US Preliminary Extended Weather thru Jan 11

The Medium Range Fcst Will Focus On Two Dominant Features... A
Trof Over The West As Of Early Mon And Then Ejecting Ewd
Thereafter Followed By A Larger Scale Trof Expected To Amplify Into The W-Cntrl Conus By Late Next Week.

Interestingly There Is Generally Greater Spread With Details Of The Initial Wrn Trof And Assoc Sensible Weather Impacts As The Feature Ejects Out Of The West... Than With The Later-Period Trof That In The Mean Should Support A Sfc Front From The Grtlks Swwd Into The Plains By Day 7 Fri.

Already At The Start Of The Period There Are Significant Diffs For
The Leading Wrn Trof... With These Diffs Becoming Further
Magnified With Time.

Solns Range From The Past Couple Ecmwf Runs That Track A Slow Cutoff Low Near The Wrn Us-Mexico Border And Then Newd Into The Plains To The 12z Ukmet That Has A More Phased Trof. In Varying Ways The 00z/18z/12z Gfs Runs And 12z Canadian Are Also Moderately Progressive. From A Longer Term Perspective Ecmwf Runs Have Been Consistent With Their Separated Closed Low
Albeit With A Modestly Faster Trend... While A Number Of Gfs Runs
Prior To 12z Also Had A Separated Closed Low.

Recent Runs Of The Gefs And Ecmwf Ensemble Means Both Show A Pronounced Faster Trend With The Srn Energy. The 18z/12z Gefs And 12z Ecmwf Ensemble Means Currently Offer The Most Appealing Option With Greater Flow Separation Than The Progressive Cluster Of Solns While Accounting For Trends That Recommend Somewhat Faster Progression Than Operational Ecmwf Runs.

On The Other Hand There Is Better Than Avg Agreement With The
Trailing Larger Scale Trof Fcst To Amplify Into The West Later In The Period. Latest Ensemble Means Again Provide A Good Compromise
Between The Past Couple Moderately Slow Ecmwf Runs And Potentially Fast Gfs Runs.

Multi-Day Means By Mid-Late Period Agree Fairly Well On A Core Of
Positive Hgt Anomalies Between Alaska And Hawaii And Negative Hgt
Anomalies Over W-Cntrl Noam. Means Derived From Recent Gfs/Gefs Runs Are Somewhat Weaker Than Ecmwf/Ec Mean/Cmc Mean-Derived Means With Positive Anomalies Over The East Coast/ Wrn Atlc.

Teleconnections Relative To These Features Favor Well Above Normal Temps Over A Decent Part Of The Ern Half Of The Lower 48... As Well As Increased Chances For Pcpn Ms Valley Ewd And Cntrd Over The Mid-Lwr Ms Vly/Lwr Oh Vly/Tn Vly Region. On The Other Hand The West Should See Moderately Below Normal Temps With Most Pcpn Confined To Nrn Areas.

The Preferred Blend Of 18z Gefs/12z Ecmwf Ensemble Means For Days 3-7 Mon-Fri Is Weighted 70 Pct Toward The Ecmwf Mean. This Yields A Trend From Continuity A Little Less Extreme Than An Even
Compromise For The Leading System Tracking Out Of The West.

Teleconnections Appear To Suggest More Low Lvl Flow From The Gulf Into The E-Cntrl Conus Than Fcst By The Gefs Mean Later In The Period... Again Favoring More Weighting To The Ecmwf Mean.


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