Tropical Minnesota: More sun and steam Friday

• 85 degrees: high at MSP Airport Thursday

• 71 degrees: observed dew point in the Twin Cities Thursday

• 2 weeks until the Minnesota State Fair begins

It's mid-August. We've lost about 90 minutes of daylight since late June. The Vikings are already playing pre-season games. The State Fair starts in two weeks. How did that happen?

It's that time of year in Minnesota. We savor these languid last weeks of summer in Minnesota. We burn each Dreamsicle sunset into our weather DNA and store it away for winter. We feel the lap of lukewarm lake water at our ankles and the sand between our toes.

Yes, these last weeks of summer can be the best in many ways. It's the in-between time. No frantic morning track meet getting the kids ready for school yet. Another steamy summer night at your local outdoor dining patio. One more trip to the lake.

We enjoy (endure?) a rare steamy 48 hours in Minnesota through Saturday. Sunday's cool front brings a few storms and significant dew point relief.

Tropical vacation

The air mass over Minnesota is thick with tropical moisture. Dew points in the low 70s feel "close." The dew point waffles a few degrees either side of 70 for much of Minnesota through Saturday. Southwest flow ahead of the next low pressure wave pumps heat and humidity into Minnesota. The next front pushes a few storms eastward through the Dakotas Saturday.

Three-act forecast

The bigger forecast picture still breaks down into three parts. Steamy through Saturday. Temporary relief by Monday. Heavy rainfall potential by the middle of next week.

Both the GFS and European model continue to paint a semi-stalled low pressure system over Minnesota next week. The resulting notion of multi-inch rainfall potential across southern Minnesota is creeping into the seven-day rainfall grids.

It's still too early to say if/when/where heavy rains will fall in Minnesota next week. But it's got our attention in the Weather Lab.

Unprecedented California fires

There have been bigger fires in California before. But something about the way the fires are burning in northern California this summer is turning heads of fire experts there. Explosive growth even with little wind. Unusually active nighttime fire behavior. Record "Energy Release Component" levels. And the peak of fire season still lies ahead.

Here's more on the scary fire scenario from KQED.

It comes down to this: the next couple of months.

Lately Northern California has captured national headlines with fast-moving blazes such the Rocky and Jerusalem Fires in the coast ranges about 100 miles north of San Francisco.

Unlike many epic fires in the California record, which were largely driven by wind, in the fires burning north of the Bay Area, “There really is no signifcant wind,” says Cal Fire Director Ken Pimlott. “It’s all being driven by the condition of the vegetation.”

Which is to say, not merely dry, but four-year-drought dry. Pimlott says Cal Fire measures the potential burn intensity of vegetation throughout the state, and is currently seeing “record levels” of that metric, known as the Energy Release Component.

“It’s just creating explosive growth rates,” he says.

The Jerusalem Fire went from 100 to 5,000 acres almost overnight. But the worst may be yet to come.

As summer gives way to fall, the winds typically shift and dry winds from the east sweep across California, turning an already sizzling fire season into a potential blast furnace.

“As we get into late summer and early fall, not only are we still seeing the potential for extreme fire behavior in Northern California, and the potential for a large number of fires like we’re seeing now,” says Pimlott, but “we also get into that peak window for Southern California with Santa Ana winds.”

Similar winds known as Diablos kick up in the northern part of the state.

Glacial retreat accelerating

We use the word glacial as a verb. Slow. Predictable.

But a new study based on NASA satellite ice analysis suggests the pace of glacial retreat around the globe is historically unprecedented. The visible changes to glaciers in our lifetime is astounding.

Here's more from Climate Central.

The world’s glaciers are in retreat. The great tongues of ice high in the Himalayas, the Andes, the Alps and the Rockies are going back uphill at ever greater speeds, according to new research.

And this loss of ice is both accelerating and “historically unprecedented”, say scientists who report in the Journal of Glaciology.

In the past year or so, researchers have identified rapid rises in meltwater and alarming cases of glacial retreat in Greenland, West Antarctica, the Canadian and Alaskan coastal mountains, in Europe and in the Himalayan massif. They have also watched glaciers pick up speed downhill. One satellite-based study, confirmed by on-the-ground measurements, of the Jakobshavn glacier in Greenland, confirms that the river of ice is now moving at the rate of 46 meters a day, 17 kilometers a year, which is twice the speed recorded in 2003, which in turn was twice as fast as measured in 1997.

Kerri Miller and I spoke about the accelerating pace of glacial change with Dr. Karl Kreutz from the University of Maine on this week's Climate Cast.