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US weather: ‘Potentially historic’ spring storm threatens 200 million Americans

An unusual weather phenomenon will likely result in yet another bomb cyclone to strike the midwest

Chris Riotta
New York
Tuesday 09 April 2019 20:34 BST
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Bomb cyclone spreads hits Colorado in US

Flood, snow, avalanche and fire alerts popped up this week from Idaho to Colorado, as parts of the US interior that were paralysed by blizzards and floods last month braced for round two of an unusual weather phenomenon.

Welcome to springtime in the Rockies, and parts of the Great Plains.

It’s not unusual for floods, snow and fire to co-exist in the Rockies thanks to powerful storms blowing through the mountains, melting snow swelling waterways and high winds sweeping across dry grasslands and trees that haven’t seen their first green shoots and leaves.

But what is unusual is what’s coming next. A storm system that is moving in from the Pacific Ocean is forecast to intensify and form into a new inland “bomb cyclone”.

A bomb cyclone is a rapid drop in air pressure — at least 24 millibars in 24 hours — and often is over or near oceans or seas because it requires warm moist air smacking into cold dry air, along with volatile weather from the jet stream. A reported 200 million Americans are along the path of the oncoming storm, according to meteorologists.

This would be the second such storm in less than a month. The 13 March storm caused massive flooding in the Midwest, a blizzard in Colorado and Wyoming, and produced winds of between 96 mph and 110 mph.

This week’s bomb cyclone one is expected to be similar in intensity and in snowfall, meteorologists said. Heavy, wet snow will fall from the Nebraska panhandle through south central and southeastern South Dakota into western Minnesota.

“This blizzard will further exacerbate flooding in Nebraska with the added insult of heavy snowfall to eventually melt,” said Ryan Maue, a meteorologist at the private WeatherModels.com. “This is more bad news for suffering farmers who are unable to flip the calendar on winter.”

But first, the storm is expected to flooding in Idaho and western Montana, and dump up to 2 feet (61 centimetres) feet of snow in the mountains of Montana and Wyoming as it moves in from the Pacific Ocean.

Parts of Colorado that were under a fire warning Monday are expected to see snow and temperatures drops of more than 40 degrees by Wednesday at the southern edge of the storm, meteorologists said.

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The storm has already dumped rain on parts of Oregon Sunday and Monday as it moved inland, causing flooding that closed some schools in the central Willamette Valley and forced the release of water from dams.

The Associated Press contributed to this report

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