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Severe Weather Threat Day 2 Tue Apr 9

Svr Potential Day-2 Will Be Related To Progressive/Synoptic-Scale
Trough In Mid-Upper Levels...Shifting Slowly Ewd From Wrn To Central Conus.

Moisture Channel Imagery And 12z Raob Data Indicate Deepening Shortwave Trough Over Nv And Sern Ca...Which Should Evolve To Yield Closed 500-Mb Cyclone Over Ut Through Remainder Day-1.

During 09/12-09/00z Time Frame...Primary Mid-Upper Cyclone Is Fcst
To Drift Across Swrn Co From 4-Corners Region...Then Move Slowly
Newd Across Co Through Remainder Period. Several Low-Amplitude
Vorticity Perturbations Are Expected To Move Newd From Synoptic
Trough Position Across Srn/Central High Plains...While Basal Speed
Max Aloft Shifts Slowly Newd Across Outer Sern Quadrant Of
Cyclonic-Flow Regime. Main Ribbon Of 500-Mb Vorticity Should Remain Across Nwrn Mex Through At Least 10/06z Before Fragmenting And Ejecting...Based On Stg Consensus From Latest Avbl Runs Of Operational Models And Ecmwf/Cmc.

Net Result Should Be Slgt Positive Tilt To Main Synoptic Trough...Positioned During Latter Half Of Period From Central High Plains Through Co Low To Nwrn Mex.

Complex Nature Of Cyclone Evolution Aloft Will Be Reflected At Sfc
Too. Hybrid Lee-Side/Frontal-Wave Cyclone Should Consolidate Late
Day-1 Over Ern Co Then Move Ewd Across Ks Through 10/00z.

As This Occurs...Arctic Cold Front Now Located Over Ern Wy Will Move Sewd Across Remainder Central High Plains...Reaching From Nern Ks Frontal Wave Swwd Across Nwrn Ok And Tx Panhandle By 10/00z. Quasistationary Front Will Extend From Low Enewd Over Lower Mi. Pac Cold Front Is Expected To Move Ewd From Nm Over Srn High Plains Early In Period...With 10/00z Position From Arctic Frontal Intersection Over Wrn Ok Swwd Across W-Central Tx To Davis Mtns Region. Dryline Should Mix Ewd Across W-Central Tx And Wrn Ok During Day...Reaching 10/00z Position From Edwards Plateau/ Wrn Hill Country Region Of Tx Nwd Across Nw Tx To Wrn Ok Intersection With Arctic Front. Arctic Front Will Overtake Both Pac Front And Dryline From N-S Through Remainder Period.

By 10/12z...Main Sfc Low Should Be Moving Ewd Across Nrn Mo Along
Quasistationary Front...Which Is Progged To Extend Enewd Over Wrn
Ny. Arctic Front Will Extend Swwd Across Sern Ok...Central Tx...And
Rio Grande Valley Between Lrd-Drt...Having Fully Overtaken Pac Front
And Dryline.

Srn Plains To Mo Valley Region...

Widely Scattered To Isolated Tstms May Develop Invof Dryline And
Cold Front During Mid-Late Afternoon...Increasing In Coverage
Greatly As Frontal Forcing Impinges Upon Progressively Richer
Low-Level Moisture During Evening/Overnight Hours.

Large Hail Is Quite Likely...And Conditional Risk Exists For At Least A Few Tornadoes And Serial Corridor Of Damaging-Wind Events.

Broad Swath Of Svr Potential Still Is Fcst In Roughly Same Area As Before...But Uncertainties Linger Regarding Prefrontal Tstm Coverage ...Timing And Mode. As Such...Will Maintain Similar Unconditional Numerical Probabilities As Prior Outlook. Some Small Subset Of This Area Still May Require Future Categorical Upgrade As Mesoscale Trends Warrant.

Operational Models Have Been Too Aggressive In Moistening Boundary Layer Across Much Of Warm Sector So Far...Which Continues Historical Biases In Early-Stage Return-Flow Events. By Day-2...That Bias Still Is Apparent But Not As Large. Increasing Maturity Of Upstream Marine Modification Process And Persistence Of Intervening Waa/Moisture Transport Regime Should...In Effect...Allow Reality To Catch Up To Progs By Middle Of Period... Though Progged Dew Points May Be Too Moist Over Mo Valley.

60s F Sfc Dew Points Therefore Should Be Common From Central Tx To Ia By Afternoon. Lapse Rates Aloft Will Be Steepest Over Srn Plains...But Still Favorable Into Mo Valley Region. Where Sustained Diabatic Sfc Heating Occurs...Net Result Should Be Mlcape Ranging From Around 3000 J/Kg Over Central/Nrn Tx To Around 1000 J/Kg Invof Ia Quasistationary Front.

Favorable Deep Shear Will Overspread This Sector Throughout Day As Synoptic Wave Sifts Slowly Ewd. However...Just Above Boundary
Layer...Fcst Aftn Wind Soundings Across Primary Svr Corridor Show
Some Veer-Back Tendencies With Height. This Appears Reasonable
Given Geometry Of Mid-Upper System And Assumption Of Typical Mass Response. Some Llj-Related Removal Of That Kinematic Weakness Is Evident In Time Series Of Fcst Soundings...Especially Across Portions Srn Ok And N Tx During Evening. That Area Also Will Be More Strongly Capped For Longer Period Of Time...Indicating Higher Probability Of Maintaining Discrete Storm Character Compared To Potentially Messier Storm Modes Across Nrn Ok And Ks/Mo.

As Such...Potential For Sustained Supercells With Significant/ Damaging Hail And A Few Tornadoes May Be Greatest Over Srn Ok And N Tx Prior To Linear Forcing Of Cold Fropa. However...At Least Isolated Damaging Hail Cannot Be Ruled Out Farther N Into Ks.

Low-Level And Deep Shear Should Support Potential For Svr Hail...Wind And Either Embedded-Supercellular Or Qlcs Tornadoes Throughout Near-Frontal Warm Sector Between Central Ok And Srn Ia. Backbuilding Along Or Even Slightly Behind Cold Front Will Expand Svr Potential Swd With Time Across Central/Sw Tx...But With More Quasi-Linear Character As Mid-Upper Winds Become More Parallel To Band Of Strongest Low-Level Convective Forcing.


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