Severe Weather Threat Day 1 Mon Dec 24

Ern Tx/La Area Overnight...

Little Change Needed To Previous Outlook. Latest Surface Data
Indicate The Front Along The Mid/Upper Tx Coast Has Stopped Its Sewd Progression. It Will Likely Begin To Return Nwwd As A Warm Front Over The Next Few Hours In Response To Increasing Surface Pressure Falls Over The Srn Plains.

Latest Model Guidance Including 12z Convection-Allowing Models Indicate Development Of Strong Storms Over East Central/Sern Tx After 03-06z With Activity Spreading Ewd/Newd Toward The Lower Ms Valley By 12z. Increasing Vertical Shear /Especially Along And North Of The Retreating Warm Front/ Will Support Threat For A Few Severe Storms.

Extreme Sern Al/Fl Panhandle/Swrn Ga...

Marginal Severe Threat Over This Area Will Continue To Diminish As
The Upper Trough Over The Appalachians Progresses Ewd Toward The Atlantic Coast. Current Convection Is Located Over The Ern Edge Of The Low Level Moisture Field...And Storms Should Gradually Weaken With Time As The Dynamic Forcing For Large Scale Ascent Moves East Of The Instability Axis.

Prev Discussion...

Progressive Upper-Air Pattern Was Analyzed This Morning Over Conus...Featuring Two Shortwave Troughs Of Primary Pertinence To
This Fcst Initially Over...

1. Mid-South Region To Ms/Al Coast. This Feature Will Move Ewd And Deamplify Slightly Before Moving Offshore Sc Around 03z.

2. Inland Pac Nw Ssewd Across Nv. Perturbation Is Fcst To
Strengthen Through Period And Move Sewd Across Central/Srn
Rockies...Reaching Central/Srn High Plains By 12z.

Embedded/500-Mb Closed Low Should Form By 12z Over Tx Panhandle/South-Plains Region...While Mid-Upper Height Gradient Intensifies Markedly To Its Sw-Se. By 12z...Expect 500-Mb Jet Max 90-100 Kt Over Sern Nm/Tx Permian Basin Region...With Flow Strengthening To 60-70 Kt Range Over Sfc Warm Sector In Se Tx.

At Sfc...Weak Low Now Over Nrn Ky Is Fcst To Proceed Newd Up Oh
Valley Through Remainder Daylight Hours And Weaken...With Occlusion Triple-Point Low Possibly Forming Invof Sern Ny Coastal Waters Around 06z.

Accompanying Sfc Cold Front Was Analyzed At 15z From Low Sswwd Across Nrn Al...Swrn Ms...Swrn La...And S-Central Tx. Tx Portion Of Boundary Is Decelerating...And Is Fcst To Move Nwd Across Portions Central/Se Tx Overnight As Warm Front.

Meanwhile...Lee Cyclone Is Fcst To Deepen Considerably Today Across Nern Nm And Sern Co Region...With Apch Of Amplifying Trough Aloft. During Last 6 Hours Of Period...Sfc Cyclone Will Transition To Frontal-Wave Feature And Move/Reposition Sewd Along Zone Of Frontogenesis...Reaching Position Over Central Tx By 12z.

Tx/La Area Overnight...

Convective Potential Will Increase Overnight...First N Of Sfc Front
Late Evening Through Pre-Dawn Hours With Most Intense Cells Posing Hail Threat. Activity May Develop Progressively Closer To Front Through End Of Period...Eventually Becoming Sfc-Based With
Supercells And Bow/Lewp Features Possible.

As Such...Threat Exists During Last Few Hours Of Period For Svr Hail/Gusts. Tornado Risk Exists From Any Sfc-Based And Relatively Discrete Cells In What Should Be Very Favorable Shear Environment ...But Coverage Of Sfc-Based Tstms Is Too Uncertain Attm For More Than 5% Unconditional Tornado Risk.

Deep Shear And Low-Level Hodographs Each Are Expected To Strengthen Over Returning Warm Sector Tonight...As 60s F Sfc Dew Points Contribute To 1000-1500 J/Kg Mlcape By 12z Along And S Of Front Over Se Tx. Largest Low-Level Hodographs Will Be Along Front...Where Backed Sfc Winds Will Contribute To Effective Srh 300-500 J/Kg. Srh Also Will Be Favorable Farther S Over Coastal Areas In Warm Sector...However Fcst Soundings Suggest Pronounced Eml-Base Inversion Between 850-700 Mb That May Restrict Tstm Coverage Away From Boundaries.

Central-Ern Gulf Coastal Plain...Into Monday Evening...

Bulk Of Convection Is Expected To Outrun Low-Level Destabilization
Over This Region Through Remainder Daylight Hours. However...At
Least Isolated Tstms Still May Develop Over This Area Through Around 21z...Some Of Which May Become Sfc-Based. Damaging Wind And Tornado Risks Are Nonzero But Very Conditional. Destabilization Will Be Slowed By Ongoing Clouds/Precip...Which Will Restrict Pace Of Diurnal Warming. Low-Level Thetae Advection Should Result In Potential Inflow Parcels Effectively Becoming Sfc-Based Across This Region Through Mid-Aftn...While Deep-Layer Ascent Weakens. These Offsetting Influences Will Affect Tstm Coverage...But Any Sustained/Sfc-Based Convection Has Potential To Become Supercellular.

As Such...Will Maintain Mrgl Unconditional Svr Probabilities For This Outlook.

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