Arctic blast that canceled school, mail delivery will be gone soon

Arctic blast that canceled school, mail delivery will be gone soon
World-Herald News Service

The National Weather Service office in Valley said the temperature at 6:30 a.m. in Falls City was 10 degrees below zero with a northwest wind of 5 mph producing a wind chill effect of 23 degrees below zero. Conditions are described as very, very cold and dry. 

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Sure it’s a frigid morning, but this is Nebraska. You’ll be able to hang your wash outdoors Saturday.

“Onward and out,” Becky Kern, a National Weather Service meteorologist, said of the fast-moving blast of arctic air that is closing schools across the region Wednesday, led the U.S. Postal Service to cancel delivery.

Temperatures on Wednesday morning were expected to bottom out around 15 below zero with wind chills around minus 30.

“What it boils down to is this system is going to be swept off to the east, and warmer air will take its place,” Kern said.

By Saturday, the high could approach 50, and skies are expected to be partly sunny.

Literally, Siberian air has traveled across the North Pole and down into the central U.S. this week to bring the region its bitter cold, according to Alan Reppert of AccuWeather Inc. By Wednesday evening, winds will have shifted to the south as warmer air from the nation’s southern Plains flows in behind the eastward traveling cold, he said.

And why is this shock of Siberian air traveling here? A so-called polar vortex working in tandem with a weakened jet stream, meteorologists say. The polar vortex is a swirl of intensely cold air that circles Earth’s northern pole. The jet stream is a powerful ribbon of air that circles the globe south of the vortex and acts as a barrier, keeping cold air bottled up to the north. When the jet stream weakens, it starts to meander and its loopy path allows big pools of cold air to flow south — and warm air to shift north.

As a result: Omaha is colder than Anchorage, Alaska, Reppert said. Omaha’s high topped out at 14 degrees Tuesday and is expected to peak about 2 degrees Wednesday. Anchorage is seeing highs in the mid-30s both days.

So what about global warming? The Arctic is the fastest-warming part of the globe. For complex reasons, that appears to contribute to a weakening of the jet stream, researchers say, which can make it easier for polar air to flow south. Furthermore, as the temperature records in Anchorage indicate, not all of the U.S. is abnormally cold this week.

And what’s the longer-term outlook? A slight chance of rain or snow Sunday with more seasonable winter weather returning by Tuesday. The long-range outlook is for colder-than-normal weather through mid-February, according to the Climate Prediction Center.

Reppert said he believes the area is seeing its worst cold of the winter.

“It’s going to be tough to get this cold air to come back,” he said. And even if polar air does try to surge southward, the normal seasonal changes will work against temperatures dropping as low as they have this week, he said.

“It looks like this should be the worst for this winter,” he said.

ROAD CONDITIONS

Nebraska

Iowa

Missouri

CLOSINGS AND CANCELLATIONS

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