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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Oct 21, 2021
Updated: Thu Oct 21 08:20:03 UTC 2021
D4-8 D4 D5 D6 D7 D8
 Pop.  Cities  CWAs  RFCs  Interstates  Counties  ARTCC  FEMA  Tribal

D4Sun, Oct 24, 2021 - Mon, Oct 25, 2021 D7Wed, Oct 27, 2021 - Thu, Oct 28, 2021
D5Mon, Oct 25, 2021 - Tue, Oct 26, 2021 D8Thu, Oct 28, 2021 - Fri, Oct 29, 2021
D6Tue, Oct 26, 2021 - Wed, Oct 27, 2021 (All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
 Forecast Discussion

   ACUS48 KWNS 210818
   SPC AC 210818

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0318 AM CDT Thu Oct 21 2021

   Valid 241200Z - 291200Z

   (Day 4) Models are trending toward better agreement and have
   demonstrated some run-to-run consistency regarding the evolution of
   a southern-stream shortwave trough forecast to amplify as it
   approaches the southern and central High Plains Saturday night. This
   feature will move through the central/southern Plains Sunday before
   reaching the middle/lower MS Valley Sunday evening. There are still
   some model differences, particularly with regard to the amplitude
   and speed of this system. 

   Deepening lee low should be situated over central KS by 12Z Sunday
   with a trailing cold front extending southwestward into western TX.
   A warm front will stretch eastward from the low through northern KS
   and into central MO. Partially modified Gulf air will advect through
   the warm sector beneath steeper mid-level lapse rates resulting in
   moderate instability during the afternoon. A capping inversion will
   delay surface-based thunderstorm initiation until mid afternoon when
   storms will likely develop along the cold front across central
   eastern KS into eastern OK as well as farther east along the warm
   conveyor belt into the lower MS Valley. Vertical wind profiles will
   support organized storms including supercells with potential for all
   severe hazards. Given some lingering model differences, will only
   introduce 15% category for this outlook, but higher probabilities
   might be warranted with better model agreement in later updates.

   (Day 5) - A severe threat will probably persist as this feature
   continues into the TN Valley region Monday and possibly the Middle
   Atlantic region Tuesday. However, model difference become more
   substantial at this time frame, so will defer introduction of any
   categorical risk areas to possibly the next update.

   (Days 6-7) - Models including most ensemble members are in
   reasonable agreement regarding the approach of an upper trough into
   the Plains with robust moisture return toward the early and middle
   part of next week. If these trends continue, a severe risk area may
   be introduced for portions of the central and southern Plains in the
   next 4-8 outlook update.

   ..Dial.. 10/21/2021


To retrieve previous Day 4-8 convective outlooks, enter the date YYYYMMDD (e.g., 20050310 for March 10, 2005.)
Data available since March 8, 2005.
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Page last modified: October 21, 2021
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