Storm Prediction Center Day 2 Severe Weather Outlook

All data from the SPC

Day 2 Graphical Outlook

Definition: The probability values represent the chance of severe weather occurring within 25 miles of any point, which is approximately the size of a major metropolitan area.

Day 1 & 2: The outlook contains individual severe probabilities for tornadoes, wind, and hail.
Day 3: Due to greater uncertainty, the outlook only forecasts the combined probability of all three types of severe weather.

Context: Probabilities for severe thunderstorm wind and hail are typically higher than for tornadoes because they are more common. A 15% probability for a tornado means significantly above normal odds of a tornado nearby, which should be taken seriously, even though the number seems low.

Note: The peak daily tornado probabilities in the most tornado prone portions of the country (Plains and Southeast) are slightly above 2%. Therefore, most days with any tornado probabilities are well above climatology.


SPC Category Descriptions (Click image to enlarge)



Issue Times

Day 1 Outlook - Day 3 Outlook

Day 2 Outlook Discussion

SPC AC 131729

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1229 PM CDT Sun Sep 13 2026

   Valid 141200Z - 151200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
   NEBRASKA INTO WESTERN IOWA...

   ...SUMMARY...
   Scattered strong to severe thunderstorms may impact parts of eastern
   Nebraska into western Iowa late Monday afternoon into early evening.

   ...Discussion...
   A mid-level trough will move across the northern Plains on Monday
   with a strengthening 60-70 knot mid-level jet streak. The surface
   pattern will feature a surface low across the Canadian Prairies and
   a secondary weaker surface low across the central Plains. A moist
   airmass will advect northward to the east of the surface trough with
   mid to upper 60s dewpoints advecting into Nebraska and Iowa.  

   Thunderstorms will likely be ongoing at the beginning of the period
   across eastern South Dakota and Minnesota into Iowa amid moderate
   isentropic ascent. In the wake of this morning activity, northward
   recovery will occur across northeast Kansas into southeast Nebraska
   and southwest Iowa. Within this zone, a narrow period of favorable
   conditions is forecast to develop ahead of front from southeast
   Nebraska northward. Most guidance shows storms developing within an
   environment featuring 2500+ J/kg MLCAPE and 30 to 35 knots of
   effective shear during the afternoon. This would support a supercell
   storm mode. If this discrete storm mode can be maintained, a EF2+
   tornado threat will exist given the nearly purely streamwise
   vorticity in the lowest 2km from RAP forecast soundings in the
   region. Limiting factors to this scenario are multiple storms
   developing along the front and quickly growing upscale and a lack of
   strong venting flow aloft which may result in disruptive downbursts
   before a more organized, strong low-level mesocyclone can develop. 

   Farther southwest, moderate instability and strong heating/lapse
   rates may support isolated damaging wind gusts. Some guidance shows
   ~30 knots of effective shear which could support some marginally
   rotating storms. If this occurs, some isolated large hail may be
   possible. The 5% hail probability has been extended southwestward to
   account for this threat. 

   Elevated thunderstorms will persist into the overnight period across
   southern Wisconsin and northern Illinois within a strong low-level
   jet and isentropic ascent. However, only modest elevated instability
   and limited cloud-bearing shear should preclude much severe threat
   farther east into southern Wisconsin and northern Illinois.

   ..Bentley.. 09/13/2026

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