Severe Weather Threat Day 1 Sat Aug 31

Synoptic Pattern Will Change Little Saturday With An Upper Ridge
Anchored Over The Srn Plains Into The Srn Rockies And Belt Of
Stronger Wlys Over The Nrn Tier States. Vigorous Shortwave Trough
Now Over Srn Alberta Will Crest Upper Ridge And Drop Sewd Through Nd And Mn Saturday Afternoon And Evening...Continuing Into The Great Lakes Later Saturday Night. Attendant Surface Low Will Develop Through Srn Ontario While Trailing Cold Front Advances Sewd Through The Nrn/Cntrl Plains And Upper Ms Valley.

Farther East A Positive Tilt Low Amplitude Upper Trough Will Continue Ewd And Off The Atlantic Seaboard. A Cold Front Will Advance Into The Nern States...But Trailing Portion Of This Boundary Will Stall Over The Oh Valley And Extend Nwwd As A Warm Front Into The Mid Ms Valley And Cntrl Plains Region.

Upper-Mid Ms Valley Through Ern Portions Of Nrn/Cntrl Plains...

Sly Winds Within Gradient Zone Between Retreating Sfc Ridge Over Ern Canada And Lee/Pre-Frontal Trough Will Develop Ewd Through The Nrn Plains And Upper Ms Valley Saturday. Richer Low-Level Moisture Should Remain Confined To Along And Just South Of Warm Front Across Neb/Ia...While Low 60s Dewpoints Should Be Maintained Farther North Ahead Of The Cold Front From The Ern Dakotas Into Mn. Plume Of Steep Mid-Level Lapse Rates Will Advect Above The Moist Axis Which In Conjunction With Diabatic Warming Should Result In An Axis Of Moderate Instability. Mlcape From 1500-2000 J/Kg Is Likely From Ern Nd Into The Upper Ms Valley With 2000-3000 J/Kg Farther South Across Srn Sd/Neb.

Storms Are Expected To Initiate Over The Ern Dakotas By Mid Afternoon Along Cold Front Within Zone Of Height Falls Ahead Of The Approaching Shortwave Trough. Activity Will Subsequently Develop Into Mn. Farther South...Weaker Deep Forcing And A Stronger Cap May
Delay Initiation Until Later In The Afternoon Across Srn Sd And Neb.
Winds Aloft Will Strengthen With Approach Of A Mid-Level Jet
Attending The Shortwave Trough With Effective Deep Shear Increasing To Aoa 40 Kt. Initial Storms Will Likely Be Supercells Capable Of Producing Mainly Very Large Hail And Damaging Wind...Though A Couple of Tornadoes Cannot Be Ruled Out. Activity May Eventually Congeal Into Mcs Clusters With Damaging Wind Becoming The Main Threat During The Evening And Overnight.

Oh Valley Into The Nern States...

Diabatic Warming Of The Moist Boundary Layer With Dewpoints In The Upper 60s To Around 70 Will Contribute To Mlcape From 2000-3000 J/Kg Over The Oh Valley And 1500 J/Kg Farther East Into The Nern States Where Weaker Lapse Rates And More Clouds Are Likely. Scattered Storms Are Expected To Once Again Develop Along And South Of The Front During The Afternoon Within A Weak Shear Environment. The Thermodynamic Profiles May Support A Threat For Mainly Isolated Strong To Damaging Wind Gusts Through Early Evening. A Slight Risk May Need To Be Included For Portions Of This Area In Later Updates.


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