(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 300823
SPC AC 300823
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0323 AM CDT SAT AUG 30 2014
VALID 021200Z - 071200Z
PROGRESSION OF UPPER TROUGH FROM THE MS VALLEY INTO THE GREAT LAKES
IS HANDLED A BIT DIFFERENT BETWEEN THE ECMWF AND GFS. GFS IS
NOTABLY FASTER THAN THE ECMWF WITH SHORT WAVE EJECTING ACROSS SRN
ONTARIO INTO QUEBEC DURING THE DAY4 PERIOD. EVEN SO IT APPEARS
FRONTAL CONVERGENCE AND INSTABILITY SHOULD PROVE ADEQUATE FOR AT
LEAST ISOLATED TSTMS...POTENTIALLY SEVERE...BENEATH MODEST MID-LEVEL
FLOW. ROBUST STORMS SHOULD DEVELOP ALONG THE ADVANCING FRONT FROM
SERN CANADA...SWWD ACROSS THE OH VALLEY INTO THE LOWER MS VALLEY.
WILL NOT INTRODUCE 30 PERCENT SEVERE PROBS FOR THIS FRONTAL
CONVECTION DUE TO UNCERTAINTY IN LARGE SCALE SUPPORT FROM
AFOREMENTIONED SHORT WAVE AND SUBSEQUENT STORM COVERAGE.
LATER IN THE MEDIUM RANGE PERIOD HIGH LEVEL FLOW BECOMES MORE ZONAL
ACROSS THE NRN US. IT/S LIKELY THAT SUFFICIENT MOISTURE/INSTABILITY
ARE ABLE TO ADVECT BENEATH THIS STRONGER BELT OF WIND/SHEAR. AT
THAT TIME STRONG STORMS COULD EVOLVE BUT TOO MUCH UNCERTAINTY EXISTS
TO ACCURATELY PREDICT TIME/PLACE FOR THIS ACTIVITY.
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