Severe Weather Threat thru Jun 7

Sat May 31 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for parts of Northern and Central High Plains...

Isolated To Scattered Severe Thunderstorms Are Expected Across
Portions Of The Northern And Central High Plains For Saturday
Afternoon And Evening.

Weakly Phased Mid-Level Impulses From The Pacific Nw To The Coast Of Nrn Ca Will Progress Ewd Toward The Nrn Rockies And Cntrl Great Basin...Reinforcing A Broad Zone Of Modest Swlys From Srn Ca To The N-Cntrl Conus.

Mid-Level Ridging Will Occur Downstream Across The Great Lakes And Ohio Valley And Will Extend Into The Nern States In The Wake Of A Departing Trough Off The E Coast.

The Persistent Mid-Level Cut-Off Cyclone Over The Lower Sabine River Valley Is Expected To Become Increasingly Ill-Defined Through The Period.

At The Sfc...A Front Will Extend Swwd From Nrn Mn And Will Become
Frontolytic Across The Nrn/Cntrl High Plains As Lee Cyclogenesis Is
Enhanced In Ern Mt.

A Diffuse Boundary Will Remain Draped From Parts Of The Mid-Ms Valley To The Sc Coast.

Nrn/Cntrl High Plains...

The Combined Effects Of Ern-Mt Lee Cyclogenesis And Associated Sfc Troughing To The S Will Encourage Wwd/Nwwd Transport Of Modest Low-Level Moisture On The Cool Side Of The Aforementioned Front.

Meanwhile...Diurnal Heating Of Upper 40s-Middle 50s Sfc Dewpoints
Underlying An Eml Plume/Steep H7-H5 Lapse Rates Will Support Around 1000-2000 J/Kg Of Mlcape.

Modest Mid-Level Height Falls And Diurnally Strengthening Orographic
Circulations Should Support Convective Development During The
Afternoon.

The Greatest Concentration Of This Activity Is Expected To Occur Across Cntrl Mt...Where Relatively Moist Upslope Flow Will Be Maximized.

There Should Be A Tendency For Cold Pools To Amalgamate From Initial Supercell Structures East Of Interstate 5...Supporting Multiple Convective Clusters.

This Is Where Relatively Stronger Mid-Level Flow Will Support Around 25-40 Kt Of Deep Shear...Particularly Given The Low-Level Elys.

These Elys Will Also Bolster Inflow To Breed Forward Propagation Of The Convection Into Ern Mt.

This Activity Is Expected To Evolve Into One Or Two Mesoscale Convective Systems As It Encounters A Moister Boundary Layer... Resulting In An Enhanced Risk For Svr Winds. Svr Hail -- Possibly Significant In Sern Mt -- Will Be Of Concern With This Activity.

More Isolated Convection -- Including Possible Supercells -- Is
Expected To Develop Farther S Across Wy Into Nern Co.

In Addition To Svr Winds...Svr Hail -- Possibly Significant -- Will Be Of Concern With This Activity As It Spreads Ewd Across Portions Of The High Plains.

Regarding The Tornado Potential Across The Region...One Or Two
Tornadoes Cannot Be Ruled Out Aided By Notable Directional Shear In The Low Levels.

However...Low-Level Flow Is Not Forecast To Be Strong -- Especially Where A More Discrete Convective Mode Is Expected To Evolve.

Sely H85 Flow Is Forecast To Increase In Ern Mt By Evening -- But Not Until After Convection Assumes Outflow-Dominant/Quasi-Linear Tendencies.

Upper Ms Valley...

Thunderstorm Coverage Will Diurnally Increase Invof A Comparatively
Weaker Front For Saturday Relative To That Of Friday.

With Only 15-20 Kt Of Effective Bulk Shear...Convection Will Likely Lack
Substantial Organization...While Numerous Storm-Scale Interactions
Yield Competing Inflow To Limit Overall Storm Intensity.

Regardless...A Few Multicell Clusters With Sporadic Svr Wind Gusts
And Marginally Svr Hail May Occur Around Peak Heating.

Sern Conus...

The Combined Effects Of
/1/ Sea Breeze Circulations Over Fl...
/2/ Diurnally Deepening Orographic Circulations Over The Srn
Appalachians...
/3/ Convergence Invof The Diffuse Boundary...
/4/ Ascent Along Residual Outflow Boundaries From Late-Friday
Convection...And
/5/ Diurnally Deepening Pbl Circulations...
Will Encourage The Development Of Thunderstorms Through The Day In A Low-Inhibition/Moist Thermodynamic Environment.

Moderate To Locally Strong Instability Will Support Strong Updrafts / Downdrafts.

With Pw Values Around 1.75 Inches...Water Loading May Support Wet
Microbursts With Sporadic Dmgg Winds.

Isolated Marginally Svr Hail May Also Occur Given The Strength Of Buoyancy.

However...The Paucity Of Deep Shear Will Keep Convection Disorganized And Prevent A Greater Svr Risk From Evolving.

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Sun Jun 1 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for parts of Nrn...Cntrl and Srn Plains...

Severe Storms Are Expected To Develop Over The Central And Southern Plains Sunday Afternoon And Evening.

Primary Threats Will Be Large Hail And Damaging Wind.

Severe Threat Is Expected To Continue Into A Portion Of The Overnight.

Synoptic Blocking Pattern Will Begin To Break Down And Transition To
A More Progressive Flow Regime Sunday.

The Positive Tilt Upper Trough Currently Moving Into The Wrn U.S. Will Continue Ewd And Emerge Across The Cntrl/Nrn Plains Later Sunday Afternoon And Evening.

Winds Aloft Will Increase Over This Region In Association With The Ejecting Upper Trough.

Farther Downstream An Upper Ridge Will Prevail Over The Ern States.

At The Sfc A Stationary Front Should Reside From Mn Swwd Into Sd Early Sunday.

A Lee Cyclone Is Forecast To Develop Along The Front Over The Nrn Plains Sunday Evening/Night In Response To Forcing Accompanying The Nrn Stream Shortwave Trough.

As The Low Shifts Newd...Wrn Portion Of The Front Will Accelerate Sewd Into The Cntrl Plains Sunday Night.

South Of The Cold Front A Lee Trough/Dryline Will Reside Across The Srn Through Cntrl High Plains During The Day.

Portion Of Nrn And Cntrl Plains into a Small Part Of Srn Plains...

A Few Storms May Be Ongoing Over Portions Of The Nrn Plains Early
Sunday Especially Along And North Of The Stationary Front.

Farther South...Increasing Wly Flow Aloft Will Advect Plume Of Steep Lapse Rates Above The Moist Warm Sector...Contributing To A Corridor Of Moderate Instability Over The Cntrl And Srn High Plains.

Mlcape Up To 2500 J/Kg Will Become Likely As The Boundary Layer Warms During The Afternoon.

Forcing For Ascent Associated With Ejecting Impulses Embedded Within The Broader Upper Trough And Boundary Layer Mixing And Convergence In Vicinity Of Lee Trough/Dryline Should Contribute
To Initiation Of Storms By Late Afternoon As The Cap Weakens.

Other Storms May Intensify Across Sd And Neb In Vicinity Of The Front.

Increasing Height Gradient Associated With The Progressive Upper
Trough Will Result In Vertical Shear Strengthening To 40 Kt Supportive Of Organized Storms Including Supercells.

Large Hail Will Be The Initial Primary Threat.

However...Boundary Layer Temperature-Dewpoint Spreads Should Be Sufficient To Enhance Cold Pool Development.

Storms May Eventually Congeal Into Forward Propagating Mcs Clusters With An Increasing Threat For Damaging Wind During The Evening As Upscale Growth Is Augmented By A Strengthening Llj.

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Mon Jun 2 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

A Few Strong To Severe Storms Will Be Possible From The Great Lakes Into The Lower Missouri River Valley Region As Well As A Portion Of The Central Plains.

A Progressive Synoptic Pattern Will Prevail Monday.

The Nrn Stream Shortwave Trough Will Continue Through The Upper Ms Valley And Great Lakes Area...While Shortwave Ridging Builds Across The High Plains.

Farther West A Srn Stream Shortwave Trough Will Move Into Srn Ca
Monday Evening...Continuing Into The Great Basin By The End Of The
Period.

Sfc Low Is Forecast To Deepen As It Lifts Newd Through The Upper Ms Valley And Great Lakes Area.

Attendant Cold Front Will Move Sewd Into The Great Lakes With Trailing Portions Of This Boundary Likely To Stall Over Ks Before Lifting Nwd As A Warm Front Overnight.

Middle-Upper Ms Valley...Portion Of Oh Valley And Great Lakes...

Rich Low-Level Moisture Will Be Drawn Nwd Through Pre-Frontal Warm Sector Along A 35-40 Kt Swly Llj Associated With Developing Cyclone With Mid-Upper 60s Dewpoints As Far North As The Upper Ms Valley And Great Lakes Areas.

However...Widespread Clouds...Weak Lapse Rates And Areas Of Ongoing Showers And Thunderstorms Will Likely Limit Mlcape To Aob 1000 J/Kg Over Much Of This Region.

Scattered Storms Are Expected To Continue Developing During The Day Within The Weakly Capped Warm Sector.

Vertical Shear Will Remain Modest Aob 35 Kt Supporting Multicell Convection.

Depending On How Much Boundary Layer Destabilization Occurs...A Few Storms Might Become Capable Of Producing Mainly Isolated Strong Wind Gusts...But Overall Threat Appears Too Marginal At This Time To Warrant More Than 5% Severe Probabilities.

Cntrl Plains Region...

The Front Is Expected To Stall Across Ks Before Lifting Nwd As A
Warm Front Monday Evening.

Richer Moisture With Middle To Upper 60s Dewpoints Will Reside In Vicinity Of The Front Beneath Plume Of Steep Lapse Rates Resulting In Strong Instability /2000-3000 J/Kg Mlcape/.

An Ewd Advecting Elevated Mixed Layer Will Likely Result In An Inversion Based Above 850 Mb.

This In Conjunction With Building Upper Ridge Lowers Confidence In Thunderstorm Initiation During The Day.

However...Isolated Storms Might Develop Along The Front Across Ks As Well As Farther West Over The Higher Terrain As Upslope Flow Becomes Established Later In The Day.

Should Storms Initiate...Vertical Shear Will Be More Than Sufficient For
Supercells With Large Hail Possible.

Overnight A Few Elevated Storms May Develop Across Neb In Association With Strengthening Llj Augmenting Isentropic Ascent North Of The Front.

This Area Will Be Re-Evaluated For A Possible Slight Risk In The Upcoming Day 2 Outlook.

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Jun 3-7 Convective Outlook
Storm Prediction Center Norman Ok

Weather Will Remain Active Through Much Of The 4-8 Period With A
Series Of Shortwave Troughs Advancing Through The Low-Amplitude
Progressive Flow Regime.

Meanwhile...A Meandering E-W Front Will Become Established From The Cntrl Plains Area Ewd Into The Nern States And Mid Atlantic.

Tuesday /Day 4/...
Another In A Series Of Impulses Will Advance Into The Cntrl Plains And Mid-Upper Ms Valley Regions.

This Feature Will Deamplify As It Crests Upper Ridge But Will Be Accompanied By A 50 To 60 Kt Mid-Level Jet.

Meanwhile...Warm Front Will Lift Nwd Beneath The Strengthening Flow Aloft With Steep Lapse Rates Spreading Ewd Above The Moist Warm Sector.

Potential Will Exist For Storms To Develop Along And North Of This Boundary And Evolve Into An Mcs As They Develop Ewd Toward The Ms Valley Region.

Supercells And Organized Bow Echo Systems Will Be Possible Within The Strongly Sheared And Moderately To Strongly Unstable Environment.

Large Hail And Widespread Damaging Wind Will Be Possible Along With Potential For A Few Tornadoes.

Wed /Day 5/...
The Shortwave Trough Will Continue Ewd Through The Oh Valley Where An E-W Front Will Be In Place With A Moist...Unstable Warm Sector South Of This Feature Across Much Of The Oh Valley.

Belt Of Stronger Mid-Upper Flow Will Accompany The Impulse...And Storms Will Likely Redevelop During The Day In Addition To Possible Ongoing Mcs To Continue.

Vertical Shear From 35-40 Kt And A Favorable Thermodynamic Environment Will Support Potential For Both Supercells And Organized Mcs Events With Large Hail Along With Potential For Widespread Damaging Wind.

Beyond Wed...
Predictability Is Too Low For An Outlook Area At This Time...But An Active Pattern Will Likely Continue From The Cntrl And Srn Plains Ewd Into The Oh/Tn Valley And Mid Atlantic Day 6-7.


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