Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 4-8 Outlook
Day 4 - 8 Outlook
Day 4-8 Severe Weather Outlook. A depicted severe weather area indicates a 30% or higher probability for severe thunderstorms within 25 miles of a point.
D4Sat, Sep 23, 2017 - Sun, Sep 24, 2017 D7Tue, Sep 26, 2017 - Wed, Sep 27, 2017
D5Sun, Sep 24, 2017 - Mon, Sep 25, 2017 D8Wed, Sep 27, 2017 - Thu, Sep 28, 2017
D6Mon, Sep 25, 2017 - Tue, Sep 26, 2017 (All days are valid from 12 UTC - 12 UTC)
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. 1) large differences in the deterministic model solutions,
  2. 2) large spread in the ensemble guidance, and/or
  3. 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears highly unlikely during the entire period (e.g. less than a 30% probability for a regional severe storm area across the CONUS through the entire Day 4-8 period).

Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion


000
ACUS48 KWNS 200821
SWOD48
SPC AC 200820

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0320 AM CDT Wed Sep 20 2017

Valid 231200Z - 281200Z

...DISCUSSION...
A slowly evolving western trough/eastern ridge pattern should
continue throughout the extended forecast period, although models
suggest that the trough may begin to weaken and migrate eastward
with time - especially after D6/Monday.  Meanwhile at the surface, a
nearly stationary, NNE-SSW oriented cold front will gradually shift
southward across portions of the Plains in advance of a building
surface ridge across the Dakotas.  A lee surface trough will also
remain nearly stationary across eastern New Mexico and vicinity. 
Although model variance regarding specific surface boundary
positioning increases with time, the overall pattern suggests that
areas of showers and thunderstorms will continue (especially
during/after peak heating hours) from eastern New Mexico northward
to central Nebraska and into portions of the Upper Midwest around
D4/Saturday and D5/Sunday.  This general region of convection should
shift southeastward into the central and southern Plains from
D6/Monday onward.  At least a Marginal risk for severe storms should
exist during each of these periods - especially in eastern New
Mexico nearer to steeper mid-level lapse rates.  General uncertainty
regarding frontal position and magnitude of buoyancy preclude severe
probabilities at this time.

..Cook.. 09/20/2017