By AccuWeather meteorologist
Published Nov. 27, 2021 12:53 PM EST | Updated Nov. 30, 2021 1:44 PM EST
A big warmup will grip the nation’s midsection just in time for the arrival of meteorological winter, which begins Dec. 1, making for a weather pattern that will be anything but winterlike. Temperatures will soar well above normal, as much as 40 degrees in some areas, as the warmth builds across the central United States, putting some record highs in contention. The warm pattern will continue as Denver remains in an unprecedented snow drought — and AccuWeather forecasters say a localized wind phenomenon could make the temperature rise more extreme in a few spots.
Through Thursday, warmth will expand from the High Plains farther east toward the Mississippi Valley. By Wednesday, much of the nation's midsection will be at least 5-10 degrees above normal. Parts of the northern High Plains, from Wyoming into the Dakotas, and Montana will be even farther above normal, with much of the region 10-20 degrees above normal each day through Wednesday. In some places, like Great Falls, temperatures could climb even higher, shattering daily high temperature records.
High temperatures to close out November across much of the northern and central Plains are typically in the 30s and 40s. Normal high temperatures in Great Falls and Billings, Montana, as well as Cheyenne, Wyoming, are around 40 F at the end of November, while across much of the Dakotas, normal high temperatures are in the 30s by the last few days in November. Farther south, places like Wichita, Kansas, Oklahoma City and St. Louis normally see highs in the 50s to end November.
From Cheyenne, Wyoming, through Great Falls, high temperatures will be in the 60s through midweek, and could even challenge 70 at times in some spots. Wednesday and Thursday, Denver could kick off December by challenging its daily record high temperatures. The record to beat in Denver on Wednesday is 73 and on Thursday it is 74, a mark that was set all the way back in 1885. This comes as Denver is already experiencing a record-long snow drought.
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The temperature is predicted to soar 75 in Valentine, Nebraska, on Thursday, when the normal high temperature is only 39 F. Not only will the high be about 35 degrees above average, but the temperature is likely to break the old daily record high. The previous record of 74 F was set back in 1998.
"It should be a few good days to spend some time outside across much of the Plains. Residents may have a chance to put up lights or decorations for the holidays, or just get out for a walk and enjoy some milder temperatures before the winter cold inevitably sets back in," said AccuWeather Meteorologist Dan Pydynowski.
While it may be a great few days to get out and enjoy the milder temperatures in much of the Plains, some spots may also have some gusty winds to contend with accompanying the warmth. Breezy conditions can spread all the way across the northern Plains at times as a couple of disturbances slide across the Canadian Prairies to the north. However, the strongest winds will occur near the eastern slopes of the Rocky Mountains from Montana to Alberta, where a particular phenomenon called Chinook winds will occur.
"Chinook winds occur when relatively mild and moist air from the Pacific flows straight over the Rockies. All of the moisture is 'wrung out' as rain and snow over the mountains, and then descends as dry air down the other side of the mountain range. The now dry, descending air accelerates down the mountain slopes, and can create ferocious winds at times," explained AccuWeather Senior Meteorologist Brett Anderson.
In the case this week, Chinook wind gusts can roar past 100 mph in parts of central Montana from Tuesday night to Wednesday and lead to regional power outages, property damage and the potential for truck rollovers.
Another aspect of Chinook winds that Anderson explained was the exceptional warmth that they can bring. As the air descends it also becomes warmer and can cause large spikes in temperature in short periods of time in cities along the eastern slopes of the Rockies. Chinook winds are akin to Santa Ana winds in Southern California, which cause hot, dry conditions that can spread wildfires.
Chinook winds are responsible for the world's fastest rise in temperatures, which occurred in Spearfish, South Dakota, on Jan. 22, 1943. In two minutes, the temperature went from 4 below zero F to 45 F, a 49-degree change, as Chinook winds picked up. A little over an hour later, the temperature topped out at 54 F, before the Chinook winds suddenly stopped. After the winds stopped, the temperature tumbled back to 4 below zero F, a 58-degree change, in a matter of just 27 minutes.
While changes this extreme are not anticipated this week, Chinook winds could still aid in achieving record daily high temperatures in some places just east of the Rockies.
Farther east, a clipper that dove through the Great Lakes Saturday brought a brief cooldown to the Midwest on Sunday in its wake, but temperatures rebounded again on Monday. In St. Louis, after a day with high temperatures around 50 on Sunday, temperatures returned to around 60 on Monday.
Later this week, however, forecasters say a big change could be on the way, with the potential for a big push of Arctic air to replace the warmth by this weekend.
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