US Preliminary Extended Weather thru Feb 9

In One Way Or Another...The Eastern Half Of The Us Will Remain
Under The Influence Of A Cold Vortex Anchored Over Eastern Canada ...With A Series Of Alberta-Type Clipper Systems Migrating Into The Base Of The Trough...Creating Much If Not All Of The Sensible Weather Into Day 5. Was Able To Maintain Very Good Continuity From The Previous Surface Graphics Even Without The 12z Gfs/Gefs Guidance.

The 1-12z Gfs/Ecmwf Operationals Generally Accepted A Storm Track
That Arcs From The Dakotas And Upper Mississippi Valley Through
The Midwest And Into The Mid Atlantic States...Before Exiting Into
The Western Atlantic Ocean. These Clippers Will Be Generating
Periods Of Light Snowfall Across Their Northern Flanks And
Reinforcing A Canadian Airmass Into The Southern Plains And
Southeast In Their Wake.

The Flow Pattern Transitions Away From The Current One...On Late Day 5 Into Day 7 In The East...But Not Before One Last Coastal Wave Modifies Along Its Journey Eastward...From The Midwest And Ohio Valley Into The Western Atlantic Ocean.

In A Broad-Brushed Sense...Days 5-7...May End Up Being A Bigger
Weather Issue In The West...Southern Great Basin And Eventually
The Central...Southern Rockies And South Central Plains Rather
Than The East.

In That...An Amplifying Pacific Trough That Splits While Migrating Into And Through The Central Great Basin And The Four Corners Area Will Generate Broad-Scale Lift And Usher In A Much Colder And Unstable Airmass Into The Region. Several Mid-Level Shortwaves Eventually Eject Northeastward Out From The H5 Trough And Across The Northern Rockies And Northern High Plains States.

Anticipate A Gradual Slowdown Of The Upper Trough...With A
Deepening Lee Side Trough And Broad-Scale Upslope Flow Component To Take Shape From Eastern Montana...Southward Into Wyoming And Colorado In Advance Of The Upper Trough.

This Will Generate A Series Of Surface Waves That Will Generate Locally Moderate Precipitation Along The Continental Divide...Then Exit The Rockies For The Plains And Midwest. A Quick Look At The 2-00z Operational Ecmwf/Gfs Indicate A Slower...And Deeper System Than The 1-12z Ecmwf Means Over The West Coast And Great Basin...Between 8/00z And 9/00z.

The Details Of The Splitting Upper-Level Trough Are Intriguing... With Potential For A Cutoff H5 Low To Form Along The Southern End Of The Trough. This Adds Some Uncertainty To The Day 6-7 Forecast For A Precise Storm Track To Emerge From The Central Rockies.

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