Severe T-Storm US Outlook Sep 17

Day 1 Convective Outlook
Nws Storm Prediction Center Norman Ok
1109 Am Cdt Fri Sep 17 2010

...There Is A Slgt Risk Of Svr Tstms This Afternoon Into Tonight
Over Parts Of The Cntrl Plains And Mid/Lower Mo Valley...

...Cntrl Plains/Mid And Lower Mo Valley...

12z Observed Soundings And Satellite-Derived Pw Imagery Show Modest Moisture Content /I.E. Dew Points In The 50s To Low 60s And Pw Values Of 1.0-1.3 Inches/ Present Over The Region...With The True
Maritime Tropical Air Mass Displaced Well To The S...Ahead Of
Initial Frontal Surge Over Ern Tx Into The Lower Ms Valley.
Nonetheless...The Presence Of A Steep Lapse Rate Environment And
Daytime Heating Will Yield A Moderately Unstable Air Mass By
Afternoon With Mlcape Values Approaching 2000-2500 J/Kg.

As Mentioned In Previous Day One Discussions...Large-Scale Forcing
For Ascent Will Remain Negligible Through Much Of The Diurnal
Heating Cycle. However...12z Model Guidance And Morning Water Vapor Imagery Suggest That Region May Be Glanced By A Low Amplitude Impulse Translating Esewd From The Nrn High Plains. When Coupled With A Deepening/Strengthening Circulation Attendant To
Frontogenetic Cold Front...Setup Should Allow For The Development Of Isolated To Scattered Tstms Late This Afternoon Into Evening Across
Parts Of Ia/Neb.

Region Will Reside Along The Srn Fringe Of Stronger Mid And
High-Level Cyclonic Flow Attendant To Upper Low Over Cntrl Canada
With Sufficient /30-40 Kt/ Deep Wly Shear To Support Organized Storm Modes Including Supercells. While A Tornado Or Two Will Be Possible Within The First Hour Or Two After Storm Initiation...A General
Anafrontal Air Flow Regime Will Likely Result In Storms Transitioning To More Outflow Dominant With The Primary Hazards Being Large Hail And Damaging Winds. This Wind/Hail Threat May Persist Into Tonight As Low-Level Inflow Is Enhanced By A Strengthening Nocturnal Llj.

...Carolinas/Sern Va...

Short Wave Trough Currently Moving Through The Cumberland Plateau Will Progress Ewd Into The Piedmont And Coastal Plain Later Today. At The Same Time...A Cold Front Will Continue To Push Sewd Through The Region...Providing The Focus For Diurnal Storm Development. Air Mass Ahead Of The Front Is Rather Moist With Dew Points In The 60s. And While Midlevel Lapse Rates Are Not Particularly Steep...The Presence Of Strong Diabatic Heating Should Support Mlcape Increasing To 1000-1500 J/Kg This Afternoon...Along With Steepening Low-Level Lapse Rates. As Such...Some Risk For Isolated Strong Wind Gusts Will Exist With Any Stronger Storms That May Develop.

..Mead/Broyles.. 09/17/2010


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