(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).
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
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.
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