Warmest Memorial Day Weekend In Decades Has Arrived

May 28, 2021

8pm Friday…

The big weekend is here folks! I’m at work, and will be part of the weekend, but I know lots of you have plans far away from any job. Maybe headed to (or already at) the ocean beaches, Cascades, Gorge, or Central Oregon?

The forecast is easy this year…all sunshine all weekend from the Coast Range to the Idaho border tomorrow through Monday. Just a few thin high clouds at times. A thin marine layer may return to the beaches Sunday/Monday for areas of low clouds/fog, but otherwise expect abundant sunshine even out there.

Strong high pressure just offshore moves directly overhead at the surface AND high up in the atmosphere the next few days. High pressure = sinking air = mainly sunny & warm. Check out the upper-level ridge over us by Monday; this is a very warm to hot summer weather pattern along the West Coast

Temperatures at 850mb (about 4,000′) soar from around 48 degrees this afternoon, to around 65 by Monday/Tuesday afternoons. That’s about +4 celsius to +18-20 by Tuesday afternoon. That alone will push our high temperatures from around 80 tomorrow to 90 Tuesday. Those temperatures are very dependent on wind direction down here at sea level. Tomorrow will be the one day we get an easterly wind through the Gorge and over the Cascades. Then it’s back to flat or weak onshore flow Sunday/Monday. So even though upper-level temperatures climb Sunday and Monday, we didn’t go wild with high temperatures.

Tuesday is a bit more interesting as a thermal trough (and easterly flow) tries to form west of the Cascades briefly. If that occurs, we could end up INTO the 90s instead of just 90 that day. TBD.

For now, we’re going for these numbers this weekend

If these numbers are correct, IT WILL BE THE WARMEST MEMORIAL DAY WEEKEND IN 26 YEARS IN PORTLAND! That’s if you take the 3 day average of the high temperatures. You can see how it compares with some of the other warmest holiday weekends in the past 40 years. Probably just a little warmer than 2017, just four years ago.

I remember 1983…the earliest we’ve ever hit 100 in Portland AND the only 100 degree day experienced at PDX in the month of May. That was the Saturday. What I remember about that year is the cool/cloudy/drippy weather just two days later with a big marine layer and showers. Quite a swing from 100 to 63 (Saturday to Monday).

If you are headed to the Oregon Coast, or already there, this is what we expect:

And some real summer-like camping in the Cascades too, that doesn’t show up very often for Memorial Day Weekend

As for rain…the next POSSIBLE chance is next Thursday or Friday as the upper-level ridge flattens. A few disturbances could swing by and give us showers or rain.

This will finish off the driest spring on record in Portland, but I’ll save all those dry weather numbers for a Sunday or Monday blog post.

Enjoy your weekend and stay safe!

Chief Meteorologist Mark Nelsen


It Rained! Much Needed Soaking, but Summer Temps Are On The Way

May 25, 2021

10pm Tuesday…

How exciting, some nice downpours FINALLY arrived the past two days. It’s been a typical spring shower pattern; downpours in one neighborhood followed by sunbreaks and warm/dry conditions. That means we’ve seen widely varying rain totals. Today’s numbers…since midnight. A huge soaking east metro, but much lighter many other areas.

Ah, but some of you are thinking you’ve seen a lot more than these numbers show…right? Some neighborhoods have picked up more than an inch in the past two days! I see downpours passed over the Parkrose/Gateway area both days.

Meanwhile PDX, and many other locations, have seen less than 1/2″. This one ain’t pretty, but lots more numbers from the past 48 hours. ONLY LOCATIONS WITH .30″ OR MORE ARE SHOWN. Click for a better view of course.

Does this help our drought situation? Yes and no

YES: Sure, this is enough to water our lawns/gardens for a week. But this just puts off the continued drying as we head toward summer. NO: If we see a normal or drier than average June, this rainfall will just be a blip in a record-setting dry spring. And it appears Portland WILL likely end up with the driest spring on record by the time we get to next Monday night…the end of the month and meteorological spring. That’s because we don’t have any more significant rain ahead.

Tomorrow will be a spectacular spring day. A mix of morning clouds leading to widespread sunshine and warmer temperatures. Low 60s today are followed by low-mid 70s tomorrow. Fresh air after the rain too!

Another cool upper-level trough swings by just north of us Thursday. You can see it on the ECMWF ensemble forecast of 500 millibar heights Thursday. The cool colors represent lower than average heights

I’d be surprised if we get more than .30″ out of this system too. Steady rain tomorrow night quickly changes to scattered showers during the day Thursday. Ah, but then strong high pressure builds along the West Coast just in time for the holiday weekend. Check out the change for Saturday

Higher than normal heights and it becomes more obvious by Monday. That’s Memorial Day AND the last day of May. Looks like July or August.

Another way of looking at this is the 850mb ensemble chart. It shows temperature at about pass elevation (in celsius) over Portland for the next two weeks. Each single black line represents ONE of the 51 ensemble members. The green line is the 30 year average. The red line is average of ALL ensemble members (group average). Blue line is the operational high-resolution run. VERY good agreement with the dip on Thursday; the upper level trough. And then excellent agreement through at least Monday, the 31st. Agreement starts to fall apart after about the 3rd, but notice the ensemble average stays above normal through the next two weeks.

These plots are great tools. Situations like this can give us great confidence that a certain weather pattern IS on the way, not just a possibility.

HOW WARM WILL WE GET? At this time I don’t see the “perfect” east wind setup with a thermal trough west of the Cascades; because the upper-level ridge isn’t as sharp as it could be. But we’re still 6 days out from the warmest days (next Monday/Tuesday). You see those 850mb temps up around +15 or so. That’s not heatwave material for late May or early June, but very warm. Mid 80s seems like a good bet for now. That’s Sunday through Tuesday next week. Another reason to not get wild with high temp forecasts (90 or higher) is that all spring long we’ve seen the ridge offshore forecast to flop in over us, but then as we get closer to the event a trough swings down from the north and pushes the ridge slightly farther west. That would keep us a bit cooler too. We’ll see.

ANY SIGNIFICANT RAIN IN SIGHT? NOPE. Check out the ECMWF ensemble 24 hour rainfall forecast. Again, each horizontal line is one of the 51 members. It’s 6 hour blocks over the next two weeks. Time goes left to right. Not a single member (rare) shows any measurable rain from late Friday through Tuesday. One more reason we are quite confident forecasting a dry and warm weekend. You see some members forecasting rain of some sort returning later NEXT week. But many are totally dry.

To summarize

  1. You should continue watering all your lawns, plants, gardens. The late spring drying has stopped for a few days, but a lot of this moisture will evaporate or get used up by dry plants over the weekend next week.
  2. Prepare for summer weather this Memorial Day Weekend. If I recall correctly we had a warm & summer-like holiday weekend back in 2017 too…the warmest in two decades.

Chief Meteorologist Mark Nelsen


Drought Spreads As Warm & Dry Spring Continues

May 16, 2021

9pm Sunday…

I haven’t posted for awhile, mainly because the weather pattern hasn’t changed much. This hasn’t been an especially busy time for meteorologists in the Pacific Northwest!

Don’t get me wrong, it’s been a WONDERFUL spring outdoors west of the Cascades. I can’t believe how many days I’ve been greeted by bright sunshine outside the window since early March. I’ve spent almost my entire life west of the Cascades in Oregon and Southwest Washington. And I sure don’t remember a spring like this one! Day after day of dependably dry weather for outdoor activities. Sure, some years we’ve seen very dry weather in April, or May, or parts of each month. But never continuously from March through mid-late May! We were cool in March, but then since that time temperatures have been much warmer than average. We are living through a “central/eastern Oregon spring” this year west of the Cascades. It’s real nice, but you’ve noticed a lack of trees and in general a lack of green east of the mountains right? That’s what would happen here if every spring was like this one!

WHERE WE STAND RIGHT NOW

After checking some weather stats…

  1. Portland & Astoria are experiencing the driest spring on record so far (March 1st to May 16th). Only 2.01″ at PDX in the last 2.5 months! Rainwise, March was like a typical June, and both April+ May have been drier than a typical July! You see the result…grasses already are drying as if it’s late June or early July. The ground is hard and dry as if we’re in early-mid summer. Not good. Pendleton is 2nd driest, and Salem is seeing the driest in 82 years (1939). Portland hit 83 today, the 8th time this season.

2. Snowpack has melted much quicker than normal since April 1st. What WAS a great snowpack, well above average in northern Oregon, is now well below what we would typically see in mid-May. Or, in many spots it’s gone. Take a look at the Mt. Hood Test Site. Black line is this year, representing snow water equivalent. Basically how many inches of water are contained in the snowpack at 5,400′ near the bottom of Pucci Lift at Timberline. GREEN is an average year. The “X” in late April signifies the average “peak snowpack” date and number. In an average year, the snowpack at this location peaks out in late April, then melts out totally by July 1st. But this year saw an above average snowpack. It peaked early, but has been melting much more rapidly than normal. At this rate it’ll be gone at least three weeks early.

3. Many Willamette Project reservoirs (Detroit, Green Peter, Lookout Point, etc…) will not fill this year. A few have even begun to drop already. Detroit Lake is still about 18 feet below where it should be this time of year.

4. The Klamath Project has so little water that both irrigators and fish lose this time. For the first time in 114 years, no water will be sent into the main irrigational canal this year. The AP calls it the “worst water crisis in generations” in southern Oregon. Read more here. I remember 2001 and the war over water then. Looks worse this time.

Some answers to a few questions I’ve been getting…

ARE WESTERN OREGON SPRINGS GETTTING DRIER DUE TO CLIMATE CHANGE/GLOBAL WARMING?

NO – Actually spring rainfall has been very slowly rising the past 100 years. That said, it’s possible that global disruption in circulation (induced by man-made warming) can bring more extremes. Of course there is lots of debate over that. You can see in the 128 year history of Salem spring rainfall, no real obvious trend, But LOTS of ups and downs. Every year is different; we have periods of wet springs, then dry springs. This is one of those very dry years, like 1992, the first summer I was forecasting out of college.

IS THERE STILL TIME TO “CATCH UP” BEFORE SUMMER?

Technically YES, we COULD get 6″ of rain between now and the end of June. But that’s VERY unlikely. Look at the rainfall we’ve received at PDX from this point forward to the end of June over the past 10 years in the chart below. Somewhere between 2-3″ is normal for this last part of spring and early summer. If we have a June like last year (wet!), that would alleviate some short term water issues, and maybe fill more reservoirs. But July-September would still be a problem. We will need a long wet season next fall/winter. At this point the choice seems to be between “somewhat serious water issues” vs. “historic water issues”. That would be with respect to water supply, groundwater, & vegetation survival.

DOES THIS MEAN IT’LL BE A HOT SUMMER?

We don’t know. There’s no specific reason to think this coming summer will be hotter than normal, although that HAS been the trend for quite a few years. We haven’t had a “cool summer” in almost a decade. Some years we do get a soaking of rain in late August. That would be nice this year.

DOES THIS MEAN WE HAVE A TERRIBLE FIRE SEASON AHEAD?

It could be. Of course the “table is set” for a bad fire season with the early warm & very dry weather. But FAR MORE IMPORTANT is what happens weather-wise DURING fire season. I’ve seen bone-dry conditions in June, then we get occasional cool/moist periods later in July and August, leading to no significant fires.

Lightning is very important too. More lightning = more fires. Less lightning = better fire season.

WHAT’S AHEAD WEATHERWISE?

  1. There’s no sign of a significant pattern change (soaking widespread rains) in the next 10 days. That puts us into the last week of May
  2. But we WILL see some rain in these next 10 days, just not enough to alleviate drought/water concerns.
  3. Temperatures will be milder again (closer to normal) all this work week and into next weekend. There’s no sign of a heatwave. That is one thing we’ve avoided this spring, no extended periods of record breaking warm/hot temps.

A cold upper-level trough moves overhead Tuesday/Wednesday this week

Then by the weekend it’s over Idaho, bringing beneficial showers to eastern Oregon and that state. But that doesn’t leave much rain west of the Cascades.

By the middle of next week (10 days away), the troughing is much weaker and we should be mainly or all dry.

How much rain? All models agree we don’t get a big soaking from those cool showers this week. GFS here shows only 1/4 to 1/2″ at best. That’ll keep fire danger low, but barely penetrate into the top of our soil.

15 day forecast from ECMWF ensembles show the drought conditions continuing. An inch or less the rest of the month west of the Cascades.

I am more concerned now compared to 3 weeks ago when I said it wasn’t time to panic…yet. Hopefully a pattern change shows up at the end of the month or early June.

Chief Meteorologist Mark Nelsen


Bad News: Mountain Snowpack Rapidly Melting This Spring

May 5, 2021

11pm Wednesday…

A short blog post tonight! Just to point out how quickly the snow/water situation is going downhill as this warm-ish and VERY DRY spring continues…

Snowpack on April 1st…pretty good across Northern Oregon, below average across the southern half of the state

Today…what a change! Much worse. The extremely dry April and warm temperatures have taken a big toll

Now it’s important to point out that early & end of season maps can be deceiving. For example there are many lower elevation stations that don’t typically still have snow on the ground in early May. That could skew the average. But the point is that things are heading downhill quickly and I don’t see any change through mid-May. Take a look at the Mt. Hood Test Site near the bottom of Pucci lift at Timberline (5,400′)

The GREEN line is the typical accumulation of “snow water” through the season. The colored areas represent lowest to highest snowpack on record on any one date. Green area is an “average” year. At this elevation, the abundant February snows brought the snowpack up well above average (BLACK line). And a cool March preserved that snow. However the lack of precipitation in March means a peak occurred a bit earlier than normal. Now it has slipped below average! Basically A GREAT SNOWPACK IN LATE FEBRUARY AND EARLY MARCH IS NOW MELTING FASTER THAN NORMAL. The whole snowmelt season is earlier and more condensed this year. At this rate there won’t be snow on the ground more than another month…unless we go back to cool and wet weather.

Farther east, in the Blue Mountains, this site shows something similar…well above normal snowpack in March, then a rapid melt right now. It’ll be gone in a couple days…earlier than normal!

This spells trouble for our water supply. In fact Willamette Valley Project reservoirs are running well below where they should be in late spring. Most of these lakes reach their maximum “full pool” level at the end of the spring filling season. That’s right now. But two months of very little rain is a big problem.

Detroit Lake (one example) is about 17 feet below where it should be.

So…we need rain, but I don’t see anything significant through the next week. I’ve never seen it this dry at this point in the spring.

Chief Meteorologist Mark Nelsen


May Arrives With More Dry Weather

May 2, 2021

A new month is here, but the weather pattern hasn’t changed much.

We ended up with .39″ rain at PDX, making it the driest April on record.

At the last minute (the last few hours of Friday) a surge of rain fell throughout the Willamette Valley. That pushed Salem’s total down to only #20 driest. Still near the upper end, but no record. Olympia ended up 3rd driest, Astoria was 2nd driest, North Bend was #4.

Of course spring continues to be the driest on record in Portland. Same in Astoria, Eugene, and Pendleton. It’s the 2nd driest spring on record at Olympia. But only #13 at Salem. IF PDX gets less than 2.20″ or so this month, it’ll still be the driest spring on record there. But it CAN rain a lot in May. One can argue we are overdue. We haven’t seen a “wet” May since 2013! Hopefully this May (or June) we’ll get a good soaking at some point

May in our area sees a gradual transition from the cool spring weather to (usually brief) periods of summer conditions. In many years we see at least a few days in the 80s, or even some brief 90s, before a return to more seasonal temps in the 60s/70s.

What do I see through this first 10 days of May? First we have a very weak/dying front moving overhead tomorrow afternoon. Little or no rain with this one. Then a strong ridge of high pressure pops up briefly Wednesday. A combination of strong offshore flow & thermal trough (in blue) west of the Cascades should give us one day of 80 degree weather Wednesday. Check out the offshore flow for 5pm Wednesday.

We might even get temps 75-80 Wednesday midday/PM on the northern Oregon coastline. Due to 850mb temps forecast between +15 and +17C over Salem, it’s possible we hit 85 and our warmest day of the year.

Then it’s back to onshore flow near sea level for Thursday. At the same time a cool upper-level trough is approaching. This is right overhead Friday/Saturday for lots of showers. Maybe some thunder? We will see. Colors here represent upper-level height anomaly. Red = higher than normal heights

Unfortunately, this doesn’t appear to be a big pattern change. By Sunday the 9th the cold trough is leaving the area and higher than normal heights fill the Gulf of Alaska. This keeps significant wet systems away from us

It’s still there on Thursday the 13th.

This leads me to believe we won’t see a significant wet spell in the first 10+ days of May. Keep watering! If we get lucky, maybe 0.50″ out of the showers Friday/Saturday

By the way, we recorded a fun FOX12 WEATHER podcast last week. We caught up with Stephanie Kralevich! She was a member of the weather team here for about 9 years from 2005-2014. Some great old stories…find it in Apple Podcasts or you can listen directly here: https://www.kptv.com/podcasts/weather/

Chief Meteorologist Mark Nelsen