The NWS issues a severe thunderstorm watch ahead of overnight storms
to update 7:15 p.m.: The NWS in Sioux Falls has issued a severe thunderstorm watch until 1 a.m. for parts of central South Dakota and all of southeastern South Dakota.
Scattered hailstones up to the size of tennis balls, winds as strong as 75 mph, and some tornadoes are possible throughout the night, the weather service posted on social media.
The watch covers a large area of the state with 536,797 people.
Previous story: Meteorologists with the National Weather Service in Sioux Falls are forecasting a round of severe thunderstorms late Tuesday night, storms that could bring high winds and hail up to 2 inches in diameter in some areas in central and eastern South Dakota.
Storms are expected to develop in the central part of the state later Tuesday afternoon, but as they move east between 7 p.m. and 2 a.m., the danger shifts from rain and hail to mostly high winds, NWS technician Tim Masters said.
more: Could Sioux Falls see triple-digit temperatures this week? The NWS says we’re getting close.
The storm threat extends from Huron City to Sioux City, Iowa, and beyond, according to the NWS website.
“In central South Dakota, we will have a band of thunderstorms with large hail and damaging winds that will advance eastward through the evening and into some hours overnight,” Masters said.
By the time the storms reach U.S. Highway 81 and the Interstate 29 corridor, the storms will be mostly windy, he said. But the time frame after dark is when storms can be the most dangerous, he said, adding that if residents don’t have multiple ways to get warnings after they sleep, it could create dangerous and even life-threatening situations.
“It probably won’t be a very big derecho where everyone gets wind,” Masters said. “There will be more isolated storms producing wind gusts up to 70 mph.”
High temperatures, and thermal indicators continue throughout the week
Much of the preparation for Tuesday night’s storms is tied to the high temperatures and humidity in the area, Masters said, and there will be chances for some thunderstorms later in the week as the hot days continue.
As of Tuesday afternoon, areas to the west and southwest of central South Dakota are expected to fall under a heat warning from 2 to 8 p.m., with heat indexes reaching triple digits, with some as high as 105, according to the NWS website .
“When it gets hot and humid in the afternoon, that’s fuel for thunderstorms,” Master said. “So when a small wave appears in the atmosphere, it will interact with the hot, humid air and help things grow.”
What is the five-day forecast?
As for what could happen after Tuesday night’s storms, here’s the forecast for the rest of the week in Sioux Falls, according to the NWS:
Wednesday: Sunny and hot, with a high near 95. North wind 5 to 10 mph.
Wednesday night: Mostly clear, with a low reaching 72. Southeast winds 5 to 10 mph.
Thursday: Chance of showers and thunderstorms after 1 p.m. It’s sunny and hot most of the time, with a high around 98. South winds 10 to 15 mph, gusting to 20 mph. The chance of rain is 30%.
Thursday night: A chance of showers and thunderstorms before 1 a.m. Partly cloudy, with a low around 71. Southeast wind about 15 mph becoming east northeast after midnight. Wind speeds can reach 20 mph. The chance of rain is 30%.
Friday: Mostly sunny, with a high near 93.
Friday nightPartly cloudy, with a low around 68.
Saturday: Mostly sunny, with a high temperature approaching 88.
Saturday nightPartly cloudy, with a low around 64.
Sunday: Mostly sunny, with a high near 85.
Sunday night: Chance of rain and thunderstorms. Partly cloudy, with a low around 66. Chance of rain is 30%.
Monday: Mostly sunny, with a high near 87.
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How can you stay informed?
Stay with the Argus Leader for more by refreshing this page throughout the night, or visit @Argus911 on Twitter for the latest alerts with our live stream.
Also be sure to set your phone to receive emergency weather alert notifications, or follow @NWSSiouxFalls on Twitter.
If none of these work for you, other ways to receive alerts include tuning into NOAA’s Weather Radio, other news media coverage, the Emergency Alert System on radio and television broadcasts, desktop apps, mobile apps, and other alert methods provided by Local and international websites. State public safety agencies, according to the NWS website.