Severe Weather Threat Day 2 Thu Jun 13

A Shortwave Trough Over The Nrn Plains Is Cresting Cntrl U.S. Upper
Ridge...And Will Result In Amplification Of Downstream Mean Trough
Across The Mid Atlantic And Nern U.S. Thursday. Meanwhile...The
Upper Trough Over The Pacific Nw Will Move Slowly Ewd Into The Nrn
Intermountain Region.

Sfc Cyclone Will Shift Ewd Through The Mid Atlantic In Association
With Deeper Forcing Attending The Ern U.S. Shortwave Trough. By 12z
Thursday A Cold Front Should Extend From The Sfc Low Over Pa...Swwd Into The Oh And Lower Ms Valley Region. This Boundary Will Advance Sewd During The Day...Reaching The Atlantic Seaboard Later Thursday Evening With Trailing Portion Extending Into The Sern States. Warm Front Extending Ewd From The Low Will Lift Slowly Nwd Through The Mid Atlantic States...Likely As Far North As Nj.

Mid Atlantic Region...

Swly Winds Ahead Of The Developing Cyclone Will Transport Upper 60s Dewpoints Through Pre-Frontal Warm Sector Beneath Residual Plume Of 7 C/Km Mid Level Lapse Rates. The Atmosphere Is Expected To Become Moderately Unstable As Diabatic Warming Commences With Mlcape From 2000-3000 J/Kg Possible.

Meanwhile...Stronger Winds In The 700-500 Mb Layer Rounding Base Of Amplifying Shortwave Trough Will Spread Over The Warm Sector During The Afternoon. Strengthening Deep Layer Wly Winds Should Result In A Downsloping Regime Immediately East Of Srn/ Cntrl Appalachians...Suggesting It Might Be Difficult For Any Ongoing Storms Survive Crossing The Mountains. However...Pre Frontal
Trough/Convergence Axis Will Likely Evolve Farther East From The
Cntrl Carolinas Into Cntrl/Ern Va. Additional Storms Will Likely
Develop Along This Convergence Zone Or As Cold Front Overtakes The Destabilizing Warm Sector. Deep Layer Wind Profiles Will Be Largely Unidirectional With Swly Flow In The Sfc-3 Km Layer South Of Sfc Low. The 0-6 Km Vertical Shear Of 30-40 Kt Will Support Potential
For A Few Supercells Especially Within 2-3 Hours Of Initiation.

However...Tendency May Be For Some Of This Activity To Evolve Into
Line Segments With Lewp/Bow Structures. Widespread Damaging Wind And Large Hail Are Expected To Be The Main Threats...Though A Few Tornadoes Cannot Be Ruled Out.

Sern States...

Low 70s Boundary Layer Dewpoints Are In Place And Will Support
Moderate Instability /2000-2500 J/Kg Mlcape/ As The Sfc Layer Warms
And Destabilizes During The Afternoon. A Belt Of Stronger Mid-Upper
Winds Will Drop Sewd Over The Warm Sector As The Upper Trough
Amplifies The East Of This Region. This Will Result In Nwly Deep
Layer Winds And Effective Shear Of 30-35 Kt That Will Become At
Least Marginally Supportive Of Organized Storms. Current Indications
Are That A Few Storms May Be Ongoing Over The Tn Valley Region ...And Additional Activity May Develop/Intensify Along The Swd Moving Outflow Boundaries. Damaging Wind And Large Hail Will Be The Main Threats.

Ern Mt And The Nrn High Plains Region...

Cold Front And Associated Upper Trough Will Advance Ewd Into A
Destabilizing Afternoon Airmass. Expect Isolated Thunderstorms To
Develop -- Initially Over Central And Ern Mt And Adjacent Nern Wy.
While Strong Capping -- Owing To The Preceding Influence Of Upper
Ridge -- Suggests That Coverage Will Be Limited...Storms Which Do
Develop Will Likely Become Severe/Supercellular Given Moderate
Instability And Ample Veering/Shear. Hail And Damaging Winds Will
Be The Primary Severe Threats Through The Afternoon. Storms Should Spread Ewd Across Ern Mt Toward Wrn Sd Into The Evening ...As A Sely Low-Level Jet Increases Across The High Plains. Shear Will Continue To Favor Severe Potential...With Continued Threat For Damaging Winds And Hail And Possibly An Isolated Tornado.

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