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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Sep 22, 2017
Updated: Fri Sep 22 08:02:03 UTC 2017
D4-8 D4 D5 D6 D7 D8
 Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions

D4Mon, Sep 25, 2017 - Tue, Sep 26, 2017 D7Thu, Sep 28, 2017 - Fri, Sep 29, 2017
D5Tue, Sep 26, 2017 - Wed, Sep 27, 2017 D8Fri, Sep 29, 2017 - Sat, Sep 30, 2017
D6Wed, Sep 27, 2017 - Thu, Sep 28, 2017 (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 220759
   SPC AC 220759

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0259 AM CDT Fri Sep 22 2017

   Valid 251200Z - 301200Z

   The slow-moving longwave trough over the West will finally begin to
   weaken and eject northeastward toward the western Great Lakes region
   around D5/Tuesday.  Ahead of this trough, surface cyclogenesis
   should occur in Wisconsin that, when combined with weak
   surface-based destabilization, may result in a risk for isolated
   severe storms during the afternoon and evening.

   Beyond this period, models diverge substantially with regard to a
   remnant cut-off low over the Southwest and a downstream trough near
   the Great Lakes.  Despite differences in the mid/upper synoptic
   pattern, models generally suggest varying degrees of surface ridging
   across the northern Rockies and central Plains that should result in
   a cooler, drier airmass spreading into these areas.  With modified
   maritime air shunted south of more active westerlies (nearer the
   Great Lakes and vicinity), it appears that any organized severe risk
   should be on the decrease.

   ..Cook.. 09/22/2017


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: September 22, 2017
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