{"id":5519,"date":"2026-08-12T16:02:39","date_gmt":"2026-08-12T16:02:39","guid":{"rendered":"https:\/\/ialert.com\/blog\/?p=5519"},"modified":"2026-08-12T16:02:39","modified_gmt":"2026-08-12T16:02:39","slug":"plains-severe-thunderstorms-aug-12-3","status":"publish","type":"post","link":"https:\/\/ialert.com\/blog\/news-events\/plains-severe-thunderstorms-aug-12-3\/","title":{"rendered":"Plains Severe Thunderstorms: Slight Risk of Large Hail and Damaging Wind From Iowa to the High Plains, August 12, 2026"},"content":{"rendered":"<p> <iframe src=\"https:\/\/ialert.com\/blog_outlook.php?event=plains-severe-thunderstorms-aug-12\" title=\"Plains Severe Thunderstorms: 30% \n  Damaging Wind Risk in Illinois, Large Hail on the High Plains, August 12, 2026\" loading=\"lazy\" style=\"width:100%;border:0;\" \n  height=\"660\"><\/iframe><\/p>\n<p><strong>Plains severe thunderstorms<\/strong> are the top weather story for Wednesday, August 12, 2026. The NOAA Storm Prediction<br \/>\n  Center has issued a Slight Risk, the second of five severe categories, from the central and northern High Plains through the mid<br \/>\n  Mississippi Valley into the lower Ohio Valley. Inside it the SPC has drawn a 30% damaging wind probability over central and eastern<br \/>\n  Illinois, the highest severe wind probability in the country today.<\/p>\n<p><strong>Key points:<\/strong><\/p>\n<ul>\n<li>Slight Risk (level 2 of 5) runs from western South Dakota and Nebraska across Iowa into Illinois, Indiana, and northern<br \/>\n  Kentucky.<\/li>\n<li>A 30% damaging wind probability covers central and eastern Illinois plus Davenport, Iowa, the highest wind probability drawn<br \/>\n  nationwide today.<\/li>\n<li>Damaging wind is the lead hazard with today&#8217;s plains severe thunderstorms, and a 15% wind probability covers the rest of the Slight<br \/>\n  Risk.<\/li>\n<li>A 15% large hail probability sits over the western High Plains near Scottsbluff and Chadron, Nebraska, and Rapid City, South<br \/>\n  Dakota.<\/li>\n<li>A 2% tornado probability covers Indianapolis, Louisville, St. Louis, Peoria, and Champaign. No hatched significant-severe area is<br \/>\n  drawn today.<\/li>\n<li>Storm clusters were already moving from eastern Iowa into northern Illinois at issuance; High Plains storms develop late afternoon<br \/>\n  into evening.<\/li>\n<\/ul>\n<h2>Where Plains Severe Thunderstorms Are Most Dangerous Today<\/h2>\n<p>Today&#8217;s <strong>plains severe thunderstorms<\/strong> Slight Risk spans two connected corridors. The eastern one runs through the mid<br \/>\n  Mississippi Valley and lower Ohio Valley, taking in Des Moines, Cedar Rapids, Davenport, Waterloo, and Council Bluffs in Iowa; Peoria,<br \/>\n  Springfield, Champaign, Bloomington, and Joliet in Illinois; Indianapolis, Lafayette, and Terre Haute in Indiana; plus St. Louis and<br \/>\n  Louisville. The western one covers the High Plains, where Omaha, Grand Island, North Platte, Rapid City, and Pierre all sit inside the<br \/>\n  polygon.<\/p>\n<p>Damaging wind is what earns the category. The Slight Risk polygon and the combined 15% and 30% wind areas are all but identical,<br \/>\n  matching to within a fraction of a percent of their area, so the wind threat alone lifted this corridor to level 2 of 5. The 30% core<br \/>\n  sits over central and eastern Illinois and reaches into far eastern Iowa, covering Peoria, Champaign, Bloomington, Decatur, Danville,<br \/>\n  Galesburg, Kankakee, Joliet, and Davenport.<\/p>\n<p>Everywhere else inside the risk area carries a 15% damaging wind probability, meaning a 15% chance of a damaging wind report within<br \/>\n  25 miles of a given point. That covers Omaha, Des Moines, Sioux City, Indianapolis, Terre Haute, Evansville, Louisville, and St.<br \/>\n  Louis.<\/p>\n<p>Large hail is the second hazard with today&#8217;s <strong>plains severe thunderstorms<\/strong>, and it peaks well west of the wind<br \/>\n  threat. A 15% large hail probability covers Scottsbluff, Chadron, Alliance, and Sidney in Nebraska, Rapid City in South Dakota, and<br \/>\n  Sterling in northeast Colorado. A wider 5% probability runs from Grand Island and Sioux City northward through the Dakotas to Fargo and<br \/>\n  Bismarck, with a second 5% area over Illinois and Indiana that takes in Chicago, Rockford, Indianapolis, and St. Louis.<\/p>\n<p>A 2% tornado probability applies to Indianapolis, Louisville, St. Louis, Springfield, Peoria, Champaign, Evansville, Lafayette, and<br \/>\n  Terre Haute. Two percent is low in absolute terms, but worth knowing given storms were already in progress there at issuance. SPC uses<br \/>\n  a five-tier system to rate severe weather potential; for the full breakdown see <a \n  href=\"https:\/\/ialert.com\/blog\/weather-articles\/severe-weather-outlook\/\">the iAlert guide to SPC outlook risk categories<\/a>.<\/p>\n<p>A Marginal Risk, the lowest of the five tiers, covers three separate areas around the <strong>plains severe thunderstorms<\/strong><br \/>\n  corridor. The largest wraps the Slight Risk, running north through the Dakotas and south and east through Missouri, Tennessee, Georgia,<br \/>\n  and the Carolinas, taking in Chicago, Rockford, Cincinnati, Nashville, Atlanta, and Charlotte. A second runs from lower Michigan<br \/>\n  across Lake Erie into Pennsylvania, New York, and New Jersey. A third sits over the lower Colorado River Valley near Yuma, Arizona.<\/p>\n<p>In that Great Lakes and Northeast area, Detroit, Cleveland, Buffalo, Rochester, Scranton, and Erie carry both a 5% damaging wind and<br \/>\n  a 5% large hail probability. Philadelphia, Harrisburg, Allentown, and Trenton carry the 5% wind only.<\/p>\n<figure class=\"wp-block-image size-full\" style=\"max-width:880px;margin:28px auto;padding:10px;border:1px solid #dde3ec;border-radius:6px;background:#ffffff;\">\n    <img decoding=\"async\" src=\"https:\/\/ialert.com\/blog\/wp-content\/uploads\/2026\/08\/ialert-plains-severe-thunderstorms-wind-risk-august-12-2026.jpg\" alt=\"Plains severe thunderstorms damaging wind risk \n  map for August 12, 2026, showing the SPC 30 percent damaging wind probability over central and eastern Illinois inside a 15 percent area from western South Dakota and Nebraska \n  across Iowa into Indiana\" width=\"1600\" height=\"865\" 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 damaging wind probabilities for August 12, 2026. The 30% area (red)<br \/>\n  over central and eastern Illinois is the core of the plains severe thunderstorms threat and the highest wind probability drawn anywhere in the country today. The 15% area (yellow)<br \/>\n  surrounds it from western South Dakota and Nebraska across Iowa into Indiana and northern Kentucky. The 5% area (brown) widens it north through the Dakotas, south through the<br \/>\n  Southeast, east into the Northeast, and over the lower Colorado River Valley. Source: NOAA Storm Prediction Center.<\/figcaption><\/figure>\n<h2>Meteorologist&#8217;s Take on Today&#8217;s Plains Severe Thunderstorms<\/h2>\n<p>The eastern half of today&#8217;s <strong>plains severe thunderstorms<\/strong> setup was already underway at issuance. Radar and satellite<br \/>\n  imagery at 12:36 UTC (8:36 a.m. EDT \/ 7:36 a.m. CDT) showed several storm clusters from Iowa into the Ohio Valley, the most notable<br \/>\n  over far eastern Iowa moving into central and northern Illinois.<\/p>\n<p>The air mass downstream is very moist and extremely unstable. The 12 UTC Davenport, Iowa sounding measured 4,300 joules per kilogram<br \/>\n  of mixed-layer CAPE, an unusually large reservoir of storm fuel for mid-August. That air mass sits near the terminus of a 35-knot<br \/>\n  west-southwesterly low-level jet over northern Missouri. The SPC expects the combination to drive a gradual intensification of storms<br \/>\n  across Illinois through the morning, with a risk of scattered severe gusts and wind damage.<\/p>\n<p>Two things temper the eastern threat. The SPC notes considerable uncertainty about how additional storm clusters evolve across the<br \/>\n  Midwest this afternoon. Outflow from the morning storms over eastern Indiana and central Kentucky will also likely hold down the severe<br \/>\n  risk farther east across parts of the Ohio Valley. Even so, a moist and destabilizing boundary layer keeps scattered wind damage and<br \/>\n  isolated large hail in play with the stronger storms into the evening.<\/p>\n<p>On the Plains, east and southeasterly low-level flow holds modest moisture across the Dakotas, increasing southward across Nebraska<br \/>\n  into northern Kansas. Near-60-degree dewpoints should spread west into eastern Colorado, Wyoming, and Montana beneath steep lapse<br \/>\n  rates. Ample heating gives moderate buoyancy and more than 30 knots of effective shear, enough to organize the scattered storms<br \/>\n  expected to develop later this afternoon. Initial cells carry the large hail and severe gust threat.<\/p>\n<p>Some clustering may occur during the evening, but confidence remains low on which corridors the severe threat will focus. That is<br \/>\n  the honest read on the western half of today&#8217;s <strong>plains severe thunderstorms<\/strong>: the ingredients are in place, the<br \/>\n  placement is not.<\/p>\n<p>The Great Lakes into Northeast threat runs on different ingredients. A belt of stronger northwesterly flow aloft extends from lower<br \/>\n  Michigan into New York and Pennsylvania, and vertically veering wind profiles give more than 35 knots of effective shear with elongated<br \/>\n  hodographs. That is more shear than the Plains have today. What holds the area to a Marginal Risk is thermodynamics: midlevel lapse<br \/>\n  rates stay modest and MLCAPE reaches only about 1,000 to 1,500 joules per kilogram, so storms there carry damaging gusts and marginally<br \/>\n  severe hail.<\/p>\n<p>Two lower-end areas round out the day. Across the Tennessee Valley and Southeast, midday storms in a very moist, strongly unstable<br \/>\n  air mass could produce water-loaded downdrafts capable of wind damage, helped by precipitable water near 2 inches. Over the lower<br \/>\n  Colorado River Valley, widely scattered storms near a weak upper trough may produce isolated severe gusts, which is what put Yuma in a<br \/>\n  Marginal Risk.<\/p>\n<h2>How to Stay Safe During Plains Severe Thunderstorms<\/h2>\n<p>Damaging wind is the lead hazard across today&#8217;s <strong>plains severe thunderstorms<\/strong> corridor, and the 30% area over<br \/>\n  Illinois is where it is most likely. Gusts reaching severe criteria start at 58 mph, enough to bring down limbs and power lines. Move<br \/>\n  vehicles under cover, bring in anything loose, and track cells on <a href=\"https:\/\/ialert.com\/analysis.php?tab=radar\">iAlert live radar<br \/>\n  and alerts<\/a>.<\/p>\n<p>Large hail is the bigger concern on the High Plains. Hail at severe criteria is at least one inch in diameter, enough to dent<br \/>\n  vehicles and crack windshields. Garage a car if you have the option, and do not wait out a hailstorm in the open.<\/p>\n<p>If a Severe Thunderstorm Warning is issued for your county, move to an interior room on the lowest floor, away from windows. Anyone<br \/>\n  in the 2% tornado probability zone should know their shelter spot in advance. Check <a \n  href=\"https:\/\/ialert.com\/analysis.php#alerts\">active weather alerts for your area<\/a> and keep a weather app or NOAA Weather Radio<br \/>\n  within reach, because plains severe thunderstorms are expected to continue into the evening.<\/p>\n<h2>Plains Severe Thunderstorms FAQ<\/h2>\n<h3>Where is the highest risk from today&#8217;s plains severe thunderstorms?<\/h3>\n<p>The 30% damaging wind area over central and eastern Illinois, covering Peoria, Champaign, Bloomington, Decatur, Danville, Galesburg,<br \/>\n  Kankakee, and Joliet, plus Davenport, Iowa. It is the highest severe wind probability the SPC has drawn anywhere in the country<br \/>\n  today.<\/p>\n<h3>How large could hail get in today&#8217;s plains severe thunderstorms?<\/h3>\n<p>The 15% large hail probability sits over the western High Plains near Scottsbluff and Chadron, Nebraska, Rapid City, South Dakota,<br \/>\n  and Sterling, Colorado. The outlook states no maximum diameter and draws no hatched significant-severe area, so expect hail at or above<br \/>\n  the one-inch severe threshold rather than a giant-hail event.<\/p>\n<h3>Is there a tornado threat with today&#8217;s plains severe thunderstorms?<\/h3>\n<p>Yes, but a limited one. The SPC shows a 2% tornado probability covering Indianapolis, Louisville, St. Louis, Springfield, Peoria,<br \/>\n  Champaign, Evansville, Lafayette, and Terre Haute. That is the lowest tornado tier the SPC issues, and no hatched area is drawn, but<br \/>\n  storms already in progress make a shelter plan worth having.<\/p>\n<h3>When will the worst of today&#8217;s plains severe thunderstorms arrive?<\/h3>\n<p>Storms across Iowa and Illinois were already active at the 12:36 UTC issuance and should intensify through the morning. Storms on<br \/>\n  the High Plains develop later in the afternoon and evening and may cluster after dark. The outlook period for today&#8217;s plains severe<br \/>\n  thunderstorms runs through 12 UTC Thursday, August 13.<\/p>\n<h3>Why are today&#8217;s plains severe thunderstorms only a Slight Risk with a 30% wind probability?<\/h3>\n<p>A 30% damaging wind probability normally corresponds to an Enhanced Risk, level 3 of 5. The SPC held the categorical outlook at<br \/>\n  Slight Risk in this issuance while drawing the 30% wind area over Illinois. Watch for a possible upgrade in the next update if the<br \/>\n  Illinois cluster holds together through the morning.<\/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 Convective Outlook, issued<br \/>\n  12:36 UTC August 12, 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 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 for your area, iAlert<br \/>\n  sends you an immediate notification by email, text message, or phone call, 24 hours a day, 7 days a week.<\/p>\n<p>  <a href=\"https:\/\/ialert.com\/services\/severe-weather-alerts.php\" style=\"background: #C41226; color: #ffffff; padding: 10px 22px;\n  text-decoration: none; border-radius: 3px; font-weight: bold; display: inline-block;\">Sign Up for Severe Weather Alerts &rarr;<\/a>\n  <\/div>\n","protected":false},"excerpt":{"rendered":"<p>Plains severe thunderstorms threaten large hail and damaging wind from Iowa and Illinois to the Dakotas and Nebraska on August 12, 2026.<span class=\"more\"> <a href=\"https:\/\/ialert.com\/blog\/news-events\/plains-severe-thunderstorms-aug-12-3\/\">Read More&#8230;<\/a><\/span><\/p>\n","protected":false},"author":6,"featured_media":5528,"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 Risk Aug 12","rank_math_description":"Plains severe thunderstorms threaten large hail and damaging wind from Iowa and Illinois to the Dakotas and Nebraska on August 12, 2026."},"categories":[719],"tags":[772],"class_list":["post-5519","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\/5519","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=5519"}],"version-history":[{"count":5,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/posts\/5519\/revisions"}],"predecessor-version":[{"id":5532,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/posts\/5519\/revisions\/5532"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/media\/5528"}],"wp:attachment":[{"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/media?parent=5519"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/categories?post=5519"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ialert.com\/blog\/wp-json\/wp\/v2\/tags?post=5519"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}