NWS Storm Prediction Center - Day 4-8 Convective Outlook

Day 4-8 Severe Weather Outlook Issued on Sep 20, 2018
Updated: Thu Sep 20 08:43:03 UTC 2018
D4-8 D4 D5 D6 D7 D8
 Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions

D4Sun, Sep 23, 2018 - Mon, Sep 24, 2018 D7Wed, Sep 26, 2018 - Thu, Sep 27, 2018
D5Mon, Sep 24, 2018 - Tue, Sep 25, 2018 D8Thu, Sep 27, 2018 - Fri, Sep 28, 2018
D6Tue, Sep 25, 2018 - Wed, Sep 26, 2018 (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 200841
   SPC AC 200841

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0341 AM CDT Thu Sep 20 2018

   Valid 231200Z - 281200Z

   Latest runs of the medium-range models appear to be in good general
   agreement through Day 6 (Tuesday 9-25), after which differences
   begin to gradually emerge, complicating attempts to ascertain
   convective potential through the middle of next week.

   Prior to this, models consistently depict that the trough moving
   across the Pacific Northwest at the start of Day 4 will gradually
   expand/deepen as it moves across the western and into the central
   U.S. through Day 6.  In response to the approaching trough, a cold
   front is progged to move into the northern and central Plains Day 4,
   and the across the Plains and into the Upper Great Lakes Day 5.  Day
   6, as the upper system continues to expand/advance eastward, the
   front is forecast to cross the Upper Great Lakes/Midwest/southern

   As the front crosses the central and eastern U.S., an increase in
   convective potential will accompany it.  However, in general, it
   appears that the stronger flow aloft will be confined to northern
   portions of the frontal zone, where warm-sector instability will
   likely remain more limited.  While portions of the central Plains
   and upper Midwest on Monday the 24th (Day 5), and the upper Great
   Lakes and Midwest on Tuesday the 25th (Day 6), may require attention
   in later outlooks, once any potential risk becomes more certain, no
   areas will be issued at this time.

   ..Goss.. 09/20/2018


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.

Data courtesy the Storm Prediction Center

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