May 22, 2013
General Agreement Exists Amongst The Gfs/Ec/Uk/Cmc Global Models In The Evolution Of A Large Scale Positive Tilt Trough Across The Wrn U.S. Through D4/Mon.
However...It Is Immediately Thereafter And Beyond When Substantial Differences Appear And Persist Amongst The Medium Range Guidance...Thus Introducing Considerable Uncertainty In The Forecast For Next Week.
The Ecmwf Exhibits The Greatest Departure From Prior Runs And Is An Outlier In Developing A Cutoff Low Within The Base Of The Positive
Tilt Trough Across The Southwest And Baja Through D5/Tue.
The Gfs...And To Some Extent The Other Global Models And Gfs
Ensemble...Maintain A More Progressive And Phased Deep Upper Trough And Stronger Cold Front That Spread East And South Across Mid/Lower Ms Valley Through D6/Wed.
But...Even Amongst The Gfs Ensemble Members...Uncertainty In The Amplitude Of This Trough Is High With The Standard Deviation In 500mb Heights Across The Cntrl U.S. Exceeding 90m At The 120h Forecast Valid D5/Tue Evening.
Despite The Spread In Gfs Ensemble Members...There Remains A Low Probability Severe Weather Threat From Arklatex To Ms Delta Regions As The Cold Front Associated With The Upper Trough Develops Into An Axis Of Potential Instability Through D5/Tue Evening.
With Latest Model Solutions And Ensemble Members Exhibiting Such Divergent Outcomes However...Forecast Confidence In A More Widespread Severe Weather Threat Has Decreased Since Yesterday.
Thus...Predictability Appears Too Low To Maintain A Severe Weather Area At This Time.
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