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Metro Detroit weather: Potentially big storm to watch

New computer models suggest storm could hit Metro Detroit

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DETROIT – Mostly cloudy skies to start Friday should become mostly sunny by mid- to late afternoon.

Highs in the mid 20s (-5 degrees Celsius) will feel like 5 to 10 degrees (-15 to -12 degrees Celsius) once again due to a west wind at 10 to 20 mph.

Friday’s sunrise is at 7:44 a.m., and Friday’s sunset is at 5:51 p.m.

We reached an important psychological weather milestone this week. Our average daily high temperature rose from 32 degrees (0 degrees Celsius) to 33 degrees (0.5 degrees Celsius), which means we have passed rock bottom and are starting the ascent of warmer temperatures heading toward spring.

Obviously, this is a slow process, but I thought you’d want to know that we’re now on the upswing. In case you missed the news, Woody the Woodchuck, the Howell Nature Center’s own groundhog, predicted Thursday that there will be six more weeks of winter. Of course, if you look at the calendar, we have six more weeks of winter anyway.

It will be mostly clear Friday night, with lows in the low teens (-11 degrees Celsius).

Saturday will be mostly sunny to start, then clouds will increase by afternoon. Highs will be in the upper 20s (-2 degrees Celsius).

Light snow is possible Saturday night (especially the farther north you are), but I don’t expect much impact.  Lows will be in the mid-20s (-5 degrees Celsius).

Any Sunday morning light snow should come to an end, and the rest of the day should be mainly dry. Highs will be in the low to mid-30s (1 degree Celsius).

Monday looks mostly cloudy, but dry. Highs will be in the mid-30s (1 degree Celsius).

Tuesday storm potential

Tuesday is where things get interesting. Earlier this week, the long-range computer models were developing a rather strong storm system, and tracking it well to our west, which meant that we’d get well into the system’s warm air.

Thursday's models have shifted that track much farther south, which means the moisture streaming in ahead of the storm could start as a multi-hour period of snow and ice. Whether that wintry weather changes over to rain is highly dependent on where the low pressure area tracks. Take a look at these two computer models for Tuesday evening:

While both models are tracking the low in an east-northeast direction, the GFS model has the low near Chicago at that time, while the ECMWF model has it near St. Louis.

These forecast positions will very likely change over the weekend as the upper air support for this system moves off the Pacific and over the continent, where our weather balloons can study them and get that data into the computer models. But for the purpose of Thursday's discussion, there are very important ramifications in the difference between these two models.

The GFS track would get most of us south of that warm front and into the warm sector, which would mean the wintry mix well in advance of the storm would change over to rain and temperatures would soar into the 40s (well above 5 degrees Celsius).

If the ECMWF verifies, that low would track much farther south and the warm air would stay farther south, too. This would make for a much more serious winter weather event for some of us, as some areas could receive an extended period of snow and ice.

The two maps demonstrate how different the large-scale aspects of the storm are being portrayed. Keep in mind that it’s the smaller-scale thermodynamics that dictate what type of precipitation we get, and those change dramatically based upon the larger scale changes. That’s why I can't possibly tell you with any confidence what kind of precipitation we’ll get Tuesday into Tuesday night, and any meteorologist who does is being irresponsible and unethical.

My science does not allow specificity in situations like this five days in advance. I’ll keep a very close eye on the models and update you again in Friday's article. Over the weekend, I’ll try to send an update on Twitter to keep you up to date (if you don’t follow me already, find me at @PGLocal4).

What's certain is that after the storm passes by, we’ll have at least two very cold, windy days with snow showers.

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