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< Day 3 Outlook    
Day 4-8 Severe Weather Outlook Issued on Sep 17, 2014
Updated: Wed Sep 17 08:59:02 UTC 2014
D4-8 D4 D5 D6 D7 D8
 Population  Cities/Towns  CWAs  Interstates  Counties  FEMA Regions

Severe Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4Sat, Sep 20, 2014 - Sun, Sep 21, 2014 D7Tue, Sep 23, 2014 - Wed, Sep 24, 2014
D5Sun, Sep 21, 2014 - Mon, Sep 22, 2014 D8Wed, Sep 24, 2014 - Thu, Sep 25, 2014
D6Mon, Sep 22, 2014 - Tue, Sep 23, 2014 (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 a 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 highly unlikely during the entire period (e.g. less than a 30% probability for a regional severe storm area across the CONUS through the entire Day 4-8 period).
 Forecast Discussion

   ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 170858
   SPC AC 170858

   DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0358 AM CDT WED SEP 17 2014

   VALID 201200Z - 251200Z

   ...DISCUSSION...
   THE ECMWF AND GFS MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH A SUBTLE
   UPPER-LEVEL TROUGH OVER THE UPPER MS AND MID MO VALLEYS AND MOVE
   THIS FEATURE EWD INTO THE MID TO UPPER MS VALLEY ON SATURDAY/DAY 4.
   A COLD FRONT IS FORECAST TO MOVE SEWD INTO KS...NEB..IA AND WI
   DURING THE DAY...ALONG WHICH THUNDERSTORM DEVELOPMENT WITH SOME
   POSSIBLY SEVERE...WILL BE POSSIBLE LATE SATURDAY AFTERNOON. THE
   MODELS AMPLIFY THE UPPER-LEVEL TROUGH AND MOVE IT EWD ACROSS THE
   GREAT LAKES REGION ON SUNDAY/DAY 5. ALTHOUGH THE ECMWF SOLUTION IS
   SLOWER WITH THE SYSTEM...BOTH ECMWF AND GFS HAVE A COLD FRONT SUNDAY
   AFTERNOON LOCATED FROM THE UPPER OH VALLEY SWWD INTO THE MID MS
   VALLEY. THUNDERSTORMS MAY DEVELOP ALONG THE BOUNDARY AND A FEW COULD
   BECOME SEVERE LATE SUNDAY AFTERNOON. BOTH MODELS MOVE THE
   UPPER-LEVEL TROUGH EWD INTO THE OH AND TN VALLEYS ON MONDAY/DAY 6
   WITH THE ECMWF AGAIN THE SLOWER SOLUTION. A COLD FRONT REACHES THE
   CAROLINAS AND GULF COAST STATES MONDAY AFTERNOON...ALONG WHICH
   THUNDERSTORM DEVELOPMENT WILL AGAIN BE POSSIBLE LATE MONDAY
   AFTERNOON. MODEL SOLUTIONS DIVERGE SHARPLY ON TUESDAY/DAY 7. 

   AT THIS POINT...THE GREATEST SEVERE THREAT DURING THE DAY 4 TO 8
   PERIOD IS FORECAST ON SATURDAY AFTERNOON IN THE UPPER MS VALLEY AND
   WRN GREAT LAKES REGION. UNCERTAINTY CONCERNING INSTABILITY AND
   TIMING REMAINS TOO HIGH TO WARRANT ADDING A SEVERE THREAT AREA.

   ..BROYLES.. 09/17/2014

   CLICK TO GET WUUS48 PTSD48 PRODUCT


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: September 17, 2014
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