US Extended Forecast thru Oct 31

The Latter Half Of This Medium Range Period (Mainly Days 5-7)
Features A Break Down Of The Amplified Flow Across The North
American Continent. The Strong Amplified Ridge Along The West
Coast And Split-Flow Breakdown In The Far East Central And
Northeast Pacific Will Undergo A 36-48 Hour Transition Period... And From 2 Distinctly Different Source Regions.

The Southern Flanks Of The Ridge Will Be Eroded By An 'Inside
Slider' System Featuring A Compact And Vigorous H7-H3 Layer
Circulation Migrating Through The Great Basin...And The Northern
Flanks Of The Upper Ridge Axis...Aligned Along The West Coast Of
Canada Will Be Eroded By A Series Of 'Typhoon-Infused' Waves... Crashing Into The Alaska Panhandle.

The Effects Of These Perturbations Work Their Way Downstream Into
The Eastern Half Of The Conus...With The "Inside Slider' Ejecting
Across The Central Plains And Exiting The Conus Invof The Great
Lakes In The Day 6-7 Time Frame. This System Erodes A Rather
Stable Surface Ridge That Has Held Firm Across The Eastern

...Model Preferences...

The Overall Synoptic-Scale Features Driving The Pattern Change Are
In Rather Decent Agreement...With The 25/00z Naefs/Ecens Means And The 'Trend' Of The 25/06z Gefs Leading The Way. The Transition
Period Seems To Be Where The Deterministic Runs And Individual
Ensemble Members (Or Clusters Of Members) Are Showing The Greatest Variance And Injecting 'Uncertainty' Into The Forecast.

The Earlier Gefs And Gfs Cycle Runs Have Been Generally Displayed
Their 'Fast Bias' And Wpc Continues To Rule These Solutions Out... Opting For A Slower Transition Of The Pattern. At The Very Least... The 25/06z Gefs/Gfs Have Slowed The Ejection Of A Strong Cyclone Migrating Through The Central Plains And Great Lakes. The 25/00z Deterministic Canadian Is Deeper And Faster Than The 25/00z
Deterministic Ecmwf With This Day 5-6 System.

To Mitigate The Spread At The Surface...We Recommend A Blend Of
The Naefs/Ecens Means And Split The Difference Between Their
Respectively Deterministic Runs With Respect To The Depth And
Projected Track Of The Surface Low Through The Midwest And Cold
Front Into The South Central States...Western Ohio Valley.

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