Severe Weather Threat thru Dec 13

Fri Dec 6 Convective Outlook
No Svr Tstm Areas Forecast...

A Cold Surface High Will Remain Entrenched Across Much Of The
Central States...To The East Of The Rockies.

The Shallow Leading Edge Of This Air Mass Appears Likely To Advance Off Northern And Mid Atlantic Coastal Areas Early Today...but It May Stall Along The Southern Appalachians...In Advance Of A Developing Weak Surface Frontal Wave...Which May Contribute To A Slow Acceleration Of The Front Through Much Of The Remainder Of Alabama/Mississippi And Southeast Louisiana Later Today And Tonight.

Mid/Upper Subtropical Ridging Is Forecast To Remain Strong Across
Much Of The Southern/Eastern Gulf Of Mexico...The Florida
Peninsula/Caribbean/And Bahamas Into The Nearby Western
Atlantic...And May Maintain A Significant Influence Across Gulf And
South Atlantic Coastal Areas.

As A Strong Upstream Short Wave Trough Digs Near The Pacific Coast...Into Lingering Larger Scale Western U.S. Upper Troughing... The More Substantive Mid-Level Height Falls Associated With A Short Wave Impulse Now Crossing The Southern Rockies Are Expected To Shift From The South Central Plains Toward The Lower Great Lakes Region.

Cntrl Gulf Coast Into Western Carolinas...

On The Western Periphery Of Low-Level Ridging Associated With The
Mid-Level Subtropical Ridge...A Return Flow Of Moisture Off The Gulf
Of Mexico Into The Southeast Is Expected To Continue...With Perhaps
Another Surge Of Richer Moisture.

Much Of This May Occur Above/To The Cool Side Of The Shallow Southeastward Advancing Surface Front...But Seasonably High Boundary Layer Moisture Probably Will Be Maintained In At Least A Narrow Pre-Frontal Corridor.

Models Suggest That This Will Support Weak To Modest Cape...And An Environment Conditionally Favorable For Severe Storm
Development...Including Supercells...In The Presence Of Sufficient
Deep Layer Shear.

Guidance Suggests Warm Sector Shear...Both Deep Layer And Low-Level...May Even Be A Bit Stronger Than Yesterday.

However...With Appreciable Mid-Level Height Falls Remaining Well To
The North And West Of The Surface Cold Front...Forcing For Convective Development In The Warm Sector Today Is Unclear...And
Likely To Remain Weak...With Considerable Lingering Mid-Level

It Still Appears That Any Convective Development Near The Front Itself Will Tend To Quickly Be Undercut By It...So Any Severe Weather Potential Seems Contingent On Storms Forming Ahead Of It.

Much As The Case Yesterday...Probabilities For This Seem Low...But Perhaps Not Completely Negligible.


Sat Dec 7 Convective Outlook
No Svr Tstm Areas Forecast...

Cyclonic Flow Aloft Is Forecast To Prevail Across Most Of The U.S.
Again Day 2...As A Large Trough Centered Over The Wrn U.S. Moves Ewd Across The Rockies.

Cold Continental Air Is Forecast To Remain In Place Across Most Of The Country...Though Somewhat Higher Theta-E Air Will Linger Over Parts Of The Sern U.S. -- Along The Ern Periphery Of The Wrn U.S. Trough.

As Weak Ascent Evolves Across The Southeast Ahead Of The Advancing Trough...Weak/Elevated Instability May Be Sufficient To Support Showers -- And Embedded Lightning Strikes...Mainly Through The Second Half Of The Period.


Sun Dec 8 Convective Outlook
No Svr Tstm Areas Forecast...

Amplification Of The Upper Pattern Is Forecast Across The U.S. Day 3 ...As The Long-Wave Trough Shifts Into Central Noam.

The Amplification Will Occur As An Initial/Embedded Short-Wave Trough Ejects Newd Across The Plains Toward The Great Lakes... While A Second Digs Swd Out Of Wrn Canada -- Crossing The Great Basin And Reaching The Swrn U.S. Late.

Though A Cold Continental Airmass Will Reside Over Much Of The
Country...Higher Theta-E Air Will Remain Over The Southeast.

Still...With Weak Lapse Rates Aloft Yielding Little Cape...Convection -- In The Form Of Showers And Embedded Thunderstorms -- Is Expected To Remain Weak/Sub-Severe.


Dec 9-13 Convective Outlook

A Large Upper Trough Is Progged To Continue Crossing The Central And Ern U.S. Through Day 7 /12-12/...Before Eventually Moving Into The Atlantic.

At The Surface...High Pressure Is Forecast To Spread Sewd Days 4-5...Before Eventually Covering Much Of The U.S. E Of The Rockies.

A Cold Front At The Leading Edge Of This Cold Surge Should Provide A Focus For Showers And Scattered Thunderstorms.

As The Front Nears The Atlantic Coast...Weak Surface-Based Instability But Ample Shear Expected Over The Area Could Yield A Low-End Risk For Isolated Severe Weather...But Risk Remains Well Below Thresholds Which Would Require An Areal Delineation.

As The Front Moves Offshore Day 5...Severe Risk Should Remain
Negligible Through The Rest Of The Period.

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