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Severe Weather Threat thru Apr 13

Sun Apr 6 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Of Svr Tstms for parts of Ern Tx...La...Ms and Al...

The Only Change To The Outlook Is To Remove The Slight Risk Area
From Parts Of Cntrl And East Tx.

Thunderstorms Have Markedly Decreased In Coverage To The West Of A Line From Just West Of Houston Extending Nwd To Tyler.

This Area Is Being Impacted By Subsidence In The Wake Of A Vorticity Max Over The Arklatex And Will Be Affected By Drier Air Advecting In From The Northwest This Afternoon.

To The East Across La...Ms And Al...A Severe Threat Will Continue
From This Afternoon Into The Overnight Period As A Well-Defined 70
To 90 Kt Mid-Level Jet Moves Into The Region From The Southwest.

This Feature Will Create Strong Deep Layer Shear Profiles Over The
Top Of A Moist Airmass Creating Conditions Favorable For Rotating
Storms.

Prev Discussion...

The Primary Feature Of Interest During The Day One Period Is A
Srn-Stream Short-Wave Trough Over The Srn Plains Into Nwrn Mexico
Which Will Shift Ewd Into The Srn Plains And Lower Ms Valley.

An Associated 500-Mb Jet Streak Will Strengthen To 90-100 Kt As It
Emerges From The Base Of The Parent Trough Before Moving Into The Lower Ms Valley Tonight In Tandem With A Lead Vorticity Maximum.

In Response To The Progression Of This Upper-Air System...A Sswly Llj Will Broaden And Intensify To 50+ Kt While Migrating From The Wrn
Gulf Of Mexico Through The Lower Ms And Tn Valleys Into The Cntrl / Srn Appalachians By 07/12z.

At The Surface...Low Pressure Over The Lower Tx Coast Will Deepen
While Developing Newd Into Wrn Parts Of Ky/Tn By Daybreak Monday.

An Associated Warm Front Will Lift Nwd Through Ms And Al Into Tn With The Ern Extension Of This Boundary Shifting More Slowly Nwd Through Parts Of Ga And Sc.

Meanwhile...A Cold Front Will Strengthen While Advancing Ewd/Sewd Into The Lower Ms Valley.

Cntrl/Ern Tx to The Cntrl Gulf Coast States Through Tonight...

A Corridor Of Elevated Tstms Are Ongoing As Of Mid Morning From
Portions Of N-Cntrl/Cntrl Tx Into Cntrl Ms With This Activity
Largely Being Forced By Warm And Moisture Advection Occurring At The Terminus Of The Llj Above The Surface Warm Front.

This Regime Is Expected To Persist Today While Gradually Shifting Ewd/Newd Into The Lower Ms Valley With Marginally Severe Hail Being The Primary Severe Weather Threat.

The Inland Development And Intensification Of The Llj Will Promote
The Poleward Flux Of A Seasonably Moist Air Mass /I.E. Pw Values Of
1.50-1.75 Inches/ Along And South Of The Warm Front And Migratory
Surface Low With Mlcape Increasing To 500-1000 J/Kg Within The
Expanding Warm Sector.

Increasing Height Falls/Dcva Ahead Of The Midlevel Trough Coupled
With Low-Level Convergence/Uplift Invof Surface Low And Associated
Warm/Cold Fronts Will Foster Initial Surface-Based Storm Development By Late Afternoon Over Parts Of Sern Tx Into Srn La With This Activity Moving/Developing Ewd/Newd Through A Large Part Of Ms...Al And The Wrn Fl Pnhdl This Evening Through The Overnight Hours.

The Colocation Of The Above-Mentioned Low And Midlevel Wind Maxima Will Result In Strong Low-Level And Deep-Layer Shear... Particularly From Sern La Through Ms/Al During The Latter Half Of The Forecast Period.

When Coupled With The Moist/Low Lcl Boundary Layer And At Least Modest Instability...The Setup Will Be Supportive Of Supercells And Bowing Structures Capable Of Tornadoes /Some Possibly Ef-2+/ And Wind Damage...Namely Along And South Of The I-20 Corridor.

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Mon Apr 7 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Of Svr Tstms for parts of Ern Gulf Coast States and Carolinas....

Ern Gulf Coast States...

An Upper-Level Trough Extending Swwd From The Ozarks Into The Srn Plains Will Gradually Move Ewd On Monday.

At The Sfc...A Deepening Low Will Move Nnewd Into The Oh Valley As A Trailing Cold Front Advances Ewd Into The Tn Valley And Cntrl Gulf Coast States.

Widespread Thunderstorm Activity Should Be Ongoing Ahead Of The
Front In The Tn Valley And Lower Ms Valley At The Start Of The Period.

This Convection Should Move Ewd Across The Cntrl Gulf Coast
States During The Morning And Into The Srn Appalachian Mtns... Carolinas And Ern Gulf Coast States During The Afternoon.

As Low-Level Convergence Increases Ahead Of The Front... Squall-Line Development Will Be Possible On Monday Afternoon Or Evening.

Early In The Period...Moderate Instability Should Already Be In Place In Far Se La And Srn Ms Where Sfc Dewpoints May Approach 70 F In A Few Locations.

Strong Deep Layer Shear Will Also Be In Place Due To A 75 To 100 Kt Mid-Level Jet.

This Environment Could Support A Marginal Severe Threat With Isolated Damaging Wind Gusts Possible In Far Se La...Srn Ms And Srn Al.

In Spite Of Widespread Cloud Cover And Precipitation...The Area With Moderate Instability May Expand Enewd Across Parts Of Srn Al And Srn Ga By Afternoon.

The 21z Nam Forecast Sounding At Montgomery Al Shows A Sfc Dewpoint Of 65 F...Sbcape Of 1000 J/Kg...0-6 Km Shear Of 65 Kt With A Unidirectional Wind Profile.

This Should Support A Wind Damage Threat And Possibly A Tornado Threat With Cells That Have Access To The Greatest Instability.

The Wind Damage Threat May Increase During The Late Afternoon When Squall-Line Development May Occur From Srn Nc Swwd Across Sc...Ga Into The Fl Panhandle.

A Tornado Threat May Also Persist With Rotating Storms Embedded In The Line Or If Cells Can Remain Discrete Ahead Of The Line.

At This Point...Will Not Add A 30 Percent Severe Probability Contour Due To Expected Widespread Cloud Cover And Uncertainty Regarding The Amount Of Destabilization.

Oh Valley...

An Upper-Level Trough Will Move Ewd Into The Lower Oh Valley On
Monday As A Sfc Low Tracks Newd From Wrn Ky Into Oh.

Thunderstorm Development Will Be Possible From East Of The Low Extending Swd Along A Narrow Corridor Of Low-Level Moisture.

Mid-Day Forecast Soundings For Lexington Ky Warm Temps Into The Mid 60s F With Sbcape Around 800 J/Kg.

In Addition...Strong Deep Layer Shear Should Be Present With 500 Mb Temps Around -15 C.

This May Be Enough For A Marginal Hail Threat With Cells That Develop In Areas That Heat Up The Most.

A Few Of The Cells Could Also Be Associated With Strong Wind Gusts.

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Tue Apr 8 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

A Highly-Amplified Upper Trough Will Translate Slowly Ewd From The
Ms Valley To The E Coast.

Early In The Day A Cold Front Will Be Near The E Coast But Will Quickly Depart.

The Exception Will Be Over Fl. Here...Thunderstorms Will Be Likely As The Front Passes Quickly.

Poor Lapse Rates Aloft Should Generally Preclude Any Severe
Potential...Although Gusty Winds Will Be Possible.

Elsewhere...A Weak Low-Pressure Trough Will Affect The Lower Ms
Valley Where Low To Midlevel Lapse Rates Will Be Very Steep As
Heating Occurs Beneath The Midlevel Thermal Trough.

The Result Will Be Low-Topped Diurnally-Driven Thunderstorms Capable Of Very Small Hail And Gusty Outflow.

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Apr 9-13 Convective Outlook
Storm Prediction Center Norman Ok

An Amplified Upper Trough Will Exit The Ern States On Wed/D4... Allowing High Pressure To Settle Across The Sern U.S.

This Surface High Will Keep Low-Level Moisture Offshore For Several
Days...With Only A Modest Return Of Sly Flow And 60 Dewpoints Across The Srn Plains In The Fri/D6 - Sun/D8 Time Frame.

Models Indicate A Srn Stream Shortwave Trough Affecting The Srn U.S...But Timing Is Unpredictable At This Time.

However...Severe Storms Would Be Most Likely Across The Srn Plains Or Lower Ms Valley On Sun/D8 When Low-Level Moisture Would Be More Robust.


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