Severe Weather Threat thru Jul 31

Thu Jul 24 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for N Plains to Mid Mo River Valley...
Slgt Risk Svr Tstms for parts Of Nc And S Va...

A Few Severe Thunderstorms With Large Hail And Damaging Winds Will Occur From Eastern Montana Into North Dakota Late This Afternoon And Tonight.

Strong Storms Capable Of Locally Damaging Winds May Affect Parts Of The Central And Southern Appalachians And The Southern
Mid-Atlantic States Today.

Isolated Strong To Severe Storms With Hail Are Expected This Afternoon And Tonight From Southeast North Dakota And Eastern South Dakota Into Parts Of Iowa And Minnesota.

Ern Mt Into Nd...

A Vigorous Upper Low Over Srn Bc And Associated Short Wave Trough Extending Swd Into The Pacific Nw Are Expected To Move Enewd Toward The Canadian Prairies Through Tonight...With Strong Wswly Winds Aloft Progressing Enewd Across Mt And Nd. The Primary 500 Mb Height Falls And Dynamic Forcing For Large Scale Ascent Will Remain North Of The International Border. At The Surface ... A Strong Cold Front Will Move Ewd Across Ern Mt This Afternoon And Continue Ewd Across The Dakotas Tonight.

Warm Temperatures And A Capping Inversion Aloft Associated With The Eml Is Likely To Limit Thunderstorm Development To The South Of The Upper Level Jet...With 12z Model Guidance Including Convection-Allowing Models Indicating The Primary Storm Axis Will Be From Nern/East Central Mt Across Parts Of Nd Late This Afternoon And Tonight. The Steep Mid-Level Lapse Rates Coupled With Increasing Low-Level Moisture In The Wake Of Current Elevated Storms In Ern Nd Will Result In Strong Instability With Cape Exceeding 2500-3000 J/Kg This Afternoon And Evening Ahead Of The Cold Front And High Plains N/S Trough. Increasing Convergence Along The Front And Some Ascent Aloft Will Gradually Weaken The Cap Resulting In Convection Initiation By Mid-Late Afternoon Over Mt... With Activity Increasing In Coverage Across Nd Into Tonight.

Strong Deep Layer Shear Will Favor Updraft Rotation With Initial Supercells Capable Of Very Large Hail...Severe Winds And An Isolated Tornado Or Two. There Is Potential For The Storms To Merge Into A Bowing Line Segment And Spread Rapidly Ewd Across Nd During The Night...With A Continuing Threat For Damaging Winds And Large Hail.

Sern Nd/Ern Sd/Swrn Mn And Ia...

Current Elevated Storms Over Sern Nd And Ern Sd Will Pose A Threat For Isolated Large Hail This Afternoon. In Addition...Elevated Storms Are Expected To Persist/Redevelop Tonight Along The Ern Edge Of The Eml/Cap Within A Strong Warm Advection Zone Within The 850-700 Mb Layer...In Association With An Intensifying Low Level Jet. Large Hail Will Be The Primary Threat From These Elevated Storms.

Parts Of Va And Nc...

Strong Storms Are Occurring Over Ern Nc At This Time Within An Environment Characterized By A Very Moist Air Mass With Surface Dew Points In The 70s And Sufficient Shear /25-30 Kt In The Lowest 6 Km/ To Enhance Storm Organization And Intensity. Other Storms Are Expected To Develop In The Wake Of These Current Storms Where Visible Imagery Indicates Breaks/Thinning Of Clouds Which Will Promote Stronger Diabatic Heating And Destabilization.

Water Vapor Imagery Shows A Well-Defined Short Wave Trough Crossing The Central Appalachians Region Which Is Expected To Aid In Development Of Additional Storms This Afternoon And Evening. Stronger Cells Will Have Potential To Produce Damaging Wind Gusts And Isolated Large Hail.

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Fri Jul 25 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Isolated Severe Thunderstorms Will Be Possible In Parts Of The Mid To Upper Mississippi Valley From Friday Morning Into The Afternoon.

Other Marginally Severe Thunderstorms Will Be Possible Friday Afternoon And Evening Across Parts Of The Central And Northern Plains.

Se Mn/Sw Wi/Ern Ia/Nw Il/Ne Mo...

An Upper-Level Ridge Will Move Across The Nrn Plains Late Tonight And Into The Upper Ms Valley Friday Morning. A Well-Developed 40 To 55 Kt Low-Level Jet Will Be In Place Across The Mid Mo Valley With The Nose Of This Feature Located In Nrn Ia And Srn Mn At The Start Of The Period.

The Models Suggest That An Elevated Convective Cluster Will Be Ongoing On The Nose Of The Low-Level Jet With These Thunderstorms Moving Sewd Across Ern Ia And Nwrn Il During The Morning. Forecast Soundings At Lacrosse Wi At 15z Show Mucape Near 1200 J/Kg With 40 To 50 Kt Of Effective Shear. This Combined With Steep Mid-Level Lapse Rates May Be Enough For A Hail Threat With The Stronger Cores. An Isolated Severe Wind Gust Can Not Be Ruled Out If Any Of The Cells Can Become Sfc-Based As Sfc Temps Warm Late Friday Morning.

Upper Ms Valley...

An Upper-Level Ridge Will Move Across The Upper Ms Valley On Friday As A Shortwave Trough Moves Into The Nrn High Plains. At The Sfc...A Low Will Move Sewd Across The Mid Mo Valley As A Cold Front Advances Ewd Into The Upper Ms Valley. A Corridor Of Low-Level Moisture Should Be In Place Ahead Of The Front With Sfc Dewpoints In The Mid to Upper 60s F. This Should Result In The Development Of Moderate Instability Across Much Of Wrn And Cntrl Mn By Afternoon.

Model Forecasts Differ On How Much Convection Will Initiate Along And Ahead Of The Front Friday Afternoon With The Upper-Level Ridge Being Problematic. If The Nam Scenario Verifies...Then Scattered Thunderstorms Will Be Possible During The Mid To Late Afternoon Across Cntrl And Nrn Mn. Forecast Soundings For Bemidji Mn At 00z/Sat Show Mlcape Around 1500 J/Kg With 40 Kt Of Deep-Layer Shear. This May Be Enough For A Marginal Severe Threat If Cells Can Initiate And Develop During Late Day. Isolated Damaging Wind Gusts And Hail Would Be The Primary Threats.

Cntrl And Nrn Plains...

An Upper-Level Ridge Will Move Ewd Into The Upper Ms Valley Friday As A Subtle Shortwave Trough Moves Into The Nrn High Plains. The Srn End Of The Shortwave Trough May Aid Convective Development Across The Cntrl High Plains Friday Afternoon. Isolated Thunderstorms Are Forecast To Initiate In The Higher Terrain Of Se Wy And Ne Co With This Activity Spreading Ewd Into Cntrl Plains During The Evening. Forecast Soundings For North Platte Neb At 03z/Sat Show Mlcape Around 2000 J/Kg With 30 Kt Of 0-6 Km Shear.

This May Be Enough For A Marginal Severe Threat With Hail And Strong Gusty Winds Possible. However...Convection May Struggle Due To The Warm Air Aloft And Any Activity Should Remain Isolated.

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Sat Jul 26 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for Cntrl Plains to Oh Valley/Lower Great Lakes...

Clusters Of Severe Storms Will Be Possible From The Central Great Plains To The Great Lakes And Central Appalachians.

A Vigorous Mid-Level Cyclone Over The Srn Prairie Provinces Will Accelerate Se Into The Upper Midwest By Early Sun. A Broad Belt Of Strong Mid-Level Wlys Should Be Prevalent From The Nrn Plains To The Lower Great Lakes. At The Surface...A Quasi-Stationary Front Should Be Draped Across Parts Of The Cntrl Plains To Lower Great Lakes. An Occluded Front Will Extend S Of The Primary Canadian Cyclone Across The Upper Midwest.

Cntrl Plains To Oh Valley/Lower Great Lakes...

S Of The Quasi-Stationary Front...A Strong To Extremely Unstable Air Mass Should Be Present From Parts Of The Cntrl Plains To Midwest As The Plains Eml Plume Is Advected E Towards The Nrn Appalachians. Waa-Driven Elevated Tstm Clusters Should Be Ongoing At 12z/Sat Over Parts Of The Midwest. In The Wake Of This Activity...Capping Should Largely Inhibit Surface-Based Tstm Development Until Late Day. The Degree Of Inhibition Should Generally Be Less Compared To D2...Owing To Minor Height Falls And Cooler 700 Mb Temperatures /Especially E Of The Ms River/.

Scattered Clusters Of Storms Should Form By Evening Within The Frontal Zone. Given The Degree Of Instability...Along With Strengthening Deep-Layer Shear...An Organized Mcs Or Two May Develop. Large Hail Will Be Most Probable During The Late Afternoon And Evening...With Potential For One Or More Swaths Of Damaging Winds During The Evening Into Sat Night.

If Shorter-Term Mesoscale Predictability Increases...Areas Of Higher Severe Probabilities May Be Evident In Later Outlooks.

Upper Ms Valley...

Deep-Layer Shear Will Be Favorable For Organized Convection Along The Occluded Front Sat Afternoon/Evening.

The Primary Uncertainties Are
1) Richer Low-Level Moisture Remaining S Of The Cntrl Plains To Midwest Front
2) Potential Elevated Storms Over Sd Late D2 Hindering Diurnal Destabilization and
3) Strength Of Convergence Along The Occluded Front.

Still...An Isolated Severe Hail And Locally Damaging Wind Threat Appears Possible.

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July 27-31 Convective Outlook
Storm Prediction Center Norman Ok

A Relatively Active Severe Weather Pattern Beginning D3/Sat Should Continue Through D5/Mon.

Oh/Tn Valleys To The Mid-Atlantic On D4/Sun...

Amplification Of The Ern Conus Trough Is Anticipated With The Aid Of A Shortwave Impulse Crossing The Upper Midwest To Great Lakes. A Swath Of Strong 700-500 Mb Wlys Should Overspread The Mid-Ms Valley To Mid-Atlantic. With A Surface Cyclone Gradually Deepening From The Great Lakes To Northeast...A Cold Front Should Push Se Across The Nrn/Cntrl Appalachians To Mid-South.

With An Eml Plume Possibly Extending To The Mid-Atlantic Coast Within A Zonal Flow Regime... Potential Instability/Shear Combination Would Favor A Broad Area Of Organized Severe. The Primary Uncertainty Is With The Degree Of Convective Overturning On Sat Into Early Sun...Which Could Potentially Be Extensive. This May Have Deleterious Effects On Total Buoyancy And Renders The Need For Greater Mesoscale Predictability To Highlight 30 Percent Or Higher Probabilities.

Southeast On D5/Mon....

With Lower Potential For Convective Overturning In Prior Days...At Least Moderate Buoyancy Should Develop Ahead Of The Cold Front On Mon Afternoon As It Continues To Move Sewd. 700-500 Mb Wlys Should Be Weakening As The Great Lakes Shortwave Impulse Shifts Across The St Lawrence Valley...With The Bulk Of Stronger Flow Likely Lagging The Front. Still...Sufficient Deep-Layer Shear May Exist For At Semi-Organized Clusters Primarily Producing Damaging Winds.


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