9:00 am Update Wednesday:
Everything is on track. Here’s a look at timing for the cold front.
3:30 PM Update Tuesday:
Winter Weather advisories have been added to the list of alerts across I-25.
10:30 AM Tuesday Update: I’m updating graphics and wording in this entire article. If it’s your first or second time reading, read through all of it. There’s new information. At the bottom of this blog, you’ll find some winter and cold stats that we may challenge.
The Denver Coliseum will be open as a warming shelter through Friday. Read more.
Here’s a look at timing and expect impact levels for the upcoming cold.
Original post: Hey weather fam! We have some serious cold coming this week. Possibly cold that we haven’t seen in 40 years. A huge spill of arctic air is going to drop temperatures 40-55º below normal for high and low temperatures Wednesday night through Friday morning.
Windchill, windchill, windchill. That’s going to be the biggest concern in this forecast.
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Wednesday night, Thursday, Thursday night. Thursday will be the coldest day of the upcoming week. We also have some snow moving in Wednesday night through Thursday morning which, even if light snow, will be impactful with the incoming cold.
I’ll go into the details of what’s happening below but Wednesday night, low temps will drop into the single digits and teens BELOW zero region wide. Windchills could be as cold as -40º in the city and colder on the Plains. Thursday afternoon, high temps may not break above zero in and around Denver and especially on the eastern Plains. Windchills windchills will stay in below zero all day (in the negative teens most likely). Thursday night, lows will drop into the single digits and teens below zero again with windchills as cold as -40ºF. Friday we start a gradual warmup. Highs Friday will be in the teens and 20s. There will be light snow on the ground by Thursday morning for many.
Forecast – Cold
I’ll talk about the snow below but the bigger story here is the cold. You’ll hear this cold blast of air called a lot of different things but it’s really just an abnormally cold blast of cold air. Cold like this has happened before, albeit, it does not happen that often so there still needs to be messaging to go along with that.
With highs possibly staying below zero on Thursday in Denver, it made me look up the last time that happened. Turns out, the high temperature of -1ºF on February 5, 2014 was the last time Denver on a sub-zero high. The coldest high i’ve found in Denver weather records (which go back to 1872) was -10ºF which happened on February 3, 1883. We’ve had lows in the teens and 20s below zero on many occasions.
Here’s a look at the cold air that will quite literally be spilling into the country from Canada. Those deep blues and purples is the cold air pouring in.
The good news about this cold, for us at least in Colorado, is that it will be relatively short lived. Maybe 36-48 hours at best. It will be colder for much longer in the High Plains, Great Lakes region and parts of the deep south who are bracing for cold not seen in years.
The cold incoming will impact Montana, Wyoming and the Dakotas first. For an idea of what kind of cold they’re expecting, take a look at this image.
This is some really gnarly cold and it will have been impacts on livestock and the general population in these areas.
Monday AM 8:30 AM UPDATE: The NWS has issued Wind Chill Alerts for all of eastern Colorado.
Most models are hinting at some VERY cold air moving through.
As it stands, the GFS and EURO models are showing high temperatures on Thursday between 0º and -11º. Since Denver has never had a -11ºF high temp reading, it’s fair to say this probably won’t happen. The NWS is going with a high of -1º in Denver but I bet this lowers a bit. More shockingly, the GFS and EURO are forecasting overnight lows Wednesday night to between -10º and -25ºF. Temperature readings in the negative teens are not uncommon in Denver. In fact, the last time it happened was this year when it hit -11º on February 3. The 20-40mph winds are what is going to make this cold more intense.
*notice on all forecasts, the warmup we see into next week looks rather nice.
High temperatures this time of the year in Denver are in the lower 40s. The temp anomaly, or change in average temp compared to forecast temp, shows some colors that we don’t normally see.
Temperatures will range from 20 to 55º colder than whats normal Thursday afternoon. This goes for low temps too.
The windchill will be the most intense and dangerous of the upcoming weather. Here’s a look at how windchills are calculated. It’s a direct measure of air temp vs. wind speed.
It doesn’t take a strong wind to really take the feels-like temperature down.
Wednesday, Thursday and Thursday night will have the coldest wind chills. Notice Wednesday evening the sharp cold front moving through.
From the maps, you’ll notice SW Colorado doesn’t get the worst of this cold. Cold air is very dense and heavy. It takes a lot for it to get over these Rocky Mountains of ours so while the Eastern Plains of Colorado and Northern Colorado will be frigid, the San Luis Valley and SW Colorado will be cold.
Wednesday will be generally a pleasant day until the cold front moves through. It should move through Ft. Collins around 2pm, Denver around 5 pm, Colorado Springs around 8 pm. Cold fronts tend to come in a bit quicker than expected so keep that in mind.
Also, snow will follow the cold front pretty quickly so if these times get pushed up we could start to see some issues arise for the evening commute Wednesday. The Thursday morning commute looks absolutely frigid and snowy.
This is going to be extreme cold for anyone or anything outside. It’s honestly best to hunker down Wednesday night, Thursday and Friday morning if you can.
Here’s an animation of the cold front swinging through. The numbers you see are ACTUAL air temperatures. Denver will go from a high near 50º on Wednesday to a low in the negative teens. Possibly rivaling on of our bigger temperatures drops in a 24-hour period.
Forecast – Snow
As we’ve seen with other cold fronts this season, we get some upslope flow behind it and usually a little pulse of moisture, too. That’ll ring true for this as well. Again, the best timing for snow is right after the cold front, through early Thursday morning.
Here’s an animation of the cold front and the following snow.
It’ll be brief, <6 hours of snow for the I-25 corridor but it may be intense for a bit. As soon as the front moves through, the snow will start.
For most areas, this will be light snow but any and all that falls will stick immediately. Here’s a look at the forecast right now. Winter storm alerts are in place for the central and northern mountains.
Snowfall is trending up due to the cold air.
Since this cold front is dragging the jet stream down, winds from the jet stream will create areas of enhanced snow at times. This is shown in the yellow circles as some banding.
Generally, models are showing 2-5″ from FoCo to Denver will less south. I’d bank on some snow though based on what I know and what happens in these situations. This looks like more of a snow for the Palmer Divide and points north. Southern Colorado may miss out on higher totals but could still have enough to cover roads.
Some of the high resolution weather models are starting to come in and showing some potential higher totals. Regardless of the amount, roads will be dicey from Wednesday night to Friday. Keep this in mind.
With how cold it’ll be, there will be no problems with snow sticking on the roads immediately. Take care driving from Wednesday to Friday.
The central and northern mountains should see a nice dosing of snow with this storm. Upwards of 4-10″ could accumulate. There will be travel impacts from Wednesday to Friday there.
I’ll update this story as needed and will likely post it again Tuesday for fresh eyes.
Here’s a quick look at some of the coldest temperatures ever recorded in Denver. Surprisingly, we won’t be challenging too many of these but the Thursday high temperature is in jeopardy.
On top of this, we could see one of our largest temperature changes within a 24-hour period with this front.
Enjoy the weather!
~Andy
Also, check on your family around the country. This is a wide-reaching storm!
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