Severe Weather Threat thru Feb 22

Sat Feb 15 Convective Outlook
No Svr Tstm Areas Forecast...

The Large-Scale Pattern Will Remain Progressive Through The D1
Period With The Most Prominent Feature Being An Intense Short-Wave Trough Which Will Pivot Nnewd From The Sern U.S. To Off The New England Coast By Tonight.

On Its Heels...A Lower-Amplitude Perturbation Will Translate From The Nrn Plains To Tn Valley And Srn Mid Atlantic.

In The West...Another Strong Short-Wave Trough Will Move Onto The British Columbia And Pacific Nw Coasts During The Latter Half Of The Forecast Period.

In The Low Levels...A Surface Cyclone Over N-Cntrl Nc As Of 12z Will
Move Offshore By Late Morning With A Trailing Cold Front Continuing
Swd Through The Remainder Of The Fl Peninsula.

Elsewhere...A Pacific Front Will Accompany The Above-Mentioned Short-Wave Trough Onto The Pacific Nw Coast This Evening.

Pacific Nw Coast This Evening Into Tonight...

Forcing For Ascent And Steepening Lapse Rates Attendant To The
Short-Wave Trough May Promote A Few Lightning-Producing Convective Elements Along The Pacific Front...As Well As Within The
Post-Frontal Onshore Flow Regime.

Near-Shore Waters Of The Nc Outer Banks Today...

While The Majority Of Tstm Activity Will Remain Over The Gulf Stream ...A Few Lightning Strikes Will Be Possible Near The Coast Today Within A Zone Of Intense Forcing For Ascent/Dcva Immediately Preceding The Newd-Ejecting Short-Wave Trough.


Sun Feb 16 Convective Outlook
No Tstm Areas Forecast...

Low-Amplitude/Generally Wly Flow Aloft Is Progged Across The U.S.
Day 2...As A Trough Shifts Across The Northeast...A Second Approaches The Pac Nw Late...And A Third Crosses The Rockies And
Shifts Into The Plains Late In The Period.

While Showers Will Affect The Higher Terrain Of The Pac Nw Given
Background/Persistent Wly Low-Level Upslope Flow...Risk For Any More Than An Isolated Strike Or Two Appears Minimal.

Meanwhile...Showers Associated With The Short-Wave Trough Crossing The Rockies/Approaching The Plains Will Likewise Be Accompanied By Shower Activity Across Parts Of The Intermountain West.

While This Feature Will Support Development Of A Weak Surface Low Which Should Shift Into The Plains Overnight...Warm-Sector Moisture Return Should Prove Insufficient For Thunderstorm Development.


Mon Feb 17 Convective Outlook
No Tstm Areas Forecast...

Low-Amplitude Flow-Field Aloft Is Progged To Persist Across The U.S.
Day 3...As A Trough Vacates The Northeast To Be Followed By The
Approach Of A Second Feature Advancing Out Of The Central U.S. And
Across The Great Lakes/Oh Valley Region.

Meanwhile... Quasi-Zonal Flow Will Prevail Across The Wrn States.

As The Aforementioned Trough Shifts Across The Great Lakes And Oh Valley...An Accompanying Surface Low And Attendant/Weak Cold Front Will Move Across The Ern Half Of The Country.

While Scattered Showers Should Accompany The Surface System As It Advances To The E Coast By The End Of The Period... Thunderstorms Are Not Expected.

Farther W...Showers Are Forecast To Continue Across Higher Terrain
Areas Of The Nwrn Portion Of The Country...Within The Persistent
Wly/Low-Level Upslope Flow Regime.

However...Any More Than An Isolated Strike Or Two Near The Pac Nw Coast Appears Unlikely.


Feb 18-22 Convective Outlook

Medium-Range Models Remain In Decent General Agreement Through Day 6 /Thu. 2-20/...Depicting A Quasi-Zonal Upper Flow Field Across The U.S. Early In The Period Followed By Gradual Amplification Through Day 6 As A Large Trough Develops Across The Wrn And Central Conus.

While The Gfs And Ecmwf Ensemble Mean Remain Similar -- Both
Depicting Lower Amplitude Troughing And Likewise A Significantly
Weaker Surface System...The Latest Deterministic Run Of The Ecmwf
Reveals A Much Stronger Trough -- And Associated/Major Cyclogenesis Invof The Ms Valley Region During The Afternoon Of Day 6.

Despite These Differences However...Timing Of The Main Features Remains Quite Similar Within The Different Models...All Suggesting That The Surface Frontal System Will Cross The Ms Valley By Afternoon/Early Evening And Reach The Appalachians By The End Of The Day 6 Period at 12z Fri.

With Model Differences In Depiction Of The Large-Scale Pattern Much
More Substantial Days 7-8 In The Wake Of The Day 6 System...And With Days 4-5 Likely To Remain Relatively Benign With Respect To
Convective Potential...The Main Focus Attm Is On Day 6.

A Surface Low Is Forecast To Reside Invof Ks/Ok/Mo Early In The
Day...Developing Nwd Toward The Upper Great Lakes As The Strongest Mid-Level Support Ejects Newd.

Along The Trailing Front...A Forced Line Of Convection May Evolve During The Afternoon Across Parts Of The Mid Ms/Oh Valley Region -- And Then Shift Ewd Across The Oh/Tn Valleys Overnight.

While Flow Aloft Should Be Quite Strong...Meager/Low-Topped Instability Is Expected To Hinder Storm Intensity.

Therefore -- Though Isolated Damaging Wind Gusts Would Be Possible Along The Convective Line...A 30% Equivalent Risk Area
Does Not Appear To Be Justified.

Farther Sw -- Across The Lower Ms Valley/Arklatex Area -- Greater Low-Level Moisture Is Progged Thus Suggestive Of Potential For A Slightly Greater Cape Development Than Areas Farther Ne.

That Being Said...Much Weaker Ascent Is Forecast...Given The Upper System Shifting Well Ne Of This Region And The Likelihood For Veered Low-Level Flow Yielding Only Weak Frontal Convergence.

These Factors -- Plus A Weaker Flow Field Aloft -- Again Suggest That
While Some Severe Risk Is Evident With Storms Expected To Extend
Trail Swwd Along The Front Into This Region...The Degree Of Severe
Risk Does Not Warrant Areal Outlook Inclusion Attm.

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