Sometimes it snows in April. Sometimes the sun shines while the heavens boom with thunder. And sometimes tornadoes crop up just to disappear within seconds.

It's Minnesota weather. Luckily, most Minnesotans have easy access to weather apps to help monitor the skies. But for many residents, that app might be missing critical details.

That's because a large swath of Minnesota — stretching from the Canadian border down the western side of the state, then snaking east along the Iowa border — is within an area where the National Weather Service's radar does not reach below 6,000 feet.

That area is home to tens of thousands of residents, half the state's tribal lands and many popular summer tourist destinations. And in two regions in that swath — most of Lake of the Woods County on the state's northern border and a diamond-shaped area in western Minnesota — radar doesn't reach below 10,000 feet.

"It's not necessarily that there is no coverage at all but weather surveillance at that low level is lacking," said Tara Goode of Climavision, a Kentucky-based company that makes radar systems to help fill the voids.

The gap forms because the National Weather Service's radar is emitted in a straight line and the earth's curvature creates space under the beam that grows with distance. So the farther away a city is from NWS radar towers — in Mayville, N.D.; Duluth, Chanhassen, Minn., Sioux Falls, S.D., and La Crosse, Wis. — the greater the radar gap.

"When the [radar beam] is looking over their head, it's looking way up in the atmosphere. And down low is where a lot of the volatile severe stuff tends to pop up," Goode said.

The National Weather Service, which set up the system of powerful NEXRAD Doppler radar systems in the 1990s, contends only 2% of all injuries caused by tornadoes nationwide occur during unwarned events at low altitudes. Furthermore, predicting severe weather takes experts to analyze radar data, as well as satellite data, weather models and ground spotters.

"No one argues the importance of radars and that optimal coverage is beneficial to hazardous weather detection, but humans are responsible for issuing hazardous weather warnings, not the radar," states a 2020 report on radar gaps written by the director of the NWS.

But those humans — both spotters and everyday folks — are the ones Tina Lindquist is worried about.

"We have volunteer weather spotters that we're putting out into weather when we're not even sure what they're going into," said Lindquist, deputy director of Grant County Emergency Management.

About half of Grant County is in the diamond-shaped part of the state where radar doesn't reach below 10,000 feet. That gap became more evident last year as derechos moved across the state.

"We had responders' vehicles that were lifted off the road in high winds and moved into ditches and fields," Lindquist said.

No one was hurt during those Grant County storms, but in May 2022, an experienced weather spotter was killed while checking the skies in southern Kandiyohi County.

Ryan Erickson, 63, had served as a volunteer firefighter since he was 18 and spent about five years as fire chief in Blomkest. Erickson, like many volunteer firefighters and first responders, was often called on to monitor conditions and report real-time ground-level conditions during severe weather.

"It's not like he was a rookie who didn't know what he was doing," said Ace Bonnema, deputy director of Kandiyohi County Emergency Management. "He lost his life because a grain bin blew over and crushed him. That's what got me going. We need to do something about this."

Bonnema and Lindquist are part of an ad hoc group formed by the Association of Minnesota Emergency Managers working to find solutions to the radar gap.

Emergency management leaders don't expect the federal government to build more large NEXRAD radars, as the system was a one-time acquisition. The NWS also hasn't finalized future plans for improving radar coverage, and the organization could be facing budget cuts.

But companies such as Climavision offer smaller radar systems that can be placed on existing infrastructure. In October, Climavision plans to install an X-band radar system on a water tower in Wendell, a small city in Grant County, as part of a pilot project. It'll be the first X-band system in the state, Goode said.

The company will cover the radar's installation, maintenance and operations, and its data will be available at no cost to support public safety efforts. Climavision also will sell radar data to businesses such as insurance, agriculture and media companies.

"This is a great way public and private entities can work together," Goode said.

The NEXRAD sites were selected to provide coverage of runways at major airports, protect resources at military bases and cover areas of the country with a high frequency of severe weather events, according to Todd Krause, meteorologist at Chanhassen's National Weather Service office.

The network of about 140 radars in the contiguous United States provide coverage of about 75% of the land mass and nearly 95% of the population at 6,000 feet above the ground level.

The 2020 report on radar gaps analyzed 12,000 tornados from 2008-2016 and found "no statistically significant difference" in warning services inside or outside the zones under 6,000 feet.

"The bottom line is that radar coverage, even outside of the coverage by radar beam at 6,000 feet, allows forecasters to rarely, if ever, miss warnings for [the most damaging] tornados," the report states.

Still, critical events do crop up under the radar. When a EF1 tornado struck Bemidji in the early morning hours of July 4, 2018, the county didn't activate the tornado sirens because the tornado didn't show up on the radar and damage was reported only after the storm passed through.

The radar gap also misses snowstorms and other weather events. Last December, several motorists became stranded in a blizzard in west-central Minnesota and had to be rescued, Bonnema said.

"A lot of them said they were from the metro area and said they looked at their radar and it looked fine out here," he said.

"It comes down to a lack of information in the low-level atmosphere," Lindquist said. "The meteorologists are doing a great job. But they don't know what they don't know."