Day 4-8 Severe Weather Outlook Issued on Aug 8, 2013
Updated: Thu Aug 8 09:02:04 UTC 2013
Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4
Sun, Aug 11, 2013 - Mon, Aug 12, 2013
D7
Wed, Aug 14, 2013 - Thu, Aug 15, 2013
D5
Mon, Aug 12, 2013 - Tue, Aug 13, 2013
D8
Thu, Aug 15, 2013 - Fri, Aug 16, 2013
D6
Tue, Aug 13, 2013 - Wed, Aug 14, 2013
(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 080900
SPC AC 080900
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT THU AUG 08 2013
VALID 111200Z - 161200Z
...DISCUSSION...
LONGER RANGE MODELS INCLUDING MOST ENSEMBLE MEMBERS CONTINUE TO
INDICATE THAT SYNOPTIC PATTERN WILL REMAIN DOMINATED BY UPPER
TROUGHS OVER THE ERN U.S. AND WEST COAST...AND A RIDGE ALONG
THE SPINE OF THE ROCKIES. A COLD FRONT IN THE EASTERN U.S. WILL MOVE
PROGRESSIVELY SWD INTO THE SERN STATES AND GRADUALLY WEAKEN.
HOWEVER...ANOTHER REINFORCING FRONTAL SURGE WILL MOVE SWD THROUGH
THE GREAT LAKES AND OH VALLEY DAY 5-6 IN ASSOCIATION WITH A
SHORTWAVE TROUGH DROPPING THROUGH BASE OF BROADER UPPER TROUGH. SOME
SEVERE THREAT MAY EXIST WITH STORMS THAT DEVELOP ALONG THIS BOUNDARY
OVER A PORTION OF THE GREAT LAKES AND OH VALLEY GIVEN INCREASING
FLOW ALOFT ASSOCIATED WITH AMPLIFYING WAVE IN BASE OF THE UPPER
TROUGH. HOWEVER...THE RICHER MOISTURE LIKELY TO REMAIN CONFINED TO
SOUTH OF THE STRONGER WINDS ALOFT...AND TOO MUCH UNCERTAINTY EXISTS
AT THIS TIME REGARDING QUALITY OF THERMODYNAMIC ENVIRONMENT TO
INTRODUCE A HIGHER END CATEGORICAL RISK.
RICHER MOISTURE WILL BEGIN RETURNING NWWD THROUGH THE CNTRL AND NRN
HIGH PLAINS DURING THE FIRST HALF OF THE 4-8 PERIOD...AND POTENTIAL
WILL EXIST FOR STORMS TO DEVELOP OVER THE MOUNTAINS AND INTENSIFY AS
THEY SPREAD EWD. OTHER STORMS MAY ALSO DEVELOP DURING THE
EVENINGS/OVERNIGHT OVER THE CNTRL/NRN PLAINS WITHIN NOCTURNAL WARM
ADVECTION ZONES. HOWEVER...MUCH OF THIS REGION WILL REMAIN BENEATH
AN UPPER RIDGE AXIS...AND ANY ENHANCED SEVERE THREAT AREAS WILL
LIKELY DEPEND ON TIMING OF SMALLER SCALE IMPULSES MOVING THROUGH THE
RIDGE. AT THIS TIME PREDICTABILITY REMAINS TOO LOW TO INTRODUCE A
30% OR GREATER CATEGORICAL RISK AREA.
..DIAL.. 08/08/2013
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