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Day 4-8 Severe Weather Outlook Issued on Apr 21, 2011
Updated: Thu Apr 21 22:13:20 UTC 2011
Day 4-8 Severe Weather Outlook Graphics Issued on Apr 21, 2011
D4Sun, Apr 24, 2011 - Mon, Apr 25, 2011 D7Wed, Apr 27, 2011 - Thu, Apr 28, 2011
D5Mon, Apr 25, 2011 - Tue, Apr 26, 2011 D8Thu, Apr 28, 2011 - Fri, Apr 29, 2011
D6Tue, Apr 26, 2011 - Wed, Apr 27, 2011 (All days are valid from 12 UTC - 12 UTC)
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 210859
   SPC AC 210859
   
   DAY 4-8 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0359 AM CDT THU APR 21 2011
   
   VALID 241200Z - 291200Z
   
   ...DISCUSSION...
   WHILE SOME DETAILS VARY...THE 00Z ECMWF/GEFS/UKMET ARE IN AMPLE
   GENERAL AGREEMENT WITH THE EXPECTED AMPLIFICATION OF THE LARGE SCALE
   PATTERN LATE THIS WEEKEND/EARLY NEXT WEEK...HIGHLIGHTED BY A
   PROMINENT WESTERN/CENTRAL CONUS UPPER TROUGH.
   
   ON DAY 4/SUNDAY...THE SOUTHERN HIGH PLAINS WILL LIKELY BE A FOCUS
   FOR AT LEAST SOME SURFACE BASED SEVERE THREAT NEAR/EAST OF A DRYLINE
   ACROSS WEST TX AND PERHAPS INTO OK. OTHER ELEVATED STORMS CAPABLE OF
   SEVERE HAIL ARE PROBABLE SUNDAY NIGHT FROM OK INTO THE OZARKS/LOWER
   MO VALLEY. BUT GIVEN LINGERING UNCERTAINTY REGARDING THE EXTENT OF
   PRE-DARK SURFACE BASED DEEP CONVECTION...LARGELY OWING TO
   ANTICIPATED MODEST LARGE SCALE FORCING FOR ASCENT/ONLY WEAK HEIGHT
   FALLS...TOO MUCH UNCERTAINTY CURRENTLY EXISTS TO DELINEATE A 30
   PERCENT EQUIVALENT SEVERE RISK AREA.
   
   FOR DAY 5/MONDAY...HAVE INTRODUCED A SEVERE RISK AREA FOR PORTIONS
   OF THE SOUTHERN PLAINS TO THE ARKLATEX/OZARKS. WHILE TIMING/SPATIAL
   DETAILS VARY TO A DEGREE...REASONABLE CONFIDENCE EXISTS THAT A
   SOUTHERN STREAM SHORTWAVE TROUGH WILL OVERSPREAD A MOIST AIRMASS TO
   THE EAST OF THE DRYLINE/COLD FRONT. AS SUCH...SEVERE STORMS SEEM
   LIKELY MONDAY/MONDAY NIGHT ACROSS THIS REGION.
   
   INTO DAYS 6/7 TUESDAY/WEDNESDAY...AS THE NEXT PORTION OF THE CENTRAL
   CONUS UPPER TROUGH PIVOTS EASTWARD...A RELATIVELY
   WIDESPREAD/MULTI-ROUND SEVERE THREAT IS EXPECTED FROM THE SOUTHERN
   PLAINS EAST-NORTHEASTWARD INTO THE MIDWEST AND LOWER/MIDDLE MS RIVER
   VALLEY. WHILE SEVERE STORMS SEEM LIKELY EACH OF THESE
   DAYS...SPECIFIC PREDICTABILITY IS STILL QUITE LIMITED IN THIS TIME
   FRAME.
   
   ..GUYER.. 04/21/2011

   CLICK TO GET WUUS48 PTSD48 PRODUCT

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