Severe Weather Threat Day 1 Tue Jun 11

Nrn And Cntrl High Plains Into The Mid-Upper Ms Valley Area...

Have Made Only Minor Adjustments To Current Forecast As Scenario
Still Appears To Be On Track. Storms Are Developing Over The Nrn
Rockies. Increasing Isentropic Ascent On Nose Of Strengthening Llj
And Height Falls Ahead Of Ejecting Shortwave Trough Will Promote
Additional Storms Over Sd/Wrn Neb This Evening...Especially North Of
E-W Boundary And Continuing Ewd Into The Overnight. Activity Will
Likely Grow Upscale Into Clusters And Line Segments With Damaging Wind And Large Hail Likely.

Cntrl Il Into The Oh Valley...

A Few Storms Continue Developing Across Cntrl Through Nern Il This
Afternoon...But Activity Is Elevated Above A Capping Inversion. The
Overall Severe Threat In This Region Remains Conditional...And It
Appears Unlikely That Storms Will Be Able To Root In The Boundary
Layer Given Relatively High Lfcs...Weak Mesoscale Forcing And Weak
Cold Pools With Ongoing Storms. Will Maintain 5% Severe
Probabilities Given The Conditional Nature Of The Threat.

Prev Discussion...

Elongated Subtropical Ridge Now Extending From The Srn Rckys Into
The Cntrl/Srn Plns Will Expand Ewd This Period In Wake Of Upr
Impulse That Crossed The Tn Vly Yesterday. At The Same Time... Potent Shortwave Trough Now Over Ut Will Continue Ene Into The Nrn/Cntrl High Plns This Eve...Before Turning E As It Crests The Ridge To Reach Sd/Neb Early Wed.

Given The Above Pattern...Expect Stout Eml...Well-Depicted In The
Morning Raob Data...To Remain In Place Into Tngt From The N Cntrl Hi Plns Ewd Into Mid-Ms/Lwr Oh Vlys.

At The Sfc...Cntrl High Plns Lee Low Should Remain Nearly Stnry
Today Before Advancing E Across Srn Neb Tngt Ahead Of Upr Trough. A Corridor Of Fairly Rich Boundary Layer Moisture And Low-Lvl Ely Flow Will Persist N Of A W-E Front Extending E From The Low Into Mid-Ms Vly.

Combination Of Low-Lvl Moisture Inflow...Sfc Heating...And Approaching Upr Trough Likely Will Lead To Strong Tstm Development By Mid To Late Aftn Over Parts Of Ern Wy And Wrn Sd. This Activity Likely Will Grow Upscale Into A Svr Mcs That Moves Generally E Along The Nrn Fringe Of The Eml Cap And Along Low-Lvl Moist Axis Through Early Wed.

In The Meantime...Sctd Areas Of Strong To Locally Svr Diurnal Storms May Occur Today Over Parts Of The East And Intermountain West.

In Addition...Wdly Sctd Elevated Storms With Hail May Occur Early Wed In Strengthening Waa Zone On Ne Fringe Of The Eml Over The Oh Vly.

N Cntrl High Plns To Mid Ms Vly Today Through Early Wed...

Low-Lvl Moisture Will Further Increase Across Sd...Nrn Neb...Ern
Wy...And Se Mt Today In Ely Upslope Flow N Of Stalled Front/Lee Low.
Coupled With Strong Sfc Heating And Increasing Upr Lvl Divergence /Dcva With Approach Of Ut Upr Vort...Setup Will Become
Favorable For Strong Tstm Development Near The Higher Terrain And
Along Lee Trough And By Mid To Late Aftn. Combination Of Strong
Instability /Mucape To 2500 J Per Kg/ And 40 Kt Wswly Deep Shear
Likely Will Yield Sctd Supercells Capable Of Very Large Hail... Locally Dmgg Wind...And Tornadoes...Especially In Sw Sd...Ne Wy...And Nw Neb.

Given Very Deep/Strong Eml...Presence Of 40-50 Kt Unidirectional Wly
Mid/Upr-Lvl Flow...And Moist/Ely Low-Lvl Flow...Setup Appears
Favorable For Upscale Development Into A Svr Forward-Propagating/
Possible Derecho-Producing Convective System. Such A System Could Extend A Risk For Svr Wind...Hail..And Isold Tornadoes E Into Ne Neb/Nw A/Se Sd Area By 12z Wed.

Farther E...Smaller...Somewhat Elevated Convective Systems/Storms May Form During The Overnight Over Parts Of Il/Ind/Oh In Zone Of Strengthening Waa/Moisture Transport On Nern Fringe Of Eml.

Srn New England/Lwr Hudson Vly/Nj This Aftn...

Sfc Heating In Narrow Corridor Of Clearing On Sw Side Of Cloud
Shield Associated With Cape Cod Area Sfc Low May Support Development Of Sctd Strong Aftn/Eve Storms With Gusty Winds In Associated Zone Of Weak Low-Lvl Confluence.

Parts Of Ga/Sc This Aftn...

Wdly Sctd Strong Storms Also May Form In Zone Of Weak Ascent On
Trailing Sw End Of Upr Impulse That Crossed The Tn Vly Yesterday.
Wind And Thermodynamic Environment May Support An Instance Or Two Of Locally Dmgg Wind/Marginally Svr Hail.


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