fireworks begin at 10pm.  Have a fun and safe holiday!

Chief Meteorologist Mark Nelsen

Hottest Day of 2015, But Big Cooldown On The Models

July 2, 2015

Today was the hottest of the year here in Portland; we hit 97 degrees


All of the metro area was in the upper 90s, with McMinnville (and possibly Salem) hitting 100 degrees.

If you hate the heat, you’ll want to stay hidden in a cave or underground bunker for a few more days.  I don’t see any significant drop in temperatures until after Monday


But notice the last bullet point on the graphic!  Over the past two days models have been giving us major hints that something is going to change as we head into mid-July.

The hot weather has been caused by persistent upper-level high pressure over the Western USA.  There is a slightly change for the middle of next week when the ridge splits into an offshore part and the rest retreats farther east of us.  That should give us more marine influence and a better chance of high temps dropping down into the 80s.

Beyond that, there is a common theme across all models today showing an upper-level trough developing near the West Coast in the middle of the month.  Take a look at the ensemble average 500 millibar heights for 16 days from now.  From the GFS, the GEM, & ECMWF.




They all look quite similar don’t they?  The show the ridge weakening and shoving much farther west out over the mid-Pacific.

This should lead to normal to below average temperatures.  Wow, that will be the first time we’ve seen that in about 5 weeks.

Here is the 12z ECMWF ensemble chart showing pretty good ensemble agreement on the cool down.  850mb temps come down right to average NEXT weekend (not this coming weekend) and stay there.


Last night’s monthly run of the ECMWF was similar, showing warm to hot first week, then big change during week 2:



We sure haven’t seen a below average deviation like that on the monthly run for quite a while.  Here is week 3 and week 4:



It’s interesting that any sort of significant ridging is totally absent anywhere on the map in late July and early August.  Taking a closer look at maps from WeatherBell it looks a bit different.  Apparently WSI’s contouring is a bit more coarse.  Heights are indeed above average during both of these weekly periods; just not dramatically so.  My gut feeling based on the info above is that we’ll have a below-normal period in mid July, then return back to normal conditions the latter part of the month.  Regardless, it’s also interesting that in the coming 1-2 weeks we’ll see temperatures go DOWNHILL instead of UP.  The old saying “summer doesn’t begin until after the 4th of July” is going to be wrong this year!

Chief Meteorologist Mark Nelsen

Dang, It’s Hot Today!

July 1, 2015

We are in the mid 90s at 6pm…wow, what a scorcher today!  We have hit 95 in Portland, tying the hottest temperature so far this year (last Friday).  It’s possible there has been a “between-hour” high temp of 96; we’ll find out when the climate report comes out around 7:30pm.  Check out the near-100 degree temps in the valley.


As of today we’ve hit the 90 degree mark 10 times already this summer.


Add in a few more over the next 4-5 days and we will have already had our normal yearly “allotment” of 90 degree days! The crazy warm weather continues…

A Historic June In Pacific Northwest

June 30, 2015

There’s a good chance you won’t see a June like this in many years!  We broke record after record…




  1. June was a full degree warmer than an AVERAGE July or August!
  2. Warmest night on record in June…71 degrees
  3. Not the driest, but 25 consecutive dry days is a new record
  4. Most sunny days, plus least # of cloudy days in June

Not on the chart, it’s the driest April-June we’ve ever seen here.  No, you’re not crazy, the ground is the driest you have ever seen it this time of year:


Of course we didn’t get the extreme heat at the end of the month like Eastern Oregon has seen.  It could have been worse!  Take a look at Hermiston:


We’re not done with the hot stuff yet.  The past two days my forecast has busted…yes it appears I have a “cold-bias” in my forecasting.  For whatever reason (possibly the warmer than normal offshore water?) surface temperatures have been consistently warmer than one would expect with significant onshore flow (yesterday & today) and 850mb temps in the +16 to +19 range.

The onshore flow goes just about flat tomorrow, then back to weak onshore Thursday before strengthening Friday.  As a result we should see temperatures JUMP a few degrees tomorrow.  94-97 should be common high temp numbers on the 1st of July.

When will the hot weather end?  The GFS says early next week high temps should drop quite a bit and it shows weak troughing nearby.  Yet the ECMWF keeps a narrow hot ridge centered between an upper-level low off California and a trough to our north.  Hmmm, they are once again at odds with each other.  Their respective ensembles seem to mainly support the operational runs as well.  So…I’m not sure if next week is the end of the hot weather or not.

Chief Meteorologist Mark Nelsen

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.


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:


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

Record Temps Today; More Heat Tomorrow

June 26, 2015

11pm Friday…

Portland hit 95 today, but that was one of the “cooler” metro area temps:


Salem hit 100 and you can check out the triple-digit heat east of the Cascades and in Southern Oregon!


It’s been a crazy June, the warmest we’ve seen since PDX became the official Portland observation site around 1940.  It’s also likely the warmest we’ve seen since record-keeping began downtown just 10 years after the Civil War!

Some more records…today was the 6th day at/above 90 degrees here, which ties the June record.  We’ll break it tomorrow.


Due to the very hot and extremely dry conditions, Multnomah County has taken the unprecedented step of banning all open flames…INCLUDING FIREWORKS until further notice.  Luckily that’ll save me some money and it’ll be

Thunderstorms did develop as expected in the central/southern Cascades and they lasted long enough for one strike up around Detroit.  They are done now but expect another round tomorrow afternoon/evening farther north.  We MIGHT see some lightning to our east this time Saturday evening.

Still a chance for a thunderstorm through the day Sunday, then increasing onshore flow plus best dynamics shifting the action north and east mean we’re done with that threat.

Once we get past a scorcher tomorrow (slightly warmer with light wind), a good marine push plus lots of high/mid clouds Sunday means at least a 10 degree drop in high temps.

Temps stay reasonable Monday-Tuesday…in the mid-upper 80s, then a 2nd heat wave arrives Wednesday through the 4th of July.

How hot is “Round 2″ going to be later next week?  Morning models were real scorchers with easterly wind likely pushing temperatures to around 100 again over Independence Day weekend.  00z GFS not quite as crazy, but it’s pretty clear we have a 2nd heatwave as we head into the the 4th of July holiday weekend.

Stay cool this weekend!

Chief Meteorologist Mark Nelsen

A Scorcher Today; Turning Humid With Some Smoke Too

June 26, 2015

9am Friday…

Temperatures will approach 100 degrees this afternoon in the metro area as everything appears to be in place for a 4-7 degree warm up from Thursday’s temperatures.  We were 91-94 in the metro area Thursday, so that puts us in the 95-100 degree range by 4-6pm.

Weather Geek talk follows…

1. 850mb temperature was 21 deg (C) on the morning sounding over Salem, headed for around +24 this afternoon.  If we had easterly wind all the way down to sea level (through the Gorge), this atmosphere would allow a high temperature 100-104 in P-Town.

2. Onshore flow is weaker through the Gorge and winds have turned offshore above the surface.  Yesterday it was 1-2 millibars, right now only 0.7 between PDX-DLS.  West wind has pretty much shut down at the surface now east of the Coast Range.  Up above, sounding shows northeasterly wind all the way up to around 6,000′.  Onshore flow is SLIGHTLY stronger up the Columbia River this morning; that accounts for the high dewpoints (near 60) and humid feel to the air.  I have a feeling some of that will “mix out” this afternoon since it’s such a shallow layer.  Still, dewpoints will likely remain in the 55-60 degree range all day, slightly humid for our area.  We’ll see if they jump this evening.

3. Skies are totally sunny, except for some smoke approaching from the south.  Fires in Southern California and near Lake Tahoe have put a layer of smoke into the atmosphere (way up) and it has made its way into the southern half of Oregon.  The southerly wind higher up around 8,000′ and above will push that farther north.  Might be a nice reddish sunset tonight.  My guess is that we’ll need to get used to fire smoke much of the rest of the summer with big fires already burning in Alaska, Western Canada, & here in the USA West.

4.  Temps are running warmer in the hills already at 9am.  Wanderer’s Peak SE of Estacada (at 4,400′) is already 80 at 9am!  It was 68 at the same time yesterday.

Looking ahead, we’re still on for a good marine push Sunday night and Monday, with an upper-level disturbance depressing the ridge significantly the atmosphere cools quite a bit.  Thus the 80s for Monday and (we’ll see) Tuesday.  Then the ridge pops back the 2nd half of next week.  You can see it in the ECMWF ensemble chart; follow the red line:


You see the dip Monday/Tuesday, then the rise through the 4th of July weekend, then FINALLY a drop to just a bit above normal the week after the 4th.

There is disagreement among models with respect to details for the big holiday weekend.  It will definitely be very warm, that’s not an issue, but at times models have been showing a shot of cool air into Montana and its associated high pressure allowing a thermal trough to develop west of the Cascades.  That is a classic extreme heat situation.  A bunch of our 100+ days have occurred in a scenario like this in the past.  So part of the 3 day period (Friday-Sunday the 3rd-5th) could be scorching hot OR it may just be 85-90 degrees with weak onshore flow.   The 12z GFS and last night’s ECMWF show the first scenario.

Main message here is that unusually warm weather continues for at least another 10 days.

Chief Meteorologist Mark Nelsen


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