The National Weather Service Storm Prediction Center's latest Day 1 outlook places a Slight Risk of severe thunderstorms across the Upper Mississippi Valley, with the highest tornado probabilities—5% within 25 miles—centered on northern Minnesota cities including Hibbing, Brainerd, Bemidji, and Alexandria. A 2% contour extends to nearby areas such as St. Cloud and Willmar. This stems from an embedded shortwave trough, strong deep-layer shear of 35-45 knots, and a strengthening low-level jet that supports supercell development late this afternoon and evening, with effective SRH rising to 250-300 m²/s². Large hail and damaging winds are also possible as storms organize along a cold front. Updated model runs and the next SPC outlook, due around 2000Z, could refine these boundaries or probabilities as new observational data arrives.
Experimental AI-generated summary referencing Polymarket data. This is not trading advice and plays no role in how this market resolves. · UpdatedWhich cities face tornado risk on September 11?
Chicago, IL
2%
Houston, TX
2%
San Antonio, TX
2%
Dallas, TX
2%
Austin, TX
2%
Fort Worth, TX
2%
Columbus, OH
1%
Charlotte, NC
1%
Indianapolis, IN
2%
Denver, CO
2%
Nashville, TN
1%
Oklahoma City, OK
2%
Memphis, TN
2%
Louisville, KY
2%
Atlanta, GA
3%
Kansas City, MO
50%
Omaha, NE
3%
Minneapolis, MN
2%
Wichita, KS
50%
New Orleans, LA
50%
Tampa, FL
50%
St. Louis, MO
2%
Birmingham, AL
2%
Des Moines, IA
2%
Little Rock, AR
2%
$1,299 Vol.
Chicago, IL
2%
Houston, TX
2%
San Antonio, TX
2%
Dallas, TX
2%
Austin, TX
2%
Fort Worth, TX
2%
Columbus, OH
1%
Charlotte, NC
1%
Indianapolis, IN
2%
Denver, CO
2%
Nashville, TN
1%
Oklahoma City, OK
2%
Memphis, TN
2%
Louisville, KY
2%
Atlanta, GA
3%
Kansas City, MO
50%
Omaha, NE
3%
Minneapolis, MN
2%
Wichita, KS
50%
New Orleans, LA
50%
Tampa, FL
50%
St. Louis, MO
2%
Birmingham, AL
2%
Des Moines, IA
2%
Little Rock, AR
2%
The SPC Day 1 Convective Outlook assigns tornado probability percentages (2%, 5%, 10%, etc.) to geographic areas across the US. If the city's coordinates fall inside any area rated 2% or higher, that city resolves "Yes". If a city is outside all tornado probability areas, or only within areas rated below 2%, that city resolves "No".
The SPC outlook is published as machine-readable geographic data (GeoJSON) at spc.noaa.gov. Each city's coordinates and the polygon boundaries are publicly verifiable. Borderline cases can be independently confirmed using the polygon data (excluding the hatched SIGN overlay, which is not a probability rating) and the city's listed coordinates. The point-in-polygon test is performed on unprojected WGS84 (EPSG:4326) coordinates, which is the native coordinate system of the SPC GeoJSON data.
Resolution is based on the scheduled 01:00 UTC Day 1 Convective Outlook update issued on the following UTC calendar day. The SPC Day 1 outlook covers a 24-hour period from 12:00 UTC to 12:00 UTC the following day. Subsequent revisions published after that scheduled update will not be considered. If the SPC Day 1 Convective Outlook has not been published by the time the market closes, this market will resolve to "No".
The resolution source for this market is the NOAA Storm Prediction Center at spc.noaa.gov.
This market uses coordinates 41.8781, -87.6298 for Chicago, IL.
Market Opened: Sep 11, 2026, 8:13 AM ET
Resolution Source
https://www.spc.noaa.gov/products/outlook/day1otlk.htmlResolver
0x65070BE91...The SPC Day 1 Convective Outlook assigns tornado probability percentages (2%, 5%, 10%, etc.) to geographic areas across the US. If the city's coordinates fall inside any area rated 2% or higher, that city resolves "Yes". If a city is outside all tornado probability areas, or only within areas rated below 2%, that city resolves "No".
The SPC outlook is published as machine-readable geographic data (GeoJSON) at spc.noaa.gov. Each city's coordinates and the polygon boundaries are publicly verifiable. Borderline cases can be independently confirmed using the polygon data (excluding the hatched SIGN overlay, which is not a probability rating) and the city's listed coordinates. The point-in-polygon test is performed on unprojected WGS84 (EPSG:4326) coordinates, which is the native coordinate system of the SPC GeoJSON data.
Resolution is based on the scheduled 01:00 UTC Day 1 Convective Outlook update issued on the following UTC calendar day. The SPC Day 1 outlook covers a 24-hour period from 12:00 UTC to 12:00 UTC the following day. Subsequent revisions published after that scheduled update will not be considered. If the SPC Day 1 Convective Outlook has not been published by the time the market closes, this market will resolve to "No".
The resolution source for this market is the NOAA Storm Prediction Center at spc.noaa.gov.
This market uses coordinates 41.8781, -87.6298 for Chicago, IL.
Resolution Source
https://www.spc.noaa.gov/products/outlook/day1otlk.htmlResolver
0x65070BE91...The National Weather Service Storm Prediction Center's latest Day 1 outlook places a Slight Risk of severe thunderstorms across the Upper Mississippi Valley, with the highest tornado probabilities—5% within 25 miles—centered on northern Minnesota cities including Hibbing, Brainerd, Bemidji, and Alexandria. A 2% contour extends to nearby areas such as St. Cloud and Willmar. This stems from an embedded shortwave trough, strong deep-layer shear of 35-45 knots, and a strengthening low-level jet that supports supercell development late this afternoon and evening, with effective SRH rising to 250-300 m²/s². Large hail and damaging winds are also possible as storms organize along a cold front. Updated model runs and the next SPC outlook, due around 2000Z, could refine these boundaries or probabilities as new observational data arrives.
Experimental AI-generated summary referencing Polymarket data. This is not trading advice and plays no role in how this market resolves. · Updated

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