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Metro Detroit weather: Warm air knocking on door

Warm weather arrives after week of waiting

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DETROIT – Metro Detroit has waited a week for warm weather, and it’s now making its move.

Warm air is heading into the area, and the difference is already noticeable for anyone who's been outside, as temperatures are dramatically warmer than they were Thursday at this time. Residents in the Thumb have lagged behind a bit Friday, but the warm weather is coming.

A lot of people have been asking about what’s going on with the weather, and the answer is pretty simple. A jet stream, the snakelike band of strongest wind aloft, is shifting far to our north. That does two things: It allows warm air to flow up this way and shifts the storm track north of us.

Some people think the change between the warm air to the south and the cold to the north is caused by the jet stream, but it’s the other way around. The sharp temperature contrast is what causes the jet stream.

As the band of strong wind flows around the planet, valleys (called troughs) and mountains (called ridges) develop. If you’re under a trough, it’s colder. If you’re under a ridge, it’s warmer (I say "under" because the jet stream is aloft).

We were under a sharp trough on Wednesday and Thursday this week, so it was colder.

Starting Saturday and through much of next week, we’ll be under a ridge, so we’ll be warmer. Keep in mind that the jet stream is also the general storm track. The farther you are from the actual jet stream, the quieter the weather typically is.

How warm will we get?

Skies on Friday night will be mostly clear, though some patchy fog might develop late at night. Lows will be in the upper 30s (3 to 4 degrees Celsius). South-southwest winds will increase to 10 to 15 mph by dawn.

It will be mostly sunny on Saturday, with highs near 60 degrees (15 degrees Celsius) south of 8 Mile Road, and generally in the mid- to upper 50s (12 to 14 degrees Celsius) north of 8 Mile Road. It will become breezy Saturday afternoon, with a southwest wind at 10 to 20 mph.

Saturday’s sunrise is at 7:25 a.m., and Saturday’s sunset is at 6:10 p.m.

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It will be partly cloudy Saturday night, with some late-night patchy fog possible. Lows will be in the upper 30s (3 to 4 degrees Celsius).

Sunday will be partly cloudy and not as warm, though it will still be well above our average high of 36 degrees (2 degrees Celsius) with highs in the low to mid-50s (11 to 12 degrees Celsius).

It will be mostly clear Sunday night, with some late-night patchy fog possible. Lows will be in the mid-30s (1 degree Celsius).

Monday will be mostly sunny, with highs in the low 50s (11 degrees Celsius). It will become partly cloudy Monday night, with lows near 40 degrees (4 to 5 degrees Celsius).

It’s not clear if we’ll get any sunshine on Tuesday (the ECMWF model says yes, the GFS says no), but it does appear that some rain showers are possible at some point during the day. Highs will be in the mid-50s (13 degrees Celsius).

Any lingering showers Tuesday evening should end, with skies becoming partly cloudy during the night. Lows will be in the low to mid-40s (6 degrees Celsius).

It will be partly cloudy Wednesday, with highs in the mid-50s (14 degrees Celsius). It will be partly cloudy Wednesday night, with lows in the low 40s (5 degrees Celsius).

Thursday will be partly cloudy and breezy, with highs in the low to mid-50s (11 to 12 degrees Celsius). It will become cloudy Thursday night, with a late-night shower possible. Lows will be in the low to mid-40s (6 degrees Celsius).

Friday will be windy and warm (the last day of this warmth), with showers and thunderstorms possible during the afternoon. Highs will be in the mid-50s (13 degrees Celsius).

Rain showers are likely Friday night, with lows in the mid- to upper 30s (2 to 4 degrees Celsius).

Saturday is back-to-reality day. It’ll be windy and cold with snow showers and highs in the upper 30s to low 40s (4 to 5 degrees Celsius). Depending on how the Friday storm materializes, temperatures could fall on Saturday, with the high being set early in the day.

It will be partly cloudy and breezy on Sunday, with some flurries or scattered light snow showers. Highs will be in the mid-30s (2 degrees Celsius), which is pretty close to our average high.

A word about this winter

On Friday, I received a question via email:

"Hi, Paul. I've been hearing that our winter in Michigan this year is based on a weak La Niña, and that overall we should have expected an overall colder than average winter with above-average snowfall of 42 inches for the season. However, contrary to what has been said, clearly it seems like it's been much warmer with less snowfall. I know we've felt the biting cold and snow throughout December, but it seems it's been warmer and less snowy throughout January through now. I just wanted to ask, what has caused this warmer than average pattern change in our La Niña season? It's always interesting reading your articles on weather on ClickOnDetroit. Thanks!"

Thanks for the question, Tairssir!

Since some of you are probably wondering the same thing, I’ll answer it for all of you. Yes, we had La Niña this winter (it’s now gone), and La Niña years tend to be cooler years for the U.S. (and the planet as a whole), and we sometimes get some pretty brutal winters when we have La Niña.

So what happened?

First of all, the La Niña we had was a weak one, so perhaps it didn’t have as much of an effect as usual. More importantly, there’s more to our weather than just La Niña and El Niño. There are many other ocean circulation patterns that I monitor, such as the North Atlantic Oscillation, the Arctic Oscillation, the Antarctic Oscillation, the Pacific Decadal Oscillation, the Pacific-North American Pattern and others.

Why ocean circulation patterns? We have discovered over the last several decades that there is a great interaction between the oceans and the atmosphere (specifically, the jet stream pattern). El Niño and La Niña are the most prominent of these, with the biggest impact.

It’s likely that one (or some) of those other patterns, in concert with a weak La Niña, trended us toward the milder winter. This was a surprise to me. While I didn’t expect a harsh winter, I certainly expected a much more "wintry" winter than we’ve had.

There’s something else to take note of, and those of you who watched my climate change webcast saw a fascinating explanation about this. As I mentioned above, La Niña years are cooler years for Earth, and El Niño years are warmer. Global warming is affecting this.

La Niña years have become as warm as El Niño years used to be. It’s certainly possible that this is also a factor. If you want to see a recording of that live webcast, click here. It’s a non-political educational video with the truth about the subject. It's just science. No politics.

One final thing to remember: It’s only February. We’ve had some pretty big snowstorms in March and even April. Please don’t accuse me of being Mr. Buzzkill, but Detroit’s biggest snowstorm in recorded history was April 6, 1886, when we received 2 feet of snow. Quoting the great philosopher, Yogi Berra, "it ain’t over until it’s over."


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