US Extended Forecast thru Jan 14

Extended Forecast Discussion
Nws Weather Prediction Center College Park Md
Valid 12z Fri Jan 10 2014 - 12z Tue Jan 14 2014

Overview And Preferences...

The Medium Range Period Will Feature A Re-Building Of The Ern
Pac/West Coast Mean Ridge With A Downstream Trough That Should
Head Into The Ern States By Next Tue.

Model/Ensemble Agreement With The Large Scale Pattern Is Quite Good Through The Next Seven Days But Some Detail/Timing Diffs Exist... Notably With Ejection Of A Srn Plains/Nrn Mexico Shrtwv Mid-Period And Progression Of A Cold Front Into/Through The East Late In The Period.

Overall A Soln Close To A 00z Ecmwf/Ecmwf Mean Blend Offers The Best Starting Point Relative To Continuity And Teleconnections.

Guidance Evaluation...

Early In The Period The Primary Uncertainty Will Be The Degree Of
Separation Between Streams Within The Overall Plains/Nwrn Mexico
Trough... Impacting The Timing And Strength Of Individual Shrtwvs
Crossing The Northeast And The Srn Plains/Nrn Mexico.

Among Latest Guidance The 06z Gfs Is A Deep Extreme With The Nern Shrtwv By Late Sat-Sun While The 00z Gfs/Gefs Mean Are Fast With Ejecting The Srn Shrtwv.

The 00z Ecmwf/Ecmwf Mean Best Represent The Remaining Consensus. The 06z Gefs Has Adjusted Toward The Preferred Cluster For This Part Of The Fcst.

Ahead Of Upstream Energy A Fairly Vigorous System Is Fcst To Track
Just N Of The Pac Nw Around Early Sat. As The System Is Coming
Ashore The Initially Favored 00z Ecmwf/Ecmwf Mean Blend Is
Somewhat On The Weaker Side Of The Full Guidance Spread So The
Manual Fcst Adjusts The System Slightly Stronger Though Not To The
Extent Of Latest Gfs/Cmc Runs.

Progression/Amplification Of This Incoming Energy Will Support
Newd Acceleration Of The Early-Mid Period Srn Plains/Nrn Mexico
Shrtwv And Bring A Cold Front To The East Coast By Next Mon-Tue.

So Far Ecmwf/Ecmwf Mean Runs Have Been Slower With This Front Than Gfs/Gefs Mean Runs As Well As 00z Cmc Mean.

Multi-Day Means By D+8 Are Very Similar In Highlighting Two Cores Of Positive Hgt Anomalies... One Off The Pac Nw Coast And Another Just Se Of The Canadian Maritimes.

The Composite Of Corresponding Teleconnections Suggests Enough Warmth/Pcpn Along The East Coast To Recommend The Slower Frontal Timing Of The Ecmwf/Ecmwf Mean.

Sensible Weather Highlights...

Even With A Fairly Amplified Mean Pattern... Pacific Origin Of Air
Moving Into/Across The Lower 48 Should Lead To Above Normal Temps At Most Locations During The Period.

Warmest Temps Relative To Normal Should Be Across The Nrn Tier During The Weekend And Over The East Early Next Week.

Strong Flow Aloft Will Bring Considerable Mstr Into The Nrn Half Of The West Coast And Nrn Rockies During Fri-Sun With Up To Several Inches Of Rnfl Or Liquid Equiv In Snowfall Psbl Depending On Elevation.

Ahead Of The Mean Trough Aloft The Ern Half Of The Conus Should See Two Periods Of Enhanced Pcpn That Should Be Primarily Rnfl Except For Perhaps Extreme Nrn Areas... One During Fri-Sat And The Second From Sun Into At Least Mon.

Highest Totals For The Combined Events Are Currently Expected From Near The Cntrl Gulf Coast Newd Into The Tn Vly Or Srn Aplchns.

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