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Best weekend weather of summer on the way

Plus: Explaining something weird on Sunday's radar

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DETROIT – What a day!  Abundant sunshine, comfortable humidity, and light wind made for a spectacular Pure Michigan summer day.  Skies overnight will be mostly clear (perhaps with some patches of cirrus clouds passing by from time to time), so it should be spectacular viewing as the International Space Station flies overhead this evening!  It's easy to see, and you don't need binoculars or a telescope!  Just look low in the southwest at 9:48 PM, and you'll see a bright "star" fade into view and rise upward into the sky.  For the next six minutes you'll watch the Space Station slowly, silently fly overhead, before fading from view low in the east-northeast.  If you've never seen this before, it's pretty cool:  think about the astronauts and cosmonauts up there conducting science experiments in the name of humanity, and their many sacrifices during their six-month tours of duty.

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It'll be another wonderful sleeping night, with lows near 60 degrees (15 degrees Celsius) near Detroit, and cooler than that in suburban locations.  Air will be nearly calm, so don't expect much of a breeze coming in the windows.

Mostly sunny (perhaps becoming partly cloudy in the afternoon) on Wednesday, with highs in the low to mid 80s (29 degrees Celsius).  South wind at 5 to 10 mph.

Wednesday's sunrise is at 6:20 a.m., and Wednesday's sunset is at 8:59 p.m.

Becoming mostly cloudy Wednesday night, with a shower or thunderstorm possible later at night.  Lows in the upper 60s to near 70 degrees (20-21 degrees Celsius).

Mostly cloudy with periods of showers and thunderstorms on Thursday.  Highs in the upper 70s to near 80 degrees (26-27 degrees Celsius).

Showers and thunderstorms end Thursday night, with lows in the mid 60s (17-18 degrees Celsius).

Partly cloudy on Friday, with highs in the upper 70s (26 degrees Celsius).

Becoming mostly clear Friday night, with lows near 60 degrees (15 degrees Celsius).

And then comes our weekend, and the best weekend weather of the summer!  Look for mostly sunny skies both Saturday and Sunday, with highs in the low 80s Saturday (27-28 degrees Celsius), and in the mid 80s on Sunday (29 degrees Celsius).  I hope you have plans to take advantage of this spectacular weekend we'll have...it'll be terrific.

Explaining something weird you may have seen on Sunday's radar:

If you were following the radar Sunday afternoon, you may have noticed something really weird.  I was off Sunday, but still watching closely and updating my Twitter followers about the severe weather in our area, when I saw it.  Check out this radar image I was able to grab from RadarScope...

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Did you see "the snake?"  Do you even see it now?  Here, let me circle it for you...

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Yes, that looks pretty weird.  What is it?  It's called an "outflow boundary" or, if it's rushing out ahead of a storm, a "gust front."  You see, the core of a thunderstorm drags down a shaft of colder air from aloft.  When that cold air reaches the ground, it spreads out.  The lead edge of that is basically a mini-cold front...the front edge of the cooler air flowing out from the storm.  If the air is unstable enough, these outflow boundaries sometimes initiate new thunderstorms.  Sometimes, an outflow boundary flowing toward an existing severe thunderstorm shifts the wind direction flowing into that storm, and actually creates rotation that spins up a brief tornado.  And sometimes, when the atmosphere is not unstable enough, the outflow boundary simply generates a bank of clouds.  In this image, the outflow boundary developed on the south side of the storms to the north, and moved southward.  Here's a photo I took of just that this past Sunday evening, as I looked north at the boundary...

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The thing that concerns me the most is when a gust front rushes out ahead of a fast moving, severe thunderstorm.  Frequently, severe wind gusts from the storm arrive with that gust front...BEFORE the rain begins.  That's why I tell you to take shelter immediately when a warning is issued, because those who decide to wait until the first rain drops before heading inside, may find themselves outside when branches and limbs suddenly start raining down around them as the severe wind gust hits.

So, these outflow boundaries are very important to us meteorologists...you'd hear us frequently talking about "boundaries" during severe weather events if you were in the office with us.


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