Cool Memorial Day Weekend ahead, but not all wet

May 24, 2022

7pm Tuesday…

The big holiday weekend is approaching quickly! Last year was the 2nd warmest Memorial Day Weekend on record in Portland. That sure isn’t happening this year!

(kptv)

We have seen some warmer weather lately which has been nice. I’ve been able to work in the yard and garden sans mud. But May is still running (so far) the coolest since 2011.

(kptv)

Those numbers are for Portland, but I checked Salem which has been influenced less by the urban heat island. This month was close to the average temperature from the early 1960s to early 1980s. That WAS a cool period, but the point is that this “chilly May” isn’t really all that bad and we’ve sure seen it before.

We’ve all had a chance to get outside and enjoy dry weather for several days now. No measurable rain the last 4 days at PDX is the first time we’ve seen 4 consecutive totally dry days since early February! A few passing showers have dropped a trace today, with some of you picking up measurable rain this evening. Definitely more than I expected. Of course we picked up our typical May rainfall in the first half of the month:

(kptv)

High pressure strengthens a bit tomorrow and Thursday for warmer temperatures. I expect low-mid 70s both days. But then things are going downhill once again. The warm upper level ridge overhead will be replaced by a wet westerly jet stream by late Friday. Even California will get some showers…unusual in late May

(kptv)

By Monday, a chilly upper-level trough is sitting over the western USA. We will be on the cool side of that jet stream Saturday, Sunday, and Monday.

(kptv)

Right now it appears we won’t see that many showers Friday, but an organized (& wet) system comes through the region Saturday. Showers may even show up in the driest parts of central & north-central Oregon Saturday. Then expect lots of leftover showers Sunday. The good news? Most of the cool/wet airmass has moved to the south and east by Memorial Day itself. That means the 3rd day of the weekend could be best.

(kptv)

Weather this long weekend might be better along the beaches…not so many “pop-up” showers Friday and Sunday near the chilly ocean water. This is what I’m thinking for the northern Oregon and southern Washington coastline

(kptv)

With a cold airmass over us through the weekend, higher elevations are NOT the place to be. Expect snow as low as 5,000′ during the overnight hours. Passes will be fine, but it’s a cold/wet camping experience at the Cascade lakes!

(kptv)

By the time May ends and June arrives (Wednesday), the cold trough is gone and that means much warmer and more typical weather.

(kptv)

Just 4 days later the Starlight Parade is on tap…it’s too far out to see if another trough will be dropping in for a visit. For now it seems safe to say that we’ve got a few days of showers from late Thursday through Sunday, then drying the middle/latter part of NEXT week. You can see the gap in the ECMWF ensemble chart

(kptv)

SUMMARY

1) A cool and somewhat showery weekend is on tap across the ENTIRE Pacific Northwest. But not a soaker every day

2) Wettest should be Saturday and Sunday. Much more reasonable (or mainly dry?) Friday and Monday

3) Expect mountain snow down to 5,000′ at times

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4) Even the driest parts of the region in the Cascade rain shadow (Central Oregon) will get at least a few showers

Chief Meteorologist Mark Nelsen


How can we be in a drought with so much rain, and why are forecasters talking about it?

May 16, 2022

7pm Monday…

It’s a totally fair question I’ve been getting on social media and even on email…

WHY ARE YOU TALKING ABOUT DROUGHT AND RECORD RAINFALL AT THE SAME TIME? or…

HOW CAN WE POSSIBLY BE IN DROUGHT? MORE “FAKE MEDIA” WEATHER NEWS? (someone actually suggested that 2nd one)

Two answers:

1) The Portland television market is much larger than you think. We broadcast to temperate rain forests and also to very dry deserts. Some areas ARE in severe drought right now, but others (everywhere west of the Cascades) have plenty of water for the next few months. No drought here!

2) East of the mountains, regular rain & mountain snow has improved conditions slightly over the past 6 weeks. But it takes a long time to erase a 2-3 year long drought!

First, the USDA Drought Monitor shows the current extent of drought. NO drought from Eugene north to the Canadian border. We have plenty of water this year west of the Cascades. Notice the Cascades themselves are just fine too.

Now take a look at the Portland TV market viewing area. These are counties where Portland television is the dominant local TV news source. There are about 200 TV markets around the USA.

Portland TV Market
Portland TV Market

Notice it ends at Albany west of the Cascades (Eugene is its own TV market), and does not include Bend/Deschutes county east of the mountains. Yet it extends to Baker and Harney counties! “Gerrymander” is the word of the year, and it applies to our viewing area. All Portland TV stations focus on these areas. You’ll notice our forecasts generally cover these areas. Sometimes I’ve had people ask why we don’t forecast for Medford or Klamath Falls. That’s because they have their own TV stations down there.

Now lay that over the Drought Monitor and you see maybe 50% of our geographic viewing area is in drought. That said, only about 10% of our viewers live east of the Cascades. Something like 85% of our viewers live just in the I-5 corridor counties from Longview to Albany, thus our focus here. But we sure don’t want to leave those of you east of the mountains out of either forecasts or drought talk…and THAT is why we cover it.

Of course April and May HAS been cooler/wetter than normal east of the Cascades in the drought areas. Notice the foothills of the Blue Mountains (Umatilla River drainage) is in good shape now after lots of mountain snow and some rain events. But back in Central Oregon things are still very bad. Redmond picked up less than 1″ of rain since April 1st! Wickiup Reservoir is already dropping since irrigation season started last month. Prineville Reservoir is below last year (a drought year) and WAY below normal.

(Credit: USBR)

To summarize (again)

IF YOU LIVE OVER OR WEST OF THE CASCADES NORTH OF EUGENE there will be plenty of water this summer and we are not in a drought

IF YOU LIVE IN MOST OF THE REST OF OREGON a third year of water shortages, low reservoirs, & irrigation cutoffs has begun

Chief Meteorologist Mark Nelsen


A wet & cool Pacific Northwest spring will continue

May 11, 2022

9:30pm Wednesday…

I’m hearing lots of complaining the past week or so as our chilly spring weather goes on. These last two days were quite reasonable with partly cloudy skies and dry conditions (for most of us). But even with the dry weather, we only made it within 5 degrees of normal today!

(kptv)

That’s because we’re still under the influence of a chilly upper-level low leaving to the south of us. Plus a brand new batch of cool air is swinging in tonight through Friday. You can see that 2nd upper low coming down the coastline

(kptv)

This has been the story for about 6 weeks now. Starting around April 9th, we’ve seen lower than normal upper-level heights over our region. In fact, the anomaly is just about the coldest in the entire Northern Hemisphere over the past month! Along with a cold anomaly over the Arctic Ocean.

(NOAA)

So one could argue it doesn’t get much colder than this from early April to early May. I just checked the past 30 days at PDX. Coldest since 2011. For the locals, this is running quite similar to other cold springs like 2008, 2002, & 1996.

(NOAA)

How about measuring our spring another way? Number of 70 degree days at this point in spring (at PDX)

(kptv)

Only 4 days at/above 70 degrees. That’s quite a change from the past few years. The average is around 9 days by May 10th. Again, this is similar to 2011, 2010, 2003, & 2002. In the last 10 springs, we’ve hit 80 degrees by May 10th, but not this year. We’ve only hit 75 twice. In a typical spring we see more up/down with chilly troughing followed by warm upper-level ridging.

I think the screaming message here is that WE WERE DUE FOR A CHILLY/WET SPRING AND NOW IT’S HERE. There’s nothing especially “unusual” about this spring. No, it’s not caused by climate change. And we’re not seeing any significant trends with temperature or precipitation in springtime west of the Cascades. Obviously summers are turning much warmer but that’s a different story. As mentioned in a previous post, in general springs have been just a little wetter compared to many decades back in time.

WHAT’S AHEAD?

More of the same folks! A cold front moves inland Thursday with another .25-.50″ rain west of the Cascades, then a 2nd (weaker) system comes inland Friday night and Saturday morning. So we’ve got a soaker ahead Thursday morning, then much better by evening between those systems. Behind that 2nd system, a warmer southwesterly flow (no cold upper low!) pushes temperatures up around normal for the weekend. No, I don’t see a warm and sunny weekend, but at least the showers will be warmer and we COULD make it into the lower 70s Sunday IF the showers are widely scattered. So clearly Sunday is the better day of the weekend.

By the middle of next week models agree that another cool trough drops into the region, keeping us cooler than normal through all of next work week.

(kptv)

Many times I’d look a bit farther ahead (beyond 10 days), but the past month we’ve seen models regularly push us back into climatologically normal (warmer) pattern. And each time a cold upper-trough decides to crash the party. For now I think it’s safe to say:

  1. We’ll see below normal temps through at least the 20th of the month
  2. There’s no sign of a sustained dry spell for at least the next 10 days.

I won’t be staining my decks for quite awhile…


Are springs getting wetter? Not really, but lots more rain ahead!

May 3, 2022

10pm Tuesday…

It was dry today!

Morning clouds gradually broke up to afternoon sunshine west of the Cascades. Tomorrow (Wednesday) should be a spectacular spring day. Dry and about 10 degrees warmer. All of us in the I-5 corridor west of the Cascades should make it into the 70s. I expect little or no morning cloud cover and just thin high clouds drifting across at times.

Today on Twitter I had someone ask if the heavy rain was a sign of climate change (global warming). I promptly said NO, it’s just a return to wet spring conditions we haven’t seen for awhile. But I figured it’s time to take a closer look. Here’s what I found:

1. Total rainfall has not changed dramatically in the mid-late spring the past 100 years, there is very little change in the past century west of the Cascades. That’s at Salem, Portland, or even Redmond (Central Oregon)

2. There appears to be a very slight increase in rainfall during that time.

3. We have consecutive years with wet springs, then a few dry will follow. Or quite a few years wet with a really dry one sandwiched in. You get the idea, it appears to be somewhat random.

Get ready for a few graphs. Here’s the entire April+May rainfall record from Salem. This goes back to the late 1800s. Each bar is one April/May total rainfall. Click for a better view:

(NOAA)

First, notice the wide variation from year to year. Some years very wet (1991, 1993, 1996), some quite dry (last year). The black line is the 10 year average. Not much change right? Maybe a minor peak in the late 1990s? The red line is the long term regression line. There has been a minor increase in rainfall during these 125+ years. What about Portland?

(NOAA)

Similar wide yearly variation. Same up/down motion over the decades with that 10 year average. A bit of an increase in spring rain overall like Salem. We just went through 4 dry springs, so it was time for a wet one and here we are.

In case you’re wondering about east of the Cascades, in a severe drought right now, this is Redmond

(NOAA)

Quite a change from year to year. We’re in a desert environment here, so a “wet” year is 2″ or more. 10 year average peaked around 2000 as well. Still, not a huge change over the past 80 years, but maybe a few more wet springs the past 20 years? It didn’t make it onto this image, but the regression line shows a minor increase across the entire period of record. It’s getting slightly wetter in spring in Redmond compared to many decades ago.

WHAT’S AHEAD

We’ve had some VERY dry May weather the last few years. In fact we haven’t had a wet May since 2013! I think it’s payback time…

May Rain
May Rain(kptv)

We have a LOT of wet weather scheduled for Thursday through Sunday, and possibly next Monday. After the break tomorrow, a strong westerly jet punches right in the PACNW Thursday & Friday. The view Thursday night up around 18,000′

(kptv)

Then Saturday the one upper-level trough is swinging through with a deeper trough developing way out to the west

(kptv)

By Sunday a cold upper-level trough dips farther south with rain/snow way down into Central California. We are in a cool/unstable/showery airmass that day

(kptv)

The ECMWF model is likely too wet, but I think somewhere between 1-2″ rain is likely in the western lowlands by Sunday night. Notice the 3″ of rain in the Cascades. Much of this WILL fall as rain Thursday/Friday since freezing levels will be high

(kptv)

With the cool/unstable airmass, we’ll probably get a round of thunder & hail showers once again over the weekend. And with the large upper-level low overhead, the possibility exists that significant rain COULD fall in parts of Central Oregon. Fingers crossed!

There are hints that we dry out a bit next week. But looking at the GFS ensembles, it’s clear that plenty of members bring more showers overhead later next week.

Rainy
Rainy(kptv)

At this point I’m not sold that we’re entering a warm/dry period starting next week. Models have been putting off a warming/drying trend recently. I’m thinking in this La Nina spring that we’ll see more troughs dropping in from the northwest. We will see.

The main message here is that we have a very wet 4 days ahead…I have plans to clean the garage, maybe catch up on some streaming? I know I won’t be doing any gardening after tomorrow for quite a few days!

Chief Meteorologist Mark Nelsen


April 2022 ends wettest on record, plus a possible tornado in Tigard this evening

April 30, 2022

9pm Saturday…

It’s rained a lot this month, in fact we’ve seen 24 days of measurable rain in Portland, just one under the 25 day record set in 2010. Oh that spring…yep, both 2010 and 2011 were something else. In fact we haven’t seen a cool/wet spring since that time. It’s possible that we’re now in “payback mode” for all the warm/dry springs we’ve seen recently. I am quite confident we won’t have a dry start to May, after tomorrow.

With just 3+ hours to go, it IS the wettest April we have seen in Portland. I think we are done with the rain so these should be the final numbers. Official PDX records go back to 1940.

(kptv)

Records have been kept at various locations around downtown Portland since the 1870s too. At that location, it’s probably the wettest since 1937 (over 6″), and only 1883 was wetter with almost 8″ of rain.
Do you remember LAST April? The DRIEST on record

(kptv)

Some other numbers around the region…

(kptv)

Notice Portland is wettest in the Willamette Valley. This is not the wettest April on record in either Salem or Eugene. Both have seen 7″ at some point. April 2003 was one real soaker. It’s also disappointing how little snow/rain made it into Central Oregon. We’ve seen lots of westerly flow in the lower part of the atmosphere and the Cascades block much of that moisture. The far eastern 1/3 of the state has done well though. Breaking the month down a bit more, only 6 dry days, but only 3 were really wet with more than 1/2″ rain. Lots of showery days.

(kptv)

We’ve all notice the cool temperatures too, but that hasn’t been record-breaking. 3 degrees below normal and the coldest in 11 years. This April is similar temperature-wise to 2003, 2008, & 2011.

(kptv)

Last night’s stratiform (steady) light/moderate rain combined with some heavy cells east metro this afternoon led to some big rain numbers. Gresham and Corbett areas picked up 1.00″to almost 2.00″. The 1.53″ and 1.65″ and 1.33″ numbers in Corbett are part of PGE’s new fire weather network. High quality Campbell Scientific instruments. They’ve also installed some of those around North Plains, Scotts Mills, and a few other fire-prone spots.

Heavy rain east Multnomah county
Heavy rain east Multnomah county(NOAA/NWS)

As the last of the showers were winding down this evening, it appears a weak tornado (or landspout?) touched down at Cook Park in Tigard. I’ll admit I briefly thought this video was fake, but then watched a couple more times. A child could have been crushed or anyone seriously injured as that heavy metal roofing few through the air. Notice the circular motion. If you listen closely you can hear the rush of wind and see it on the parent’s clothing just before it tears the roof off. Maybe a landspout? A gustnado? That 2nd one seems less likely since there was no widespread gusty wind occurring anywhere nearby, this was a highly localized gust. There are 3 home weather stations within a mile and they didn’t pick up any significant wind.

Enjoy tomorrow because May starts with dry weather…for one day. I think it’s very unlikely we stay dry as a wet system comes inland Sunday night and again late next week. I’m somewhat confident the streak of very dry Mays will end this year. Seems like 1″ of rain is likely just in the next week, possibly more. We will see if we get a “wet” May. that hasn’t happened since 2013! That would require a continuation of the cool/wet pattern with frequent upper-level troughs moving through the region.

(kptv)

That’s it for now. Happy May!


Spring 2022 turns cool & wet

April 19, 2022

Meteorological spring in the Northern Hemisphere runs from March 1st to May 31st. It’s the 3 month period between winter and summer. This year was looking a bit like last year through the first few days of April; a bit warmer and drier than normal.

How things have changed the past 10 days! Numerous rounds of cold showers and mountain snow have been the rule since the 10th. Take a look at temperatures so far this month in Portland. The dark blue days are high temps 10 degrees or more below average. So far we are running close to 4 degrees below average, one of the coldest first 18 days of the month we’ve seen.

Then the precipitation. Lots of it. As of this evening it’s the 8th wettest April on record with lots more rain ahead.

Compare that to the last two very dry Aprils. In fact we’ve already picked up more rain this spring than the last four!

Of course snow has been falling heavily at times the past 10 days. All basins in Oregon have seen significant improvement with PLENTY of water now available in the central/north Cascades and NW Oregon. We won’t need to worry about drought in the NW quarter of the state this summer. But a different story continues in central, south, & SE Oregon. It’s more a matter of “bad” instead of “terrible” for the irrigation season. You can’t erase two years of drought with 1-2 weeks of heavy mountain snow and rain

On April 1st, it was looking like we might have a quick melt-off once again. But check out the SWE (snow water equivalent) just east of Government Camp. That’s inches of water in the snowpack. Black line is this year. Notice it has suddenly swung back upward right when it is typically melting (green line)

The same thing at Clear Lake about 5 miles SE of that location. A dramatic change from two weeks ago!

WHAT’S AHEAD?

A cool upper level trough will be swinging through the region tomorrow and Thursday. The atmosphere was marginally unstable today and we could have seen thunderstorms west of the Cascades. But thick cloud cover kept things from getting going. Tomorrow should be a bit more interesting. A system moves overhead in the morning, followed by a cool and unstable airmass flowing in from the southwest. Models are giving us low Lifted Index, relatively high CAPE, and the SW to NE storm movement has historically been good for thunderstorms and possibly funnel clouds. Assuming we get plenty of sunbreaks, I expect scattered thunderstorms to pop up midday and into the afternoon hours. I’ve seen much better setups with better dynamics, but it always seems to easy to get a few storms going in April-May-June around here. Typically they are weak, but we’ll see if anything more significant shows up tomorrow. The NAM-3km shows the best CAPE around 5-6pm, although it shows more than other models.

My gut feeling is we have a typical spring shower/downpour day (with sunbreaks) on tap for tomorrow with a few embedded thunderstorms. Probably a funnel cloud or two as well. Check out this great timelapse of a funnel cloud last Wednesday evening.

ANY DRY WEATHER AHEAD?

Not really, at least more than a couple days at a time. I’d like to get a few cold weather veggies planted and I’m thinking that could be next Monday. That’s because it appears we’ll get some brief upper level ridging this coming weekend, then another cool/wet trough swings through next Tuesday/Wednesday. There are hints we turn a bit drier right after that time…around 9-10 days from now. You can see that in the ECMWF ensemble chart which takes us into the first few days of May. So the short answer is NO, I DON’T SEE A LONG DRY/WARM SPELL IN THE NEXT 10 DAYS.


The April 2022 bomb cyclone snowstorm

April 18, 2022

I almost never use the term “freak” while describing weather events, because media can easily overuse the word. But one week ago we saw a freak mid-April snowstorm in far NW Oregon and SW Washington. I use the term because, just like the heatwave last June, the setup is unlikely to be repeated again in my career (or lifetime?). The reason for this post (a week later) is that I want a good record of the event. I was out of the area. In fact I was on the other side of the planet, somewhere between Greece and Montenegro on a large ship. With little/no internet. Typically April is a “safe month” for a chief meteorologist to take a vacation. I hit the wrong week this year.

April is generally considered a relatively mild month weather-wise in our region. Cold showers mixed with warm sunny spells is normal. Sometimes those cold showers can contain snow pellets, hail, or even snow mixed in. At 1,000′ in the hills it’s not even unusual to get snow in April. I’ve had brief morning snowfalls a few times at my home the past 18 years in that location. There was nothing really unusual about Tuesday and beyond last week – lots of cold showers with thunder and hail. We have had some very mild Aprils lately, in fact April has been turning warmer as our climate warms. Notice how often we used to have sub-50 degree highs in the past compared to now.

But in the past 8 days we have reverted to a chilly pattern similar to what we’ve have seen in the past. We hit 75 the day I flew out of PDX. But then things went downhill around the 10th

That snowstorm one week ago goes WAY beyond a normal chilly April weather setup though. It was the perfect “snow storm” pattern that would have given us 10-15″ snow in the metro area if it would have been December-early February. Maybe most interesting is that it was almost perfectly forecast by models, yet (just like June heat wave) meteorologists were doubtful that such an extreme event could occur so late in the season and downplayed snowfall totals. I would have gone for lighter snow just like local mets did that Sunday ahead of time.

500mb forecast charts show cold air dropping south as a cold upper-level low sweeps across the area Sunday night through Monday night. 1st image is Sunday afternoon, next is Monday 8am. All these charts are from the WRF-GFS model.

By Tuesday another cold trough was swinging through, then the last of the really cold stuff moved by Wednesday

What has happening down below? The approaching trough spun up a very deep surface low. Notice on Sunday it’s about 1014 millibars (mb)

It crosses the coastline Sunday night around Lincoln City, then is east of Madras by 5am Monday. This wasn’t about “cold east wind” like wintertime. It was about very heavy precipitation dragging the snow level down lower than it would typically be during an event like this in April. At this points a breezy northwest wind had picked up across the snow storm area.

So at this point it’s down to around 993 mb. That’s a 20 mb. drop in 24 hours – technically a bomb cyclone passed right across Oregon last Monday! It’s rare to see a low deepening AFTER it crosses the coastline. By 11am Monday it’s way over in NE Oregon and you can see the dynamic cooling is ending over NW Oregon and SW Washington. Most lower elevation spots are changing back to rain at this point.

Those are some serious atmospheric dynamics (lifting and atmospheric cooling) going on around such a quickly deepening low pressure area. And it’s well known that the area just north of a surface low can give some great precipitation and snow totals. Take a look at the precipitation forecast from Sunday evening through Monday evening. 1 to 1.5″ likely, a big April soaker!

Now look at the snowfall forecast from the WRF-GFS from Sunday evening. Just about nothing south of Wilsonville or Chehalem Mtn. A foot is possible in foothill locations (and West Hills), 5-8″ in parts of Clark County and hills of Clackamas/Multomah counties. And 2″ in lowest elevations along Columbia River in middle of metro area.

To make a forecast of 2″ snow in Portland in mid-April, when that hasn’t happened anytime after first few days of March? I think I would have said Trace-1″ and left it at that. Quite a good performance by models!

The final snow totals…

FINAL THOUGHTS

  • This was a historic event for our area. I’d say it’s similar to getting a couple of 90 degree days in mid-October. Or maybe similar to a 3″ snowfall in the city for Halloween? A freak snow storm for sure!
  • 1.6″ fell at NWS Portland, and 2.0″ downtown, both the latest on record. 0.3″ fell the next day (officially), but that was mainly graupel and temperature didn’t fall to freezing. We will see if that number remains.
  • The weight of extremely wet snow (falling at 33-34 degrees) approaches that of an ice storm. Lots of trees either snapped off or fell over under the weight. I lost all or part of two ornamental trees, yet they’ve been fine through several 1″ ice storms. No leaves on those trees either.
  • It’s unlikely this will happen again in our lifetimes, or at least in the next 20 years. Everything had to work out PERFECTLY to get the heavy/wet snow down to sea level. Timing + precipitation intensity. Similar, but not as extreme, events occurred in April 1963 and April 1936.
  • If it had occurred 6-10 hours later, it’s likely no snow would have stuck in the lowest elevations. Notice that Portland officially picked up 1.5-2.0″ snow, out of 1.40″ precipitation that day. It just barely worked out in the lowlands. The high later that day was 51 degrees! If we had been 25-30 degrees with this setup, a solid 10-18″ could have fallen in the entire metro area. The track of the low was similar to the January 1998 snow storm.
  • Out of all that drama, we didn’t get a freezing temperature in Portland. Latest frost is still March 10th.

ABOUT THAT FORK

Each February, I have people asking me if winter is “over” in February. And each year they ask if it’s okay to turn on outside water spigots, take off the chains, or if we’re done with the chance for an all-day snow event. So about 15 years ago I started “forking winter”. Twice during that time I’ve been burned. In late March 2012 a heavy/wet snowfall of 1-8″ occurred in parts of the Willamette Valley. Then this year we had a real snowstorm 6 weeks after I pulled out the fork. To be clear, March and the first week of April was very mild this year and we are definitely in spring. Yes, it can snow in spring every 10-30 years in the lowlands. Just like it can get hot in fall or spring too, but that doesn’t mean it’s summer. I’m guessing the same people thinking I should drop the fork thing will be asking next February 20th… “Is winter over?” We will see!

Chief Meteorologist Mark Nelsen