Severe Weather Threat Day 3 Mon Feb 18

Models Indicate That The Large-Scale Pattern Over The Northeastern
Pacific Will Undergo Significant Amplification During This Period.

Downstream Of A Building Mid/Upper Ridge...A Vigorous Short Wave
Impulse Appears Likely To Dig Toward The California Coast...Within
The Southern Branch Of A Split Belt Of Westerlies Emerging From The Mid Latitude Pacific.

As This Occurs...Guidance Suggests That Large-Scale Troughing East Of The Rockies Will Gradually Consolidate And Progress Eastward Toward The Appalachians...Perhaps In Phase With An Impulse Embedded Within A Lingering Strong Subtropical Jet Near The Gulf Coast.

Strongest Mid-Level Forcing For Upward Vertical Motion Seems Likely
To Generally Overspread The Great Lakes Region Late In The Period ...Accompanied By The Center Of A Fairly Deep And Deepening
Surface Cyclone.

This Will Be Rather Far Removed From A Developing Return Flow Of Moisture Off A Gulf Of Mexico Boundary Layer...Which Will Be Only Slowly Modifying In The Wake Of Recent Drying/Stabilization.

However...There Does Appear To Be A Window Of Opportunity For Sufficient Destabilization To Support The Development Of Thunderstorm Activity...Ahead Of A Cold Front Advancing Toward The Lower Ohio/Mississippi Valleys And Western Gulf Coast.

Potential For Severe Weather Still Appears Low...But It May Not Be Completely Negligible Late Monday Afternoon And Evening.

Parts Of Ern Texas And The Arklatex Into The Ozark Plateau...

A Narrow Corridor Of Moistening Along A Rather Strong Southerly
Pre-Frontal Low-Level Jet...Expected To Be Nosing North Of The Ozark
Plateau Into Portions Of The Middle Mississippi And Lower Ohio
Valleys By Mid Day Monday...May Contribute To Weak Destabilization
And Thunderstorm Development Above A Residual Cool/Stable Surface Based Layer.

This Activity May Persist And Spread Eastward Into The Lower Ohio And Tennessee Valleys Through The Remainder Of The Afternoon And Evening Hours...Before Diminishing In A More Stable Environment.

To The South/Southwest Of This Initial Activity...Continued Weak
Moisture Return...Coupled With Surface Heating Near A Developing
Pre-Frontal Dry Line...May Contribute To Weak Boundary Layer
Destabilization Across Parts Of Eastern Texas And The Arklatex Into
Southwest/Central Arkansas.

As This Occurs In The Presence Of Strong Deep Layer Shear...It Does Not Appear Out Of The Question That The Environment Could Become Marginally Conducive For Organized Strong/Severe Storm Development...Including Supercells.

With Mixed Layer...And Most Unstable...Cape Expected To Remain Rather Weak /On The Order Of 500 J Per Kg Or Less/...This Potential May Be Confined Roughly To The 18/21z To 19/01-03z Time Frame...Before Radiational Cooling Stabilizes The Boundary Layer.

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