DETROIT - Here we go again. Just last week we had a storm system bring a wintry mess of precipitation our way.
Tonight, a nearly identical storm will approach, with a couple of aspects that make this storm more concerning.
From a big picture perspective, tonight’s forecast is pretty simple: snow will develop after midnight, then change to sleet (those little ice pellets), then to freezing rain.
All of this will change over to regular rain during the day on Tuesday.
The snow’s time of arrival, and the subsequent changeovers, will occur at different times based upon how far north or south you are in our area (the changes will occur from south to north).
So, to help you plan and prepare, below is a series of highly localized maps to show you the likely times of transition. We think our high-resolution in-house RPM model has a very good handle on things, but keep in mind (as with all computer models), these times could vary somewhat. But this serves as an excellent general portrayal of the next twenty-four hours:
Snow arrives first for you, but you also get the earliest transition to ice and, unfortunately, likely the heaviest ice accumulation (more on this below).
Snow arrives around 2:00 a.m., changes to sleet then freezing rain toward rush hour, and remains as freezing rain through the morning until changing to rain by early afternoon.
The snow arrives latest for you…probably not until after 3:00 a.m., but you’ll also keep the snow the longest because you’ll be colder than the rest of the area.
So you’ll have a few inches of snow before your changeover to ice and, for the same reasons just mentioned, you’ll keep the ice the longest…probably not changing to rain until late afternoon.
As mentioned at the beginning, there are a couple of things about this storm that have us a bit more concerned than with the last one.
First, it appears that the period of sleet will be shorter…that means more freezing rain to accumulate on trees and power lines.
Second, we’ll have more wind than with last week’s storm, so there could be more power outages.
There undoubtedly will be school closings on Tuesday, we think many superintendents will be waiting until morning to make the decision…they’ll get up early and check in with Brandon Roux on Local 4 News Today, take a look at conditions in their communities, and then make their decision. As with last week, the condition of the neighborhood streets will likely drive this decision.
Of course, ClickOnDetroit.com has the best, easiest to use school closing page…check it out when you wake up.
Also remember that our free weather app has radar with the various colors showing what type of precipitation is moving your way…similar to what we show on TV. This will help you track the storm…just download it free from the App Store…search under WDIV.
Temps and ice
Temperature-wise, we’ll drop into the mid-20s (-4 degrees Celsius) tonight, with the southern half of the area seeing a slow rise toward dawn.
Wind will increase from the northeast to 10-15 mph…some models suggest even stronger wind, which would significantly worsen the impact of ice on power lines and tree limbs.
It appears that snow will be generally an inch or two before the ice arrives south of I-696 / I-96…2-3” north of I-696 / I-96…and 4-5” north of I-69).
As for ice, it’ll be a close call with the quarter-inch threshold, above which power outages start to increase. But the best opportunity for exceeding that threshold appears to be in our South Zone (Lenawee and Monroe Counties), which is why the National Weather Service just issued an Ice Storm Warning for that area…significant power outages are possible there.
Most of the rest of the Metro Area is under a Winter Weather Advisory, with Sanilac County under a Winter Storm Warning due to the heavier snow plus ice.
Why is this happening?
Let's now explain what's happening. If the atmosphere is below freezing from the ground all the way up to the clouds, then our precipitation obviously falls as snow.
Now let's bring in a wedge of above freezing air aloft. In this diagram, south is to the left, and north is to the right...so the warm air is flowing in from left to right (south to north).
Precipitation falling from the clouds begins as snow, but then some degree of melting occurs as the snowflakes fall through that warm wedge. If the wedge is very thin (to the right in this diagram), then the snowflakes don't melt completely, and just fall as wet snow. If the wedge is a little thicker, the snowflakes melt completely into rain drops, but those drops then freeze into little balls of ice (sleet) as they fall through the below freezing air beneath that warm wedge.
In the thicker part of the wedge, the snowflakes melt into drops, which survive the trip all the way to the surface…which is below freezing since that warm air is still aloft. Those drops therefore freeze into ice on contact with anything exposed to them.
In tomorrow’s case, we’ll see all of this…a transition from right to left on the above graphic as the warm air streams in aloft from left to right.
As we showed above, all of us will eventually changeover to plain ol’ rain during the day Tuesday…earliest to the south and latest to the north. Highs should reach the upper 30s (4 degrees Celsius).
The rain ends Tuesday evening, but winds really pick up, and lake effect snow bands will stream across the state…we’ll get some of them.
Temperatures falling back into the mid 20s (-4 degrees Celsius) means that standing water will freeze into ice. By the way, wind gusts could approach 40 mph by late Tuesday night.
Windy with snow showers on Wednesday, and near steady temperatures in the mid to upper 20s (-3 degrees Celsius). Wind could gust to 40 mph.
Snow showers taper off Wednesday night, with lows in the low to mid20s (-5 degrees Celsius).
Our next weather system isn’t being handled consistently by the computer models, but it appears that we’ll see some light snow from Thursday afternoon through Friday morning.
Then, mercifully, we’ll finally hit a quiet spell through the middle of next week, with highs not too far from 30 degrees (-1 degree Celsius), and overnight lows in the mid teens (-10 degrees Celsius).
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