Vacation Time

July 19, 2017

I will be on vacation most of the next 2 week, heading both north into Canada and south to Diamond Lake.  It’s the best weather of the year so time to get outside and the weather looks quite slow as well.   No posts until at least Sunday the 30th.


Another Perfect Day

July 17, 2017

11pm Monday

For many of us this summer season has been just perfect.  Pete Ferryman even mentioned it’s the best summer he can remember recently.  I think there are 3 reasons for that.

  1. NOT MANY GRAY MORNINGS  We have seen very few gloomy marine layer days in the past month.
  2. COOL NIGHTTIME TEMPS  Wow, what a change from the last 5-6 summers!  This morning was another chilly one with lows down into the 40s in many parts of the metro area. Homes cool off quickly in the evening and air-conditioning is hardly needed.
  3. LACK OF EXTREMES In past 11 days…every single day has been between the lower 70s and mid 80s.  No showery 67 degree days, but no 90+ days either.

Look at the lows last night…as cold as 40 out in Colton, but low-mid 50s in the city

PDX Observed Low Today

This continues our summer theme; a real lack of “very warm” nights.  I doubt many of us are complaining

60 Degree Nights Portland

Those numbers are up through July 18th…remember how unbearable Summer 2015 was?  For sleeping this summer has been the best since 2011.  Little or no air-conditioning needed!

And of course our daytime highs have been quite reasonable since that brief hot spell back in late June

High Temp Last 13 Days

But what I’ve really noticed is the sunshine.  It seems like almost every morning I’ve been waking up to sunshine (or at least partly cloudy skies) since the 3rd week of June.  I don’t care if highs only make it into the low-mid 70s; a sunny start to a day really raises my mood!

I expect more of the same for the next week or two.  Other than a brief passage of a disturbance this Thursday, I don’t see a setup for rain showers.  Even then, the chance of getting measurable rain Thursday is looking quite low.

Chief Meteorologist Mark Nelsen

 


Eclipse Weather: Hopefully Better Than Today!

July 13, 2017

11pm Thursday

There will be tremendous pressure on meteorologists in August to produce a sunny forecast on a certain day about 5 weeks from now.  Will it be sunny across the Pacific Northwest at 10am on Monday August 21st?  Of course that’s the date/time for the big solar eclipse.

We don’t know about the weather or cloud cover this far ahead of time of course;  we won’t start seeing glimpses of what might happen until at least 7-10 days ahead of time.

But we CAN go back in time and see what has happened historically.    Take a look at NOAA’s work on historical cloud cover over the region on that date:

Eclipse Cloud Climatology 3

The best place to be based on past weather is east of the Cascades.  The worst is along the coastline.

The WORST CASE SCENARIO for the eclipse would be a wet upper-level low sitting over the Pacific Northwest giving almost all of us mostly cloudy or cloudy skies.   The BEST CASE SCENARIO would be tomorrow’s weather…a thin marine layer that gives mostly or all sunny skies to the entire region, including the coastline.  Neither scenario is very likely.  More likely is some sort of cloud cover SOMEWHERE west of the Cascade crest.  Look at what happened today with a thick marine layer!  9am satellite pic:

Satellite GOES16 Vis Only

If the eclipse was today, almost no one west of the Cascades below 4,000′ would have seen it!  But everyone in the Cascades and east of the mountains would have had a cloud-free view.

It all depends on what kind of weather pattern we are in, but again, the best chance for clear sky is over and east of the Cascades.  I’ll be stationed both Sunday night and Monday morning/midday in Madras doing live reports on FOX12.

Keep your fingers crossed!

Chief Meteorologist Mark Nelsen


The Perfect Weather Pattern? July So Far

July 10, 2017

10pm Monday

The weather is extremely slow this week once again as we continue under an unusually stable summertime weather pattern.  Let’s be honest, it’s pretty boring in the weather center.  That’s fine though, summer is time for hiking, camping, bicycling, and all sorts of water sports.  Time for some vacation days!

Today is our 24th consecutive dry day in Portland; not unusual, but as mentioned in previous posts it started a bit earlier than normal.  In fact the rainfall anomaly (percent above/below average) for the past 2 months shows spring ended and summer started drier than normal; quite a turnaround from winter and early spring.

 

Temperatures have been running about 2 degrees above normal here in Portland, but anywhere east of the Cascades it has been a scorching hot first 1/3rd of July:

4 of the past 5 years we’ve seen these above normal temps in early July.

There is no sign that we’ll see a return to either cool and showery weather (unusual in mid to late July) or extreme heat in the next 10 days.  Take a look at the 500 millibar (18,000′) height anomaly for this coming Saturday.  It shows the western ridge strengthening once again, but far enough to our east to avoid a heat wave west of the Cascades:

 

Looking ahead to NEXT Wednesday, the 19th?  The ridge weakens a bit, but upper-level heights are right around normal.  Normal above = average tempratures down here where we all live.

Then out to Day 10…

The ridge might try to strengthen a bit again…maybe some warming.  But nothing extreme heat-wise.  Keep in mind this is from the ECMWF ensembles, which is a collection of many different runs as opposed to looking at just one run of the model.  Note the GEFS ensembles (from the somewhat inferior American equivalent GFS model)

show little or no rain in the next two weeks, which seems reasonable in the pattern shown by the Euro model above.  I think most of us would say we deserve this unusually stable summer weather pattern after the winter of nearly constant rain, freezing rain & snow.  So get out and enjoy what nature is providing you this Summer of 2017!

Chief Meteorologist Mark Nelsen


Happy Independence Day!

July 3, 2017

10pm Monday

The weather looks excellent for our nation’s big holiday!  A little on the warm side in the afternoon, then just right for fireworks

Independence Day Fireworks Forecast

I’ll be doing some emceeing out at the Corbett Fun 4th Festival after 5pm…look for the bright flag shirt!  Plus the only fireworks show east of I-205 in Multnomah County.  Let me tell you, conditions will be FAR better than 6 months ago in the same location!

Weaker onshore flow the next 3 days means warming temperatures as we stay in the “sweet spot” between a blazing hot upper-level ridge centered over Utah and a cool upper-level trough way offshore.

Jet Stream Forecast 2017

We will see just enough of nature’s air conditioning west of the Cascades (ocean air) to keep our high temperatures at or below 90 degrees…no heat wave for us.  But for you folks east of the Cascades?  This will be the hottest period so far this summer.

Looking farther ahead, we’re heading through our 3rd dry week with no rain in sight.  Relatively high heights (upper-level ridging) holds through the next 1-2 weeks.  So our stable summer weather pattern will continue as long as the strong ridge is sitting just to our east.  Notice the lack of rain on the European model ensemble forecasts for Salem.  Each horizontal line is one member.  Green says .10″ rain accumulation.  Only 2 of 51 members generate .10″ = most likely it’ll be dry or mainly dry for the next 2 weeks.

KSLE_2017070312_eps_precip_360

June just finished of course and it appears we’ve broken the string of 5 cool & wet months (December-April).  Both May and June were warmer than normal across most of the West, including Oregon.  Here’s the temperature anomaly for the past 60 days:

anomimage

Precipitation has turned around dramatically since the very wet winter and 1st half of spring.

precip

Only coastal Oregon and parts of Western Washington were around average, it’s been drier across the rest of our viewing area and Oregon.

That warm & dry pattern continues through early July…stay cool and keep watering your plants/lawns/trees!

Chief Meteorologist Mark Nelsen


4TH OF JULY: LOOKING DRY

June 28, 2017

Due to our mild & dry pattern, it appears the big holiday will be pretty reasonable this year.  Most likely high temperatures somewhere between 70-80 degrees, pretty normal for this time of year.

Mark IndependenceDayHistory

I remember sitting through some very chilly fireworks shows here in Northwest Oregon, but my 16-year-old son hasn’t seen a wet Independence Day.  You have to go all the way back to 2000 to find a wet one!

That’s especially strange considering that any one July 4th has a 24% chance of getting measurable rain in Portland.  And this one is always surprising…JULY 4TH HAS A HIGHER RAIN CHANCE THAN ANY OTHER JULY DAY!  It’s just a fluke of course, but bizarre that it happens to occur on a holiday.

You may remember the sweltering 4th just 2 years ago during the great heat wave of 2015.  Last year was a bit cool though.

Mark IndependenceDayHistory2

Regardless, we’re in pretty good shape this year!

Chief Meteorologist Mark Nelsen


Stable & Dry Summer Weather Pattern Arrives Early

June 27, 2017

10pm Tuesday

Today was about as “average” as it gets for a late June day.  We hit our typical high of 76 with afternoon sunshine following the morning cloud cover.  And of course it was dry as well.  Here in Portland we haven’t seen measurable rain in 11 days:

Mark Dry Spells Summer Recent

Remember that 2012 dry spell?  It didn’t start until early September!  That was a strange early fall dry period.

We have turned dry because those showery spring upper-level lows have weakened and are staying well to the north.   So basically weather maps and models look just like July/August right now and we have entered the warmest/driest time of the year in the Pacific Northwest.  It’s time to hit the rivers, mountain lakes, Gorge, Coast, hiking, camping, bicycling and anything else you wait all fall/winter/spring for. We’ll get just enough onshore flow over the next week to keep hot weather away, but we WILL see a thinner marine layer the next few days.  That means slightly warmer temperatures.

Then a few weak disturbances slide by later this weekend and the first half of next week; that will increase the onshore flow = increasing morning clouds & cooler temps.

Take a look at the Global Ensemble Forecast System (GEFS) temperature anomaly (departure from normal) over the next 16 days.  The general trend is clear…warming the next few days, a downturn but only to around or slightly below average around the 3rd/4th.  Then warming again after the 4th.  A very stable pattern with mainly above average temps.

gefs_anomaly

A different way to look at it; the ECMWF ensemble chart showing maximum temperature from its 51 different members

ecmwf_15day_maxtempensemble

You see quite a few members showing this Friday as the warmest day (the 30th) and then warming again around the 5th/6th.  This shows good agreement among two different models.

As for rain…it looks very dry.  Sure, we can always sneak in some sprinkles or marine air drizzle, but that’s about it.  The GEFS says little or no rain the next 16 days.  Each horizontal line below is one of the 21 ensemble members.

gefs_precip_16days

So enjoy the weather…you’ve waited MANY months for these few guaranteed warm and dry weeks of the year.

By the way, on a side note, today is “melt-out” day at the Mt. Hood SNOTEL Test Site.  This evening the snowpack is just about all gone at that 5,400′ elevation.  The last week it has been melting very quickly.  3 days ago there was 10″ of water content in the snowpack, this evening it will be down to just under 2″ by midnight.  That’s the threshold I use for this graph showing the melt-out date for the past 36 years:

MtHoodMelt

Until the last 3 years the average date hadn’t changed much, but the very early melt-out the past two years (late May and early June) mean the trend is EARLIER for snowmelt AT THIS ELEVATION on the mountain.  We’re only talking a few days, but something to keep an eye on in coming years.  With a warming climate one would assume the date will gradually creep earlier and earlier.  We’ll see.

Chief Meteorologist Mark Nelsen