US Short Term and Extended Forecast thru Nov 14

Short Range Forecast Discussion
Valid 12Z Thu Nov 7 2013 - 12Z Sat Nov 9 2013

***Widespread rain with cold front over Eastern U.S. on Thursday***

***Rain and snow for the Pacific Northwest and Northern Rockies***

***Relatively quiet weather for the Central U.S.***

There are two primary weather systems that are noteworthy over the next couple of days.

The first one is a large upper level trough along with a surface cold front that will move steadily eastward towards the coast on Thursday. Ahead of the cold front, moisture will surge northward from the Gulf of Mexico and allow for widespread light to moderate rain. Given limited instability with this system, thunderstorms should be isolated at best. After the front exits the coast, colder and drier conditions are
expected for Friday and into the weekend.

The other system will be affecting the Pacific Northwest on Thursday, and entering the Northern Rockies by Friday morning. A surface low is forecast to intensify as the system approaches the coast, bringing
moderate to locally heavy rainfall to Washington and Oregon, and snow to the higher elevations of the Cascades. Gusty winds are also likely with this system. Rain and higher elevation snow is also expected to develop over parts of Idaho, Montana, and Wyoming as the system moves inland.

Elsewhere, the central states remain quiet through the work week, but
should see a rise in temperatures as the Pacific front makes its way
toward the region.

Across the great lakes, some light lake effect rain and snow showers are likely as northwesterly winds blow across the lakes.

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Extended Forecast Discussion
Valid 12z Sun Nov 10 2013 - 12z Thu Nov 14 2013

...Overview...

The Central/Eastern Pacific Will Be The Dominant Driver Of The
Forecast Over The Conus During The Medium Range.

A Well-Advertised Strong Upper High Is Forecast To Build Over The Central Aleutians Around Tue/D5 Which Should Allow Energy To Dig Well Southwestward In The Mid-Latitudes Between 140-150w. The Ensembles Have Had A Tough Time With This Progression But Have Shown A Steady Shift Westward With The Trough Axis Over The Past Several Cycles.

In The Subtropics... Ridging Initially Over Florida Should Move Westward Past The Baja By The Middle Of Next Week.

The Combination Of These Key Features Favors Troughing Over Southeast Canada Into The Northeast Us... With Ridging Over The Rockies.

...Model/Ensemble Preferences...

The Various Deterministic Models And Multi-Center Ensemble Members Have Been Woefully Poor At Maintaining Continuity Through The Forecast Period Over The Past Several Days Of Model Cycles... In
Large Part Due To The Complicated Upstream Amplified Flow And
Lower Forecast Skill Over The High Latitudes Near Alaska And
Northeastern Russia.

Normalized Standard Deviation Of 500mb Heights Over The Conus Per The Ecmwf Ensembles Continue To Show Ensemble Spread Above The Recent 30-Day Average... And Would Suggest Below To Much Below Normal Confidence In Anything Other Than The General Synoptic Ridge/Trough Pattern.

Gefs Standardized Ensemble Spread /Per The Suny Albany Website/ Paints A Similar Picture. As Such... Have Continued To Rely On The Gefs And Ecens Means For The Forecast Which Offer Much Less Wavering Than Their Deterministic Offspring.

In The West... The 00z Ecmwf Clusters Nearer To The Gefs/Ecens
Means As The Upper Low Lifts Northward Along 135w Until About 00z
Wed/13 When It Then Takes The Energy Into Sw Bc Rather Than
Farther North. Recent Gfs Runs Are Much Farther Northwest And Thus
Keep More Precip Offshore. Again... Stability In The Ensembles Is
Lacking So The Final Answer Is Not Yet Written.

In The East... The Models Have Intermittently Shown Sfc
Cyclogenesis Along The East Coast By Wed-Thu/D6-7 As Troughing
Deepens Along 85w.

Prefer Not To Jump On Any Particular Model At This Time Given The Large Uncertainty In The Sampling/Forecast Of The Multiple Source Regions Of This Energy. In Addition... Minor Changes Of Timing/ Interaction Within A Similar Evolution Of Mid-Level Energy Has Resulted In Very Different Forecasts For The Surface From Recent Model Runs.

Nevertheless... The Forecast Of A Respectable Canadian High Pressure To Drop Southeastward /850mb Temps Near -1.5 Std Dev/ Combined With Still Warm Western Atlantic Waters Would Support At The Least A Strong Baroclinic Zone Just Offshore... But How Far Offshore Remains The Question. In Short...The Potential Exists.

..Sensible Weather Highlights...

In The West... The Southwest Flow Into Coastal Wa/Or And Northern
California /With Origins In The Subtropics/ Combined With A Warm
Front Lifting Northward And A Cold Front Limping Eastward Should
Focus Moderate To Locally Heavy Rainfall Especially Along The
Coast.

Generally Light Precip Should Skirt The Northern Tier As Well As Eastern Florida And South Texas... Before Perhaps Increasing Late In The Period Over The Southern Plains Should Se Flow Return To The Region Coincident With The Lingering Frontal Boundary.

In The Mid-Atlantic/Northeast... Anything From Dry To Wet To White Is Possible Even To The Coastal Plain... And It Would Be Unwise To Mention Specific Threats At This Lead Time.


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