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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Dec 15, 2017
Updated: Fri Dec 15 09:17:03 UTC 2017
D4-8 D4 D5 D6 D7 D8
 Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions

D4Mon, Dec 18, 2017 - Tue, Dec 19, 2017 D7Thu, Dec 21, 2017 - Fri, Dec 22, 2017
D5Tue, Dec 19, 2017 - Wed, Dec 20, 2017 D8Fri, Dec 22, 2017 - Sat, Dec 23, 2017
D6Wed, Dec 20, 2017 - Thu, Dec 21, 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 150915
   SPC AC 150915

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0315 AM CST Fri Dec 15 2017

   Valid 181200Z - 231200Z

   ...Monday/Day 4 and Tuesday/Day 5...
   The medium-range models including the ECMWF, GFS, UKMET and Canadian
   show anticyclonic southwest mid-level flow across the Southeast on
   Monday and Tuesday. A moist airmass is forecast to be in place
   across the Gulf Coast region where scattered thunderstorms should
   persist early in the week. Although large-scale ascent will be
   lacking across the Gulf Coast States, lift associated with enhanced
   low-level flow should support scattered thunderstorm development
   Monday and Tuesday. Strong low-level and deep-layer shear will be
   enough for a marginal severe threat. A few damaging wind gusts and a
   marginal tornado threat will be possible.

   ...Wednesday/Day 6 to Friday/Day 8...
   On Wednesday, the models develop an upper-level trough in the
   northwestern states and move this feature quickly into the central
   U.S. on Thursday. West to southwest mid-level flow is forecast to
   remain in the Southeast as a cold front moves into the region on
   Friday. Thunderstorm development will be possible along the front
   during the day. This convection may move eastward to southern
   sections of the Eastern Seaboard Friday afternoon as is suggested by
   the GFS solution. However, other model solutions do not move the
   front that quickly east and show much less convective potential. For
   this reason, uncertainty is substantial on Thursday and Friday.

   ..Broyles.. 12/15/2017


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: December 15, 2017
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