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Day 4-8 Severe Weather Outlook Issued on Aug 25, 2021
Updated: Wed Aug 25 09:01:03 UTC 2021
Day 4-8 Severe Weather Outlook Graphics Issued on Aug 25, 2021
Day 4 Severe Weather Outlook Graphics Issued on Aug 25, 2021
Day 4 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 107,782 3,507,368 Minneapolis, MN...Sioux Falls, SD...Duluth, MN...Plymouth, MN...Brooklyn Park, MN...
Day 5 Severe Weather Outlook Graphics Issued on Aug 25, 2021
Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 6 Severe Weather Outlook Graphics Issued on Aug 25, 2021
Day 6 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 7 Severe Weather Outlook Graphics Issued on Aug 25, 2021
Day 7 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 8 Severe Weather Outlook Graphics Issued on Aug 25, 2021
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Sat, Aug 28, 2021 - Sun, Aug 29, 2021 D7Tue, Aug 31, 2021 - Wed, Sep 01, 2021
D5Sun, Aug 29, 2021 - Mon, Aug 30, 2021 D8Wed, Sep 01, 2021 - Thu, Sep 02, 2021
D6Mon, Aug 30, 2021 - Tue, Aug 31, 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

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 250859
   SPC AC 250859

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0359 AM CDT Wed Aug 25 2021

   Valid 281200Z - 021200Z

   ...DISCUSSION...
   Global models appear to be in reasonably good large-scale agreement
   with respect to large-scale/synoptic features across the U.S. for
   the first couple of days of the medium-range period, before timing
   and evolution differences begin to increase -- primarily within the
   belt of westerly flow over northern portions of the country, north
   of the southern U.S. ridging.

   On Sunday/Day 4, a short-wave trough is forecast to advance slowly
   eastward across the north-central states.  This will allow surface
   low pressure initially progged over the South Dakota vicinity to
   develop northeastward with time, into southern Manitoba/western
   Ontario overnight.  Trailing from the low, a cold front crossing
   Minnesota during the afternoon/evening time frame should focus storm
   development, in the wake of earlier-day storms.  With enhanced
   southwesterly flow aloft on the eastern fringe of the advancing
   upper trough, shear sufficient for organized storms -- and attendant
   potential for severe weather -- appears to warrant inclusion of a
   15% risk area.

   Day 5, as the system advances, storms -- and possibly some severe
   risk -- should spread across the Upper Great Lakes region.  However,
   with potential for early-period storms/cloud cover, questions exist
   regarding the afternoon thermodynamic environment.  As such, no risk
   area will be introduced across this area, at this time.  

   Beyond Day 5, uncertainty increases as the evolution of the overall
   large-scale pattern begins to differ more substantially amongst the
   models.  Of note, models suggest some potential for a Gulf of Mexico
   tropical cyclone that could approach the coast Day 6.  In any case,
   overall predictability concerns preclude issuance of any additional
   risk areas through the end of the period.

   ..Goss.. 08/25/2021

   CLICK TO GET WUUS48 PTSD48 PRODUCT
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Page last modified: August 25, 2021
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