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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Mar 23, 2017
Updated: Thu Mar 23 09:01:03 UTC 2017
D4-8 D4 D5 D6 D7 D8
 Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions

D4Sun, Mar 26, 2017 - Mon, Mar 27, 2017 D7Wed, Mar 29, 2017 - Thu, Mar 30, 2017
D5Mon, Mar 27, 2017 - Tue, Mar 28, 2017 D8Thu, Mar 30, 2017 - Fri, Mar 31, 2017
D6Tue, Mar 28, 2017 - Wed, Mar 29, 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 230858
   SPC AC 230858

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0358 AM CDT Thu Mar 23 2017

   Valid 261200Z - 311200Z

   An active severe weather pattern should continue across parts of the
   CONUS though the forecast period, although predictability decreases
   substantially Day 6/Tuesday and beyond.

   ...Day 4/Sunday - Day 5/Monday...
   An upper trough/low is forecast to move eastward across the
   southern/central Plains Day 4/Sunday. Latest model guidance remains
   in reasonable agreement with the placement of this trough, and its
   corresponding surface low position over western OK and the eastern
   TX Panhandle by Sunday evening. The degree and quality of low-level
   moisture return across the southern Plains remains the primary
   uncertainty for Day 4/Sunday, as convective initiation along a
   dryline extending southward from the surface low appears probable.
   The deterministic GFS is more aggressive compared to the ECMWF and
   many GEFS members regarding greater surface dewpoints across
   central/eastern OK into north TX. If future model trends show better
   agreement on more substantial low-level moisture return ahead of the
   dryline, a greater severe weather risk could develop. For now, have
   expanded the 15% risk area eastward to encompass more of eastern OK.

   The upper trough will continue eastward across the lower MS Valley
   and Southeast on Day 5/Monday. Some disagreement regarding the
   strength/amplitude of the trough is evident amongst deterministic
   guidance, but they remain in general agreement on the
   placement/timing. Enough low-level moisture return should occur
   across the lower MS Valley to support surface-based convection.
   Although some uncertainty with convective evolution from Day
   4/Sunday into Day 5/Monday remains, the overall forecast combination
   of instability and shear appears to support a severe weather threat
   across parts of the Mid-South and lower MS Valley where models
   forecast convection to develop by Monday afternoon. A 15% area has
   been included across this region for Day 5/Monday.

   ...Day 6/Tuesday - Day 8/Thursday...
   Model spread increases from Day 6/Tuesday through the remainder of
   the extended forecast period. Another western CONUS upper trough/low
   should develop eastward across the Southwest/southern High Plains
   vicinity on Day 6/Tuesday. However, medium-range model guidance
   becomes increasingly dispersive regarding this feature and its
   eastward/northeastward ejection across the southern and/or central
   Plains. The GFS solution would imply any meaningful severe threat
   would remain confined to parts of TX and the lower MS Valley in this
   time frame, while the ECMWF suggests the southern/central Plains and
   lower to mid MS Valley may have some severe risk. For now, this
   disagreement is too substantial to justify the inclusion of 15% risk
   areas, although they may be needed in later outlooks pending better
   model agreement/consistency.

   ..Gleason.. 03/23/2017


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: March 23, 2017
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