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Severe Weather Threat thru Nov 22

Fri Nov 15 Convective Outlook
No Svr Tstm Areas Forecast...

The Large-Scale Pattern Over The Conus Will Remain Characterized As Broadly Cyclonic And Multi Stream With A Number Of Transitory
Perturbations Embedded Within This Flow Regime.

One Impulse Over The Lower Ms Valley Will Weaken While Approaching The Mid-Atlantic Coast Late Tonight. Farther Upstream ...A Short-Wave Trough Over The Great Basin Will Progress Sewd Through The Four Corners Region In Advance Of An Amplifying Short-Wave Trough And Attendant Strong Mid And Upper-Level Jet Streaks Advancing Equatorward Into The Pacific Nw And Nrn Inter-Mountain Region.

In The Low Levels...A Large Anticyclone Present E Of The Ms Valley
Will Develop Ewd While A Lee Cyclone Deepens Over The Cntrl High
Plains.

Four Corners This Afternoon/Tonight...

Despite The Presence Of A Relatively Dry Air Mass...Cooling Midlevel
Temperatures And Daytime Heating Will Support Steepening Lapse Rates And The Development Of A Weakly Unstable Environment. Low-Level Uplift Along Favored Terrain Coupled With Dcva/Height Falls Associated With The Approaching Short-Wave Trough Will Foster Isolated Tstms Later Today. A Strengthening Tropospheric Wind Field May Promote Locally Strong Wind Gusts...Though No Severe Weather Is Anticipated.

Nc Outer Banks Tonight...

Frontogenetic Forcing Associated With A Coastal Boundary Will Be
Augmented By Dcva Attendant To A Srn Stream Short-Wave Trough
--Currently Over The Lower Ms Valley-- To Promote An Increase In
Showers And A Few Tstms.

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Sat Nov 16 Convective Outlook
Slgt Risk Of Svr Tstms for Mo Valley & Mid/Upper Ms River Valley...

Middle/Lower Mo Valley To Middle/Upper Ms River Valley...

An Amplifying/Progressive Upper Trough And Intensifying Polar Jet
Will Generally Spread East-Southeastward Over The Northern Rockies And Much Of The Northern/Central Plains To Midwest Saturday And Saturday Night.

In Association With A Lead Shortwave Trough And/Or Leading Edge Of Height Falls...Surface Cyclogenesis Is Expected To Occur In Earnest Saturday Night Into Early Sunday Over The Upper Midwest.

Meanwhile...Airmass Modification Will Continue To Occur With Moist Advection Contributing To An Increasingly Prevalent Corridor Of Upper 50s/Lower 60s F Surface Dewpoints Saturday Night To The East Of The Aforementioned Surface Low And A Cold Front.

Initially...Elevated Showers/Tstms Are Likely To Occur Saturday
Morning Into Afternoon Across Portions Of The Upper Midwest/Upper Ms River Valley.

While A Few Stronger Storms Capable Of Some Hail Cannot Be Entirely Ruled Out...The Relatively More Probable Severe Risk Should Not Occur Until Saturday Night.

Regarding Saturday Night...The Exact Timing/Quality Of The Northward Flux Of Low-Level Moisture Is A Key Question...But At Least Some Evening/Overnight Severe Risk Should Exist Given Increasing Moisture And The Arrival Of Stronger Forcing For Ascent. Current Thinking Is That Elevated Storms Capable Of Severe Hail Would Be The Most Probable Concern Saturday Night Especially In/Near The Slight Risk.

That Said...Sufficient Low-Level Moisture May Be In Place By The
Evening/Overnight Hours For The Possibility Of At Least Some Near
Surface-Based Storms Across Portions Of Ia/Mo. Should This Be The
Case...Damaging Winds/Isolated Tornado Risk Would Be Possible.

Ozarks Vicinity...

Farther South...The Severe Weather Potential Through 12z Sunday
Appears Even More Conditional Across Areas Such As Southern
Mo/Northern Ar And The Adjacent Ms River Valley Vicinity.

Steadily Increasingly Low-Level Moisture Could Become Sufficient To Support At Least Near Surface-Based Storms Late Saturday Night/Early Sunday.

Given A Highly Sheared Environment...This Region Will Be Closely
Reevaluated For Damaging Wind/Isolated Tornado Potential And A
Possible Expansion Of The Categorical Slight Risk.

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Sun Nov 17 Convective Outlook
Slgt Risk Of Svr Tstms For Part of Tn & Oh Valleys & Great Lakes...

A Shortwave Trough With Attendant Strong Upper Jet Embedded Within Base Of The Synoptic Trough Will Eject Negatively Tilted Through The Mid Ms And Oh Valleys Sunday...Reaching A Portion Of The Nern U.S. Toward The End Of The Period.

This Feature Will Induce A Sfc Cyclone That Is Forecast To Undergo Significant Deepening As It Moves Newd From The Upper Ms Valley Into The Great Lakes Sunday Afternoon.

Cold Front Trailing From The Low Will Sweep Through The Mid Ms...Oh And Tn Valleys...While A Warm Front Lifts Nwd Through The Oh Valley And Great Lakes.

Oh And Tn Valley Regions...

A Strong 50+ Kt Swly Llj Will Advect Partially Modified Gulf Air With Dewpoints In The Upper 50s To Low 60s Into The Oh Valley And
Great Lakes Region With Mid 60s Likely Farther South Across The Tn
Valley Area.

The Moisture Return Will Be Accompanied By Widespread Clouds That Will Limit Diabatic Heating Of The Boundary Layer In Much Of Pre-Frontal Warm Sector. Moreover...Areas Of Showers And A Few Thunderstorms Will Probably Be Ongoing Over A Portion Of The Oh
Valley Warm Sector.

Thus The Primary Destabilization Mechanism Will Probably Be Moisture Advection...But Sfc Based Instability Will Likely Remain Somewhat Marginal /Mlcape Aob 500 J/Kg/...Especially With Nwd And Ewd Extent Into The Oh Valley And Great Lakes.

Nevertheless...The Deepening Cyclone Will Be Accompanied By An
Increase In Frontogenetic Forcing Along The Cold Front Sweeping Ewd Through The Oh Valley.

Storms May Increase During The Day Along Pre-Frontal Warm Conveyor Belt Beneath Diffluent Upper Jet Exit Region. Other Storms Will Initiate Along Strengthening Cold Front.

Potential Will Exist For Pre-Frontal Storms To Develop Supercell
Structures Given Strength Of Vertical Shear And Size Of Hodographs
Along Llj...But Extent Of Any Tornado Threat Will Depend On Degree
Of Boundary Layer Destabilization.

Otherwise...Storms Will Likely Evolve Into Lines Along The Cold Front With A Threat For Widespread Damaging Wind As The Activity Develops Ewd Through The Oh And Tn Valley Regions.

Ny And Pa...

Storms Will Eventually Outpace The Moist Axis Sunday Night And
Encounter Much Weaker Instability As They Approach The Nern States. However...At Least A Modest Threat For Isolated Damaging Wind With Remaining Low Topped Convection Cannot Be Ruled Out Late This Period.

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Nov 18-22 Convective Outlook
Storm Prediction Center Norman Ok

As Strong Shortwave Trough Lifts Newd Into Sern Canada...Attendant
Deep Sfc Low Will Occlude Across Wrn Ontario While Trailing Cold
Front Advances Ewd And Off The Atlantic Seaboard Monday Afternoon.

Swrn Extension Of This Boundary Will Move Into The Gulf Of Mexico.

Instability Will Remain Very Meager In Pre-Frontal Warm Sector From
The Mid Atlantic Into The Nern States. Nevertheless...A Strongly
Forced Band Of Low Topped Convection With Little To No Lightning
Should Continue Along The Front.

Given Strength Of The Low-Level Flow Associated With A 60-70 Kt Sly Llj...Some Threat For Damaging Wind May Still Exist With This Activity From Coastal Va Into Srn New England.

However...Confidence In A More Widespread Event Is Not Sufficient At This Time To Introduce A Categorical Area For Monday (Day 4).

Days 5-8...Severe Potential Is Expected To Remain Low.

A Large Area Of Cp High Pressure Will Advance Through The Ern Half The U.S. Day 5-6 With A Secondary Reinforcement Possible Days 7-8...Maintaining Offshore Flow And Stable Conditions Inland.


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