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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Aug 19, 2017
Updated: Sat Aug 19 08:48:03 UTC 2017
D4-8 D4 D5 D6 D7 D8
 Population  Cities  CWAs  Interstates  Counties  ARTCC  FEMA Regions

D4Tue, Aug 22, 2017 - Wed, Aug 23, 2017 D7Fri, Aug 25, 2017 - Sat, Aug 26, 2017
D5Wed, Aug 23, 2017 - Thu, Aug 24, 2017 D8Sat, Aug 26, 2017 - Sun, Aug 27, 2017
D6Thu, Aug 24, 2017 - Fri, Aug 25, 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 190846
   SPC AC 190846

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0346 AM CDT Sat Aug 19 2017

   Valid 221200Z - 271200Z

   The mid-latitude westerlies may undergo further amplification
   through the middle of the coming work week, including the evolution
   of large-scale troughing across much of the Great Lakes, Ohio Valley
   and Northeast.  Within this regime, models suggest that one
   significant short wave impulse could support significant
   cyclogenesis across Quebec, accompanied by a trailing cold front
   which may advance through much of the eastern U.S. before weakening.
   There remains a signal within model output that pre-frontal forcing
   for ascent may be favorably timed with peak diurnal destabilization
   across parts of the lower Great Lakes region and upper Ohio Valley
   on Tuesday to support considerable vigorous thunderstorm activity. 
   In the presence of 30-50 kt deep layer mean flow and shear,
   organized severe storm development appears possible, with
   potentially damaging wind gusts the primary hazard.  Continuation of
   this threat across southern New England and the northern Mid
   Atlantic on Wednesday remains more unclear, with possible early day
   progression of the front off the coast.

   Thereafter, late next week into early next weekend, upper
   troughiness may linger across parts of the Upper Midwest/Great Lakes
   and Atlantic Seaboard, as subtropical ridging becomes increasingly
   prominent across the Intermountain West and Rockies.  Although short
   wave developments within this regime remain more uncertain, there
   appears little obvious at the present time to suggest anything more
   than perhaps generally low severe weather potential.

   ..Kerr.. 08/19/2017


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: August 19, 2017
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