4Warn Weather – All systems are go for one of the severest winter storms to ever hit our area. And I say this not based upon the amount of snow we’ll get but, rather, based upon the severity of the overall conditions that we will experience, not to mention the timing…on the huge travel day just before Christmas.
Meteorological Set-up:
An intense core of jet stream wind – between 150 and 170 mph (not a typo) – will cross the Pacific Northwest Tuesday night and head southward into the central U.S. This will be the impetus triggering formation of the low-pressure system that we deal with in a few days.
Since that “jet streak” is still offshore, it cannot be studied by our land-based weather balloon network (called radiosondes), which is why some of the fine tune details of this storm are still up in the air. And I want to be clear about something before you read this forecast: very small changes in the storm’s position could have massive implications on the weather we get. But I have been able to develop some confidence in the overall scenario.
General Timing:
While we could see some raindrops or wet snowflakes during the day on Thursday, any precipitation should be light. The steadier rain will move in for Thursday night. Sometime either very late Thursday night or Friday morning, drastically falling temperatures will cause the rain to change to snow, and snow or snow showers will then persist the rest of the day into Friday night.
One major concern I have is the potential for 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. I actually remember this happening years ago late on a Saturday December afternoon…my wife and I were heading downtown to the Local 4 holiday party and every single freeway in the city had freeway-closing crashes, with massive gridlock across the entire area. If you will be out on the roads late Thursday night / early Friday morning, 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 Friday night 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.
Wind:
To me, the most important aspect of the storm is the potential wind. The low-pressure system will probably be one of those bomb cyclones you here me sometimes talk about.
Put simply, the pressure will drop rapidly, and the faster the pressure changes, the stronger the resulting wind is. Some computer models I’ve looked at today indicate that there could potentially be 60 to 65 mph wind just a few thousand feet above the ground. That means that we could easily see 50+ mph wind gusts here at the surface developing Friday afternoon into Friday night.
Wind that strong will undoubtedly cause at least scattered power outages. I urge you to be prepared with alternative places to go for heat should you lose power. This strength of wind, if combined with moderate to heavy snow, would also create blizzard or near-blizzard conditions. Visibility could be near zero at times, and travel will be extremely treacherous. The wind on Saturday will still gust between 35 and 40 mph, perhaps diminishing to 30 mph gusts on Christmas Eve.
Related: How a blizzard differs from a winter storm
Temperature:
Obviously, with rain falling Thursday night, temperatures will be above freezing. Once that Arctic cold front comes through, temperatures will drop from the 30s (1 to 3 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 afternoon or evening), 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 near zero (-18 degrees Celsius). And wind chills between zero and -5 degrees (-18 to -20 degrees Celsius) will be common through Christmas weekend. You do not want to be stranded out in this bitter cold.
Snow Amounts:
The greatest uncertainty with this storm is the snow amount, because very small changes to the storm’s track will greatly impact how much snow stacks up. Let me explain: there is a single “bucket” of water vapor in the atmosphere available to create precipitation. We meteorologists call this precipitable water. If all of that water vapor coalesces into snowflakes and falls as snow, then we get the maximum amount of snow based upon the amount of precipitable water available.
However, if temperatures in the air column above are above freezing and rain falls, then that’s less precipitable water available to fall as snow when the temperature drops, which obviously cuts back on snow amounts.
So, any snowfall forecast at this point is highly speculative, but based upon everything I’ve seen so far today, here are my initial feelings: areas that see the longest duration rain (farthest east) will probably see only 3 to 4 inches of total snow through Saturday. However, and here’s where things get so tricky, areas farther north and west who see the earliest transition to snow may reach double-digit snow totals.
Again, determining the placement and timing of that rain-snow line is going to be critical. There will likely be significant refinements to this part of the forecast as a result. And keep in mind the additional snow that falls under those lake effect snow bands on Saturday will add to the stack…and the exact orientation of those bands will determine their orientation across the area.
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 (-29 degrees Celsius).
Final Thought:
This will be a highly significant, impactful winter storm. I am not hyping this. Rather, I am 4Warning you, as I have been doing since last Thursday morning on Local 4 News, that this storm will severely disrupt travel. I do not know, obviously, if Metro Airport will suspend operations at some point Friday afternoon and evening, but this is a very real possibility. I have already been bombarded with texts, e-mails, and social media questions from friends and family asking about relatives traveling here on Friday.
Let me tell you what I have told all of them: while some of the details with this storm could change, PEOPLE SHOULD NOT PLAN ON TRAVELING HERE ON FRIDAY, AND ESPECIALLY FRIDAY AFTERNOON AND EVENING. And Saturday travel could be extremely difficult based upon how widespread and intense those lake effect snow bands are. PLEASE be smart about this storm. 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 early Friday morning (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 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.
In fact, I just posted three new videos on the app with some discussions about various aspects of the approaching storm. Again, the 4Warn Weather App is FREE.
Remember to download the free 4Warn weather app -- it’s easily one of the best in the nation. Just search your app store under WDIV and it’s right there available for both iPhones and Androids! Or click the appropriate link below.