Wednesday, April 20, 2016

The Big Meltdown Followed By A Cool Down

The record breaking temperatures of the past few days and warmer than normal temperatures of this month have resulted in substantial melt of the formidable snowpack we started with on April 1.  And the rivers are responding.

To illustrate the snowmelt, here is the plot of snow water content at Stampede Pass at 4000 ft on the eastern side of the WA Cascades (normal snowpack is the light blue).  We were near normal around April 1, but have lost about 20% since then.

This massive melt of water is causing a number of rivers on the eastern slope of the Cascades  to approach flood stage, with predicted floods on some.  To illustrate, here are the hydrographs, showing the observed and predicted river levels and discharge for the Okanogan, Stehekin, and Naches rivers--all are predicted to flood during the next few days.

Spring flooding from snowmelt is not unusual, but it was generally absent last year because the snowpack was so poor.

During the next day, we are about to transition to a far cooler, wetter pattern as the ridge of high pressure weakens and moves westward.  The upper flow pattern changes substantially.  Here is the 500 hPa (18,000 ft) upper level map for 5 PM today (Wednesday). Big ridge centered over the Rockies, with a weak disturbance (trough) over Oregon--which has brought some thunderstorms to western Oregon and SW Washington.

 72 hours from now (5 PM Saturday), the ridge has weakened and westerly/southwesterly flow has invaded the West Coast.
As a result, over the next 72 h precipitation will return:  light over WA, but substantial to the south over Oregon and CA (see below).  Such precipitation is unusual for CA this late in the season and very welcome.
Want to be impressed?

The forecast total precipitation over the next two weeks by the GFS model is quite wet for the Northwest (see below), with some areas getting 4 inches or more.  Temperatures will return to normal.  I think folks are ready for some normal weather again.


Rod said...

Happy for California!

Lori said...

Yes! I am ready for cooler weather to return, and some rain. Back to normal--yay!
Was hiking at Heather Lake yesterday. Snow all around at lake level but the melt was incredible and scary for this time of year.

Loren Herrigstad said...

What is surprising me are the forecasts for rain and showers that were supposed to start Wednesday — but we keep getting sunny days. Thursday was supposed to be gloomy and showery, yet once again I am looking at bright sunshine and cloud-free skies outside my window in southwest Washington State.

So why are forecasters, even the National Weather Service, getting forecasts even 24 hours in advance so consistently wrong this week? Having both urged and helped a relative cover piles of stacked wood Wednesday against the forecast onset of rain, I'm looking little short of idiotic today. With all these forecast computer models, and decades of accumulated experience now, I expect forecasters to get next day forecasts more accurately than forecasting rain and getting bright sun instead.

So please, let's do a better job of getting forecasts right here, or go back and retool the models. This degree of blatantly erroneous forecasting, especially in the high-tech Twenty-First Century, is just not acceptable!

Matt Thompson said...

Thank you for the update. Normal would be nice for a bit. I had heard it is supposed to be a bit on the cool side, all over the west, to start May. Heat in the East apparently, but we will see.

Michael Kennedy said...

The prior 4 consecutive days have been, in my opinion, remarkable for the record shattering high temps. The 89 degrees on 4-19 crushed the prior record by 12 degrees which is huge. However, I was most astonished by the 30 degrees above average for that day - 89 vs 59. I do realize that Seatac data and records are only 70 years old. Can this 30 above average be put into context by suggesting the opposite anomaly - what if the high temp for the 19th was 30 degrees below the average and only reached 29 for a high. I think that most people with even a little weather / climate experience would say that is highly improbable. The climate is indeed changing and seems to be changing in one direction.

Reader said...


We try to plan a bike ride each week. When it became apparent it would be too hot on Tuesday, we moved it to Wednesday. Wednesday morning we were thinking Thursday would be more appropriate because it was cooler and no rain expected until the evening. Here in Olympia, except for some rain before 7:00 am, the day was dry, just as NOAA forecast.

There is a nice graph the NOAA weather service displays, the Hourly Weather Forecast. If you are not using it already, you might consider checking it. The main icon and weather description for the day may announce rain but when you check the hourly graph, you may find the rain is not forecast until later in the day.

As to stacking the wood, consider that while you stacked wood on Wednesday, you then got a nice Thursday and, this Friday, here in Olympia at 7:00 am we have already had .21 inches of rain.

Snoqualmie Joe said...

And here we go again, NOAA forecasts are out and it looks like the west is headed for another above average temperature outlook and another warm summer. Some in the PNW may enjoy that type of warmth but I moved here to get away from the heat!

John Marshall said...

When I was young (a very long time ago), we complained or rejoiced about the weather.

Now people mostly complain about the weathermen.

Back then, weather was nature or God, depending on your perspective. Now weather is a decidedly human responsibility. If it is isn't as expected, then its a human failing. Humans changing it. Humans not predicting it accurately.

Most days I think this represents progress for the weather forecasting profession.

But on other days I'm not so sure.

Ellen K said...

I loved the nice weather but ready for rain to return. Otherwise I'd have to start watering my garden, which I usually avoid until July. And want a more 'normal' hiking season this year. Last year most of the mountain flowers were bloomed out by late July.

sunsnow12 said...

Michael said – “I was most astonished by the 30 degrees above average for that day - 89 vs 59. I do realize that Seatac data and records are only 70 years old. Can this 30 above average be put into context by suggesting the opposite anomaly”

How about January 31, 1950? Avg. low 37; actual low 0. 37 degree variance the other way. In fact the entire month of January that year was off the charts - the average temperature that month was 25. Here is Scott Sistek a few years ago talking about it – ( And it has not been repeated – in fact we have not come close. So when put in perspective of the opposite type of anomaly, I liked this week better – personal opinion only!

Karl Fredrickson said...

I agree with Michael Kennedy's comment. When was the last time we had a 30 degree below normal cold wave? If global warming is just adding a bit of warming to our normal weather, shouldn't we still be getting some 25 degree below normal cold waves? I think it's time to consider that climate change may be starting to have some scary nonlinear effects in addition to the gradual warming we've seen over the past decades.

Matt Thompson said...

Snoqualmie Joe: Don't trust NOAA for hardcore prediction. They 100% blew the winter prediction here, and I have a hunch that with El Nino leaving rapidly, the summer will probably be normal for the most part. It is too early to say anything about summer with everything in flux, especially with ENSO go towards neutral. I think a lot of models are off at this point.

Michael Kennedy said...

Sunsnow - Point taken, thanks for looking that up. I had a suspicion that that period had greater differences. I think that because it was 65 years ago matters and occurred in a period / past when there generally more snow and freezing temps. You could ski at Mt Pilchuck in the winter and now it is mostly a hiking trail. I joke that warming is not a bad thing for western WA but deep down, I am concerned.

sunsnow12 said...

Michael -

I wanted to add here that if you are looking for more recent examples of large negative variances, some of the midwest and east coast winters of the last few years have had many. Case in point: Chicago, on January 6th 2014, was -16. The average low for that day is 17. 33 degree negative variance.

The interesting thing is if you google "polar vortex climate change", you get 269,000 results... ie there are plenty of people who believe a negative variance is also a sign of climate change. Cliff said this back in 2014 about it (1/6/14):

"It is SO frustrating that every major weather event causes such claims and counterclaims to be aired, with many media outlets unable to do the minimal research that would allow them to give the public more dependable information. All this bogus reporting has done substantial damage, with many American's believing that global warming is already causing our winter weather to become more extreme, while the observational evidence suggests no such thing. One day some sociologists will study this situation and the psychological elements that drove it."

If you get a chance google it, it's a great blog post!

Snoqualmie Joe said...

Matt Thompson: Yes they did and I am hoping they blow the summer prediction as well! Would love to see a more temperate summer this year!

Matt Thompson said...

Snoqualmie Joe: What I find about NOAA is really excellent data collection. They really have a gold mine, if you are talking about raw data. But for whatever reason, their predictions are not good. The current 30 day prediction for May is what it was a few months ago, that is, it didn't change much at all. They didn't change anything in fall or winter either. It was the same thing everymonth, below normal precipitation, above normal temps. So I wouldn't trust them at all at this point. There are other sources for better prediction. I like the blog section of Weather Underground where you can find numerous articles on the weather and upcoming trends.

Snoqualmie Joe said...

Well right or wrong, we are once again heading towards the 80 degree mark for the third time this April. I can only imagine what it means for this summer.