Updated winter storm snow predictions, timeline for Metro Detroit: In-depth forecast, analysis

Winter storm warning takes effect Thursday night for SE Michigan

Winter storm warning. (WDIV)

4Warn Weather – So many of you read and found useful my article on Tuesday that, for simplicity, I will keep the same format with updated information. The bottom line is that there is no chance that this storm will miss us. Some of the severest winter conditions that we have experienced in a long time will hit the area just before Christmas, causing very dangerous travel conditions, not to mention possible power outages (some will be without heat as bitter cold arctic air streams in).

People sometimes ask me what the “real” story is … as if I’m holding back information for some reason. Let me be clear about this: I am not hyping this storm, and I am not withholding any information. I’ll tell you what I’m telling the family and close friends who have been personally asking me about people traveling to or from here on Friday: NOBODY SHOULD TRAVEL IN AND OUT OF THIS AREA ON FRIDAY.

Could there be a part of the day where things aren’t quite as bad as other parts of the day? Sure, that could happen. But the potential for true blizzard conditions is very real, and trust me on this, you don’t want to be stranded in those conditions. Those who do get stranded on the side of the road could be stranded for a long time. It will be a life-threatening situation. Here’s the latest:

Meteorological set-up

The intense core of jet stream wind that I wrote about yesterday -- an astounding 170 mph -- has now crossed the Pacific Northwest, and will dive southeast into the central U.S. This will plunge the jet stream southward, which opens the flood gates for arctic air to dive through the Plains. The big dip in the jet stream (called a trough) will be oriented from northwest-to-southeast, which is less common than the more typical northeast-to-southwest oriented troughs that cross the country.

This less common orientation is called a “negatively tilted trough” (if you were watching Local 4 News early Monday morning, I explained this with graphics). When that happens, and especially with an intense core of jet stream wind at its base, strong low-pressure systems are generated, which will cause the storm that we’ll deal with. By dawn Thursday, the low will be in the southeast Colorado/northeast New Mexico area, intensifying rapidly as it tracks northeastward.

In fact, the low will deepen so fast that it will likely qualify to be called one of those bomb cyclones that you hear about occasionally…but usually associated with those east coast Nor’easters.

General Timing:

Rain possibly mixed with some wet snowflakes will develop Thursday afternoon, with steadier rain Thursday evening. Today’s computer models have sped up the storm just a tad, but that “tad” means that the changeover from rain to accumulating snow will occur between 7:00 p.m. (west) and 3:00 a.m. I am still very concerned about a FLASH FREEZE.

If temperatures plummet immediately below freezing when the rain changes to snow, then wet paved surfaces will instantly become a sheet of ice. Fortunately, with the faster nighttime timing, there will be fewer cars on the roads when this occurs. However, if you will be out on the roads Thursday night, I urge you to remember this (watch the thermometer on your dashboard, too…once the temperature drops below 32 degrees, watch out).

The bitter cold air coming in streaming across the relatively warm waters of Lake Michigan will generate intense lake effect snow bands that will extend all the way into southeast Michigan late Friday into Saturday. Not everybody gets into these bands, but several inches of snow are possible just from them. The snow should let up on Christmas Day. The National Weather Service has issued a Winter Storm Warning for all of southeast Michigan in effect from 7:00 p.m. Thursday through 4:00 a.m. Saturday.


As I mentioned above, the low-pressure system will be deepening rapidly, and this means that the pressure will be changing rapidly as well. And the faster the pressure changes, the stronger the wind is. Wind will increase dramatically later Thursday night through the day on Friday, when gusts above 50 mph are possible.

This obviously means that there will be at least scattered power outages, and remember that it is not safe for DTE crews to be up in those buckets trying to repair lines when the wind is gusting that strong, so it may be a while before power is restored. Make arrangements with family or friends AHEAD OF TIME to head over to their place at any hour should you lose power because, as you know, no power means no heat.

One positive is the time of year: There are no leaves on the trees, so this wind will blow through the tree canopy, rather than hitting the wall of leaves, so that’s less pressure on limbs and branches. However, gusts of this strength mean that weak or diseased limbs could come down. Gusts on Saturday should still be in the 35 to 40 mph range.

One last thing I want to mention, and I’m cycling back to the fast change in pressure, which can cause all sorts of discomfort to people with joint issues, past surgical procedures on joints, and even trigger migraines. I still remember my brother, who blew out his ACL in a high school football game, a few years later calling me at work and asking if a big storm was coming, because his knee was aching terribly. And yes, a big storm was coming.


Obviously, with rain falling Thursday evening, temperatures will be above freezing. Once that arctic cold front comes through overnight Thursday night, temperatures will drop from the 30s (1 to 2 degrees Celsius) into the upper teens (-7 degrees Celsius) in just a few hours. The bitter cold will stay with us through the entire Christmas weekend. And if you are flying south (hopefully not flying out Friday), be aware that this severe cold wave will make it all the way down to Florida.

For example, Myrtle Beach, South Carolina this weekend will have highs in the upper-30s to low-40s (4 to 5 degrees Celsius). Sarasota, Florida will have highs only in the upper-40s (9 degrees Celsius). Miami, Florida will have highs in the low-60s (16 degrees Celsius). New Orleans, Louisiana will have highs in the mid-to-upper-30s (2 to 4 degrees Celsius) Friday and Saturday, and only in the low-40s (5 degrees Celsius) on Sunday. So be prepared for this if you’re heading south prior to this weekend.

Wind chill

As you know, the wind makes you feel colder, and please understand that wind chill is a scientifically derived statistic that gives us a real perspective on the perceived temperature on exposed skin. By Friday afternoon, the wind chill will drop to zero (-18 degrees Celsius). And wind chills between zero and -15 degrees (-18 to -26 degrees Celsius) will be common through Christmas weekend. You do not want to be stranded out in this bitter cold.

Snow amounts

As I explained yesterday, the snowfall forecast is very challenging, because it is very dependent upon how soon the rain changes to snow. The bottom line is that all of us will get significant snow, with the orientation setting up probably with those in the east getting the least, and those in the west getting the most.

As far as total snow amounts through Saturday, and this is still preliminary (remember, we’re still two-to-three days out), the heaviest snow may fall generally northwest of a line from Adrian to Ann Arbor to Pontiac to Port Huron, with this area potentially getting as much as 7 to 12 inches, with 5 to 7 inches likely southeast of that line.

Something else to remember is that the lake effect snow bands I mentioned earlier could drop a few inches of additional snow on those unlucky enough to be under one of them Friday night and Saturday -- but I’ve included this possibility in the snow ranges above.

One complicating factor is that the very strong wind will literally fracture the falling snowflakes into smaller crystals, which do not accumulate as high … so it is very difficult to assess just how high the snow will pile up even if I correctly predict the amount of moisture (called precipitable water) available to drop as snow. Something else to remember is that the high wind will cause considerable blowing and drifting.

A weather observer may have a wind-swept measuring area with little snow on it, but a four-foot snow drift a short distance away. It will be very difficult to measure how much snow actually falls.

Salt’s effectiveness

Temperatures this weekend will be so cold that, at night with no solar radiation through the clouds helping, salt won’t work. In fact, if salt applied during the day melts residual snow on the roads, then that resulting saltwater solution (called brine) could even refreeze at night. I vividly remember the bitter cold that followed the big January 2nd, 1999 winter storm ... it was one of the harshest stretches of winter weather we’ve ever seen here, with two weeks of that severe cold. Because of what I just described above, I remember road crews not salting at all until relatively warmer temperatures arrived.

Slippery, packed-down snow remained on the freeways for nearly a week, unsaltable because the smooth sheet of ice that would have resulted had they salted would have been even more dangerous. However, I do want to remind you that other ice melting products, such as magnesium chloride (my favorite), calcium chloride, etc. work down to -20 degrees -- use those on your driveway and sidewalks.

Final thought

This will be a very severe winter storm, a very rare storm for our area. The last time we had a storm like this was the Groundhog Day Blizzard of 2011, which is also the last time we had a Blizzard Warning issued here. The wind this time will be much worse than that storm (I just checked the records from Metro Airport…the highest gust they got in that storm was 40 mph).

Snowfall in some areas will be comparable to that storm. PLEASE be smart about this. Have a place to go if you lose power. Have a full tank of gas in your car. Have food to get you by if you’re unable to get out for a few days. And most importantly, remember that we at Local 4 have been preparing for this storm all week. We will have everything you need to know on our newscasts, on ClickOnDetroit.com, and on our 4Warn weather app. If you are one of the few who doesn’t have the nation’s best weather app, you’d better get it now.

The app is FREE, and easily downloadable onto your cell phone from the app store. Just search under WDIV. The real-time radar will be very helpful showing you where the rain versus snow is Thursday night (it’s color coded just like we show you on TV so you can easily see where the change occurs), and also where those lake effect bands are later Friday and on Saturday.

And our FutureCast takes the current radar and projects the rain and snow forward into time to help you plan. Plus, we 4Warn meteorologists post short (one minute or less) videos with personal, specific messages about our weather.

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.