US Final Extended Weather thru Apr 15

...Pattern Overview And Level Of Predictability...

The Pattern Entering The Medium Range Period...Day 3/Thu... Includes A Combined Rex/Omega-Block Across Much Of Canada... Resulting In Split-Flow Over The Conus With A Mean Longwave Trough Over The Plains And Mean Ridges Along The Coasts.

While The Rex Portion Of The Block Is Expected To Dissipate During
The Medium Range Period...The Remaining Portion Of The Block... Including Mean Troughs Over Southwestern Western And
Southeastern Canada Are Not.

Persistence Of This Blocking Pattern Along With Another Rex-Block Over The Pacific Contributes To Above Average Complexity With The Shortwave Pattern...Particularly Along The West Coast...Where These Blocks May Interact.

This Complexity Shows Itself With Above Average Solution Spread Forming As Early As Day 4/Fri...Which Is About 1 Day Ahead Of Average. To Address The Spread...The General Preference Is For A Solution Closest To The Ensemble Means...Which Are In Good Agreement Through The Entire Period...With Accompanying Average Confidence For Day 3...Then Below Average Thereafter.

...Guidance Evaluation And Sensible Weather Highlights...

Beginning With Day 3/Thu...The Deterministic Solutions Agree With
A Weak Cold Front Reaching The Intermountain West...Which Will
Serve To Accelerate The Trough Eastward Out Of The Plains.

However...The Spread With The Plains Trough Is Still Considerable
With The Gfs And Most Of Its Ensemble Members Faster Than The
Ecmwf And Its Respective Ensemble Members. A Solution Between
These Camps Is Preferred...Which The Models Have Trended Toward
The Last Several Days.

Strong Baroclinic Zones And Heavy Precipitation Will Accompany This Particular System From The Mississippi River Valley Eastward Thursday And Friday.

By Day 5/Sat...The Gfs/Canadian Are The Most Progressive With The
Mean Trough Over Western Canada Affecting The Pacific Northwest... While The Ecmwf/Ukmet Are Slower And More Amplified. Given The Above Mentioned Considerations...A Solution About Midway Between Is Preferred...Which Is Close To The Ensemble Means.

Meanwhile...A More Subtle But Potentially Significant Shortwave
Trough Is Expected To Cross Mexico...With Timing Between The
Faster Ecmwf And Slower Gfs Preferred...As It Possibly Begins To
Interact With The Residual But Mostly Higher-Based Portions Of The
Frontal Zone Over The Gulf.

By Day 7/Mon...The Ecmwf Becomes About 1 Day Faster Than The Gfs In Allowing The Trough Over Southwestern Canada To Dig Across The Pacific Northwest...With A Significant Cold Frontal Passage And Accompanying Swath Of Precipitation...With The Operational Canadian And The Ensemble Means About Midway Between. Given The Large Spread...These Intermediate Solutions Are Most Preferred Until The Event Nears.

Elsewhere...The Trough Crossing Mexico Next Weekend Has The Potential To Support Moderate Or Heavy Precipitation Along The Gulf Coast Region As It Interacts With The Reforming Warm Front Lying Somewhere Along The Central Gulf Coast. Model Qpf Details Are Suspect However...With The Gfs Appearing To Suffer From Grid-Scale Feedback. Thus...Relied Upon Non-Gfs Details Including The Ensemble Means For The Pops And Qpf Across This Region.

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