US Preliminary Extended Weather thru Jan 17

For The Most Part Guidance Maintains Reasonable Agreement And
Continuity With The Expected Large Scale Pattern Thru Day 7 Thu.

Flow Within The Positively Tilted Mean Trof Over Cntrl Canada Into
The Swrn Conus As Of Day 3 Sun Is Fcst To Separate... With A
Broadening Nrn Stream Trof Heading Into The Ern Half Of Noam Late
In The Period While An Upr Low Closes Off Near The Wrn Half Of The
Us-Mexico Border By Wed.

Within This Consensus Evolution Some Detail/Timing Issues Remain With The Leading Slow Moving Wavy Sfc Front Crossing The Ern Conus... Upstream Flow Over Canada And Nrn Conus... And The Developing Closed Low Along The Us-Mexico Border.

By Day 7 Thu The 12z Ecmwf Also Introduces Some Uncertainty With
Ern Pac Flow Rounding The Ern Pac Ridge.

Models/Ensembles Exhibit Some Day To Day Waffling With The Exact
Timing/Posn Of The Ern Conus Front... Favoring A Continuity/ Consensus Soln.

Persistent Gulf Inflow Ahead Of The Front And Flow Aloft Nearly Parallel To The Front Are Still Expected To Support Locally Hvy Rnfl Within An Area From Ern Tx Thru The Tn Vly And Possibly Into The Cntrl-Srn Aplchns.

Some Wintry Pcpn Is Psbl On The Nwrn Periphery Of The Mstr Shield.

The Front Should Finally Depart Into The Atlc By Day 7 Thu As The
Broadening Nrn Stream Trof Reaches Ern Noam... Leading To A
Drier/Cooler Trend Over Most Areas.

Regarding This Trof Aloft Late In The Period The 12z Gfs Trends A
Little Fast Relative To The Majority Soln Cluster While The 18z
Gfs May Be A Bit On The Stg/Sharp Side With A Trailing Shrtwv
Reaching The Ms Vly/Grtlks By Wed-Thu.

Thus Far Models Have Been Inconsistent With A Sfc Low That May Track Along The Us-Canadian Border Around Tue-Wed... Favoring The Ensemble Means Over This Area Until There Is Better Agreement.

Meanwhile The 12z/18z Gefs Means And 12z Ecmwf Mean Agree Well
With The Closed Low Expected To Develop Along The Us-Mexico Border Around Tue-Wed.

Recent Ecmwf Runs And The 12z Gfs Fall In This Cluster As Well But The 18z Gfs Is A Fast Extreme Along With The New 00z Run.

Finally Over The Ern Pac/West Coast Late In The Period... The 12z Ecmwf Is Questionably Stg With A Shrtwv/Embedded Upr Low Which The Model Brings Toward Bc And The Pac Nw Day 7 Thu. Rising Hgts Over A Majority Of The West With Time Should Eventually Support A Warming Trend Over The Region. Expect Limited Pcpn Even In The Vicinity Of The Late Period Upr Low Which Should Not Be Accompanied By Too Much Mstr.

Thru Early Day 6 Wed An Avg Of The 12z Ecmwf/12z Ecmwf Mean/18z
Gefs Mean Offered A Reasonable Account For Best Guidance
Clustering And Continuity Where Feasible... With Ern Pac Concerns
In The 12z Ecmwf Limiting The Fcst To The Ensemble Means From Late Day 6 Onward.


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