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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Aug 13, 2020
Updated: Thu Aug 13 08:41:03 UTC 2020
D4-8 D4 D5 D6 D7 D8
 Pop.  Cities  CWAs  RFCs  Interstates  Counties  ARTCC  FEMA Regions

D4Sun, Aug 16, 2020 - Mon, Aug 17, 2020 D7Wed, Aug 19, 2020 - Thu, Aug 20, 2020
D5Mon, Aug 17, 2020 - Tue, Aug 18, 2020 D8Thu, Aug 20, 2020 - Fri, Aug 21, 2020
D6Tue, Aug 18, 2020 - Wed, Aug 19, 2020 (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 130839
   SPC AC 130839

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0339 AM CDT Thu Aug 13 2020

   Valid 161200Z - 211200Z

   ...DISCUSSION...
   ...Sunday/Day 4 and Monday/Day 5...
   On Sunday, the medium range models are in good agreement with an
   upper-level trough in the lower Great Lakes and northwest mid-level
   flow from the Great Plains eastward to the southern Appalachians. By
   Sunday afternoon, a cold front is forecast to be located from the
   Great Lakes to the mid Mississippi Valley, with the western end of
   the front in the southern Plains. Isolated thunderstorms will be
   possible along the front during the late afternoon and early
   evening. Moderate instability and relatively weak deep-layer shear
   will be sufficient for a marginal severe threat. But confidence for
   a severe threat in a specific area is low.

   On Monday, the models remain in decent agreement. A cold front is
   forecast to move into the Southeast with an axis of instability
   extending from the Gulf Coast states westward into central Texas.
   Marginally severe thunderstorms will be possible Monday afternoon
   along the front, especially in locations that heat up the most.
   However, uncertainty is considerable for Monday's forecast.

   ...Tuesday/Day 6 to Thursday/Day 8...
   From Tuesday to Thursday, models solutions diverge. While most
   models have an upper-level ridge in the western U.S. and an
   upper-level trough in the eastern U.S., the distribution of
   instability is widely varied. The GFS develops a pocket of moderate
   instability each afternoon from eastern sections of the central
   Plains eastward into the Missouri Valley. The ECMWF develops pockets
   of instability primarily in the northern Plains each afternoon.
   Thunderstorms associated with an isolated severe threat will be
   possible wherever these pockets of instability set up. At this
   point, the ECMWF presents the best scenario for a severe threat
   because deep-layer shear is expected to be stronger in the northern
   Plains. But confidence in any one of these scenarios is low at this
   time.

   ..Broyles.. 08/13/2020

   CLICK TO GET WUUS48 PTSD48 PRODUCT


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: August 13, 2020
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