The Scottsbluff-Gering area in far western Nebraska was first impacted around 3:45 p.m. MDT Thursday by a storm that dumped hail up to baseball size (2.75 inches in diameter). The NOAA Storm Prediction Center relayed a report of "severe damage to houses including windows and roofs … crops … vehicle windshield … and trees."

Around 1:30 a.m. MDT Friday morning, the second storm moved in, dropping hail of golf-ball-size and larger (up to 2 inches in diameter). The National Weather Service in Cheyenne, Wyoming, issued a severe thunderstorm warning for Scottsbluff that was dubbed a "severe thunderstorm emergency," wording that is not in standard NWS use.

The night crew opted to strengthen the wording because of the storm's intensity and time of day and because it was approaching a city hit hard hours earlier, said NWS-Cheyenne lead forecaster Jerry Claycomb. Prior to reaching Scottsbluff, the storm dropped baseball-sized hail in far eastern Wyoming.

"The storm was getting stronger and stronger and radar was showing bigger and bigger hail," said Claycomb. "Since Scottsbluff had already gotten hit once yesterday afternoon, they wanted to get maximum exposure on the warning."

A full assessment of damage had not yet been conducted as of midday Friday. In some cases, it might be difficult to separate the damage from the two storms.

The Scottbluff area got yet another blast of severe hail on Friday evening, when a thunderstorm pelted the area with hail up to an inch in diameter.

An Active August Pattern for Hail

The central High Plains are sometimes referred to as "Hail Alley" for their frequency of large hail, especially in late spring and early summer. The activity typically decreases by late summer.

This week has brought an unusual amount of severe weather for mid-August across the High Plains, where moist, unstable air has been backed up along a stationary frontal zone.

Thursday alone brought more than 100 reports of severe hail, including 12 reports of giant hail (at least 2 inches in diameter).

On Tuesday, a hailstorm near Bethune, Colorado, dropped a hailstone measured by the Colorado Climate Center as 4.83 inches in diameter. The hailstone is the largest on record for Colorado, pending confirmation by the NOAA State Extremes Climate Committee. The previous record-largest hailstone for the state was 4.5 inches.

The next evening, another hailstorm moved through the same area, dropping 2.5-inch-diameter hail northeast of the town of Stratton.

Double Hail Trouble: A Rare Event

A locked-in-place weather pattern can easily produce giant hail at any one spot on two consecutive days, as was the case on Tuesday and Wednesday in far eastern Colorado.

What's much less common is for destructive hail to strike twice on the same afternoon and night, as it did in the Scottsbluff-Gering area from Thursday afternoon into early Friday.

"I cannot immediately recall any recent instances of back-to-back large hail events hitting the same community within a 24-hour period," said Steve Bowen, a meteorologist and head of catastrophe insight at the insurance broker Aon.

"Since there are a number of locations in prime 'Hail Alley,' I'm sure it has likely happened before," he added.

In the predawn hours of Dec. 5, 1977, two severe thunderstorms separated by three hours each deposited giant hail on eastern parts of Birmingham, Alabama. The first storm, around 2:45 a.m. CST, produced 2.5-inch-diameter hailstones, while the second one dropped 2-inch hail around 6:20 a.m.

"They were the two most intense hailstorms I've ever experienced in my mostly Southern life," said meteorologist John Knox, now at the University of Georgia.