Atmospheric river of moisture will trigger storms and tornadoes this week

An atmospheric river is a long, narrow region in the atmosphere that can carry moisture thousands of miles, like a fire hose across the sky.

We talk about them a lot in the West because large-scale storm systems bring the region up to 40% of its annual precipitation.

Apparently, atmospheric rivers also occur in the eastern US, unleashing a river of moisture like the one we’ll see this week.

The reason atmospheric rivers on the East Coast aren’t talked about much isn’t because they’re rare. In fact, they are quite common.

“Atmospheric rivers are more frequent on the East Coast than on the West Coast,” said Jason Cordeira, an associate professor of meteorology at Plymouth State University. “They just aren’t as impactful and generally don’t produce as much rain.”

While Cordeira noted that it’s hard to give an exact number of how many atmospheric rivers impact the East each year, he says a rough estimate would be between 80 and 100 per year!


The West receives about half that number of atmospheric rivers each year, but they account for twice the annual percentage of precipitation.

“The west coast has a much more arid climate. And they usually get rainfall for only half the year,” Cordeira said.

The East Coast accumulates its annual precipitation from several sources: afternoon storms, cold fronts, and hurricanes, which can bring MUCH higher amounts of rain than an atmospheric river.

“Some of the strongest atmospheric fluvial events that are perfectly oriented can produce 6 to 8 inches of rain,” Cordeira reported. “Those totals are dwarfed by how much rain we can get from a hurricane.”

Some recent hurricanes, like Harvey, which hit Houston in 2017, have resulted in rainfall totals measured in FEET, not inches.

This week’s atmospheric river won’t leave Harvey’s mark anywhere, but it could affect the same areas as Harvey.

The Deep South will be hit again by a series of storms this week, along with the Plains, Rocky Mountains and the Pacific Northwest.

So it goes without saying that this week’s weather will have a much larger scope.

It has certainly been a very active stretch of severe weather in the South and Southeast, as this is the fourth week in a row that active weather has affected the same areas.

However, as we move into April and May, we should start to see the storm tracks move a little further north into what is traditionally known as “Tornado Alley”, which is what we will start to see this week. .

storm timeline

A series of storm systems will impact the US this week from coast to coast. It will bring everything from blizzard conditions to tornadoes to flash flooding, an exhausting week to say the least.

The Storm Prediction Center (SPC) has placed an “enhanced risk” level 3 out of 5 for severe weather today for central Arkansas, however anywhere from San Antonio to the Ohio Valley could see storms today.

“A tornado threat, in addition to the risk of (potentially significant) hail and locally damaging wind gusts” will be possible today, the SPC wrote.

While this is happening in the central part of the country, a robust system will enter the Pacific Northwest and traverse the country in dramatic fashion today, bringing heavy rain to coastal areas of Washington, Oregon, and California, and several feet of snow to the Cascades.

“This system will deepen as it moves inland, setting the stage for an intense winter storm late in the season that will affect the Rocky Mountains and Northern Plains,” the Weather Prediction Center (WPC) said. “More than a foot of snow is likely to accumulate between eastern Montana and central North Dakota on Tuesday.”

Blizzard warnings are in effect for parts of the Dakotas and Montana from Tuesday through Thursday.

“Total snow accumulation between 12 and 24 inches [are forecast]”, said the National Weather Service (NWS) office in Bismarck. “Winds gusting to 50 mph [are also possible].”

Heavy snow and strong winds will make travel to those areas nearly impossible due to melting conditions and will also create avalanche hazards. Many of the western mountain ranges have some form of avalanche danger today, so be sure to check here before you head out, especially in the interior of the country.
We wrote a story earlier in the season about what causes extreme avalanche dangers and why you only have 15-30 minutes to be found alive after burial. Click here to read more.

After the system blankets the west with its late-season snow discharge, the storm will amplify as it heads east. It will combine with the available moisture provided by the atmospheric river we are talking about and result in the perfect setup for severe weather conditions.

The tornado threat will be even stronger for Tuesday and Wednesday in the middle part of the country. But the storms will affect areas much farther north than previous rounds of severe weather we’ve seen over the past three weeks.

On Tuesday there is again a level 3 of 5 “increased” risk of severe storms from Dallas to Omaha, including more than 16 million people. Although it is the area with the highest probability of storms, about 40 million people will have some chance of seeing storms.

“Any thunderstorms that may develop in this very favorable thermodynamic environment are likely to quickly become severe,” the SPC warned. They mentioned that any supercell (strong thunderstorm) will be capable of producing tornadoes, saying “some of the tornadoes could be strong.”

By Wednesday, we enter the third day of this severe multi-day event. The main threat area will move east with the third day of a level 3 out of 5 “increased risk” of severe weather. The bullseye will be from north Louisiana to the south side of Chicago and will include places like Shreveport, Little Rock, Memphis, St. Louis and Indianapolis.

“Large to very large hail, damaging winds and tornadoes will be possible,” the SPC said. “Strong tornadoes can occur.” Dallas, Houston, New Orleans and Chicago could also see storms.

The good news is that the serious threat will end in time for the Easter weekend. We could still see some persistent rain in the eastern half of the country and some snow in the Rocky Mountains, which could affect egg hunts and sunrise services. While things might change from time to time, at this time the SPC does not have any areas highlighted for severe weather over the Easter weekend as of now.

As if severe storms and blizzard conditions weren’t enough headlines this week, extremely cold air will follow the front, causing overnight temperatures to drop into the single digits for parts of the Northern Plains.

“Low temperatures in the single digits are possible and this could cause problems,” the NWS office in Billings said. “Don’t be fooled by the sun, it’s going to be fighting a very cold air mass.”

And as the climate crisis continues to change the dynamics of our climate, expect atmospheric rivers to become more intense as well.

“It is expected that as the air temperature increases, the air will be able to hold more water vapor and therefore any storm that is made up of water vapor will have more,” Cordeira explained. “So an atmospheric river, which is defined as a region of water vapor, is likely to become more intense. Its frequency may not be more common, but its intensity could increase.”

The weather in focus

The drought-stricken West is getting even drier, according to the latest drought monitor.

“Central Washington, Idaho, and northwestern Montana also saw increases in drought extent or severity as short-term drought continues to build on long-term moisture deficits dating back to last year,” according to the drought monitor. “Many parts of southern Idaho and the rest of the West have set records for the driest three-month period (January through March) going back 100 years or more.”

Texas is also facing extreme drought with 95% of the state in some level of drought. At 26,000 square miles, Texas has more area of ​​”exceptional drought” than any other state, according to the latest US Drought Monitor. The 26,000 square miles of exceptional drought is larger than the state of West Virginia (or more than three times the size of Massachusetts).

The drought is only making fire conditions worse. From Texas to Kansas, there will be extreme fire danger, especially on Tuesday as dry conditions and 50+ mph winds blanket the area. Read more here.
Our friend, Bill Weir, went and walked along the bottom of Lake Powell. This is what he saw.

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