Severe threat west, many dry weekend hours

Timing is everything in life. And weather.

Low pressure sliding through the Upper Midwest this weekend favors severe storms in the Dakotas early, then the severe threat shifts into Wisconsin by late Saturday. The timing of the low's passage overnight across Minnesota should mean nighttime and early morning thunder. Sun returns Sunday before shower chances increase again Sunday night.

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NOAA

Saturday's early morning arrival of storms in the Twin Cities should (in theory) reduce the severe threat for eastern Minnesota and the metro area.

Overnight we watch a likely Mesoscale Convective System (MCS) blow up in the Dakotas spawn a bow echo with damaging winds that could survive the trip in western Minnesota in the wee hours of Saturday. Again, in theory the line of storms should fade below severe limits as it approaches the Twin Cities around sunrise Saturday morning.

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Here's another look at probable timing of storms as we move through Saturday morning.

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Bow echoes are notorious for damaging wind events. The forward momentum of the MCS can reach 50 mph. Damaging straight line (downburst) winds are most likely near the apex (tip) of the advancing bow echo. Tornadoes can spin up the the so called "bookend vorticies" on each end of the bow. Think of it as the wake flow your canoe paddle makes as you push it through the water.

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NOAA

The highest chance for damaging winds is in western Minnesota in the wee hours of Saturday morning.

Wet Grandma's Marathon

Further north the forecast for rain still looks likely for Grandma's Marathon and Duluth Saturday morning. Bring the rain gear and expect temperatures in the low 60s during the race.

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Duluth NWS

The good news? As the front clears Saturday afternoon the forecast favors drier skies the rest of the weekend. We may actually squeeze in more dry hours than wet in the metro on summer solstice weekend 2015.

Rock The Garden: Mostly dry with a chance?

Rock the Garden at the Walker Art Center looks mostly dry, but I can't rule out a chance of a pop up shower or thunderstorm Saturday. I'll be there Doppler watching and providing weather support for 89.3 The Current this weekend.

Here's a closer breakdown of the potentially dry hours this weekend.

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Weatherspark

Summery next week

Next week looks like summer as warmer air nudges north into Minnesota. Some mid-80s by the middle of next week? Where's the nearest beach?

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Weatherspark

Pope's encyclical reactions mount

Pope Francis long anticipated encyclical “Laudato Si” (“Be praised”) continues to generate worldwide comment.

I'm impressed with the quality of the science near the top of the document. As I said on our special hour long Climate Cast on MPR News stations Thursday, the opening paragraphs of Pope Francis' letter reads more like a science journal than a religions text.

Perhaps that's not surprising. It turns out the pope is a scientist.

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NOAA

This New York Times piece has some good perspective from Michael Mann who I have interviewed on Climate cast.

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The new papal encyclical on the environment is a ringing call to action, a critique of consumerism and a prophetic warning about the dangers of ignoring what Pope Francis calls “the ecological crisis.”

But amid all his soaring rhetoric, did the pope get the science right?

The short answer from climate and environmental scientists is that he did, at least to the degree possible in a religious document meant for a broad audience. If anything, they say, he may have bent over backward to offer a cautious interpretation of the scientific facts.

For example, a substantial body of published science says human emissions have caused all the global warming that has occurred over the past century. Yet in his letter, Francis does not go quite that far, citing volcanoes, the sun and other factors that can influence the climate before he concludes that “most global warming in recent decades is due to the great concentration of greenhouse gases” released mainly by human activity.

Michael E. Mann, a climate scientist at Pennsylvania State University, pointed out that the bulk of the evidence suggests that solar changes and volcanoes have slightly counteracted the warming effect of greenhouse gases. “Human activity is most likely responsible not just for ‘most global warming’ but all of it, and then some, because natural factors have been acting slightly in the other direction,” Dr. Mann said.

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IPCC

The Wall Street Journal has some perspective on how the pope cites markets as a contributing factor to climate change.

The 183-page document, which Pope Francis addresses to “every person living on this planet,” includes pointed critiques of globalization and consumerism, which he says lead to environmental degradation.

“The Earth, our home, is beginning to look more and more like an immense pile of filth,” he writes.

The encyclical’s severe language stirred immediate controversy, signaling the weight the pontiff’s stance could have on the pitched debate over how to respond to climate change.

“Economic powers continue to justify the current global system where priority tends to be given to speculation and the pursuit of financial gain,” he writes. “As a result, whatever is fragile, like the environment, is defenseless before the interests of the deified market, which become the only rule.”

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EPA

So did the Pope get the science right? Mostly according to ThinkPrograss.org.

 ThinkProgress asked three climate scientists to weigh in on three specific passages in the encyclical that get wonky about the science of climate change, and got varied answers. However, all three said Francis (who himself has a technician’s degree in chemistry) was correct that humans are causing potentially catastrophic climate change via greenhouse gas emissions.

“Based on what I have seen of the science in the encyclical, most climate experts would find little to disagree with,” said Anthony Broccoli, a professor of environmental sciences at Rutgers University.

In passages 23, 24, and 25 of the encyclical, Francis discusses the science of climate change at length. “A very solid scientific consensus indicates that we are presently witnessing a disturbing warming of the climatic system,” it reads. “[A] number of scientific studies indicate that most global warming in recent decades is due to the great concentration of greenhouse gases (carbon dioxide, methane, nitrogen oxides and others) released mainly as a result of human activity. Concentrated in the atmosphere, these gases do not allow the warmth of the sun’s rays reflected by the earth to be dispersed in space.”

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US Coast Guard

Mashable's Andrew Freedman, another Climate Cast guest, has some perspective on why he thinks the Pope's letter was too conservative on the actual ground truth and accelerating pace of climate changes today.

The reality is that global warming is happening more swiftly, and having more severe and increasingly evident repercussions worldwide, than the pope's encyclical says. Here is how he describes the scientific consensus on global warming:

A very solid scientific consensus indicates that we are presently witnessing a disturbing warming of the climatic system. In recent decades, this warming has been accompanied by a constant rise in the sea level and, it would appear, by an increase of extreme weather events, even if a scientifically determinable cause cannot be assigned to each particular phenomenon.

... It is true that there are other factors (such as volcanic activity, variations in the earth’s orbit and axis, the solar cycle), yet a number of scientific studies indicate that most global warming in recent decades is due to the great concentration of greenhouse gases (carbon dioxide, methane, nitrogen oxides and others) released mainly as a result of human activity.

None of this is incorrect, per say, judging from numerous reports by groups including the U.N. Intergovernmental Panel on Climate Change and the National Academy of Sciences, as well as hundreds of studies in peer-reviewed scientific literature. But it's a huge understatement to say that "a number of scientific studies" blame global warming on manmade greenhouse gases.

That's akin to saying, "Well, a number of studies say that smoking can cause cancer," which leaves open the possibility that a number of credible studies say the opposite.

There will be much more perspective in the coming weeks no doubt. One trend to watch: Will the pope's conservative theme of taking care of our planet and personal responsibility for our actions resonate among climate skeptics?

Stay tuned.