Vacation Time

July 7, 2014

I have this week off; it’s summer vacation time.  So no posts, but you aren’t missing much anyway.  Enjoy the sunshine, marine air with its clouds, and blue skies…

I’ll be back on Monday the 14th

Chief Meteorologist Mark Nelsen

Happy Independence Day! Nice Weekend Weather

July 3, 2014

Did you know the 4th of July is the wettest day in July…on average?  More on that in a minute…but first we have a very nice weekend coming up.  Other than a weak weather system giving us lots of high clouds Friday and maybe even a coastal sprinkle, expect widespread sunshine and warming temps Friday through Sunday.


The average high temp for the 4th is 78 degrees, and the chance for getting measurable rain is 24%, which also happens to be the highest chance for rain of any July day!  Interesting eh?  Even more fascinating is that my kids, heading into 7th/8th grade, have never seen rain on the 4th!  Maybe we need to retire the old “summer starts after the 4th of July” statement?


Speaking of summer, temperatures warm through Monday or Tuesday as very high upper-level heights (lots of warm air) build over the West Coast.  It’s not going to be a sharp upper-level ridge, but more a very large area of warm air.  So we won’t see a thermal trough with the easterly wind like earlier this week.  Luckily that means no real hot weather; I think it’s unlikely we’ll get above 90 degrees.  And a high of 90 in Portland in early-mid July is nothing unusual; about 10 degrees above average.  Such a large ridge will keep the marine layer squashed quite low so we won’t see much morning cloud cover through at least Tuesday/Wednesday.

Summer 2014 is definitely here.

Chief Meteorologist Mark Nelsen

Today was “Melt-Out Day” on Mt. Hood

July 2, 2014

Have you ever wondered how long it takes all the snow in the Cascades to melt?  Of course it depends on the elevation, with higher elevations (cooler temps) taking longer.  Well today was the day the Mt. Hood Test Site saw the last of its snow melt.  Actually the snow depth sensor finally went to zero yesterday, but the “snow pillow” that measures snow water equivalent is still seeing a little.  I’m not a sensor expert, but decided today was close enough.

I’ve had some spare time at work the past few days, so I wanted to see if the date at that location is earlier or later than in the past.  You might be surprised at what it shows!  Data at that location at 5,400′ goes back to 1981.


You can see the earliest was the drought year 1992 when the snow disappeared by May 25th.  The latest was just three years ago in 2011, when the last of the snow disappeared the 2nd week of August.  Now the data period is quite short; only about 30 years, so don’t try to draw any earth-shattering conclusions, but the trend is definitely for a slightly later melt-out in the past 9 years.

I think it’s fair to make these two statements as well:

1. At the 5,400′ elevation on Mt. Hood, the snow is not melting any earlier than in previous decades.  If anything it is sticking around longer.

2. The Cascade snowpack AT THAT ELEVATION and IN THAT LOCATION is sure not disappearing!


When I get some more time I think it would be interesting to see if lower elevation locations are similar, such as 3-4,000′ spots.

Chief Meteorologist Mark Nelsen

99 Final High Temp Today

July 1, 2014

Sophie High Was it the warmest day of this summer?  One would hope so, but historically it’s unlikely we’ve had our warmest temperature so far.  Take a look at just the past 10 years.


Last year the 97 on June 30th was the hottest of the summer.  The average over the past 10 years is July 28th, and you can see in about half the years the hottest of summer is in late July or August.

Cool marine air is surging inland nicely at 11pm with temperatures in most of the Willamette Valley down to around 70.  That cool air will continue to pour in through tomorrow.  High temps should be 15-20 degrees cooler as a result.  Part of the cooling will come from extensive mid-level clouds the first part of tomorrow due to an upper-level disturbance moving by.

Ahead of that disturbance this evening there is quite a bit of thunderstorm action moving north along the east slopes of the southern Oregon Cascades…actually heading into the Central Cascades at this hour.  So I wouldn’t be surprised to see flashing to our southeast within a couple of hours.

Chief Meteorologist Mark Nelsen

98 Today…As of 5pm

July 1, 2014

What a mid-summer scorcher today, take a look at the high temps!


We get the high temperature from official observing sites every 6 hours, which in summer is 5pm and 11pm.  Now the 5pm temperature IS 98 degrees, which means it’s possible we’ve gone to 99 and don’t know it.  Portland NWS also puts out a climate summary around 7:20pm just for the PDX site which means for that site only we’ll really know what the high temp was.  Got all that???

More later…

Chief Meteorologist Mark Nelsen

July 1st: One Day Heat Wave Ahead!

June 30, 2014

The next 48 hours should be fun as we see an abrupt switch to strong offshore flow (rare in July) tonight through Tuesday afternoon, pushing high temps into the mid-upper 90s in the valleys.  Then just as quickly we get a surge of wind off the chilly Pacific Tuesday evening through Wednesday, so high temps will drop 14-18 degrees in one day.  Further cooling Thursday means highs in the mid 70s.  So I think everyone can find something they like in the next 3 days.

The Details

  • We’re forecasting 97 for a high at PDX Tuesday, at least a 10 degree jump from today.  That is the warmest we saw last summer too.
  • That will be the warmest so far this season, we hit 91 back on May 14th, the first 90 of the year.
  • It will not be a record because there was a heat wave during this time in 1942 and we hit 105 on July 1st!
  • No high humidity…we’ll see dry east wind, our typical hot weather pattern.
  • Gusty east wind develops at the west end of the Gorge and over the Cascade foothills by sunrise, then it’ll surface in some areas in the lowlands
  • The Oregon Coast should be very warm, especially north of Pacific City, but light west wind after the noon hour should cap Lincoln City and Newport’s high temps below 80.
  • There is only one very warm and sunny day coming at the coastline…that’s tomorrow.

BMAC Summer Highs 10 years


June has not seen any temperature extremes, in fact until today (June 30th) we didn’t even get above 81!  A bit weird considering the month was average temperature-wise.  One would think at some point we would have seen an 85 or 90 but no.

Tomorrow’s forecast high temperature has been steadily creeping upward the past few days, partly due to confidence in a sharp thermal trough setting up west of the Cascades, but also due to 850mb temps warming in successive model runs.  The 12z suite of models (NAM, GFS, ECMWF) are all showing +22 to +23 deg. C over Salem tomorrow afternoon.  Looking at my chart of past cases with easterly flow at that temperature, we should see a high between 96-100 degrees, so my 97 might be slightly low.  Everything appears perfectly aligned for maximum heating tomorrow, including a drop off of the wind at max temperature time around 4-6pm.  There is even a chance we hit 100 tomorrow afternoon at PDX.

Since the upper-level trough is shifting east rather quickly later tomorrow and Wednesday, the center of warmest weather will shift quickly east of the Cascades tomorrow night and Wednesday.  That means a pretty decent onshore flow will immediately follow tomorrow’s offshore flow.  And that equals a quick cooldown.

The rest of our 7 day forecast has ridging to the east and upper-level trough to the west, with us in the middle.  That pattern will bring us the morning clouds and afternoon sun routine.  Here is a glance at the 12z ECMWF 850mb ensemble chart:


Note the huge spike tomorrow followed by cooler temps through the 5th, then a bit warmer than average next week.  The GFS disagrees


showing temps near average through the 8th, and the operational run is the chilliest of all the members.  So (normal operating procedure) I ignored the GFS.

Chief Meteorologist Mark Nelsen



2.00″ In One Hour! Flooding Rain, but No Thunder This Evening

June 25, 2014

Here are the final numbers from this evening’s deluge:


Notice the really heavy stuff (1.00″ or more) was centered along the west slope of the West Hills from Forest Heights down to Garden Home.  That includes the western edge of Portland and eastern part of Beaverton.  The highest total comes from a home weather station located just south of US 26 east of OR 217.  That station recorded 2.05″ from 5:40pm to 6:40pm, plus or minus a few hundredths.  That is officially a Gully-Washer, or at least that’s what I’ve decided.  This is what you shouldn’t do…drive into a flooded area:


This was the result of a car driving through water under US26 on Baltic Avenue on the westside…


muddy water up above the doorline.


At 10pm the driver said the water was up to his knees!

There was another area of heavy showers on the east side of Vancouver and then up into Battle Ground.  I saw some 1.00 to 1.50″ totals in isolated spots up there.  But check out the official totals at the airport observing sites


Almost nothing (or nothing) fell in Scappoose, Hillsboro, Aurora, and Troutdale.

Back to regular showers the next few days, then warmer the early part of next week.  Initial signs are a trough approaching as we head towards the 4th…

Chief Meteorologist Mark Nelsen


Get every new post delivered to your Inbox.

Join 286 other followers