US Preliminary Extended Weather thru Mar 16

...Subtropical Plume Targeting Heavy Rainfall In Washington

Per Earlier Discussions And Forecasts...
The Active Region Of The Country At The Start Of Day 3 Will Be In The East.
By The End Of The Day 7 Period...There Should Be A Well-Marked 'Blocky' Upper-Level Low And Trough In Eastern Canada...An Active Southwest Flow Pattern Aloft Along The West Coast...And A Low-Amplitude Ridge In The Central Portion Of The Lower 48. The 8/12z Gefs/Ec Means Did Well To Capture The Developing Pattern At Mid-Latitudes Through Day 5.

Little Has Changed Along Both Coasts In The Medium Range Forecast.

There Will Be A Continued Focus On A Subtropical Connection In The
Eastern Pacific Beneath A Deep Cutoff Low Invof 40n 155w And A
Quasi-Stationary Ridge Along 120w.

Likewise In The East...The Persistence Of An Upper-Level Low In Eastern Canada And The Northeast Will Provide An Alley Way For Canadian Cold Fronts And Secondary Surface Wave Development Along The Base Of The Upper-Level Trough (Invof The Outer Banks).

The Overall Flow Pattern Aloft And Leading Edge Of The Canadian Airmass Boundary...Favors A 'Confluent' Storm Track That Wraps The Bulk Of The Strengthening Cyclogenesis Off The East Coast And Into The Canadian Maritimes With Much Of The Intense Weather Coming Ashore In Newfoundland And Labrador. But In A Cold Northwest Flow...The Medium Range Temperature Forecast In The Upper/Eastern Great Lakes...New England And Along The Northeast Coast Remains Below Normal.

The 8/12z Operational Gfs/Ecmwf Were In Much Better Agreement In
The Northwest With The Timing Of A Series Of Progressive Shortwave
Systems Migrating From The East Central Pacific To The Pacific
Northwest Coast...Then Migrating These 'Milder' Subtropical
Airmass Systems Into The Northern Rockies.

However...Day 6-7...A Major Portion Of The Upper-Level Trough In The Eastern Pacific Will Be Migrating Into The West Coast...With Active Weather And A Deep Surge Of Maritime Polar From The Gulf Of Alaska Spreading Through Much Of The Northwest... And Northern California/The Great Basin.

Looks Like A Dry/Breezy Spring-Time Weather Pattern Tracking
Through The Central/Southern Plains Through The Period...As The
Upper-Level Ridge Axis Continues To Amplify And Sweeps Eastward To A Position Near 110w Longitude On Day 7. Warmer Conditions Are
Projected For The Southern Plains And Southwest...With 70s And 80s
(Possibly A Few Lower 90s)...Anticipated For Much Of The Southern
Plains. There Will Be A Rather Distinct Nw-To-Se Demarcation Line
For The Advancing Warmth However Across The Northern And North
Central Plains. Generally Along And Northeast Of The Missouri
Valley Is Where Highs Will Struggle To Reach The 60s.

For The Manual Graphics...The Western And Central Portions Of The
Country Generally Used The Ecmwf With Some Aspects Of The Gfs To
Follow The Progression Of Several Surface Waves And Their
Attendant Pacific Fronts Through The Central Plains...Then
Downstream Into The East Central States And Off The Atlantic Coast
Through Day 5/6. The Ec Ensemble Means And The 8/12z Operational
Ecmwf Were Utilized For The Day 6-7 Details From West To East As
The Upper-Level Trough In The West Begins To Carve Out A Deep
Shortwave Over California/Nevada.

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