US Extended Forecast thru Jan 4

Extended Forecast Discussion
Nws Weather Prediction Center College Park Md
Valid 12z Tue Dec 31 2013 - 12z Sat Jan 04 2014

...Overview And Model Preferences...

Persistent Ridging Along The Western Coast Of North America Into
Alaska Will Continue To Favor Downstream Troughing East Of The
Continental Divide.

A Lobe Of The Polar Vortex Will Rotate Through Southern Canada Early In The Period But The Large Scale Ridge/Trough Pattern Will Remain Into Next Weekend.

The Ecmwf Has Been The Steadiest Of The Deterministic Models Through About Day 5 In Recent Runs /Though Not Perfect/ While The Others Have Bounced Around In Timing/Amplitude Of The Embedded Systems Out Of The Northeast Pacific And Through The Central Conus.

The Ecens/Gefs Means Compare Favorably To Each Other And Recent Trends Cannot Rule Out One Over The Other With Respect To The Forward Propagation Of Sfc Systems.

Nevertheless... Relied On The Sharper Ecmwf/Ecens Mean Tue-Wed/ D3-4 To Better Handle The Cold Air Diving Southward Before Transitioning To An Ecens/Gefs/Naefs Blend For The End Of The Period.

The Signal Is Still Quite Present For Some Sort Of Coastal System Around Fri/D6 But The Models/Ensembles Vary Widely From No Effect Along The Coast Like The 12z/27 Ecmwf To A Miller Type-B Scenario Like Some Gfs Runs.

For Now... Will Keep Low Pressure Off The Coast But Not Quite Out To Sea Until The Guidance Tightens Up.

...Sensible Weather Highlights...

Much Below Normal Temps Will Again Invade The Northern Tier...
With Less Harsh Departures Down To The Gulf Coast And Florida For
The Middle/End Of Next Week.

Still A Fair Amount Of Spread Among The Ensemble Members With Respect To Min/Max Temps North Of 40n /30-40f Spread/ But The Ecens Members Were Colder Than The Gefs Members... And Leaned That Way As A Start.

Along/West Of The Divide Upper Ridging Will Allow For Near To Above Normal Temperatures And Little In The Way Of Precip Except For The Pac Nw Into The Northern Rockies But Amounts Should Be Relatively Minimal.

Bigger Focus For Precip Should Be Along The Tx Coast Into The Lower Ms Valley As Sfc Low Pressure Organizes And Moves East
Wed-Thu But Again Ensemble Spread Ranges From Zero To About 3
Inches Or So... But The Means Have Been Consistently Showing At
Least A Modest Rain Event.

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