Severe Weather Threat thru Mar 17

Mon Mar 10 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

The Only Change To The Forecast Has Been A Minor Wwd Expansion Of The General Thunderstorm Area In S Tx.

Isolated Thunderstorms Are Currently Developing Over The Higher Terrain Of Nrn Coahuila Mexico...Aided By Orographic Ascent Beneath A Mid-Level Cyclonic Perturbation.

This Activity Could Cross The Rio Grande River Into S Tx Later Today As The Disturbance Moves Ewd.

No Other Changes Have Been Made To The Ongoing Forecast.

Prev Discussion...

Two Strong Shortwave Troughs Will Affect Parts Of The Conus Today ...With Both Systems Posing Some Risk Of Thunderstorms.

Northwest Us...

Water Vapor Loops Show A Progressive Upper Trough Moving Across
Parts Of Ore/Northern Ca. The Associated Pocket Of Cold Mid Level
Temperatures And Marginal Instability Will Promote The Development
Of Scattered Showers And A Few Thunderstorms Across Parts Of
Wa/Ore/Id/Nv. This Threat Should End From West To East This
Afternoon And Evening As The Upper System Moves Eastward.

Tx/La...

A Weakening Upper Low Over Northern Mexico Will Continue To Move
Slowly Eastward Toward South Tx. Scattered Thunderstorms Have Been Occurring Beneath The Cold Pool Aloft With This System...And Will Likely Continue Through Tonight. Weak Instability Should Preclude Any Risk Of Organized Severe Storms.

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Tue Mar 11 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

A Mid-Level Shortwave Impulse Currently Crossing The Pacific Nw And Nrn Ca Will Progress Ewd And Cover The Nrn/Cntrl Rockies And Great Basin Early D2/Tue.

On D2/Tue...A Higher-Latitude Shortwave Trough Will Dig Ssewd Into The N-Cntrl Conus From The Srn Canadian Prairie Provinces.

Strong Mid-Level Flow Accompanying The Amplifying Trough Will Effectively Shear The Wrn-Conus Impulse Ewd -- The Ern Extent Of Which Will Quickly Progress Across The Cntrl Rockies/Plains To The Mid Ms Valley Before Phasing With The Amplifying Trough.

A Sfc Low Will Develop Ewd Along A Front From N-Cntrl Ks To Ern Oh...Which Will Be Reinforced By Abundant Cold Advection Overtaking The Great Lakes Region...Middle/Upper Ms Valley...And Plains.

Mid Ms/Lower Oh Valley Region...

Richer Boundary-Layer/Tropospheric Moisture /E.G. Pw Aoa 1.5 Inches/ And Relatively Higher Buoyancy Will Be Relegated To The Gulf Of Mexico...Of Which Abundant Gulf Convection Will Occur.

However...Sly/Swly Low-Level Flow Located To The S/Se Of The Front
Will Promote The Influx Of At Least Partially Modified Gulf Moisture... With Middle/Upper 50s Sfc Dewpoints Forecast To Extend Into The Region During Peak Heating In Advance Of The Sfc Low.

During The Afternoon...Diabatic Sfc Heating On The Warm Side Of The Boundary Will Contribute To 0-3-Km Lapse Rates Around 7-8 C/Km Though With Only Marginal Buoyancy...While Modest Mid-Level Height Falls And Cooling Occur.

The More Substantial Increase In Low-Level/Deeper Ascent Is Not Expected Until The Evening...When The Exit Region Of A Mid-Level Speed Max Accompanying The Shearing Impulse Approaches Somewhat Richer Moisture Over The Mid Ms Valley...And A Reinforcing Cold Surge Overtakes A Trough Trailing Ssw Of The Sfc Low.

In Response...Sfc-Based Convection May Develop Along These Merging Sfc Features In Cntrl/Ern Mo Tue Eve Before Spreading Ewd To The Lower Oh Valley Tue Night...While A Swly Llj Increases To 40-50 Kt In Advance Of The Mid-Level Speed Max.

With H5 Wswly Flow Increasing To 45-55 Kt Through The Evening Above The Strengthening Llj...Low-Level And Deep Shear Will Be
Sufficiently Strong For Convection To Become Organized -- Perhaps As A Line In Proximity To The Synoptic Cold Front.

Strong Synoptic Pressure Rises Succeeding The Front Coupled With The Strengthening Llj Suggest Sporadic Damaging Winds May Occur With The Most Intense Convection...Despite The Paucity Of Tropospheric Moisture.

Central/Ern Gulf Coast And Vicinity...

Abundant Convection Will Progress Ewd Across The Gulf Of Mexico In
Tandem With A Mid-Level Shortwave Trough Crossing The Gulf Waters.

The Nrn Periphery Of This Activity Could Graze The Coast And Vicinity From Srn La To The Fl Big Bend.

However...As This Convection Largely Processes Higher Boundary-Layer Theta-E S Of The Coast...Any Inland Convection Supported By Dcva And Modest Warm Advection Preceding The Trough Should Be Mainly Elevated And Likely Sub-Severe.

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Wed Mar 12 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Middle Atlantic...

Complex Mid Level Flow Regime Over The Middle Of The Conus Should Induce Sfc Cyclone Over The Mid Ms Valley Late Day2 That Will Track Enewd And Deepen Significantly Over The Delmarva Wednesday Afternoon...Sub 990mb Sfc Low.

Per Latest Ecmwf...Strong 12hr Height Falls Will Focus Across This Region Sharpening Baroclinic Zone East Of The Appalachians And Drawing A Meager Corridor Of Modified Low Level Moisture Nwd Across Va/Md.

While Forecast Instability Is Expected To Remain Somewhat Marginal...Modest Boundary Layer Heating And Significant Mid Level Cooling Should Contribute To Sufficient Buoyancy For Sfc-Based Convection Attaining Levels Necessary For Lightning.

While Deep Layer Flow Will Strengthen And Deepen From The West...Frontal Convergence Should Aid Isolated Thunderstorm Development Within A Strongly Sheared Environment.

Diurnal Heating Will Likely Prove Instrumental For Robust Convective Development Given The Marginal Moisture Expected.

Fl...

Low Latitude Deamplifying Short-Wave Trough Should Eject Across The Fl Peninsula Early In The Period.

Models Suggest Weak Lapse Rates/Instability Will Preclude More Than Weakly Organized Convection Closely Tied With Mid-Level Trough And Associated Low-Level Transient Sfc Boundary.

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Mar 13-17 Convective Outlook
Storm Prediction Center Norman Ok

Mean Long-Wave Ridge Is Expected To Hold Across The Wrn U.S. During The Medium Range Period While Several Strong Short-Wave Troughs Will Dig Sewd In Varying Forms/Speeds Along/East Of The Rockies.

Both The Ecmwf And Gfs Agree Modifying Influence Of Maritime Air Mass Will Struggle To Advance Inland As A Propensity For Offshore Flow Is Expected Through The Period.

Late This Weekend Sely Low Level Trajectories May Allow Moisture/ Weak Instability To Return To Portions Of Tx.

At That Time Deep Convection May Ultimately Evolve Across The Srn Plains If Short-Wave Depicted By Models Materializes.


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