U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 270724 


Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0224 am CDT Wednesday Aug 27 2014 


Valid 291200z - 301200z 


..no severe thunderstorm areas forecast... 


... 
widespread showers and thunderstorms are forecast to spread 
gradually eastward across the central United States on Friday...most 
numerous within a zone from the upper Great Lakes 
south-southwestward to the Southern Plains. Isolated severe risk 
will be possible with stronger storms...mainly over the northern 
half of this area -- from roughly Missouri to the Great Lakes. 


... 
Gradual eastward advance of an upper trough over the central U.S. Will 
continue day 3...with this feature likely reaching the upper Midwest 
overnight. Meanwhile...a much more significant trough within the 
main belt of westerlies is forecast to move into western noam through the 
period. 


At the surface...a weak cool front crossing the central U.S. Is 
forecast to become ill-defined as it shifts eastward through the 
day...while a stronger front progresses eastward across the upper Great 
Lakes/southeastward across the northern plains. Farther west...a cold front is 
forecast to cross the northwestern U.S. Ahead of the aforementioned upper 
trough. 


..lower Michigan vicinity southwestward to eastern Kansas/northestern OK/northern Arkansas... 
Showers and thunderstorms ongoing at the start of the period should 
become increasingly widespread through the day from Texas northeastward to the 
upper Great Lakes region...as the central U.S. Trough makes gradual 
eastward progress. Model differences -- primarily with respect to timing 
-- emerge this period between the GFS and NAM...with the NAM 
depicting a much faster advance of this trough. In any case...with 
the cyclonic flow field surrounding this system expected to remain 
modest...and given likelihood that convection and associated cloud 
cover will become widespread...severe risk is prognosticated to remain 
tempered once again. Thus...will introduce a 5% risk area from 
lower Michigan southwestward across the lower MO valley/Ozarks 
plateau...corresponding to the anticipated zone of slightly stronger 
flow aloft. 


.Goss.. 08/27/2014