The astonishing heat wave of the beginning of winter envelops the United States and Canada and breaks records

A widespread and intense heat wave roasted large parts of the United States and Canada, shattering daily and monthly temperature records.

Why is this important: Winter is the hottest season in the United States, and the lingering heat shortens the snow season in places like Colorado and Montana, where the mountain snowpack is a critical source of water during the months. summer.

The big picture: British Columbia saw its highest temperature ever recorded during the month of December, with a maximum of 72.5 ° F recorded at Penticton, which is 250 miles east of Vancouver. This tied the country’s all-time high for the month.

In numbers : Temperatures on the plains, parts of the Rockies and in the central states are up to 35 ° F above average for this time of year.

• Four states have matched or broken records for the hottest temperatures seen in December: Washington, Montana, Wyoming and North Dakota, according to weather historian Maximiliano Herrera.
• In Denver, Colorado, which often accumulates heavy snowfall in early and late winter, it hasn’t snowed yet, setting a record for the last measurable snowfall. The high temperature forecast for Thursday is in the mid-1970s, about 30 ° F above average for this time of year.
• Records are expected to fall Thursday in Denver, Omaha, Oklahoma City and Kansas City, Missouri, among others. According to Herrera, Hettinger, North Dakota, located just north of the South Dakota border, hit 21C on Wednesday, setting a monthly record for the state.
• In Cheyenne, Wyo., The temperature reached 70 ° F on Thursday, setting a state record for December. A monthly record was also set in Nebraska, according to the National Meteorological Service.
• The heat, combined with powerful atmospheric riverine events coming from the Pacific Ocean, consumed the snowpack in the Pacific Northwest and the Canadian Rockies, contributing to low-level flooding.

The context: The immediate cause of the heat is a sprawling area of ​​high pressure, or heat dome, parked across the west, with the clockwise airflow around it pumping air sweet across the region.

• This meteorological feature has deflected storms far north and kept cooler air – a record cold currently lurking in Alaska, for example – from spreading south.
• Long-term trends also favor more frequent and intense episodes of extreme heat. This ongoing event is likely to make the already out of balance balance between hot and cold records in the United States for 2021 even more in favor of hot milestones, perhaps by a margin of more than 2 to 1.
• If the climate did not warm up, one would expect such recordings to have a ratio of about one to one, especially over the course of a decade or more, but those numbers are also skewed.

And after: The National Weather Service’s Climate Prediction Center strongly favors maintaining milder-than-average conditions in much of the lower 48 states over the next two weeks, after a temporary cooling over the weekend.

• Beyond that point, however, there may be a pattern change in the works, in part thanks to a typhoon currently traversing the northwest Pacific Ocean.