Metro Detroit weather: Trying to decipher the Christmas forecast

Chance of rainfall on Christmas Day

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DETROIT – What were you doing at 10:58 a.m. Tuesday? I know what I was doing: Looking toward the sun, because at that moment, we reached the winter solstice -- the official start of astronomical winter.

But did you know that winter is actually our shortest season? The explanation is pretty cool -- check out my quick article here. It’s a very short read -- just a minute or two -- but well worth it!

Challenging forecast

Alright, onto the forecast, which is getting more and more challenging for the same reasons that many other forecasts of this nature are so difficult.

A massive upper-level storm developing off the West Coast is going to generate lots of smaller upper level disturbances that will move across the country. Each disturbance is the genesis of a surface low pressure system (the “L” on the maps we show on TV).

So what’s the problem? The parent massive upper air system is off the coast, and those mini disturbances cannot be precisely located by our land-based radiosonde (weather balloon) network. Once that big system gets closer to the coast, perhaps the computer models will have enough data to get a better handle on things.

But until then, I have much lower confidence in the forecast details as we head into the end of the week, which means Christmas, of course.

Tuesday night

On Tuesday night, our second cold front in the past 24 hours will cross the area. Aside from a few flurries or very light, non-impactful snow showers, it won’t have much overnight impact that you need to worry about. It’ll just funnel in some cold air that’ll be with us Wednesday.

Lows Tuesday night will be in the low to mid-20s (-6 to -5 degrees Celsius), which is pretty close to average for this time of year.

Wind, however, will shift from the south to the west after that front passes by, at 10 to 20 mph, so you’ll definitely notice the wind chill if you head out early Wednesday morning.

Tuesday’s sunset is at 5:04 p.m., and Wednesday’s sunrise is at 7:59 a.m.

Wednesday

Partly cloudy and breezy Wednesday, and perhaps even becoming mostly sunny before the afternoon is out. Highs in the low 30s (-1 to 0 degrees Celsius), with that west wind at 10 to 20 mph making it feel chillier, of course.

Increasing clouds Wednesday night, with lows in the low to mid-20s (-5 degrees Celsius).

Thursday

Happy Festivus! Thursday has become more interesting, as a band of snow will develop ahead of an approaching warm front. Areas roughly north of M-59/Highland Road/Hall Road will likely get the steadiest snow for the longest period of time, so you could conceivably even pick up an inch or two, with rapidly diminishing amounts as you head south of there.

As long as that warm front makes progress through the area, we should warm into the mid-30s (3 degrees Celsius), so that means it’ll be a nice packing snow for the kids in areas that get enough of it!

Mostly cloudy Thursday night, with near steady temperatures in the low to mid-30s (-1 to 0 degrees Celsius).

Friday

It still appears that either rain or rain showers will develop Friday, with highs reaching the mid-40s (8 degrees Celsius).

Showers will probably extend into Christmas Eve, then end overnight, with lows on Christmas morning very mild, in the upper 30s (3 to 4 degrees Celsius).

Weekend forecast

Merry Christmas! The Christmas Day forecast could be changing, as some computer models now suggest that another batch of rain could move in during the day. Highs should reach the mid-40s (7 degrees Celsius), so at least it won’t be bitter cold.

Showers end Saturday night, with lows near 30 degrees (-1 degree Celsius).

At this point, I’m holding out for a dry day Sunday, with highs in the upper 30s (4 degrees Celsius), but some models now suggest yet another system swinging through Sunday night or Monday, with snow and/or a mix changing to rain.

Again, I have lower-than-average confidence in the forecast heading into Christmas weekend. I’m as frustrated as you are about this (more, actually), as I know it’s a major travel weekend. But I’ve always promised you that I will be brutally honest about my confidence in any particular forecast, and I remain true to that promise.

Hopefully, Wednesday’s computer models will start developing a better handle on things.

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About the Author:

Local 4 meteorologist Paul Gross was born in Detroit and has spent his entire life and career right here in southeast Michigan. Paul has researched, written and produced eight half-hour documentaries for WDIV, as well as many science, historical and environmental stories.