After a record breaking heatwave and an astounding number of deadly tornadoes in the U.S., we now head into the grand finale for 2021. We also finished the first month in the meteorological winter of 2022/22. Parts of Canada slid into extremely low, frigid cold temperatures reaching even below -50 °C, thanks to the southern lobe of the Polar Vortex aloft grazing south. This pool of more seasonal temperatures will be racing south towards the United States as we enter the New Year 2022.
The Southeast will be experiencing unseasonably warm temperatures just days after the southern U.S. experienced its warmest Christmas ever. On Wednesday, severe storms and tornadoes are possible in the Lower Mississippi Valley, Tennesee, Alabama, Georgia.
Many of you will be asking: What’s the deal with winter 2021/22? Will it arrive soon? According to recent changes in weather patterns across North America, we should soon see a significant return of seasonably cold temperatures.
A strong jet stream is moving across the U.S. this week from west to west. It is sandwiched between the unusually warm weather in the southern and southeastern Contiguous U.S., as well as the pool of extremely cold weather in Canada. These high-level winds are slowly diminishing until the end. This will allow the cold from Canada spread further south into Great Plains.
However, the cold has already reached the far northern states. Temperatures in Montana and North Dakota are now at 30-35 degrees Fahrenheit, with even lower wind chills.
It will also move towards the Upper Midwest on Thursday. A second kick by the northerlies will allow colder weather to spread further south towards the south on December 31st and New Year 2022.
Below is a video animation that shows the spread of Arctic cold temperatures from Canada to the United States. You can also see how extreme cold persists into January and intensifies on the northwestern North American continent in the early next week.
On the first day in 2022, a winterstorm will form at the edge the cold pool. This storm will cause a snowstorm for the Midwest, Great Lakes, and enhance severe weather potential for the Southeast U.S. Significantly warmer temperatures will bring an October-like entry to the East in January 2022.
Before we dig deeper into the unfolding weather situation across North America, let’s first see what is the main driver behind the recent pattern, known as the Polar Vortex.
THE POLAR VORTEX
There are six layers of atmosphere around the Earth. The lowest two, the troposphere or the stratosphere, are responsible for the most important weather patterns for all life.
The troposphere is the lowest layer and all weather changes occur here. It extends from the Earth’s surface (this means from the sea level) up to 12 km up in the sky. Its depth varies from 8 km to close to 20 km depending on where it is located. It is the thickest layer above the equator and it becomes thicker above the poles.
There is a deeper layer above the troposphere. The stratosphere. This layer is approximately 11-50 km thick, and it is also very dry. This is the Ozone layer, which plays an important role in the protection and growth of our planet.
For our weather, however, there is another important feature in the stratosphere known as the Polar Vortex. This massive, three-dimensional ring of extremely powerful winds surrounds the North and South poles. These winds are placed about 20 to 50 km above the Earth’s surface. Both the troposphere and the stratosphere layers are also crucial for the climate, as the Polar Vortex covers most of the bottom half of the atmosphere from the Earth’s ground up into the stratosphere.
The Polar Vortex is therefore an important factor in winter weather at high and mid-latitudes. Although it is spinning above the weather in the troposphere it is still directly connected with the lower part of our atmosphere. It acts as one large hemispheric circulation, giving our daily weather a shape.
But how does the Polar Vortex form?
Typically, as the calendar turns into autumn, the polar regions receive much less sunlight over time due to the inclination of the Earth’s axis. This puts the north polar region in a position where it can begin cooling down. Despite the fact that the polar regions are becoming cooler, the atmosphere further south remains quite warm because it continues to receive more sunlight and energy.
The pressure is also affected by the falling temperatures in the polar regions. The same process occurs in the stratosphere over us. As the temperature differential between the North pole region and the equatorial area increases, a large lowpressure (cyclonic), circulation develops across polar stratosphere.
The Polar Vortex acts as a large cyclone that covers the entire north pole and the mid-latitudes. The chart above shows the Polar Vortex at 30 km (18 mi) altitude, which is close the top of the stratosphere in winter. You will often see 10 mbar-level charts when studying the Polar Vortex behavior.
BELOW -50 °C IN CANADA, RECORD SNOW IN SIERRA NEVADA (CALIFORNIA)
Recent activity in North America’s weather has been characterized by a deep trough that passes over the western half of the continent and strong blocking High in the U.S. This has boosted the westerly Jet across, with multiple frontal system racing into the western U.S.A. Rockies.
This pattern is well-correlated with the La Nina winters (ENSO), which are more known for heavy precipitation in west, packing mountain ranges with deep powder. This month, California’s Sierra Mountains saw record-breaking snowfall.
The Central Sierra Snow Laboratory has set a new record for the snowiest December in its history. A total of more than 16 feet (193.7 inches) of snow has been reported by Dec 27th, that’s nearly 5 meters! The monthly total isn’t even complete yet.
It has been very snowy the past 7 days all along the Sierra Mountains, with many weather stations reporting 80-120 inches (6-10 feet) of snow. The seasonal snow depth has risen to 16 feet. This extremely deep snowpack is also great news for drought relief overall, as much of California’s soil moisture comes from snowmelt off the Sierra Nevada.
Further north, the Northwest U.S.A. and western Canada have experienced the most severe cold in 20 years. Many areas in Alberta and British Columbia saw temperatures plunge to the mid-40s.
Across the Northwest Territories, temperatures are even more frigid and have plunged below -50 °C. This is the second-lowest temperature recorded in winter season 2021/22 outside of the ice caps.
Rabbit Kettle station and surrounding areas of this Canadian state have ended even below -51 °C, as seen below.
To scale the intensity of the extreme Arctic cold, remember that the last time Canada had below -50 °C in December was back in 1998.
POLAR VORTEX LOBE COMES WITH AN ALBANG
As we have discussed earlier, the main driver behind this unusually significant, record-challenging December’s cold across western Canada and the Northwest U.S. is the Polar Vortex spinning above the North Pole. According to the, it led to daily record lows. NWS SeattleMonday, December 27th. Daytime temperatures in Seattle haven’t been so cold for more than 20 years.
This week’s active dynamics are mainly due to the dipole weather patterns across the northern Pacific and western North America. A strong upper ridge (blocking high) has formed over Alaska and the Aleutians. This has resulted in record heat in the region beneath the dome of the unseasonably hot air mass. To its east, a much deeper trough has moved into western Canada and the Northwest U.S.
This has resulted to a massive transporting of much colder and frigid Arctic air masses between these large-scale features far south across North America. The flow is meridional. It flows directly from north towards south towards the Pacific Northwest.
MIDWEST WINTER STORM WITH SIGNIFICANT SNOW FOR THE NEW YEAR’S DAY
Friday, December 2021 will be over. The very cold air mass residing across the Northern U.S. toward the Great Plains will accelerate its progress. This will allow for the formation of a surface depression on the lee side the Rocky Mountains, moving towards the northeast, and organizing into a winter thunderstorm.
It will rain across the central Plains and mid-Mississippi Valleys on the first day of the new year. On Saturday, precipitation will change to snow as it moves across Kansas, Iowa, Illinois, and the Panhandle. On the first day in 2022, heavy snow is expected to fall from northern Kansas and Nebraska to northern Illinois and southern Wisconsin.
Chicago might finally get some snow after its record-breaking period of no snow on the ground. It is almost hard to believe that a city that is used to having a lot of snow during winter, has finally received its first 0.1″ of snow on December 28th, for this winter season 2021/22.
Chicago’s last snowfall was 236 days ago, March 15th 2021.
There is also a slight chance of freezing rain near the cold front that runs from Kansas to Ohio Valley on Saturday. However, any dangerous or significant ice accumulations are not expected at this time.
As the winter storm continues into the Great Lakes through Saturday night, cold northerly winds will accelerate the cold temperature in the system’s wake. It will become even more frigid cold across eastern North Dakota and Minnesota, with temperatures forecast to plummet to around -35 °F on Saturday morning, staying around -15 to -20 °F also during the day, with even lower wind chill temperatures.
Temperatures are forecast to plunge below freezing as far south as portions of the southern Plains on New Year’s Day (Saturday).
Temperatures are forecast to first cool down during the day and plummet into 10-15 °F through Saturday night in Oklahoma. The temperature contrast between the surface and underground temperatures is quite significant. The south will also experience a cold day as the surface coldfront continues to move east-southeast on Sunday.
The forecast calls for temperatures below freezing as far south as southern Texas on Sunday morning, with the 32 °F isotherms extending across northern Louisiana to western Tennessee and farther northeast.
SEVERE WEATHER AND TORNADOES POSSIBLE ACROSS THE SOUTHEAST U.S. ON NEW YEAR’S DAY
While the air mass in its wake will be 20-35 °F below normal, it will be more than 30 °F warmer than normal ahead of the frontal system. Spreading across the Southeast U.S. and far towards the north into the Ohio Valley and farther towards the Northeast U.S. We have to be aware this will also again increase severe weather potential, possibly even with tornadoes on New Year’s Day.
Above: The Severe Weather Outlook by the Storm Prediction Center (SPC) calls for a 15 % chance of severe thunderstorms across the Southeast U.S. on New Year’s Day.
While the cold front will already introduce storms on New Year’s Eve over the Lower Mississippi Valley, those could become particularly severe on Saturday when the front blasts into the unstable and very warm air mass across Tennesee, Mississippi, Alabama, and Georgia. On Saturday night and Sunday, the front will continue towards the Carolinas.
This holiday weekend will see severe thunderstorms, heavy rain, and tornadoes.
SOME RELIEF OVER THE WEEKEND FOR CANADA, BUT POLAR VORTEX CAN ADD EVEN MORE FRIGID COLDER NEXT WOKE.
We can also take a look at how the weather pattern development evolves after the New Year’s weekend holidays. While the quick check over the pressure patterns wouldn’t hint at the trigger immediately, there is something brewing on the Arctic horizons. The North Pacific’s powerful dipole pattern appears to extend into next weeks, but there is one crucial difference.
The strong blocking High over Alaska, the Aleutians and the Aleutians shifts to the west and extends further into Arctic Region. This allows for a new blast of extremely cool air mass towards Gulf of Alaska, resulting in a coastal surface low. The result is the strengthening of the northerlies, leading to *much* colder weather return for Alaska and western Canada.
Below is the attached chart showing the 2m North American temperature for January 5, 2017. As we can see, the temperatures across eastern Alaska, the Canadian Yukon, Northwest Territories, and northern British Columbia could face near -50 °C (below -50 °F).
To understand the intensity of Arctic outbreaks, we often use the Meteogram forecast chart. The Meteogram for Whitehorse (Yukon, Canada) hints at what’s coming up for the northwestern part of the North American continent. While the region is currently at around the normal temperature for this time (10 °F or -12 °C), it is forecast to remarkably drop for nearly 50 °F (30 °C) compared to the current values.
These are very cold temperatures, and they are not typical for the region used to such temperatures. As we see, the average daily temperatures are staying around -40 °F (-40 °C) from Monday through Wednesday next week.
Now let’s also take a look at how intense the cold pool is underway.
The attached charts are for Calgary (Alberta), Canada and Wichita (Kansas), U.S. Wichita is currently running at around average temperature, but the cold blast is well-visible on New Year’s Day. Plunging about 20 °F (or 12 °C) below normal on both Saturday and Sunday.
Calgary’s long-term average temperature at 850mbar level (approx. 1300-1400 meters above sea level) is around 19 °F (-7 °C) at the end of December.
So the temperatures this week are about 20-30 °F (10-15 °C) below normal. The temperatures will return to normal this weekend as the cold pool moves away into central Canada.
But even more intense, frigid Arctic cold is scheduled to arrive early next week with temperatures pushing to below -20 °F (-30 °F). That could again bring some areas well below -40s or even -50 °C on some of the days around January 5 to 7th, 2022.
***The images used in this article were provided by Windy, Pivotalweather, and WXCHARTS.
The Severe weather Europe team wishes everyone Happy Holidays!
A strong North Pacific Ridge rises into the Arctic Circle, pushing colder weather and the jet stream deeper across the United States in January 2022
Source: Severe Weather