Day 4-8 Severe Weather Outlook Issued on Jul 29, 2013
Updated: Mon Jul 29 09:00:04 UTC 2013
Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4
Thu, Aug 01, 2013 - Fri, Aug 02, 2013
D7
Sun, Aug 04, 2013 - Mon, Aug 05, 2013
D5
Fri, Aug 02, 2013 - Sat, Aug 03, 2013
D8
Mon, Aug 05, 2013 - Tue, Aug 06, 2013
D6
Sat, Aug 03, 2013 - Sun, Aug 04, 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 290859
SPC AC 290859
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT MON JUL 29 2013
VALID 011200Z - 061200Z
...DISCUSSION...
MEDIUM RANGE MODELS INDICATE SEASONABLY STRONG NORTHWEST MID/UPPER
FLOW WILL PREVAIL LATE THIS WEEK THROUGH THE WEEKEND...WITHIN A
CONFLUENT REGIME BETWEEN SUBTROPICAL RIDGING...CENTERED OVER THE
SOUTHERN ROCKIES...AND UPPER TROUGHING...CENTERED OVER THE EASTERN
CANADIAN PROVINCES. ON THE SOUTHERN FRINGE OF THIS STRONGER
FLOW...A PLUME OF VERY WARM DEEPLY MIXED AIR EMERGING FROM THE
PLATEAU REGION SHOULD BEGIN ADVECTING EAST OF THE HIGHER TERRAIN
...ABOVE A MOIST/MOISTENING BOUNDARY LAYER...ALONG A
QUASI-STATIONARY FRONTAL ZONE ACROSS THE NORTH CENTRAL PLAINS INTO
MIDDLE MISSISSIPPI/LOWER OHIO VALLEYS AND SOUTHERN MID ATLANTIC
COAST REGION.
THE FRONTAL ZONE MAY BECOME THE PRIMARY FOCUS FOR VIGOROUS
THUNDERSTORM DEVELOPMENT THROUGH THE PERIOD. HOWEVER...DUE TO
AMPLIFIED NATURE OF THE FLOW...STEEP MID-LEVEL LAPSE RATES
ASSOCIATED WITH THE ELEVATED MIXED LAYER AIR MAY NOT SPREAD EAST OF
THE MIDDLE MISSISSIPPI VALLEY. AND THE LOWER CENTRAL PLAINS INTO
THE MIDDLE MISSISSIPPI VALLEY MAY BE IN QUESTION BY THE
WEEKEND...DUE TO REPEAT CONVECTIVE DEVELOPMENT ASSOCIATED WITH SHORT
WAVE IMPULSES MIGRATING AROUND THE PERIPHERY OF THE SUBTROPICAL
RIDGE. ANY ONE OF A NUMBER OF THESE SUBTLE PERTURBATIONS...WHICH
MAY BE EMBEDDED WITHIN THE LARGER SCALE FLOW...COULD CONTRIBUTE TO
THE EVOLUTION OF ORGANIZED CONVECTIVE SYSTEMS CAPABLE OF PRODUCING
SWATHS OF DAMAGING WIND GUSTS...AS THEY PROGRESS EAST OF THE
ROCKIES...THROUGH THE WEST NORTHWESTERLY FLOW REGIME. HOWEVER...THE
PREDICTABILITY OF THESE FEATURES IS VERY LOW...AND TOO MUCH
UNCERTAINTY STILL EXISTS TO CONFIDENTLY ASCERTAIN AND DELINEATE ANY
POTENTIAL REGIONAL SEVERE RISK AREAS.
..KERR.. 07/29/2013
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