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Day 4-8 Severe Weather Outlook Issued on Feb 4, 2017
Updated: Sat Feb 4 09:40:03 UTC 2017
Day 4-8 Severe Weather Outlook Graphics Issued on Feb 4, 2017
Day 4 Severe Weather Outlook Graphics Issued on Feb 4, 2017
Day 4 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 210,526 30,980,497 Indianapolis, IN...Memphis, TN...Nashville, TN...Atlanta, GA...Cincinnati, OH...
Day 5 Severe Weather Outlook Graphics Issued on Feb 4, 2017
Day 5 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 6 Severe Weather Outlook Graphics Issued on Feb 4, 2017
Day 6 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 7 Severe Weather Outlook Graphics Issued on Feb 4, 2017
Day 7 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 8 Severe Weather Outlook Graphics Issued on Feb 4, 2017
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Tue, Feb 07, 2017 - Wed, Feb 08, 2017 D7Fri, Feb 10, 2017 - Sat, Feb 11, 2017
D5Wed, Feb 08, 2017 - Thu, Feb 09, 2017 D8Sat, Feb 11, 2017 - Sun, Feb 12, 2017
D6Thu, Feb 09, 2017 - Fri, Feb 10, 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 040938
   SPC AC 040938

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0338 AM CST Sat Feb 04 2017

   Valid 071200Z - 121200Z

   Model differences/uncertainty persist at this time, with respect to
   evolution of the large surface storm system to move across the
   eastern third of the U.S. Day 4/Tuesday.  However a somewhat more
   consistent depiction of major features within the ECMWF and GFS
   permits what appears to be a reasonable ability to highlight a 15%
   severe risk area from roughly the mid Ohio Valley southward into the
   central Gulf coastal region.  Within this area, somewhat modest but
   sufficient CAPE development should occur ahead of a
   strengthening/advancing cold front -- particularly from the Ohio
   Valley southward -- to permit development of fairly robust updrafts
   by afternoon.  Though what appears likely to be a westerly component
   to the low-level warm-sector flow field should limit tornado
   potential, large hail and locally damaging winds will be possible --
   with potential for both rotating storms and lines/line segments. 
   Convection should eventually weaken overnight, especially over
   northern parts of the risk area as storms move into a less-unstable
   environment.  Risk may linger farther south, as storms move into the
   southern Appalachians overnight.

   By Day 5/Wednesday, greater uncertainty exists, with the GFS
   depicting the front to have moved off the Atlantic and Gulf coasts
   by midday, while the ECMWF lingers a trailing, west-to-east portion
   of the front over the Gulf Coast States/Carolinas through the
   afternoon.  Given these differences, will not highlight a risk area
   at this time for Day 5.

   Risk appears minimal for Day 6, but potential for convection could
   increase into the central U.S. Day 7 and into the East Day 8 as the
   next storm system shifts out of the Rockies.  Model differences are
   substantial enough with respect to the details, however, that no
   risk areas will be considered at this time.

   ..Goss.. 02/04/2017

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Page last modified: February 04, 2017
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