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Day 4-8 Severe Weather Outlook Issued on Sep 28, 2017
Updated: Thu Sep 28 09:01:03 UTC 2017
Day 4-8 Severe Weather Outlook Graphics Issued on Sep 28, 2017
Day 4 Severe Weather Outlook Graphics Issued on Sep 28, 2017
Day 4 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 5 Severe Weather Outlook Graphics Issued on Sep 28, 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 Sep 28, 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 Sep 28, 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 Sep 28, 2017
Day 8 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Sun, Oct 01, 2017 - Mon, Oct 02, 2017 D7Wed, Oct 04, 2017 - Thu, Oct 05, 2017
D5Mon, Oct 02, 2017 - Tue, Oct 03, 2017 D8Thu, Oct 05, 2017 - Fri, Oct 06, 2017
D6Tue, Oct 03, 2017 - Wed, Oct 04, 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

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 280859
   SPC AC 280859

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0359 AM CDT Thu Sep 28 2017

   Valid 011200Z - 061200Z

   ...DISCUSSION...
   Broadly speaking, medium-range models are in decent large-scale
   agreement roughly the first half of the period, though smaller-scale
   differences begin to emerge by Day 6 (Tuesday 10-3) which would
   affect details of the convective forecast.

   In general, the formerly progressive western U.S. trough is expected
   to gradually become cut off from the polar westerlies over Canada. 
   As this occurs, the system will evolve into a retrograding low over
   the Intermountain West through Day 6, before then progressing
   eastward toward the Plains again through the end of the period.

   Initially on Day 4 (Sunday 10-1), prior to the beginning of
   retrogressive cut-off, short-wave troughing on the eastern fringe of
   the broader cyclonic flow field will shift northeast across the
   central and into the northern Plains through the afternoon and
   evening, and then into the Canadian Prairie overnight.  

   As a surface cold front shifts slowly east across the central and
   northern Plains and the upper system moves northeast, modest
   destabilization near/ahead of the front over the central Plains is
   expected -- possibly supporting some convective development.  While
   available shear would likely prove sufficient for updrafts to
   locally organize, questions exist regarding degree of diurnal
   warm-sector convective initiation which might occur in the wake of
   the northeastward-moving mid-level feature.  As such, will refrain
   from issuing an outlook area at this time.

   Day 5 (Monday 10-2), the front will likely remain across the central
   Plains, though with retrogression of the western trough/low now
   underway, mid-level height rises are expected across the central
   U.S. which -- again -- will likely hinder overall coverage of
   potential frontal convection.  Beyond Day 5, as smaller-scale model
   differences become more pronounced, confidence in assessing risk for
   convection diminishes -- such that no outlook areas will be
   introduced into the forecast at this time.

   ..Goss.. 09/28/2017

   CLICK TO GET WUUS48 PTSD48 PRODUCT
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Page last modified: September 28, 2017
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