(SOUTHERN COLORADO) — Very cold air has been gathering over Siberia in Russia and is moving over the north pole this weekend. This extremely cold air mass will move over the pole and south across Canada early in the week and spread across the United States east of the Rocky Mountains late Tuesday and Wednesday. We expect this airmass to arrive in southern Colorado after lunch on Wednesday with temperatures plummeting once it arrives.

While I was talking about this airmass likely getting here late last week, even as some computer model guidance still kept this airmass off to our east, we are really starting to see better and more consistent agreement in the mathematical calculations that this dangerously-cold airmass will park over eastern Colorado. Pictured below are comparisons between European and American longer-term forecasting models as of Sunday morning.

While we will likely get some noticeably gusty wind Wednesday evening as this colder air arrives, any breeze at all on Thursday as the coldest air is overhead will produce wind chill values between -20° and -40° or more for areas east of the mountains late Wednesday night into Friday morning.

Calculating Wind Chill

National Weather Service Wind Chill Temperature Index chart

The wind chill temperature index was updated at the turn of the century to use advances in science, technology, and computer modeling to provide an accurate, understandable, and useful formula for calculating the dangers of winter winds and freezing temperatures. The updated index does the following:

  • Calculates wind speed at an average height of 5 feet, the typical height of an adult human face, based on readings from the national standard height of 33 feet, which is the typical height of an anemometer
  • Is based on a human-face model
  • Incorporates heat transfer theory based on heat loss from the body to its surroundings, during cold and breezy/windy days
  • Lowers the calm wind threshold to 3 mph
  • Uses a consistent standard for skin tissue resistance
  • Assumes no impact from the sun, i.e., clear night sky.

Protecting Yourself

People exposed to extreme cold are susceptible to frostbite in a matter of minutes. Areas most prone to frostbite are uncovered skin and the extremities, such as hands and feet. Hypothermia is another threat during extreme cold. Hypothermia occurs when the body loses heat faster than it can produce.

If possible, adjust your schedule to avoid being outside during the coldest part of the day, typically overnight and early in the early morning but it will be dangerous for 36 hours or more over the far eastern plains late in the week.

If you have pets or farm animals, make sure they have plenty of food and water, and are not overly exposed to extreme cold. Take precautions to ensure your water pipes do not freeze. Some landscaped plants that survive most of the winter cold may be at risk. Knowing the killing temperatures of your plants and covering them and applying extra mulch around the plant base may help them survive.

Prepare Now

Make sure your car or vehicle has at least half a tank of gas during extreme cold situations so that you can stay warm if you become stranded. This is a good time to check and update your winter car survival kit if need be. Make sure your car survival kit has the following:

Jumper cables: flares or reflective triangle are great extras
Flashlights: Replace the batteries before the winter season starts and pack some extras
First Aid Kit: Also check your purse of bag for essential medications
Baby, special needs gear: If you have a baby or family member with special needs, pack diapers and any special formula or food
Food: Stock non-perishable food such as canned food and a can opener, dry cereal and protein rich foods like nuts and energy bars
Water: Have at least 1 gallon of water per person a day for at least 3 days
Basic toolkit: Pliers, wrench, screwdriver
Pet supplies: Food and water
Radio: Battery or hand cranked
Cat litter or sand: For better tire traction
Shovel: To dig out snow
Ice scraper: Even if you usually park in a garage, have one in the car.
Clothes: Make sure you dress for the weather in warm clothes, gloves, hat, sturdy boots, jacket and an extra change of clothes for the cold
Warmers: Pack extra for body, hands, feet
Blankets or sleeping bags: If you get stranded in traffic on a lonely road, you’ll be glad to have it.
Charged Cell Phone: Keep a spare charger in your car as well