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US Preliminary Extended Weather thru Apr 20

...Overview...

An Active April Weather Pattern Is Expected In The West...And
Intensification Of The Upper-Level Trough Downstream Over The
South Central Plains Will Lead To Several Rounds Of Deep
Convection Along The Front. The Overall Ensemble Guidance Is In
Good Agreement For A Progressive Wave To Track West To East From ~110w On Day 3...To ~100w On Day 5 And ~90w Longitude Around Day 7.

...Model Preferences...

Until Day 5 (18/12z)...The 13/00z Ukmet...12/12z & 13/00z Canadian ...Along With The 12/12z Ecmwf Are Decent Pieces Of Deterministic Guidance In Their Handling Of A Deepening West Coast Trough And Embedded Impulse Driving Cooler And Windy Conditions Through Much Of California... The Great Basin And The Desert Southwest.

This Allows For The Leading Edge Of Another Canadian Airmass And Cold Front (Depicted On The Day 5 Graphic) To String Out From The Southern End Of Lake Michigan To The Ozarks And Deep Into Central Texas With An Open Gulf And Active Weather From South Central Texas Northward Into The Central Midwest.

The Deterministic Canadian/Ecmwf And Ukmet Carry Similar Depth Of A Cyclone Tracking Through The Central Great Lakes...Then Part
Ways With The Day 6-7 Progression Of The Cold Front Through The
Southeast And Southern Mid Atlantic States. The Canadian--In
Particular---Maintains A Fairly Constant Rate Of Progression Into
The Eastern Atlantic By Day 6.

In All Cases...The Deterministic Runs May Be Missing Out On The Potential For Secondary Areas Of Convection To Develop Along The Southern End Of The Front--And More Importantly--A Rather Substantial Surface Ridge In Place Off The Carolina Coast. A Slowing Down Of The Progression Of The Front Is Where The Ec Ensemble Means Were Likely To Better Represent The Frontal Positions On Day 6-7 Vs The Faster Gefs Means...And Were Weighted Much Higher Overall.

The Gfs Continues To Be The Outlier--Across Southern Alberta--With
Its Deep Lee Side Low Tracking Day 6-7 Across Saskatchewan And
Manitoba...When There Is Good Indications That A Sprawling High
Pressure System Will Be Dominant Over The Entire Western Half Of
The Conus. Little Room For Such A Deep System And The Surface
Graphics Preferred A Weaker System Tracking Across West Central
Canada Days 6-7.

...Sensible Weather Highlights...

A Rather Active Pacific Front And Tight Pressure Gradient Surges
Southward Through The West And Southwest On Days 3-4...With A
Deepening Surface Wave Emerging Out Of The Four Corners Area
Beneath A Rather Progressive Mid-Level Impulse Embedded Within The Migratory Upper-Level Trough Pressing Through The Rockies.

This Will Likely Lead To A Series Of Dryline Episodes In The Southern
High Plains Prior To Day 5...Before The Depth Of The Canadian
Airmass Overtakes The Entire Region. On Day 5...Several Surface
Waves Develop Along The Front...Likely The Result Of Clusters Of
Deep Convection Forming Along An Axis Of Deep Low-Level Moist
Convergence Streaming Nnewd From The Western Gulf Of Mexico Into The Mid Ms Valley.

Believe The Differences For Day 5-7...Especially Qpf And Timing Of The Precipitation...May End Up Being A Direct Result Of The Convective Initiation Upstream And Independent Of The Surface Cold Front...Ie Dryline-Induced Convection And Cloud Debris.

The Primary Weather Maker For The Midwest And Great Lakes Looks To Be Day 5-6 When The Best Low-Level Inflow And Cold Front Meet And Cyclogenesis Races Nnewd Through The Region.


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