US Final Extended Weather thru Feb 4

The Axis Of A Fairly Broad And Amplified Ern Noam Mean Trof Will
Drift Ewd With Time And Reach The East Coast/Wrn Atlc Around The
End Of The Medium Range Period.

Such A Posn For The Mean Trof Axis At That Time Is Consistent With Teleconnections Relative To A Stg Positive Hgt Anomaly Center Fcst By Most D+8 Multi-Day Means To Be Near 50n 30w.

Upstream An Ern Pac Ridge Will Build Into The West Days 4-5 Fri-Sat While Approaching Energy Splits. Once The Nrn Stream Portion Of This Energy Passes Thru The West The Mean Ridge Should Rebuild By Day 7 Mon Ahead Of An Amplifying Ern Pac Trof.

The Most Uncertain Part Of The Fcst Involves Exactly How Ern Pac Flow Splits Around Sat-Sun And Downstream Impacts Thereafter. Relative To The Full Guidance Spread No Operational Soln Appears Ideal Over The Entire Fcst Area Favoring A 06z Gefs/00z Ecmwf Ensemble Mean Emphasis... With The 00z Ecmwf As The Most Palatable Option To Add A Little Detail For Nrn Tier Systems Mid-Late Period.

Over The Past Couple Days The Gefs/Ecmwf Ensemble Means Show A Converging Trend With The Wrn Ridge By Day 5 Sat... The Gefs Mean Stronger And Ecmwf Mean Weaker.

Once Ern Pac Flow Splits The 06z Gfs Is Currently On The Extreme Side Of Guidance With The Strength Of Nrn Stream Energy Moving Into/Thru The West. This Leads The 06z Gfs To Bring A Rather Stg Sfc Low Toward The Grtlks By The End Of The Period.

The 00z Cmc Also Has A Stg Grtlks Sfc Low By Late Mon But With A Somewhat More Plausible Wrn Canada Origin. The Ultimate Form/Track Of Offshore Srn Stream Energy Is A Significant Question Mark With 00z Gfs/Cmc Runs Bringing A Closed Low Near The Srn Ca Coast By Late Mon Versus The Much Farther Swwd 06z Gfs/00z

The 00z Ecmwf May Be A Little Extreme With How Far Swwd Its Srn Stream Closed Low Tracks... As Per Its Occasional Bias... But Overall The Full Array Of 00z Ensemble Members Includes The Various Operational Possibilities. 70-80 Pct Emphasis On The Ensemble Means Currently Provides The Best Depiction Of Modest Strength Of Nrn Stream Energy Passing Thru The Mean Ridge And A Conservative Elongated Trof For Energy Left Behind Over The Lower
Latitudes Of The Epac.

For The Ern Half Of The Conus The Focus Remains On A Series Of
Three Features.

First Is A Cold Front Reaching Srn/Ern Areas On Fri With An Anchoring Sfc Wave Fcst To Be Weak And Progressive.

Following That... Guidance Has Been Consistent With The Idea Of A
Wave Reaching The Grtlks Around Day 5 Sat But There Has Been Some Scatter In Exact Track/Timing And Latest Solns Have Trended Weaker At Least Until The System Reaches The Canadian Maritimes By Late Sun-Mon. Modest Inclusion Of The 00z Ecmwf That Is The Strongest Of Latest Solns Balances Latest Consensus With Stronger
Continuity. The 00z Gfs Trends A Bit To The Fast Side Of The
Spread And The 06z Run Weak/Swd.

Next Wave Should Reach The Grtlks Around Day 7 Mon. 00z Ecmwf/Cmc Means Favor A Track To The N Of The 00z Gfs. 00z/06z Gefs Means Are Ill-Defined But At Least The 06z Gefs Mean Has Lowered Pressures Somewhat. The 00z Ecmwf Is A Bit On The Faster Side Of The Spread By Day 7 So Prefer No More Than 20 Pct Weighting Of Its Soln At That Time. As Mentioned Above The Stg 06z Gfs Is Questionable Due To Handling Of Supporting Energy As It Reaches The West.

It Will Be A Relatively Dry Period Across The Conus.

The Most Persistent Pcpn Will Be Across The Grtlks With Snow From Lake Effect Activity And In The Vicinity Of Sfc Lows Crossing The
Region. Some Mstr May Extend Sewd Into The Aplchns And Perhaps
Along The Fronts Trailing From The Grtlks Sfc Lows Mid-Late

Weak Wave Anchoring A Leading Cold Front/Supporting Dynamics May Generate A Band Of Lgt Snow Over Portions Of The Mid Atlc Around Fri.

Pac Nw/Nrn Rockies Pcpn Should Taper Off Early In The Period. Diffs In Handling Of Ern Pac Split Flow Mid-Period Increases Uncertainty In Determining How Much Mstr May Reach The West By Sun-Mon. Currently The Pac Nw Appears To Have The Highest Probability Of Seeing At Least Some Pcpn At That Time With Moderate Potential Over Swrn Areas.

Expect Very Cold Conds Over The Nrn Tier On Thu With Some Readings 20-30 F Below Normal. Less Extreme Readings Will Extend Ewd/Sewd.

Progression Of The Large Scale Pattern Will Support A Pronounced Warming Trend Into The Plains/Ms Vly By Sat-Mon.

Temps Over The West Should Be Moderate Aside From Colder Air Trapped In Portions Of The Grtbasin.

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