US Preliminary Extended Weather thru Mar 9

...Possible Winter Storm May Impact Sections Of The Mid-Atlc
Sometime During The Tue-Thu Timeframe...

...A Wet Pattern Is In Store For The Wrn Conus As A Mean Trof Sets
Up Over The Region...

The Mid-Latitude Pattern Will Become A Bit More Active Than The
Present Short Range Period.

The Initial System Of Interest Is An Upr Trof/Closed Low Positioned Invof The Mid Ms Valley. As This Disturbance Slides Ewrd...It Should Continue To Amplify Spreading Hgt Falls Thru The Sern U.S/Lwr Mid-Atlc.

The Guidance Continues To Diverge On Exactly How This Will Play Out...Particularly With The Posn Of The Upr Low And How Quickly It Moves Offshore. The 12z Gfs/Ecmwf Suggest The Upr Trof Will Briefly Wrap-Up Along The Coastal Mid-Atlc Before Tracking Offshore Late Wed/Early Thu. On The Contrary...The 12z Ukmet Was Much Quicker In Ejecting This System Into The Offshore Waters. Given This Idea Was Not Supported By Any Of The Global Ens Means...The Ukmet Was Not Utilized Beyond Day 4. Before This...The 12z Gfs/Ecmwf/Ukmet Had General Agreement With The Sfc Track From 05/1200z Thru 06/1200z With A Blend Of These Three Pieces Of Guidance Utilized In The Products.

The Impacts From This System Will Depend On The Track And Strength But The Potential Does Hold For A Winter Storm Somewhere Across The Mid-Atlc Region. Regardless...It Does Appear Cold Wx Will Take Hold From The Grt Plains Ewrd To Much Of The Ern U.S. With Temp Anomalies Approaching 15 To 20 F Below Climo.

The Other Major System Impacting The Conus Will Be In Response To A Deep Upr Low Which Is Fcst To Be Just Offshore Of The Pac Nw
Early Tue. As This System Tracks Inland...It Should Slowly Shear
Out Acrs The Upr Intrmtn West/Nrn Rockies Late Wed Into Thu.

However...The Mid-Level Impulses Combined With Ample Low-Level
Moisture Will Support Periods Of Heavy Pcpn Along The West Coast
Early In The Fcst Period...Particularly Along The Favored Terrain.

Further Downstream...Building Hgts Over The Intrmtn West Ewrd To
The Grt Plains Will Support Well Above Normal Temps. This Will
Predominantly Occur During The D4/D5 Period.

Looking Back To The West Coast...As One System Shears Out Acr The Interior Mtn West...Another Trof Is Fcst To Slide Down The West Coast Before Closing Off Acrs Ca By Early Fri. Deterministic/Ens Guidance Reasonably Show This Idea Although The 12z Cmc Is Further Up The Ca Coast.

Eventually This Mid-Level Energy Should Slowly Propagate Toward The E Reaching Nrn Mx/Srn Az By 09/1200z. While The Guidance Diverges On The Exact Posn Of This System On D7...Enough 552-Dm Spaghetti Members Suggest This Fcst Evolution To Feel
Reasonably Comfortable With The Models Here.

As Mentioned Earlier...The 12z Gfs/Ecmwf/Ukmet Reasonably Agreed To Support Their Blend Thru D4. Thereafter...The More Progressive
Mid-Latitude Pattern The 12z Ukmet Suggests Appeared Much Too
Quick. A Combination Of The 12z Gfs/Ecmwf And Their Respective
Means Were Used In The Hpc Blend For D5/D6 Given Inc Spread Acrs
The Board.

By D7...Enough Uncertainty In The Fcst Suggested All Ens Means... Particularly With The Timing/Strength Of The Upr Cyclone Near The Az/Mx Border. One Ramification With The Posn Of This Trof Is The Enhanced Gulf Moisture Being Drawn Toward The Srn/Cntrl Plains Which May Bring Heavy Rainfall By Late Mar 8/Early Mar 9.

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