{"id":5589,"date":"2026-08-17T11:02:41","date_gmt":"2026-08-17T11:02:41","guid":{"rendered":"https:\/\/ialert.com\/blog\/?p=5589"},"modified":"2026-08-17T11:02:41","modified_gmt":"2026-08-17T11:02:41","slug":"plains-severe-thunderstorms-aug-17","status":"publish","type":"post","link":"https:\/\/ialert.com\/blog\/news-events\/plains-severe-thunderstorms-aug-17\/","title":{"rendered":"Plains Severe Thunderstorms: Slight Risk of Large Hail and Damaging Wind Across Nebraska, South Dakota, and the Southern Appalachians, August 17, 2026"},"content":{"rendered":"<p>  <iframe src=\"https:\/\/ialert.com\/blog_outlook.php?event=plains-severe-thunderstorms-aug-17\" title=\"Plains Severe \n  Thunderstorms: Slight Risk of Large Hail and Damaging Wind Across Nebraska, South Dakota, and the Southern \n  Appalachians, August 17, 2026\" loading=\"lazy\" style=\"width:100%;border:0;\" height=\"660\"><\/iframe><\/p>\n<p>Plains severe thunderstorms are forecast to bring large hail and damaging wind gusts to parts of Nebraska and<br \/>\n  South Dakota this afternoon and evening, August 17, 2026, according to the NOAA Storm Prediction Center&#8217;s Day 1<br \/>\n  Convective Outlook issued at 06:02 UTC. A Slight Risk (level 2 of 5) covers two separate areas: one running<br \/>\n  from central Nebraska northeast into eastern South Dakota, and a second across the Southern Appalachians from<br \/>\n  eastern Tennessee into central North Carolina.<\/p>\n<p><strong>Key points:<\/strong><\/p>\n<ul>\n<li>Two separate Slight Risk (2 of 5) areas are drawn: the Plains severe thunderstorms corridor in central<br \/>\n  Nebraska and eastern South Dakota, plus the Southern Appalachians.<\/li>\n<li>Large hail probability reaches 15% only in the Plains area, near North Platte, Norfolk, Sioux Falls,<br \/>\n  Mitchell, Huron, and Watertown.<\/li>\n<li>Damaging wind probability reaches 15% in both Slight Risk areas, including Charlotte, Asheville, Knoxville,<br \/>\n  and Chattanooga.<\/li>\n<li>A 2% tornado probability is drawn over North Platte, Norfolk, Valentine, Sioux Falls, Mitchell, Huron,<br \/>\n  Yankton, and Brookings.<\/li>\n<li>Isolated severe gusts are also possible in southern and western Oklahoma and across central Montana.<\/li>\n<\/ul>\n<div style=\"background: #000000; padding: 20px 24px; margin: 20px 0; border-radius: 4px;\">\n<p style=\"color: #ffffff; font-size: 16px; font-weight: bold; margin: 0 0 6px 0;\">Get Lightning Detection Alerts<br \/>\n  for Your Location<\/p>\n<p style=\"color: rgba(255,255,255,0.9); margin: 0 0 14px 0;\">When dangerous lightning is detected near your<br \/>\n  area, iAlert sends you an immediate notification by email or text message so you know when to seek shelter and<br \/>\n  when it is safe to head back outside.<\/p>\n<p>  <a href=\"https:\/\/ialert.com\/services\/lightning_detection_alerts.php\" style=\"background: #C41226; color: #ffffff;\n  padding: 10px 22px; text-decoration: none; border-radius: 3px; font-weight: bold; display: inline-block;\">Sign<br \/>\n  Up for Lightning Detection Alerts &rarr;<\/a>\n  <\/div>\n<h2>Where Plains Severe Thunderstorms Pose the Greatest Threat<\/h2>\n<p>The SPC places the core of the Plains severe thunderstorms threat in a corridor running from North Platte and<br \/>\n  Valentine, Nebraska, northeast through Norfolk into Sioux Falls, Mitchell, Huron, Brookings, and Watertown,<br \/>\n  South Dakota.<\/p>\n<p>North Platte, Norfolk, Valentine, Sioux Falls, Mitchell, Huron, Yankton, and Brookings each carry the full<br \/>\n  set of hazards: a 15% large hail probability, a 15% damaging wind probability, and a 2% tornado probability.<br \/>\n  Watertown, South Dakota, carries the 15% hail and 15% wind probabilities but sits outside the tornado<br \/>\n  outline.<\/p>\n<p>Two cities on the eastern flank of the Plains severe thunderstorms risk area face a narrower threat. Sioux<br \/>\n  City and Le Mars, Iowa, are inside the Slight Risk and carry the 15% damaging wind probability, but only a 5%<br \/>\n  hail probability. Their hail threat is meaningfully lower than the corridor to their west.<\/p>\n<p>A separate Slight Risk covers the Southern Appalachians. Asheville, Charlotte, Winston-Salem, Greensboro,<br \/>\n  Hickory, Boone, Statesville, and Raleigh in North Carolina, along with Knoxville, Chattanooga, Johnson City, and<br \/>\n  Bristol in Tennessee, and Spartanburg, South Carolina, all carry a 15% damaging wind probability.<\/p>\n<p>Unlike the Plains severe thunderstorms corridor, none of those Southeast cities carry a hail or tornado<br \/>\n  probability. The SPC drew no hail outline and no tornado outline anywhere east of the Plains in this issuance,<br \/>\n  so damaging wind is the single hazard across the Appalachian zone.<\/p>\n<p>Greenville, South Carolina, sits roughly 200 feet outside the Slight Risk outline and inside the 15% damaging<br \/>\n  wind area. Treat Greenville as inside the Slight Risk. The categorical outline and the wind outline are drawn<br \/>\n  at slightly different resolutions, and a gap that small is a drafting difference rather than a real change in<br \/>\n  the threat.<\/p>\n<p>A broader Marginal Risk wraps the core Plains severe thunderstorms zone. Omaha, Lincoln, Grand Island,<br \/>\n  Kearney, Columbus, Fremont, and Chadron, Nebraska; Pierre and Aberdeen, South Dakota; Council Bluffs and<br \/>\n  Spencer, Iowa; Minneapolis, Mankato, and St. Cloud, Minnesota; and Fargo and Grand Forks, North Dakota all carry<br \/>\n  a 5% damaging wind probability.<\/p>\n<p>Within that Marginal zone, Lincoln, Grand Island, Kearney, Columbus, Fremont, Chadron, Pierre, Aberdeen,<br \/>\n  Spencer, and Fargo also carry a 5% large hail probability. Omaha, Council Bluffs, Minneapolis, Mankato, St.<br \/>\n  Cloud, and Grand Forks sit outside the hail outline and face a wind threat only.<\/p>\n<p>A third Marginal area covers the central Appalachians and mid-Atlantic. Richmond, Roanoke, Charlottesville,<br \/>\n  Lynchburg, and Blacksburg, Virginia; Charleston and Morgantown, West Virginia; and Huntsville, Alabama each<br \/>\n  carry a 5% damaging wind probability with no hail or tornado probability attached.<\/p>\n<p>Two smaller Marginal areas round out the outlook. Oklahoma City sits in its own 5% damaging wind area, and a<br \/>\n  fourth Marginal zone covers central and northeastern Montana, including Lewistown, Roundup, Winnett, and<br \/>\n  Glasgow, also at 5% damaging wind.<\/p>\n<p>SPC uses a five-tier system to communicate severe weather potential; see the <a \n  href=\"https:\/\/ialert.com\/blog\/weather-articles\/severe-weather-outlook\/\">iAlert guide to SPC outlook risk<br \/>\n  categories<\/a> for a full breakdown of what each level means.<\/p>\n<figure class=\"wp-block-image size-full\" style=\"max-width:880px;margin:28px auto;padding:10px;border:1px solid \n  #dde3ec;border-radius:6px;background:#ffffff;\"><br \/>\n    <img decoding=\"async\" src=\"https:\/\/ialert.com\/blog\/wp-content\/uploads\/2026\/08\/ialert-plains-severe-thunderstorms-spc-wind-risk-august-17-2026.jpg\" alt=\"SPC damaging wind probability map for Plains severe thunderstorms on August 17, 2026, \n  showing the 15% wind risk over central Nebraska and eastern South Dakota and a second 15% wind risk across the \n  Southern Appalachians, inside a 5% wind risk reaching Minneapolis, Fargo, Oklahoma City, Richmond and central \n  Montana\" width=\"1600\" height=\"842\" style=\"max-width:100%;height:auto;border-radius:4px;\" loading=\"lazy\" \/><figcaption style=\"font-size:0.86em;color:#1a3a5c;text-align:center;margin:12px 6px 2px;line-height:1.45;\">SPC<br \/>\n  damaging wind probabilities for August 17, 2026. Both 15% areas match the two Slight Risk outlines that define<br \/>\n  today&#8217;s Plains severe thunderstorms threat: one over central Nebraska and eastern South Dakota, one over the<br \/>\n  Southern Appalachians. The surrounding 5% area reaches Minneapolis, Fargo, Oklahoma City, Richmond, and central<br \/>\n  Montana. Source: NOAA Storm Prediction Center.<\/figcaption><\/figure>\n<h2>Meteorologist&#8217;s Take on Plains Severe Thunderstorms<\/h2>\n<p>A subtle shortwave trough at mid-levels will move across the northern Plains today within west-northwesterly<br \/>\n  flow. Ahead of it, a broad corridor of low-level moisture is in place, with a moist axis of surface dewpoints in<br \/>\n  the upper 60s to lower 70s F setting up from northwest Kansas north-northeast into central Nebraska and eastern<br \/>\n  South Dakota.<\/p>\n<p>Moderate to strong instability will develop along that axis by midday, with MLCAPE climbing into the 2,000 to<br \/>\n  3,000 J\/kg range. At the surface, a cold front will move southeast across the Dakotas through the day.<\/p>\n<p>Low-level convergence maximizes ahead of that front over central Nebraska and southeast South Dakota, and<br \/>\n  that is where scattered convective initiation is expected. Storms will then track southeast into stronger<br \/>\n  instability during the late afternoon and early evening.<\/p>\n<p>RAP forecast soundings valid at 00Z (8:00 pm EDT, 7:00 pm CDT) near the instability axis from northeastern<br \/>\n  Nebraska into eastern South Dakota show 0-6 km shear near 40 knots, with low to mid-level lapse rates of 7 to<br \/>\n  7.5 degrees C per kilometer. That combination supports supercells and isolated large hail where the environment<br \/>\n  is best.<\/p>\n<p>A mixed storm mode is expected across the Plains severe thunderstorms corridor, though. Both supercells and<br \/>\n  multicells will be capable of severe wind gusts. The severe threat should continue into the mid evening as a<br \/>\n  large convective cluster moves southeast into the mid Missouri and upper Mississippi Valleys.<\/p>\n<p>The Southern Appalachians run on a different setup from the Plains severe thunderstorms corridor. A separate<br \/>\n  mid-level shortwave trough will track east-southeast across the Ohio and Tennessee Valleys today, reaching the<br \/>\n  southern Appalachians by early evening, with a moist and unstable airmass ahead of it.<\/p>\n<p>Surface dewpoints in the 70s F will build moderate to strong instability there by midday. A cold front<br \/>\n  advancing southeast into the mountains will combine with topographic forcing to produce scattered afternoon<br \/>\n  thunderstorm development.<\/p>\n<p>Those storms will move east-southeast across the higher terrain and into the lower elevations by early<br \/>\n  evening. Deep-layer shear in the Appalachians is weaker than in the Plains, in the 20 to 30 knot range, so the<br \/>\n  SPC expects severe gusts to come mainly from short organized line segments. Shear in that range rarely sustains<br \/>\n  the rotating supercells that produce large hail, which fits with the SPC drawing no hail probability across the<br \/>\n  Southeast.<\/p>\n<p>Across southern and western Oklahoma, a quasi-stationary front will stay in place. Post-frontal surface<br \/>\n  dewpoints from the mid 60s to mid 70s F, moderate to strong instability, and 0-3 km lapse rates exceeding 8<br \/>\n  degrees C per kilometer favor isolated severe wet downbursts.<\/p>\n<p>Over the northern High Plains, west-northwest mid-level flow will ride over a post-frontal airmass, with<br \/>\n  surface dewpoints near 50 F across central and eastern Montana. MLCAPE only reaches the 500 to 1,000 J\/kg range,<br \/>\n  but very steep low to mid-level lapse rates could support isolated severe wind gusts from storms forming over<br \/>\n  the higher terrain of central Montana and drifting east across the upper Missouri Valley late in the day.<\/p>\n<h2>How to Stay Safe During Plains Severe Thunderstorms<\/h2>\n<p>If you are in or near the Plains severe thunderstorms risk area, prepare for large hail and damaging wind<br \/>\n  gusts, with a tornado possible in the Nebraska and South Dakota corridor. Get vehicles under cover before storms<br \/>\n  arrive.<\/p>\n<p>The SPC does not forecast a maximum hail size in this issuance. &#8220;Large hail&#8221; means at least one inch in<br \/>\n  diameter, roughly quarter size, which is the National Weather Service threshold for a severe thunderstorm.<\/p>\n<p>Secure anything outdoors that a gust could turn into a projectile. If a tornado warning is issued for your<br \/>\n  county, move to an interior room on the lowest floor of a sturdy building, away from windows, and stay there<br \/>\n  until the warning expires.<\/p>\n<p>In the Southern Appalachians and across the broader Marginal zones, the hazard is wind. Watch for falling<br \/>\n  trees and downed power lines after storms pass, and treat every downed line as energized.<\/p>\n<p>Check <a href=\"https:\/\/ialert.com\/analysis.php#alerts\">active weather alerts for your area<\/a> and enable<br \/>\n  wireless emergency alerts on your phone before Plains severe thunderstorms develop this afternoon. You can also<br \/>\n  track storm movement on <a href=\"https:\/\/ialert.com\/analysis.php?tab=radar\">live radar<\/a> as the event<br \/>\n  unfolds.<\/p>\n<h2>Plains Severe Thunderstorms FAQ<\/h2>\n<h3>Where is the highest risk on August 17, 2026?<\/h3>\n<p>The highest categorical risk for Plains severe thunderstorms is a Slight Risk (level 2 of 5), covering a<br \/>\n  corridor from North Platte and Norfolk, Nebraska, through Sioux Falls, Mitchell, and Huron, South Dakota, plus a<br \/>\n  separate area across the Southern Appalachians that includes Charlotte, Asheville, and Raleigh, NC, and<br \/>\n  Knoxville and Chattanooga, TN.<\/p>\n<h3>How large could hail get in the Plains severe thunderstorms area?<\/h3>\n<p>The SPC assigns a 15% large hail probability to North Platte, Norfolk, Valentine, Sioux Falls, Mitchell,<br \/>\n  Huron, and Watertown, meaning large hail is possible where supercells develop. The SPC does not specify a<br \/>\n  maximum diameter in this issuance. Large hail begins at one inch, and the 15% probability targets the<br \/>\n  best-environment corridor.<\/p>\n<h3>Is a tornado possible with today&#8217;s Plains severe thunderstorms?<\/h3>\n<p>Yes. A 2% tornado probability applies to North Platte, Norfolk, and Valentine in Nebraska, and to Sioux<br \/>\n  Falls, Mitchell, Huron, Yankton, and Brookings in South Dakota. The tornado threat is narrower than the wind and<br \/>\n  hail threat and is focused on the highest-shear part of the Plains severe thunderstorms risk area.<\/p>\n<h3>When will Plains severe thunderstorms develop and how long will they last?<\/h3>\n<p>The SPC expects scattered storm initiation during the late afternoon and early evening. The severe threat is<br \/>\n  forecast to continue into the mid evening as a convective cluster moves southeast into the mid Missouri and<br \/>\n  upper Mississippi Valleys. In the Appalachians, the threat could persist into the early evening as storms reach<br \/>\n  the lower elevations.<\/p>\n<p><strong>Sources:<\/strong><\/p>\n<ul>\n<li><a href=\"https:\/\/www.spc.noaa.gov\/products\/outlook\/day1otlk.html\" target=\"_blank\" rel=\"noopener\">NOAA Storm Prediction Center, Day 1<br \/>\n  Convective Outlook issued 06:02 UTC, August 17, 2026<\/a><\/li>\n<\/ul>\n<div style=\"background: #000000; padding: 20px 24px; margin: 20px 0; border-radius: 4px;\">\n<p style=\"color: #ffffff; font-size: 16px; font-weight: bold; margin: 0 0 6px 0;\">Get Severe Weather Alerts for<br \/>\n  Your Location<\/p>\n<p style=\"color: rgba(255,255,255,0.9); margin: 0 0 14px 0;\">When any NWS watch, warning, or advisory is issued<br \/>\n  for your area, iAlert sends you an immediate notification by email, text message, or phone call, 24 hours a day,<br \/>\n  7 days a week.<\/p>\n<p>  <a href=\"https:\/\/ialert.com\/services\/severe-weather-alerts.php\" style=\"background: #C41226; color: #ffffff; \n  padding: 10px 22px; text-decoration: none; border-radius: 3px; font-weight: bold; display: inline-block;\">Sign<br \/>\n  Up for Severe Weather Alerts &rarr;<\/a>\n  <\/div>\n","protected":false},"excerpt":{"rendered":"<p>Plains severe thunderstorms bring a Slight Risk of large hail and damaging wind across Nebraska, South Dakota, and the Southern Appalachians.<span class=\"more\"> <a href=\"https:\/\/ialert.com\/blog\/news-events\/plains-severe-thunderstorms-aug-17\/\">Read More&#8230;<\/a><\/span><\/p>\n","protected":false},"author":6,"featured_media":5592,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","rank_math_focus_keyword":"Plains severe thunderstorms","rank_math_title":"Plains Severe Thunderstorms: 15% Hail and Wind Risk Aug 17","rank_math_description":"Plains severe thunderstorms bring a Slight Risk of large hail and damaging wind across Nebraska, South Dakota, and the Southern Appalachians."},"categories":[719],"tags":[772],"class_list":["post-5589","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news-events","tag-spc-outlook"],"acf":[],"_links":{"self":[{"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/posts\/5589","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/comments?post=5589"}],"version-history":[{"count":8,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/posts\/5589\/revisions"}],"predecessor-version":[{"id":5599,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/posts\/5589\/revisions\/5599"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/media\/5592"}],"wp:attachment":[{"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/media?parent=5589"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/categories?post=5589"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/tags?post=5589"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}