|Day 4-8 Severe Weather Outlook Issued on Apr 23, 2011|
|Updated: Sat Apr 23 08:52:03 UTC 2011|
|D4||Tue, Apr 26, 2011 - Wed, Apr 27, 2011
||D7||Fri, Apr 29, 2011 - Sat, Apr 30, 2011
|D5||Wed, Apr 27, 2011 - Thu, Apr 28, 2011
||D8||Sat, Apr 30, 2011 - Sun, May 01, 2011
|D6||Thu, Apr 28, 2011 - Fri, Apr 29, 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).
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 230850
SPC AC 230850
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0350 AM CDT SAT APR 23 2011
VALID 261200Z - 011200Z
SUBSTANTIAL SEVERE WEATHER POTENTIAL IS EXPECTED TO SHIFT SLOWLY EWD
ACROSS THE ERN U.S. DAYS 4-6 /TUE. 4-26 THROUGH THU. 4-28/...AS A
LARGE UPPER TROUGH PROGRESSES FROM THE CENTRAL U.S. DAY 4 ACROSS THE
MS VALLEY DAY 5...AND THEN ON EWD THROUGH DAYS 6/7. MODEL
DIFFERENCES WITH RESPECT TO TIMING OF THIS FEATURE BEGIN TO EMERGE
DAY 5...BUT BECOME INCREASINGLY PRONOUNCED THROUGH DAYS 6 AND 7 AS
THE TROUGH APPROACHES THE E COAST STATES/ERN ATLANTIC.
THE PRIMARY SEVERE THREAT DAY 4 IS PROGGED FROM E TX NEWD ACROSS THE
ARKLATEX INTO THE MID MS VALLEY...AS A SHORT-WAVE TROUGH DIGS ESEWD
INTO THIS REGION...WITHIN THE LARGER-SCALE TROUGH. UNSTABLE AIRMASS
COMBINED WITH THE ENERGETIC SHORT-WAVE FEATURE AND ASSOCIATED/STRONG
FLOW FIELD SUGGESTS WIDESPREAD SEVERE WEATHER POTENTIAL -- INCLUDING
RISKS FOR LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES.
THE THREAT SHOULD SHIFT E OF THE MS VALLEY INTO THE MID
SOUTH/SOUTHEAST DAY 5...AS THE SHORT-WAVE FEATURE TAKES ON A NEUTRAL
TO EVEN NEGATIVE TILT AS IT CROSSES THIS REGION. AGAIN -- AMPLY
UNSTABLE AIRMASS COMBINED WITH THE STRENGTH OF THE UPPER SYSTEM AND
ASSOCIATED FLOW FIELD SUGGESTS WIDESPREAD SEVERE WEATHER CAN BE
EXPECTED...INCLUDING THE POTENTIAL FOR TORNADOES.
AS MODELS BEGIN DIVERGING SOMEWHAT WITH RESPECT TO TIMING AND
SMALLER-SCALE DETAILS...DEGREE OF THREAT SHIFTING ACROSS THE
APPALACHIANS LATE DAY 5 AND INTO DAY 6 BECOMES LESS CERTAIN. WHILE
SEVERE WEATHER WILL BE LIKELY WITH THE FRONT EXPECTED TO REACH THE
ATLANTIC COAST BY THE END OF THE PERIOD...WILL REFRAIN FROM
HIGHLIGHTING A THREAT AREA THIS FORECAST.
WITH THE FRONT LIKELY OFFSHORE BY THE START OF DAY 7... SEVERE
WEATHER POTENTIAL ACROSS THE U.S. APPEARS LESS
WIDESPREAD/SIGNIFICANT AND MUCH MORE UNCERTAIN THROUGH THE END OF
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