Soaking rains tomorrow, Lake Minnetonka adopts new ice out definition in 2014

This might be the quintessential spring day in Minnesota.

A chilly morning. Strong sunshine. A milder afternoon. Light winds make for a pleasant day today. The cacophony of newly arriving birds fills the air. Tender shoots of new plant life poke up from once frozen soils. Long frozen lakes are finally giving up ice and going liquid again.

Yes, the season formerly known as spring is here.

Aug. 22 -- today's sun angle and intensity is about equal to Aug. 22, right around State Fair time

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NOAA

Temps push into the 60s today across southern Minnesota with 50s up north. The now intense sunshine is much better at heating up the atmosphere over Minnesota that it was even a few weeks ago.

Soaking rains tomorrow

Today's bright sun gives way to a much needed soaking tomorrow as the next strong low pressure wave rides east.

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NOAA

Rain spreads from west to east across Minnesota early Wednesday. Scattered showers and thunderstorms fill the sky and the first real widespread spring soaking rains will linger into Thursday.

Most locations around Minnesota should pick up at least .5 to 1 inch with some (lucky) spots soaking in 1 inch-plus by Thursday afternoon.

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NOAA

Some of the more aggressive models are cranking out an inch plus for the metro with this system. Spring rainfall can vary widely from one town to the next.

Those who are fortunate enough to pick up an inch or more will likely be under any localized convection within the overall system.

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Iowa State University

 Cooler week rolls on

NOAA's Global Forecast System has done a better job than the often superior European Centre for Medium-Range Weather Forecasts model recently with our local weather patterns.

Here's a detailed look ahead, a string of days mainly in the 50s with rain possible again late Sunday onto Monday morning.

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Weatherspark

Ice out progressing nicely

The lakes are giving up their ice a little faster than last year.  More reports will come in today, but ice is now out on many Minnesota lakes south of an Ortonville-Willmar-Twin Cities line.

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Minnesota DNR

In the Twin Cities metro, lakes Harriet and Calhoun went out on Easter Sunday. Medicine Lake was ice free Monday, and Lake Minnetonka and White Bear Lake may be officially declared ice free today or tomorrow.

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Minnesota DNR

The definition of "ice out" varies from lake to lake. Here's more from the Minnesota DNR.

The definition of lake ice-out varies from lake to lake, and individual to individual. For some, ice out occurs only when the lake is completely free of ice. For others, ice out is defined as the moment when navigation is possible from point A to point B. And yet for others, ice out is when 90 percent of the lake is ice free.

Due to the variable definitions of this rather subjective observation, the participating agencies attempt to contact the same individuals each year to maintain a consistent record for a particular lake.

Ice Out
Ice gives way on lake Minnetonka. Paul Huttner/MPR News

Tonka adopts new ice out definition in 2014.

Lake Minnetonka has an interesting ice out history. Freshwater Society founder Dick Gray used to call ice out when the lake was navigable from any shore to another.

The Hennepin County Water patrol used a looser definition --  when a boat could navigate from its headquarters in Spring Park Bay in the Upper Lake through the narrows channel into the Lower lake and around Big Island.

This year the two will get together on a new definition of ice out for Lake Minnetonka according the the Freshwater Society.

Beginning in 2014, the Freshwater Society and the Hennepin County Sheriff’s Water Patrol will jointly declare and announce ice-out on the lake. Under the new procedure, a Freshwater representative and a deputy sheriff will travel in a sheriff’s patrol boat to check lake conditions. The boat will take a broad route around the Upper Lake and Lower Lake. The decision to declare ice-out will be made when the patrol boat can navigate through the lake’s bays and channels without impediment from ice floes.

Here's a look at the ice out calendar for Lake Minnetonka. Note that 2012 was the third earliest ice out and 2013 was the third latest. That's the biggest year-to-year range in 159 years of data.

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Freshwater Society

Our rain this week should help take out more lake ice in the metro and central Minnesota.

Here's a great look at how ice melts from the bottom up,  from Ed Swain of the Minnesota Pollution Control Agency.

  • In the late fall, the lake loses heat to the atmosphere, and then on a day or night when the wind is not blowing, ice forms. The ice gets thicker as long as the lake can continue to lose heat.

  • In most Januaries and Februaries, snow both reflects sunlight and insulates the lake. With a thick snow layer, the lake neither gains nor loses heat. The bottom sediment is actually heating the lake water slightly over the winter, from stored summer heat.

  • Around March, as the air warms and the sun gets more intense, the snow melts, allowing light to penetrate the ice. Because the ice acts like the glass in a greenhouse, the water beneath it begins to warm, and the ice begins to melt FROM THE BOTTOM.

  • When the ice thickness erodes to between 4 and 12 inches, it transforms into long vertical crystals called "candles." These conduct light even better, so the ice starts to look black, because it is not reflecting much sunlight.

  • Warming continues because the light energy is being transferred to the water below the ice. Meltwater fills in between the crystals, which begin breaking apart. The surface appears grayish as the ice reflects a bit more light than before.

  • The wind comes up, and breaks the surface apart. The candles will often be blown to one side of the lake, making a tinkling sound as they knock against one another, and piling up on the shore. In hours, a sparkling blue lake, once again!