US Final Extended Forecast thru Aug 31

Models Show Good Overall Agreement In Perpetuating The Existing
Longwave Pattern Across The United States For The Next 7 Days... With Troughs Across The Eastern Pacific And Western Atlantic And An Upper High Over The Plains...With The High Slowly Retrograding.

The Slowly Evolving Pattern Favors Above Average Confidence With The Extremes...Particularly With The Heat Continuing Across Portions Of The Plains. The Short Wavelength Pattern Is Less Clear However ...With The Potential For Interactions Of Troughs At Various Latitudes That Introduces Some Possibly Large Errors With Frontal Timing And Positions.

Both The 00z Gfs/Ecmwf Show Similar Interactions Yet Slightly
Different Outcomes With Portions Of The Trough Over California And
Remnants Of Tropical Storm Ivo Over The Eastern Pacific As They
Possibly Phase Near The Canada/Us Border. The Ecmwf Is The Most
Extreme...Resulting In An Usually Deep Surface Low Over Quebec... While The Gfs Is Most Southward With An Accompanying Cold
Front Influencing Most Of The East.

Given The More Unusual Appearance Of The Ecmwf And Lack Of Model Agreement...The Ecmwf Scenario Is Generally Discarded. However...Some Support Exists For The More Southward Gfs Frontal Positions To At Least Be Factored Into The Final Model Blend. Most Important Perhaps Is Retrogression Of The Upper High That Would Leave Room For The Eastern Trough To Possibly Amplify A Bit Toward The Gfs Side Of The Spectrum. Another Factor Is Model Trends That Show The Ecmwf Ensemble Mean Developing Higher Mid Level Heights Over The Plains.

Therefore...The Overall Model Preference Is Close To The Previous
Overnight Choice Of The Ecmwf Ensemble Mean...Except Hedged About 30 Percent Toward The 06z Gefs Mean. This Approach Also Happens To Be Close To Longer Term Verification That Shows The Ecmwf Ensemble Mean Verifying Best About 70 Percent Of The Time.

Aside From Heat Continuing Across The Plains...Cooler Than Normal
Temperatures Are Expected Across Most Of The Pacific Northwest...
As Well As The Great Lakes/Northeast/New England.

Meanwhile...Rain Chances Will Remain Highest Along The Periphery
Of The Upper High... Particularly The Great Lakes/Northeast And Parts Of The Southwest.


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